Wednesday, December 20, 2006

Signing off for the year

As my holiday travel nears and time to finish other things grows short, I'm signing off until after the start of the new year (unless something REALLY cool happens, in which case I'll be back on quickly). I thank all of you who are reading; in the past year, averade readership has tripled! For that, I am very grateful.

I wish you all happy holidays and a very good New Year, and I will start talking at you again in 2007!

Tuesday, December 19, 2006

The Holidays Cometh

Today the productivity of the astronomy department dropped markedly, as the coffee shop in our building closed up for the winter break. No more precious java will flow forth from the hallowed espresso machines until mid-January. So it is no wonder that most of the astronomers have left for the year.

Yours truly, however, is still plugging away, albeit in a caffeine-starved state. This evening, I was baking cookies while watching that holiday classic, "It's a Wonderful Life." And the opening of the movie contains some astronomy!

In the scene where the angels are speaking (Joseph, Franklin, and later Clarence), the angels are portrayed as galaxies. Not just any galaxies, but Stephan's Quintet, a tight grouping of five galaxies in the constellation Pegasus. Since, in reality, these five galaxies do not represent a meeting between two angels, what are we seeing?

A color picture of Stephan's Quintet was taken at Kitt Peak can be seen here. Note that four of the galaxies are a yellowish-white, and the fifth is almost pure white. The very white galaxy is much closer to us than the other galaxies; it just appears along the same line of sight. The yellow color is caused by the expansion of the Universe "redshifting" the galaxy light.

The four galaxies at the same distance are part of a "compact group." Galaxies, like people, tend to like to travel together in groups ranging in size from a few galaxies to many thousands of galaxies. Our own galaxy is in a group with the Andromeda Galaxy, the Triangulum Galaxy, and several small dwarf galaxies. The Local Group, as it is called, is pretty scattered. Andromeda is two million light-years away, and Triangulum is about three million light-years away. The Milky Way and Andromeda are each about 100 thousand light-years across. So there is a lot of room in our Local Group!

In Stephan's Quintet, on the other hand, the galaxies are very close together. Studies of pictures and spectra of the galaxies in Stephan's Quintet shows that there are two pairs of galaxies, and the galaxies in each pair are so close that gravity is pulling large streams of stars and gas out of each galaxy! We see interacting galaxies in many places, but having four bright interacting galaxies in such a small area of the sky makes this system interesting to study. Why are some groups of galaxies, like the Local Group, so spread apart, while others with similar numbers of galaxies, like Stephan's Quintet, so close together? In several billion years, the Local Group may look like Stephan's Quintet. The Milky Way will eventually collide with the Andromeda Galaxy, and the Triangulum Galaxy will probably collide with Andromeda, too. So, by studying this distant group, we can learn what might happen to our own galaxy in the distant future!

Monday, December 18, 2006

The wonders of the internet

I work with computers and on the internet every day, almost exclusively. This is true for most astronomers. So it is rare that I reflect upon how amazing what I am able to do really is. But today was one of those days where it hit me how crucial the internet is to modern astronomy.

When I got to work this morning, I had an email from the observers at the Hobby-Eberly Telescope, located at McDonald Observatory in west Texas. Over the weekend, they had taken some data for me. So, using the internet, I was able to download the data from 800 miles away. Here I had data, and I didn't have to drive 8 hours through the deserts and plains of Texas, nor did I have to stay up all night, nor did I have to worry about the weather. It was almost like magic.

Later this afternoon, I spoke via VoIP (voice over IP, or internet telephone), with a colleague in Australia, where it was Tuesday morning. I had briefly examined the data from the telescope and emailed him the results, and he wanted to chat about it. Even just a few years ago, it would have taken a couple of days to complete this exchange, by the time we sent emails to set up a time for a phone chat. And just 20 years ago the data would have had to travel by airmail. So, in a span of 8 hours, we managed to accomplish what would have taken days or weeks just a few years ago!

Of course, the downside is that people know when I am slacking (or at least they think they know). If I don't respond to email or answer an IM (instant message) though the computer says I am here, people know I am ignoring them. And sometimes a little sequestration away from the world is what I need to get work done, yet I get blamed for slacking. :) So, if you don't see me post for a few days, know that I am working hard to make the world safe for astronomy, even though I may really be playing games away from my desk for a few days.

Best Wishes!

One of my fellow postdocs here, Donna Pierce, is packing up this week to move to a faculty job at Mississippi State University for the start of the next semester.

I met Donna just a few months ago when I moved to Austin. She works on comets, quite a different topic from my work on distant galaxies! But she is a very friendly person nonetheless.

Good luck in Mississippi, Donna!

Friday, December 15, 2006

News from the Stardust Spacecraft

In this week's issue of Science magazine, the team behind NASA's Stardust mission reports their initial findings. Some of these have made the news in the last couple of days. Since the results are interesting, and since I have spoken with mission head Don Brownlee on several occassions, I thought I would blog a bit about that news today.

Stardust is a spacecraft that went through the cloud of dust around Comet Wild 2 ("Wild" is pronounced "Vilt") a few years ago. The spacecraft used a collector to pick up the dust and bring it back to Earth.

Comets are interesting to study because we know they formed in the outer parts of the solar system. Comets are full of ices that melt when close to the sun, so the comets had to form far out. We therefore expected to find that the comet was full of pristine material, "star dust" created by other stars that happened to be in the area when the comet formed.

But Stardust has found that the comet is not pristine. Yes, it has a lot of star dust, but it also has things that formed very close to the sun -- glasses and compounds that had to be made in a hot area. Some of these compounds are identical to the volcanic sands on the Big Island of Hawaii! And there is too much of this material to have been captured by the comet on previous trips past the sun.

We think that these findings show that the very early Solar System was a turbulent, violent place. Plumes of material from near the proto-sun were pushed out beyond the orbit of Pluto by processes we don't understand. And that took a lot of energy!

As is often the case, these findings raise more questions than answers. But it gives us plenty of new research to work on, so I won't complain!

Tuesday, December 12, 2006

Water on Mars?

At our daily afternoon coffee late last week, we were discussing the new images fromNASA's now-defunct Mars Global Surveyor. These pictures show changes in the gullies in a crater, suggesting that liquid water has flowed on the surface of Mars within the last few years! This would mean that Mars must have liquid water today in underground lakes or caverns, and that this water sometimes escapes to the surface, where it quickly evaporates.

Few of us here, and certainly not me, are planetary scientists, so it is hard for us to judge the data for ourselves. Must the changes in this crater be due to liquid water? I can't say. But it is fun to debate the implications. On Earth, liquid water = life. Did Mars ever have life? Could it have life now? Can living things survive in this water, which is probably very acidic and extremely salty? I don't know the answers to that, either. But it is fun to speculate! Now the question becomes how to find the water and search for life without contaminating Mars or a soil sample with bacteria from Earth. Easy enough to say, but hard to do! Do we need a lander that can traverse these craters? If the crater is full of dust, how can a lander safely land and get partway up the crater wall without slipping? How can we completely sterilize a spacecraft that, by necessity, must sit on the launch pad in Earth's weather and launch through Earth's atmosphere, which is teeming with all forms of life?

Friday, December 08, 2006

Last of the Spectra

Sorry I missed yesterday's posting, but I managed to break some software on my computer and spent a lot of time getting it working again. I shouldn't have believed those who told me it was an "easy" update I was trying to do!

Anyway, let's spend a last day with some of the neater spectra I have. Remember, just click on the spectrum to get a larger version of the picture. As a reminder, here is a spectrum of the sun:

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Remember that all those narrow lines are "fingerprints" of the elements in the sun, such as iron, magnesium, calcium, and hydrogen. Now look at this next spectrum of a star-like object called BL Lacertae:

It has almost no lines at all! It took a long time to figure out that what we astronomers were seeing was a black hole. We are looking right down close to its event horizon, where things are so hot, individual elements don't show up in visible light! For another strange spectrum, look at this spectrum of the star T Tauri:

Here, if you look closely, you can see a spectrum that looks almost like that of the sun, but there are bright lines on top of it! Those bright lines have the fingerprint of hydrogen. What we see here is a very young star about the size of the sun, with some hydrogen gas still falling onto the star.

Lastly, let's look at my favorite of all of these, the spectrum of the Crab Nebula:

This spectrum is different from the rest. In the other spectra, I smeared out the light from the star up and down so you could see the lines better. Here, I am showing the spectrum "as is." The straight vertical lines here are the streetlights of San Jose, CA. (I took those out of the other images). The horizontal lines are spectra of stars that happened to be in the way. But the crooked, knotted vertical lines are the Crab Nebula itself. Most of the light here comes from hydrogen and oxygen. The crookedness is caused by the gas of the nebula moving very fast -- almost 1000 miles each second! The light is Doppler shifted, meaning its color changes depending on how fast it is moving. So, we astronomers can use this spectrum to figure out how fast different parts of the nebula are moving. The gas here is moving so fast because the Crab Nebula is what remains of a star that exploded nearly 1000 years ago!

Wednesday, December 06, 2006

More spectra

So, remember yesterday I said that the fingerprints of the elements that make up a star are visible in its spectrum. But what about the spectra of things in our solar system? Planets and moons don't make their own light, they just reflect sunlight. So you should expect the reflected light to have a spectrum identical to the sun.

For the most part, this is true. Below are three spectra. The first is of the sun, the second is of Saturn's moon Titan, and the third is of the planet Uranus. You can click on an image for a larger view.

Notice that Titan (the middle spectrum) looks a lot like the sun, with the exception of a little less blue light and a band of red light that is ever-so-slightly diminished. If you look at a color picture of Titan, you can see that it is yellowish -- the same color as the sun, but with less blue light.

The spectrum of Uranus, on the other hand, looks much different from the sun. Some colors are completely missing, and there is almost no red light! You are still seeing the spectrum of the sun, but the atmosphere of Uranus (mostly methane) has absorbed those "missing" colors of light. Once again, if you look at a color picture of Uranus, you'll see it is a greenish blue, the same as the colors of light left in its spectrum.

Tomorrow I'll finish up showing off my spectra with a few objects from outside the solar system.

Tuesday, December 05, 2006

Learning from the colors of the rainbow

One of the main tools astronomers use to determine what we are seeing through a telescope is a spectrum. A spectrum is a splitting of light into its component colors, just like a rainbow. The picture above shows a spectrum of the sun. If you look closely, you'll see several dark lines. These lines are caused by different materials in the sun, like hydrogen, iron,calcium , magnesium, carbon, oxygen, and so on. Each element has its own unique set on lines that appear in the spectrum, just like a fingerprint. Only in the astronomy, these fingerprints get stacked, one on top of the other, to make the pattern you see here.

Different objects have different spectra. Compare the spectrum of the sun (above) to the spectrum below this paragraph. Notice any differences? (You can click on the spectra to make the images larger.)

The two main differences are: the lower spectrum has many fewer lines, and also has much brighter blue and less obvious red. The star we are looking at (Algol, in the constellation Perseus) is a very hot star. The star appears blue in color (as you can see from the spectrum) and is so hot that the normal lines from metals like iron don't show up -- those metals have lost the electrons that make the characteristic lines!

Tomorrow I'll put up a few more fun examples. But the color representation is just to help you visualize the spectrum -- we astronomers don't use color pictures like this. Instead we make graphs showing how much light we get at each specific wavelength (or color), so that we can use mathematics to uncover even more details than the human eye could ever notice.

Thanks to John Kielkopf at the University of Louisville for writing the program that colorized these spectra!

Monday, December 04, 2006

Working against the clock

As an any profession, astronomy has its share of deadlines. One of the biggest deadlines are telescope proposals, where we request telescope time for the coming four or six months. For most ground-based telescopes, these are generally due in March and September (sometimes there is a third due date in the middle of summer, if an observatory works on a trimester system). For space-based telescopes, like the Hubble Space Telescope, these proposals are due once a year, typically in late January or early February.

I am applying for permanent jobs again this fall; many of those are due this time of year. I had four applications due on Friday and another one due this week, plus several more scattered between now and the end of January.

We also have deadlines when preparing to use the telescope. Some observations require metalsmiths to mill special masks with tiny slits wherever there is a star or galaxy we astronomers are interested in. These often take a month or more to make, and I have some due soon.

So, in short, I'm swamped and behind (as usual). So, if you don't hear much from me in the next few days, know that I am trying not to neglect you all.

Thursday, November 30, 2006

Litter on Mars

Humans haven't been exploring Mars very long, and already we've left some litter on the planet. Several robots have explored the planet's surface, from the 1970s Viking Missions to the ongoing Mars Exploration Rovers, Spirit and Opportunity. Our newest spacecraft, the Mars Reconnaissance Orbiter, has a strong enough camera that it can see the bits and pieces of these robots on the surface. For example, here is a satellite picture of the rover Opportunity's landing platform, forever standing in the middle of Eagle Crater on Mars. This picture was taken from a distance of about 160 miles above the surface of Mars, and the lander is only 10 or 12 feet across.

In coming months, the Marso Reconnaissance Orbiter will look for the Viking 1 and 2 landers, the Mars Sojourner Rover, and maybe even some of the failed landers, like the Mars Polar Lander that shut off its rockets while still about 150 feet above Mars and crashed to the surface. Such a picture might clear up the mystery of what happened to the lander. Further, pictures of now-defunct spacecraft can help us to learn about the weather on Mars. How fast does dust get blown around the surface? Can we see any other changes since the last pictures were taken? And so on.

Tuesday, November 28, 2006

Looking at telescopes for holiday presents?

It's that festive time of year! It is this time of year when the typical American calls on the long-repressed shark genes in our DNA, genes necessary for instinctive movements while slowly circling parking lots looking for spaces, for sniffing out the slightest whiff of a run on the toy your child MUST have, and for being able to dart into the toy-buying frenzy and emerge with a tasty morsel of "Surfing Barbie Limited Edition 2006."

Are you thinking of buying that ever-popular astronomy related present this year? No, I'm not talking about Tickle-Me Elmo Apollo 13 Edition ("Houston, we have a problem. Tee-hee!"). I'm talking about a telescope. Maybe your child has seen the boxes in the department store that say "1000x magnification!!!" and show a Hubble Telescope picture of Saturn. Or maybe your wife/husband/girlfriend/boyfriend/etc. has always been interested in astronomy and you want to surprise her or him. Or maybe you just want one for yourself. What should you do?

First and Foremost: Do not go into a store and buy the telescope advertising the highest magnification!!! Believe it or not, magnification over about 200x is perfectly worthless, the blurring caused by Earth's atmosphere becomes visible at that point, No matter how much higher you magnify, all you will get is larger blurry spots! Plus, many inexpensive small telescopes have poorly-made lenses, and the blurring from the poor construction can be seen at much lower magnifications. And many astronomical objects, like comets, galaxies, star clusters, and nebulae, are surprisingly large, so you don't need magnification. They need light gathering power, which depends on the size of the telescope's opening (like 60 or 90 mm) and not on magnification.

Ask yourself: Is this the first telescope for the gift recipient? If so, consider getting something like high-quality binoculars with a sturdy tripod. Binoculars can be used for many things outside of astronomy. Maybe your child will lose interest in the stars, but she may develop an interest in birdwatching. Telescopes flip the image, so daytime viewing is not very useful (unless you are looking for dead birds hanging from their perches). Binoculars are also perfect for looking at nearby galaxies and bright star clusters. As a kid, I often used my dad's binoculars to look at the Andromeda Galaxy and the Orion Nebula, and I won an award for being one of the first 10 readers of "Odyssey" magazine (an astronomy magazine for kids) to spot Halley's Comet with binoculars.

If you still want a telescope: If you are pretty sure that the person getting the telescope will be an avid user, don't go cheap, but don't go all out! Most of the telescopes at big stores are cheap, poorly built, and will be disappointing. Why waste your money on that? On the other hand, many camera shops have 8-inch or 10-inch telescopes that look impressive and have lots of cool features like "Go-To" pointing and computerized controls. These can be very high quality telescopes, but do you want to spend over $1000 on a first telescope? I personally would think twice. So, shoot for mid-range. Many telescope manufacturers (including, but not limited to Meade, Celestron, Orion, and Edmund Scientific) have some nice quality, relatively inexpensive telescopes. Look them up on the web!

What kind should you buy? When you look up telescopes on the web, you will see lots of descriptions that may not make sense to you (unless you are an avid amateur astronomer, in which case you probably stopped reading several paragraphs ago). Words like: refractor, reflector, Newtonian, Dobsonian, Cassegrain, and so on. For a first telescope, I wouldn't worry too much about most of these descriptions. As your loved one gets deeper into astronomy, she will learn what these mean and be able to buy the next telescope for herself. For starter telescopes, I would urge you to consider one of the following: a 60-mm to 90-mm refractor , or a 4-inch to 6-inch reflector. Most of these will come with a couple of eyepieces, so don't buy more of those right off the bat. Edmund Scientific's Astroscan and Orion's StarBlast are often considered very good, rugged first telescopes (I don't get paid for saying that, by the way). And if the telescope comes with a "solar filter" that screws into the eyepiece, THROW IT AWAY, for safety's sake!

Still not sure? Still confused? Then don't buy the telescope. I don't want to discourage anyone from enjoying astronomy, but a bad telescope can be worse than none at all. Instead, get your loved one a subscription to an astronomy magazine, like Astronomy, Sky and Telescope, or Night Sky. Or, buy a good book with lots of pretty pictures. Find a local astronomy club and take your loved one for a visit (which is a good place to learn about telescopes, too!).

Wednesday, November 22, 2006

Astronomers are thankful, too

Turkey with telescope

Tomorrow is Thanksgiving Day. I've always liked Thanksgiving, with good food and happy times with family. So, beyond the typical things of friends and family, what are astronomers thankful for? Here's a list I've made up, in no particular order:

  • I am thankful to get paid to do my hobby.
  • I am thankful that taxpayers support astronomy research, even though there is rarely an immediate benefit.
  • I am thankful that we live in a Universe where it is possible to learn about worlds far from our own.
  • I am thankful to all the engineers who build our telescopes. I'm not very handy, so if I had to build my own, I would be lucky to be able to find the sun.
  • I am thankful for caffeine so that I can stay awake all night.
  • I am thankful for computers, so that I can deal with large amounts of data. When you are looking for a needle in a haystack, being able to look fast is a help.
  • I'm thankful for colleagues, who offer support, tell me when I'm barking up the wrong tree, and sometimes go to the telescope for me when I'm too tired to go.
I could go on and on, but I think the pumpkin pies are calling. Happy Thanksgiving!

Sunday, November 19, 2006

Back to Arizona

For the past several days, I have been back in Tucson, Arizona for the first time since moving to Texas. I am observing at Kitt Peak, three nights that look to be clear. The wind is howling a bit tonight, but we are still getting good data.

Before today, I visited the astronomy department at the University of Arizona. My old desk was still open, so I used it as a visitor's office and got some work done with local collaborators. All in all, it was a good visit, and it was nice to see colleagues again.

Wednesday, November 15, 2006

A tempest in a teacup

Today in Texas the wind is howling as a cold front sweeps through the area. It's a good day to get out of town, and I'll be doing that around noon as I head for observing at Kitt Peak in Arizona.

The weather reminded me of an article I saw in an astronomical journal a few days ago talking about "cold fronts" in the hot gas in a galaxy cluster. Cluster of galaxies, which can contain thousands of galaxies in an area "only" a few million light years across, often are surrounded by X-ray emitting gas that is several million degrees in temperature. A cold front can be caused by cold gas in a galaxy that has just fallen in to the cluster, or by many other complicated mechanisms. But, in many ways, they act like cold fronts on Earth -- moving through the super-hot gas and cooling it by a million degrees or so.

Astronomy is hard to do in the laboratory. We have yet to make a star, let alone a galaxy or a cluster of a thousand galaxies. So we often have to look to similar processes on Earth to learn the physics that we use to understand the Universe. I remember seeing a talk about 10 years ago by scientists who were studying storms in Jupiter's atmosphere by dropping fluorescent crayons into a rotating drum of water. Another talk I saw about 6 or 7 years ago involved studying why stirring hot tea causes it to cool faster, and how that knowledge can extend to rotating stars. And looking for life in the Universe often involves trying to look at the Earth in the same way we'd look at other planets, trying to find tell-tale signs that would prove the presence of life.

So, there is a lot we can learn about the universe from studying seeming mundane things, like hot tea or the weather.

Tuesday, November 14, 2006

O MGS, where art thou?

NASA currently has five operating probes exploring the planet Mars. The two most famous are the rovers Spirit and Opportunity, which have been crawling over the surface of Mars for nearly three years now.

NASA also has three working probes in orbit around Mars: the newly-arrived Mars Reconnaissance Orbiter, the 5-year-old Mars Odyssey orbiter, and the 10-year-old Mars Global Surveyor, or MGS.

The MGS just celebrated its 10th year in space -- it launched from Kennedy Space Center on November 7th, 1996. 10 years is quite old for a spacecraft, and is nearly twice as old as its planned lifetime. But the satellite seems to be showing its age. On November 2nd, NASA sent normal commands to the probe, and for some reason the probe entered a "safe mode." This means something went wrong, and the spacecraft shuts down all non-essential equipment and sends an interplanetary distress signal to Earth.

Such safe modes happen fairly often in space probes -- recently the Hubble Telescope's main camera went into safe mode, the two rovers have repeatedly entered safe modes, etc., etc. The main purpose of the safe mode is to keep the spacecraft from hurting itself while NASA tries to figure out what went wrong.

With the MGS, though, the situation is turning dire. After sending its "distress signal," it has said little else. Part of the reason for this may be that the spacecraft, when in safe mode, is supposed to turn its solar panels toward the sun, which moves its antenna away from the Earth. In case this is what happened, NASA is using its other probes around Mars to try and contact the MGS. But perhaps the MGS did not make it into the proper position, in which case its batteries would have run down by now. In this case, MGS will not be able to be recovered.

I think its important for you all to realize that, although this sounds like it may be the end of one of our space probes, this is by no means a failed mission. MGS has done much more than we intended it to do when it was launched. It has sent back nearly 250,000 pictures of Mars, and observed four Martian years' worth of weather on Mars. All spacecraft will die eventually, and MGS has lived a full and very useful life. Hopefully it is not gone, but if it is, let's celebrate instead of mourn!

Monday, November 13, 2006

Phantom glows in the night

Contrary to how it looks out in the wilderness, the night sky is not dark. It glows very faintly. Some of this light is sunlight reflected off of the moon or off of dust in the solar system. Some of the light comes from the gas in the upper atmosphere. And a tiny bit is starlight from other stars.

Since we astronomers want to study light from specific stars or galaxies, we need to get rid of this glow. In the computer age, this is done by measuring the light from a star and measuring the light from the same size of spot in an area with no stars, and subtracting the two. And this generally works very well! Sometimes it works a little too well, and you can miss interesting things.

This happened to me recently. I was looking at stars, and one of them was a little strange. It appeared to have light coming from specific wavelengths (or exact colors) that most stars don't have. The extra light that I saw had the signature of hydrogen moving toward me at high speeds -- over 100 miles per second! There are plausible explanations for this, many of which are quite interesting. But still, something didn't seem right.

When I looked closer, I noticed that my sky subtraction didn't seem to be working right for that star, so I was seeing light from the sky, not from the star. But this is still odd -- the night sky doesn't glow with the light of hydrogen, and the sky is not moving toward the ground at 100 miles per second (unless the sky really was falling. When I looked at the sky in my data for the first time, I also saw other atoms that aren't in our atmosphere. In fact, the night sky looked a lot like a nebula such as the Cat's Eye Nebula. But in pictures of this patch of sky, I hadn't seen any nebula. What was going on?

After a few hours of research, I found that the patch of sky I was looking at was on the edge of the Cygnus Superbubble, a bubble of very hot gas that was made by several groups of hot stars and supernovae. The superbubble is huge -- 15 degrees across, or 30 times the size of the full moon. This is why I hadn't seen it on my image -- the light is spread over a very large area. My pictures were only 1/10 of a degree across, or over 100 times smaller than the size of the bubble.

While I was disappointed I hadn't discovered anything new, there is still science that I can learn from this. And I have learned to take a closer look at the blank sky, because I don't know what it might be hiding!

Wednesday, November 08, 2006

The Modern Transit Science

Today Mercury transits the sun for the last time until 2016! As a reminder -- DO NOT LOOK AT THE SUN WITHOUT APPROPRIATE SAFETY!

For a while, transits lost a lot of their scientific lustre. Since we knew the distances to the planets, the traversal of Mercury across the sun became an interesting phenomenon, but nothing more.

That has changed with the discovery of planets in other solar systems. In some of these systems, the planet goes in front of the star as seen from the earth. We see the star get slightly dimmer (the planet only blocks some of the light, not all of it) and then re-brighten. We can learn a lot about the planet -- its mass, its size, and even its atmosphere, as it passes in front of its parent star.

There are uncertainties, though. What happens to what we observe if the planet passes over a starspot? Or over a flare on the star's surface? Although we can calculate what should happen, it is better to know for certain. And that is where the transits of Mercury and Venus come in to play. With luck, the transits will pass over some of the sun's active regions, and we can observe what, if any, changes there are in what we observe from Earth. We can then apply this knowledge to what we see in transits in other solar systems, and try and figure out if a star spot or stellar flare is messing up our observations.

If it is cloudy where you are, or you don't have a safe telescope, you can watch the transit live online.

Tuesday, November 07, 2006

A comet gets too close to the sun

In the Greek myth of Daedalus and Icarus, the father-son duo escape from the labyrinth by making wings out of feathers and wax and then fly out of the maze. Icarus ignores his father's warnings, flies too close to the sun, and the wings melt. Icarus falls and is killed.

Each year, many comets, real balls of ice and dust, meet the same fate. These "sungrazing" comets seem to be the remnants of one or more regular comets that orbited too close to the sun and were pulled apart into a string of thousands of miniature comets. The SOHO spacecraft, a sun-viewing spacecraft, is constantly watching the sun. It has spied over 1200 comets plunging into the sun, most of which never return -- the sun completely melts them!

Most of these sungrazing comets are very faint and unimpressive. However, this week a fairly bright one appeared. You can watch a movie at this website. The comet comes in from the lower right. The sun is hidden behind the blue disk in the middle of the picture (or else it would completely blind the camera). The white circle gives the approximate size of the sun. The bright "star" to the upper left of the sun is the planet Venus.

The science of transits

Tomorrow's transit of Mercury across the sun is more than just an interesting phenomenon. There is science to be had from transits, too.

A couple hundred years ago, astronomers realized that it was possible to use transits to determine the distances to the sun and planets. We knew their relative distances from the sun, but we could not easily put that in absolute terms. So astronomers developed a clever trick.

At different parts of the Earth, a transit begins at slightly different times because the observers are looking from slightly different angles. If you can time the start of the eclipse very accurately, and you know the distance between the two observers, you can calculate the exact distance to the planet.

Unfortunately, this didn't work. First, in the days prior to atomic clocks, GPS, and even radio, clocks were just not quite accurate enough to get a good measurement. Also, astronomers did not know about the now-infamous "black drop" effect. Astronomers decided to make timing measurements at the moment that Mercury or Venus was first fully inside the sun (because it is hard to be looking at just the right instant when the transit begins). But when explorers were watching transits, they noticed that the round planet and the round sun did not break cleanly, but a little thread of black connected them for some time after the planet was fully inside the sun.

The explanation of the black drop (which you can observe tomorrow if you have the right equipment!) is still unclear. It is probably due to a variety of things -- Earth's atmosphere, the atmosphere of Venus (when Venus transits), and imperfect instruments used for the observing. So, the measurements of the distance to the planets were not as accurate as was hoped.

These days, we measure the distance to the planets by radar -- we bounce a radar pulse off of the planet and see how long it takes to return. That's VERY accurate!

Tomorrow, we will talk about transits and modern science.

Monday, November 06, 2006

What's the black dot on the sun!

No need to worry on Wednesday if you look through a solar telescope and see a black dot on the face of the sun -- it is just the planet Mercury. Every three to thirteen years, Mercury's orbit takes it directly in front of the sun as seen from the Earth. Mercury actually orbits the sun every 115 days as seen from the Earth, but most of the time it misses the sun as seen from Earth. When the geometry is right, however, we see a transit. The last such crossing was in May, 2003, and the next one will not be until May 2016!

DO NOT try and look at the transit unless you are using a telescope with a solar filter! Mercury is too small to see with your unaided eye, and looking at the sun with a telescope or binoculars without a filter will blind you! Also, don't use "eclipse glasses" -- cardboard eyeglasses with Mylar filters -- to look through a telescope, because these glasses were only designed to look at solar eclipses with the naked eye. The extra light collected by a telescope could burn right through those glasses!

Your best bet is to find a local astronomy group that may have a solar telescope set up in your neighborhood. If there are any sunspots visible (not many are around right now), you can notice that sunspots are actually brown when compared with the pitch black of Mercury's night side.

If you live in Europe, Africa, or the Middle East, I'm sorry, but you are out of luck. The sun sets before the transit begins and rises after the transit ends. For much of the rest of the world, you can see the transit. This website will tell you what time of day you can see it. The transit lasts 5 hours, so you have plenty of time to wait for the hole in the clouds or to get out of school.

Thursday, November 02, 2006

On to Phase Two...

In astronomy, there are two types of telescope observing. "Classical" observing is what most people think an astronomer does -- she drives up the mountain, stays up all night in the same building as the telescope, and then drives down with a car full of pictures and data. This is the only type of observing I have done.

The other type of observing is known as "queue" observing. In this case, the astronomer stays at home, and the staff of the observatory does all of the observing. They may take data for several different astronomers in one night. An advantage of this type of observing is that, as the weather changes, different observing programs can be attempted. Some observing requires crystal clear weather and rock-steady skies, while other programs can be done even if we are looking through thin wispy clouds on a windy night. Queue scheduling searches for the program that can best use the existing conditions.

Another advantage of queue observing is that valuable science can be done all night long. In classical observing, it often happens that the object the astronomer is interested in moves through the sky and sets before dawn, leaving the astronomer with an hour or two in which she has to find something to do. In queue scheduling, when one person's object sets, someone else's is rising.

Some telescopes have to work in queue mode, like the Hubble Space Telescope. I can't drive on up to space to use the telescope -- its schedule has to be planned months in advance, and then replanned when each glitch messes up some observing.

There are disadvantages to queue scheduling. Since the astronomer is not there, the astronomer has to rely on other people to take the appropriate data. Sometimes in an observing run you point at the wrong object, perhaps you have bad coordinates, perhaps your finder charts (pictures of the sky you will be pointing at to help you find your target) are bad. In classical observing you pull up the internet, do a few minutes of searching, and figure out what is wrong. In queue observing, at best the observer gives up and moves on, at worst he or she takes pictures of the wrong thing, and uses up your time on a worthless object.

Queues are also less flexible. Suppose I am going to the telescope in January, and in December somebody "scoops" me by publishing data on the object I was going to observe. In classical mode, I just switch to a different object, but I still get my telescope time. In queue mode I can cancel my observations, but I can't put a new one in.

McDonald Observatory is partners in the Hobby-Eberly Telescope (HET), a large telescope with a mirror about 30 feet across in West Texas. Because of its unique design, the HET must be run in queue mode. It is set at a fixed angle, and so can only look at things 55 degrees above the horizon, giving it a donut-shaped view of the sky. As objects go across that donut (it takes about an hour), they can be observed. So, with lots of astronomers having lots of objects spread around the sky, something is always crossing the donut. But if I were to go and use the telescope myself, chances are good that, for much of the night, nothing I want to look at would be visible!

My co-workers and I were given 13 hours (about one night) of total time on the telescope this past week. Our observations will be placed in a queue to be observed sometime between January 1 and April 30, probably just as one hour here and one hour there. But I have to turn in all of my materials that the observers will need (finding charts, lists of targets, how long I want to look at each target, what camera I want to look at each target, and so on) by the end of next week. So, there's a lot of work to do in a short time to prepare. And, since this is my first time doing queue observing, I am hoping that I don't mess up!

Wednesday, November 01, 2006

An astronomy-themed Halloween

Yesterday's holiday, Halloween, is an astronomical holiday. Therefore it is only fitting that the astronomy department had a big party, including trick-or-treating, pumpkin pie, pumpkin soup, and a costume contest. My costume is shown above -- I was Captain Ahab, searching with my Handy Spyglass Telescope (HST) for the elusive White Dwarf. But the winning costume was built by one of our computer gurus, who was a human-sized LEGS mini-figure. Alas, I don't have pictures of her costume yet.

For some space humor, try today's Strange Brew comic strip.

Tuesday, October 31, 2006

Sorry for delays in posting and whatnot

For the past few days, my blogging service and web service have been trying to ignore each other. So some posts appear as I put them up, some wait a day or two. Grrr!

Let's go fix Hubble!

NASA Administrator Michael Griffin announced this morning that NASA will schedule a space shuttle flight to repair the Hubble Space Telescope, likely to launch in early 2008. You can read the full story here.

I won't bother repeating the details from the story. But most astronomers are quite elated at the news. After a rocky beginning due to a misshapen mirror, Hubble has proven to be one of the most productive telescopes ever made, making many important scientific discoveries. The fact that Hubble is as popular a telescope now as it was when it was launched shows how important it has become.

I wish the astronauts well in their training, and safety on their mission.

Monday, October 30, 2006

This concludes the test

This concludes our test of the blog posting service. Had this been an actual posting, the headline would have been followed by official information, news, or instructions.

This is a test

This is a test of the Blog Posting System. This is only a test. Beeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep.

Wednesday, October 25, 2006

Decision coming on Hubble

Ever since the loss of the Space Shuttle Columbia nearly four years ago, the final planned shuttle mission to repair the Hubble Space Telescope has been in limbo. First it was cancelled, then changed into a robot mission, then re-instated as a possible mission, and then made dependent on the last two space shuttle flights.

This Friday, NASA will inch closer to a final decision on a Hubble repair mission. Space shuttle engineers are going to be meeting to discuss whether a repair mission is relatively safe, or whether it is too unsafe to proceed. If they deem it unsafe, then that will spell the end for Hubble. If they deem it safe enough, then the NASA administrator, Michael Griffin, will make the final call.

Hubble is working away, but in worsening shape. Its batteries are old and need replaced. Its gyroscopes are old and need replacing. Its pointing system is old and needs replacing. Its main camera has been acting flaky, and its secondary camera is nearly 10 years old -- ancient for space hardware. Its only spectrograph died a couple of years ago. Two brand new instruments have been built and are ready to be put onboard.

Do I think Hubble will be repaired? I don't know. I would like to see it repaired, but I am not the person who would be putting my life on the line. Hubble repairs are not worth six or seven human lives. My hope is that the engineers will not feel pressure from any side, but have a chance to honestly express their concerns and their confidence in a repair mission.

Stay tuned!

Thursday, October 19, 2006

Upcoming travel...

My blogging will be light for the next week, as I'll be doing some travelling. However, I will update you on how things are going and any exciting news as time allows!

Wednesday, October 18, 2006

Time for job applications!

(Note: I will post any further news on the telescope damage in Hawaii as things unfold; right now there is pretty much no change over my past postings. A big thank you to UC Santa Cruz astronomer Jay Strader for feeding me information!)

Yes, now that I have just moved, it is time to start applying for jobs again. Those of you who were reading last year know what a chore the search for academic jobs is -- we apply for jobs in the fall, interview in the spring, and, if we are lucky, start the following fall. Since my new job lasts for up to three years, why start torturing myself again this year?

There are many reasons, both professional and personal. But one major reason is that the job process is quite non-scientific. Different universities have different desires, but they have to be very careful in wording job advertisements. Internal politics can play a role, as can the one person who supports an applicant being out with the flu for one committee meeting.

For these reasons, and others, I think it is best not to rest on my laurels, but to keep up the search for a permanent position. And so, having just moved to Texas, I must look forward to the possibility of moving again, put my best foot forward, and start trying to sell myself for the second year in a row!

Tuesday, October 17, 2006

More updates on the Hawaiian observatories

As I mentioned yesterday, the Keck Observatories are in pretty good shape, but will need a few more days to recover.

The Canada-France-Hawaii Telescope seems to have similar damage to the Keck telescope -- the pointing system is offline, and the dome is not working at the moment.

The Gemini North telescope has similar damage but seems to be in good shape.

I looked at web pages for a few other telescopes; only the Subaru Telescope (owned by Japan) has not posted their status, and in general it appears that no mirrors are broken, but it will take a few days to start bringing telescopes online.

Monday, October 16, 2006

Hawaiian telescope damage

I received some emails from friends about the status of the Keck Observatory's twin telescopes, the world's largest telescope. They are located about 30 or 40 miles east of the epicenter of yesterday's magnitude 6.7 earthquake, on the Big Island of Hawaii.

The mirrors do not appear to be damaged, but there are some (probably minor) problems with the telescopes. The telescopes had restraints in case of an earthquake, but the shaking may have exceeded those limits. The telescope also uses an "encoder" to tell where it is pointed on the sky, and this encoder is out of whack. All of the instruments seem to be okay, though the electronics reported a little bit of overheating. In short, the telescopes are probably offline for a few days to a week, but the engineers seem confident all can be fixed.

Most importantly, nobody was hurt. The main buildings in the town of Waimea suffered some cosmetic damage, but are otherwise okay.

I haven't heard anything about other telescopes, but I would be surprised if they were not in similar condition.

The Hawaiian Earthquake

Yesterday's earthquake near the Big Island of Hawai'i was of interest to me, not only because of a passing interest in geology, but also because of its potential impact on astronomy. Several large telescopes are located on the summit of Mauna Kea, a dormant volcano on the Big Island. These telescopes are very sensitive instruments, so the major shaking of the earthquake may well have caused some damage.

So far, I have not heard any reports from any of the observatories. However, I did notice that some websites detailing weather on Mauna Kea are back up and operating, meaning that power has been restored. The current weather seems to be lousy, though, with high humidity and cold temps, so it may be too dangerous weather-wise for much to happen on the mountain today. Almost certainly no observing was done last night.

I will certainly let you know if I hear any news. In the meantime, keep your fingers crossed. And if you'd like to help the people of Hawaii, please consider making a donation to the American Red Cross National Disaster Relief Fund. This fund is still helping the Gulf Coast residents displaced by Hurricaines Katrina and Rita, as well as helping victims of disasters across the country.

Thursday, October 12, 2006

Politics, Elections, and Astronomy Research

Last night, my home phone rang off the hook with calls from various political groups and politicians, all trying to win my vote in the upcoming elections. Of course, many of these politicians are in Arizona and having their calls automatically forwarded to my new home, so they are wasting their time. I couldn't vote for them if I wanted to.

A few people have asked me which political party would better serve science research. Now, I have to keep most of my opinions to myself or I'll get in a lot of trouble with elections commissions. But historically, science spending does not seem to be correlated with the party in power. There are some exceptions, especially with medical research, but if the amount and types of medical research funding concern you, you probably are already aware where each party stands.

More important to astronomy and other sciences than who is elected in November is the issue of the Fiscal Year 2007 budget. Congress adjourned to go campaigning without passing most spending bills for FY2007 (which has started), so Congress will have to come back after the election and pass those bills, probably as a single "omnibus" spending bill, which means that few members of congress will actually read the whole thing. They will look to make sure that the programs most important to them have been funded, and then vote for the bill.

This means that you still can make a difference! If you want to help astronomy research, write your Representative and Senators and request that they support the president's proposed fiscal year 2007 funding for the National Science Foundation and Department of Energy. President Bush suggested that both of these budgets be increased as part of his American Competitiveness Agenda. You can also suggest that funding be increased for NASA -- NASA's proposed budget will force it to instantly kill many astronomy and space science research missions.

Whenever writing your congresspersons on any issue, be sure to indicate that you are a constituent, meaning that you and/or your parents/family/friends can vote for that person. Congresspeople don't have enough time to read all their mail, so aides do that. And letters where the writer is not a constituent are often tossed aside. To find out who your Representative and Senators are, and to get their mailing and email addresses, go to this website for Representatives and go to this site for Senators.

Tuesday, October 10, 2006

Ig Nobel Prizes awarded!

Late last week, the 2006 Ig Nobel prizes were awarded at a star-studded ceremony on the campus of Harvard University. These award celebrate the "best" of research that cannot and often should not be repeated.

For example, the Ig Nobel in physics went to Basile Audoly and Sebastien Neukirch of the Université Pierre et Marie Curie (Paris), who studied why, when you bend spaghetti until it breaks, you get three or more pieces instead of just two. The short answer being, that, when the spaghetti breaks, little waves from the break travel up and down the noodle. As much of the noodle is near the breaking point, in some places this wave pushes the pasta over the limit.

(Note to kids -- this is a fun experiment to try. Bend a bunch of spaghetti until it breaks, and count how many pieces it makes. Then try to explain to mom or dad why there is spaghetti everywhere. Remember to tell them that this is award-winning physics! And then you can explore the physics of how a broom sweeps up spaghetti. Just don't tell your parents where you got the idea from.)

The Ig Nobels are given in the spirit of fun. Yes, science does address important issues facing society, but some issues are more important than others.

I think there is also a small lesson to be learned. Many of these awards are given to research that is published in a professional journal. Remember -- just because some research is published doesn't mean it is important and/or correct!

Monday, October 09, 2006

Looking through a new telescope

Blogging was quiet last week, as I was struggling to learn enough to apply for telescope time here at my new institution. It is that time of year where every American observer is preparing proposals to use telescopes, as almost every American observatory has deadlines in September and October.

A major part of proposing to use a telescope is showing that you are not going to be wasting the time. Not only does this mean you have a good project, but the project should be able to be done on the telescope you are asking for AND you need to show that you understand how to use the telescope you are asking for.

The big telescope at McDonald Observatory is the Hobby-Eberly Telescope, a joint venture between the University of Texas, Penn State (go Nittany Lions!), Stanford, and two German Universities: the Universities of Munich and Göttingen. The HET is not just another big telescope, however. It has a unique design that keeps it at a fixed angle above the ground (though it can spin around in circles). This means that there are many intricacies about planning the observing -- when are objects in the donut-shaped swath of sky the telescope can see? Does your program make the best use of this unique design?

So, I had to learn a lot very quickly about the telescope and its capabilities. I'm not positive that I learned enough, so it is quite possible I won't get time on the telescope. But, hopefully, I will get comments and even just a little data so that next time I am better prepared.

Tuesday, October 03, 2006

Astrophysicists win Nobel Prize in Physics

So, last week when I promised to try and talk about the winners of the Nobel Prizes, I was worried that the physics Nobel Prize would go to some people who worked on subatomic particles, which I don't understand all that well. But, instead, the Nobel Prize in Physics went to John Mather and George Smoot, American scientists who worked on the COBE satellite.

COBE, the Cosmic Background Explorer, was launched in 1989 with the goal of examining the Cosmic Microwave Background, or CMB. The CMB was predicted by a paper by scientists Ralph Alpher and George Gamow as part of what became known as the "Big Bang" theory. The CMB is an "echo" of the Big Bang, light left over from when the Universe cooled from a very hot soup of particles into what we see today. The CMB was discovered by Arno Penzias and Robert Wilson, who were later awarded the Nobel Prize for their work.

Before COBE, the CMB looked almost perfectly smooth. This was a problem! Look at the Universe today, and what do you see? Stars, galaxies, and LOTS of empty space. The Universe is not smooth. To turn the smooth CMB into today's Universe, there had to be tiny, tiny irregularities in the CMB. These irregularities are tiny -- If the CMB were an Olympic-size swimming pool, the ripples that became today's galaxies and stars would be waves about 1/64th of an inch high.

COBE was launched to look for these ripples. If they existed, the Big Bang would be confirmed. If they didn't exist, the Big Bang would be in a lot of trouble. John Mather was responsible for heading up the COBE satellite and experiments, and George Smoot led the scientific team that discovered the ripples in the CMB. These two scientists and their teams of scientists and engineers provided the data required to test the Big Bang theory, and the Big Bang theory passed with flying colors.

Congratulations to Mather, Smoot, and all of the scientists who worked with them!

Monday, October 02, 2006

A question for any frequent travelers

The following is not a complaint, but an honest question for any of you who fly a lot. I'm just trying to figure out human behavior.

This weekend I took a trip to California to visit family, flying out on Friday and coming back on Sunday. Both times, I sat in the aisle seat, which I chose because I like to be able to stand up and stretch without climbing over the poor bloke next to me. Anyway, both times, the person at the window next to me pulled the shade down on the window before takeoff and left it down the entire time. My question is, why?

I can think of two major reasons someone might do this. One, they don't like the window seat and had to take one. Two, something is wrong with the view (like we are over the ocean, or the sun is shining in, or with the clouds it is too bright). But neither of these seemed to fit on my flight. There were aisle seats available, and the sun was not shining in our side of the plane.

So, my question is, what is the point of a window seat if you close the window shade and it is not one of the two points I made above? Am I missing something obvious?

Again, I'm just curious. If I wanted to look out the window badly enough, I could have had a window seat, so I'm not an anyway peeved by this behavior.

As for astronomy, well, I have no burning comments today. Back to science tomorrow!

Friday, September 29, 2006

Here come the Nobel prizes

Once yearly, the Nobel Foundation awards its prizes in physics, chemistry, medicine, literature and peace. (Other "Nobel" prizes, such as the prize in economics, were established in memory of Alfred Nobel, but are not part of Nobel's will.) Starting on Monday, the 2007 prizes will be announced, culminating with the Nobel Peace Prize on the 13th of October.

Who will win? I really don't know -- I can make some guesses for the physics prize, but they would almost certainly be wrong. However, when the prize in physics is announced, I'll see what I can do about explaining the research.

Also, October 5 will feature the awarding of the 2006 Ig Nobel Prizes from Improbable Research. Stay tuned for news from there, too!

Thursday, September 28, 2006

What went boom in the night?

Supernovae are some of the most energetic events in Universe. Most supernovae are thought to come from stars eight or more times more massive than the sun that have used up all of their nuclear fuel. Gravity causes the center of the star to collapse into a neutron star or a black hole, and the energy released by that collapse causes the star to blow itself apart.

There are many things about supernovae that we do not yet understand, and many of unknowns could be solved by looking at supernovae in our own galaxy. However, the last supernova seen in our galaxy was 402 years ago, on Oct. 9, 1604. Not very many living astronomers were around for that event, and the state-of-the-art observing tool (the eyeball) is primitive compared to today's instruments.

So, much of the work on supernova is done on explosions in distant galaxies, not in our own. The exceptions to this are studies of supernova remnants -- the shreds of gas that the explosions leave behind.

There are many such remnants, but for very few of them do we know the date when the star exploded. This is very useful, because knowing the time of the explosion allows us to study how these remnants evolve over time. Some famous supernova remnants are the Crab Nebula (seen by the Chinese in 1054), the supernova of 1572 (Seen by Danish astronomer Tycho Brahe), and the supernova of 1006, one of the brightest recorded supernova, being over 100 times brighter than the planet Venus!

From Chinese and Roman records, astronomers knew of a supernova that occurred in A.D. 185, but we weren't sure what, if any, remnant it left behind. Two supernova remnants are in the right general area of the sky, but astronomers guessed that these were many thousands of years old. Some astronomers even suggested that there was no supernova, but that the event was a bright comet.

Now the mystery appears to be solved. X-ray observations of one of the two suspect remnants, RCW 86, finds that it is not several thousand years old, but only a couple thousand years old, making it an almost perfect match to the observed supernova. How could we have had the age so wrong?

One way we get the age of a supernova remnant is to measure how fast it is growing and compare it with the remnant's size. For example, if it is 10 light-years across and growing at a rate of 0.01 light years per year, we know it is 1000 years old. But some parts of Supernova 185 seem to be plowing into dense clouds of dust and gas that are slowing it down faster than other parts, giving us errors in the derived age. The X-rays in the picture above allow us to see the dust and gas getting heated up by the expanding blast for the first time.

So, mystery solved, probably, and another supernova remnant with an age known to a few months.

Monday, September 25, 2006

Retrograde Motion

Today I had an email from a reader asking about retrograde motion of planets. The question is probably a homework question, so I didn't answer it outright, but sent some hints. But the question touches on one of the toughest concepts in astronomy -- understanding motion.

Everything in the universe is in constant motion relative to most everything else. But it doesn't feel like we are in motion. When you are in a car, plane or boat, you can "feel" the motion. On a motorcycle, you can feel the wind rushing past you. During an earthquake, you feel the ground moving under your feet.

But when you look up at the night sky, there is no feeling of motion. If you stand still for a long time, you might notice that the stars have moved a bit. If you look night after night, you might notice that, over time, the stars are in a slightly different place every night, and that some of the "stars" (actually planets) move with respect to the other "fixed" stars. But you certainly don't feel like you are spinning about Earth's axis at 700 miles per hour, or orbiting around the sun at 19 miles a second, or whizzing through the galaxy at 140 miles per second. You have to watch for an entire month to see the moon go around the Earth once. The sun takes a year to make a full circuit through the skies. This is hard to visualize!

In retrograde motion, a planet such as Mars stops its normal west to east motion through the skies and starts moving east to west for a few months before resuming its normal motion. Something happened, but what?

Mars didn't change directions in its orbit. The amount of energy that would be required to stop Mars, make it orbit backwards, and then switch directions again would be mind-boggling. It just doesn't happen.

On my move to Austin from Tucson, Arizona, I drove for several hundred miles along railroad tracks. At one point, I was passing a train, and I thought it was moving the opposite direction that I was -- it looked like it! But then I passed the front of the train, and saw it was moving east, like me. I was just moving somewhat faster than the train, and against distant mountains, it looked like the train was moving backwards.

The same thing happens with the retrograde motion of the planets. We all go the same direction around the sun, but the closer a planet is to the sun, the faster it moves. We take one year to orbit the sun, Mars takes almost two, Jupiter takes eleven. So, every couple of years, we catch up to Mars and pass it. And as we pass it, it appears to move "backward" with respect to the background stars. Once we are well past Mars, we get to a vantage point where we can see Mars's "real" motion again. The same thing happens with all planets further away from the sun than the Earth.

Confused? Probably. Just remember, we are moving through space, along with all the other planets; we just don't feel the motion. And that lack of perception of motion makes concepts like this all the harder to understand.

Friday, September 22, 2006

Welcome to fall!

Tonight, at 11:03pm Central Daylight Time, fall officially arrives for the northern hemisphere, and spring arrives for the southern hemisphere. At that instant, the apparent position of the sun in the sky crosses the equator, heading south for the winter (along with birds and many retirees).

Those of you who look at sunset/sunrise times may notice that today is not exactly twelve hours from sunrise to sunset, as you would think should happen, since the term "equinox" means equal night and equal day. This would be true if Earth didn't have an atmosphere, but our atmosphere bends light so that the sun appears to rise earlier and set later then it actually does.

By the way, the legend about being able to balance an egg on its pointy end only on the equinox is just a legend. With patience, you can do that trick any day of the year. And, if you don't want to be patient, trying to balance the egg on top of a tiny pile of salt or sugar will help you a lot.

Thursday, September 21, 2006

Freezing the atmosphere

As any observer will tell you, the atmosphere is a very messy thing. Even on nights that seem very calm and crystal clear, wind currents, temperature changes, and other structures in the atmosphere cause any image to blur. Many astronomers consider this blurring (or "seeing") to be acceptable if the size of the blurry spot made by a star is less than one-half to one arcsecond. (One arcsecond is 1/3600th of a degree, or the thickness of a small finishing nail seen from a mile away.)

During the day, the seeing is usually much worse than one arcsecond, as heating from the sun sets up currents in the atmosphere.

This is what makes the above picture so amazing. It was taken by Thierry Legault in Normandy, France, and shows the Space Shuttle Atlantis leaving the International Space Station and silhouetted against the sun. You can clearly see the shape of the space shuttle and the station, even though they were 550 kilometers (345 miles) away! I did a quick calculation, and I estimate that the width of the shuttle's cargo bay is about 2 arcseconds in this image, and yet you can see even sharper details!

Some astrophotographers now use video cameras to create sharp images. Although the atmosphere is constantly roiling, there are occasional, very short periods of very steady seeing, much better than an arcsecond. These astrophotographers look through thousands of frames of video for the handful that are crystal clear, and add these together to get a very sharp image.

Thierry Legault didn't have that option, though, because the space station only took a little over half a second to cross the sun. So, Legault just took some very short exposures (1/8000) of a second. Such a short exposure "freezes" the atmosphere, which changes on the order of every hundredth of a second. That, with a little patience, preparation and luck, and you get a nice clear picture of two objects 550 kilometers away.

Thierry Legault has several more very impressive pictures on this website.

Tuesday, September 19, 2006

UFO sighted near the space shuttle!

But, before you get too excited, the mystery object is NOT an alien spacecraft. (If it WERE an alien spacecraft, it wouldn't be an unidentified flying object, now, would it?)

Chances are good that the object is a piece of the Space Shuttle itself. Why? First, it appeared after the shuttle tested some propulsion rockets. Anything not tightly attached to the shuttle would then fly off on its own. But, unlike what you probably think, the rockets would not have "shaken" the object loose. Rather, when the rockets fire, the object will continue to follow the same orbit it had been on -- it is the shuttle that moves.

The other reason for thinking this is something from the shuttle is that the object is in almost exactly the same orbit as the space shuttle. The likelihood that this happened by chance is extraordinarily low. It would be like closing your eyes, spinning around, and throwing a rock as hard as you could, only to have it follow the same path as an airplane flying overhead. Both the rock and the airplane could be going in any direction; to have it be the same would be very rare. Plus, in the case of the UFO, it also has to match the height and speed of the space shuttle.

I think most likely this is some piece of a tool that the spacewalking astronauts didn't secure right, or maybe a piece of fabric from inside the shuttle's cargo bay that was ripped off during the installation of the space station's new solar panels.

To be on the safe side, NASA has delayed the shuttle's return for a day to make sure this object is not a piece of the shuttle's thermal tiles. I think that's a good idea.

Too bad it isn't an alien spacecraft, though. THAT would be exciting!

Monday, September 18, 2006

Finishing up another paper

Friday and today I have been making edits to a paper I am about ready to submit. It is a paper presenting most of the work from my doctoral dissertation, which will finally be published four years after I earned my degree.

Despite having published several papers, I am always surprised at how long one particular aspect takes -- making figures and graphs. For some of my papers, a picture is worth more than a thousand words, as it can contain information about tens of thousands of stars. For that reason, I am a bit anal about my figures. Friday I spent the entire day on a single figure that STILL isn't done to my satisfaction, though it is close.

Not only do we need to convey information, but we have to worry about some silly details. The journals will only publish color figures at a high cost and with extra editing steps, so I work to make all of my figures grayscale or black and white. Also, the journal takes a full-page figure and shrinks it down to about 1/8 of a page, so I have to make sure my plots are still legible when they are reduced. And, now that most astronomers use Powerpoint to give research talks, I need to make sure that my figures will also look nice when pulled into the lower-resolution Powerpoint presentations.

Hopefully today I can finish that figure...

Saturday, September 16, 2006

Astronomy and the American pastime

Last night I went to the Dell Diamond ballpark to watch the Tucson Sidewinders defeat the Round Rock (Austin) Express to win minor league baseball's Pacific Coast League Championship. The Sidewinders now advance to the minor league version of the World Series, playing the winner of the International League Championship.

Although I now live in Austin, I was rooting for the Sidewinders, as I've gotten to watch them quite a bit in the last few years. Next year, I promise to root for the Express.

I did have a bit of an astronomy experience. At the game, I sat next to two college kids who came to watch the game. One, semi-obnoxious kid was from El Paso and rooting quite loudly for Tucson. The other was a local guy rooting for the Express. I was chatting with the latter gentleman, who mentioned that he had just had a dream the previous night about going to the observatory.

Coincidence? Yes, absolutely. But it gave an opening to chat for a little bit about what I do, in between pitches. I always like those easy openings.

Anyway, congrats to the Sidewinders, and have a good weekend!

Wednesday, September 13, 2006

Do our astronauts have a screw loose?

I must admit, I am a bit surprised how much news is made out of an astronaut losing a screw and bolt. Just imagine you are in the middle of the ocean wearing a few pairs of winter gloves and trying to tighten bolts. I bet most of us would lose more than one. I'd be lucky to retain any.

My October issue of Scientific American arrived today, and the cover story is on supernovae (exploding stars). I'm looking forward to reading that. Scientific American is, in my opinion, one of the best science magazines available, so you may want to give it a look. However, it does run a bit on the dense side, so there's no need to be ashamed if you can't follow it. I often have to give up on the biology articles, as I get lost after the first page or so.

Sorry to be a bit scatterbrained today, but I'm helping some collaborators get started on a telescope run, and I am short on sleep to boot.

Tuesday, September 12, 2006

Is the Big Bang in trouble?

Yesterday, Space.com posted this article, claiming that a new scientific study may call the Big Bang into question. Is this true?

The Big Bang is the most successful theory proposed for the creation and evolution of the Universe. The theory was developed after Edwin Hubble observed that almost every galaxy in the Universe is moving away from every other galaxy, now understood as the expansion of the Universe. The theory has made some remarkable predictions that were shown to be true, such as the cosmic microwave background ("echoes" of the Big Bang visible in radio waves) and the ratio of hydrogen to helium in the Universe, to name a couple. Tweaks to the Big Bang (such as the theory of Inflation) made other predictions that have been shown to be true, such as the shape of the Universe and the small variations in the cosmic microwave background. So the Big Bang theory is amazingly successful, and it would take very compelling data to cause most scientists to question it.

The study looked for shadows of clusters of galaxies on the microwave background -- extremely hot gas in the galaxy clusters should distort the wavelengths of the radio waves from the Big Bang. However, the study on Space.com found much weaker shadows from many galaxy clusters than theory would predict. The study's authors state that the most likely explanation is that we don't understand the galaxy clusters as well as we thought, and this seems a quite reasonable explanation. However, one other explanation is that we don't understand the cosmic microwave background as well as we thought, which would throw the Big Bang into question.

Given the mountain of evidence supporting the Big Bang and the likelihood that we don't understand clusters of galaxies, the study's authors (and yours truly) feel that the Big Bang is quite safe. But we must be honest and admit that there is a tiny, tiny chance that the Big Bang theory may be incomplete or incorrect.

But does such a small chance warrant a large article under the "Cosmic Mysteries" section of a media outlet? Probably not. Such stories create tempests in a teacup that mislead members of the public into thinking the Big Bang is more controversial than it actually is. Of course, the media have ever right to pick up on this story, and I certainly won't write Space.com and argue that such stories should not be printed.

More importantly, this is a warning to you, the member of the public. When you read that one scientific study or another challenges a major theory, be skeptical. More often than not, any controversy is overblown, and most of the rest of the time, the research is of questionable quality. And always feel free to ask a professional for the real skinny!

Friday, September 08, 2006

What is the largest planet?

Lost in the debate over the (dwarf) planet Pluto's status in our solar system is perhaps a more important debate: What is the largest object that can be called a planet around another star?

For objects about 13 times the mass of Jupiter, deuterium (a heavy form of hydrogen) will burn in a nuclear reaction, though once the deuterium is burned up, all nuclear reactions stop. For that reason, most astronomers are comfortable calling objects this big "brown dwarfs," the term for wannabe stars.

What about for smaller objects? Gigantic planets can form in two ways. They can form like the giant planets in our solar system -- a disk of gas and dust around the parent star forms small asteroid-like objects that collide due to gravity to make larger and larger bodies. Once these are several times the mass of the Earth, their gravity is strong enough to scoop up gas, too, and the planets rapidly grow to hundreds of times the mass of the Earth, just like Jupiter and Saturn.

The other method is that, as the parent star forms out of a big cloud of gas, a hunk of that gas splits off and collapses on its own to form something 10 times larger than Jupiter. The only difference between a planet 10 times the mass of Jupiter formed this way and ten times the mass of Jupiter formed the other way is that the latter will have a rocky core several times the mass of the Earth, while the former will be all gas. From the outside, though, it is nearly impossible to tell the difference.

Today NASA announced the discovery of a brown dwarf about 12 times the mass of Jupiter around a nearby star. One of the co-discoverers, Kevin Luhman, a professor at Penn State, claims that this object must be a brown dwarf and not a planet because it is far enough away from the parent star that there could not have been a disk of dust and gas to form the object.

The problem is that, for many objects from about 10 times the size of Jupiter to 13 times the size of Jupiter, it is unclear which process formed the planet/brown dwarf. So, what are these objects to be called? Are they a fallen star or a risen planet? Like the case with Pluto, I don't know that there is a single answer that everyone will find satisfactory. My guess is that, eventually, we astronomers will tire of the controversy and call these something like "transition objects" or some other suitably vague term. Then we can stop arguing about what to call them and start arguing about true scientific topics -- how these things form, how they change with time, how common they are. And these topics may provide us with hints as to whether one formation scenario is favored, or if both seem to come in to play. And from that, we learn more about how stars and planets form.

Thursday, September 07, 2006

Settling in

Moving to a new place is not much fun, but I think I am just about settled in. A couple of pieces of new furniture arrive today, and my home newspaper and internet should start next week. That will make for a good start.

Meanwhile, astronomy keeps marching on in spite of my absence. I am trying to catch up on reading scientific articles that have appeared in the last few weeks, collaborators are bugging me for information, and later this month it will be time for telescope proposals to be submitted. Plus, it is about time to start applying for jobs again (even though I am not yet settled!).

As part of my new position, I will be making some changes/improvements to this blog in the coming month or two, and I'll be asking for input along the way. So, there is much to do in little time. I guess I'd better get busy!

Tuesday, September 05, 2006

Landing in a new city

My move from Arizona to the great state of Texas is going fairly smoothly. I arrived late last week, as did the moving truck with all of my junk. So, today I decided to tackle the bureaucracy at the University of Texas. Getting my office was easy, as was an email account and an employee ID card. Parking will be harder. And harder yet is catching up on email. Collaborators have questions about upcoming telescope runs, I have a few papers I need to submit comments on, and I need to restart my research and write more papers. So my work is cut out for me!

See, life as an astronomer isn't all fame and fortune. Actually, it's very little of either, and moving certainly detracts from the fun of the job. But we'll see where things go in the next few weeks!

Wednesday, August 30, 2006

Where is the professor?

And why isn't he blogging? The professor is currently in the midst of a move from Tucson Arizona to Austin Texas. Bloggin will resume when life approaches some semblance of normalcy, probably soon after Labor Day

Thursday, August 24, 2006

It's Official -- EIGHT planets

Poor Pluto has suffered a couple of weeks of highs and lows, but this morning astronomers at the 2006 General Assembly of the International Astronomical Union defrocked Pluto, removing it from our list of planets in the Solar System.

Some astronomers are happy, some are mad, and some are ambivalent. But I promise that if you call Pluto a "planet," I will not call the IAU Police and have you arrested.

The passed definitions of planets are (copied shamelessly from the IAU):

  1. A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.
  2. A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape , (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite.
  3. All other objects except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".
  • The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
  • An IAU process will be established to assign borderline objects into either dwarf planet and other categories.
  • "Small Solar-System Bodies" currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

Note one glaring omission -- this definition of the word "planet" means that planets orbit the sun. So what are the objects the size of Jupiter and Saturn circling other stars? I think those are planets, but why they are excluded from this definition, I don't know.

Tuesday, August 22, 2006

A friend confirms the reality of "dark matter"

While astronomers continue an emotional debate over the definition of a planet, real science goes on. One of my friends, Doug Clowe, has headed an investigation into the dark matter content of a cluster of galaxies. What Doug and his collaborators found was that, in one cluster, the dark matter doesn't line up with the visible matter. This is solid evidence that dark matter is some strange, exotic thing and not just ordinary matter or a misunderstanding of our theory of gravity.

In the picture above, there are really three bits of information. The white and yellow are pictures of galaxies taken with an ordinary telescope. The pink "glow" is extremely hot gas, so hot it glows only in X-rays. And the blue is a map of the gravitational force, made by careful analysis of how that gravity bends and distorts light from more distant galaxies.

The amount of gas glowing in the X-rays is quite ordinary matter -- hydrogen, helium, iron, carbon, etc., -- heated to 10 million degrees. In fact, the amount of matter in the pink glow is much more than the amount of matter in the visible galaxies. So the pink glow really traces out the "ordinary" matter in the picture. The pull of gravity, which comes from a combination of dark matter and "ordinary" matter, will be strongest where there is the most matter. So, since the blue and pink do not line up, the matter that causes the gravity is NOT the "ordinary" matter that causes the X-rays. So it must be dark matter! This marks a new, independent confirmation of dark matter.

What is this dark matter? Astronomers and physicists have some ideas, but we have never directly detected dark matter in a laboratory. Such a detection would prove beyond any doubt that dark matter exists (and would win the team a Nobel prize). But, for now, astronomers can rest comfortably that dark matter actually exists.

Friday, August 18, 2006

More news from the General Assembly of the International Astronomical Society

So the big news from the 26th General Assembly of the International Astronomical Union is the pending definition of the term "planet," which, if passed, means the Solar System will have 12 or more planets. But, believe it or not, when 2500 astronomers get together, there is much more to talk about than how many planets can dance on the head of a pin.

In fact, there is so much going on that it is impossible for one person to see it all. Part of the General Assembly is that a dozen or more simultaneous, smaller meetings take place during the meeting.

In order to keep attendees updated on everything that is going on, a small daily newspaper, the Dissertatio com Nuncio Sidereo III, or "Conversations with the Sidereal (stellar) Messenger." The name is Latin and taken from the title of a book written by one of the first great astronomers, Johannes Kepler, in 1610. Putting together the Nuncius every day is hard work, especially since the editors are clearly non-native English speakers. So kudos to the editors! If you would like to read the Nuncius, keep in mind that it was written by astronomers for astronomers. But you are more than welcome to read PDF versions of it at this web site.

Wednesday, August 16, 2006

So, I was wrong. But 12 planets instead of 9?

This news release from the General Assembly of the International Astronomical Union surprised me in some ways. It is the official proposal on the definition of a "planet." Instead of demoting Pluto to a "minor planet," it actually saves Pluto and re-promotes the asteroid Ceres to planet status (see my last post for that story).

The proposed definition actually makes some sense, scientifically. It is a definition based on measurable properties -- the shape of an object and its "dynamical state," (e.g., does it orbit another, much larger planet?).

In other ways, this definition is lacking. It says that planets are "not stars," which just means that the group did not want to develop a definition for separating stars, brown dwarfs, and planets. It also ignores the fact that, while Ceres and Pluto may be round, there are many, many non-round objects that are extremely similar (asteroids and the icy Kuiper belt objects). However, this definition may be the best possible one.

The new definition is not yet "accepted." That requires a vote of the full assembly of the IAU, which will not happen for a couple of weeks yet.

Monday, August 14, 2006

A planet by any other name...

On Wednesday, the 2006 meeting of the International Astronomical Union begins in Prague. I will NOT be there, as I have to leave for the telescopes in Chile tomorrow, and a week after that I am moving from Arizona to Texas. But several thousand astronomers will be in Prague over the next two weeks to talk about research and discuss important scientific and procedural issues.

One of the biggest topics that will come up is the definition of a planet. The issue of whether Pluto will continue to be called a planet has captured the public's attention, but this will also deal with what to call objects the size of Jupiter floating through space, and what to call objects ten times the size of Jupiter orbiting other stars.

The gossip I've heard (which may be wrong) is that there is no good definition of a planet. Many of us would claim to know a planet if we saw it, but crafting a working definition is hard! Perhaps the best definition would include how planets are formed, but we can't be certain how any specific object formed.

As for Pluto, it has historically been called a planet, but now we know of dozens of objects that are very similar to Pluto in almost every way -- size, shape, where they are in the Solar System, what they are made of, having moons, and so on, and so on. So, if you want to keep calling Pluto a planet, we will end up with a couple of dozen planets in our Solar System. Or, we could set a size limit, and then we would have 8 planets in the solar system (but what about planet moons that are larger than Mercury?). And what is the rational for a size criterion?

In 1801, astronomer Giuseppe Piazzi discovered a moving object in the sky. It's orbit was between Mars and Jupiter, and it was thought this could be a new planet. The object was named Ceres, and for almost a year was known as the 8th planet (Neptune and Pluto were still unknown). Then, another, almost identical object was found between Mars and Jupiter. Within a few years, several of these were known. They were much smaller than the other planets, and so soon became known as "asteroids," and Ceres was demoted from planetary status.

Pluto has been a planet for over 70 years, but my hunch is that soon it, too, will have to be demoted to the king (or maybe just prince) of the "Kuiper Belt Objects." (Kuiper is pronounced KOI-pur).

My other hunch is that, no matter what the definition of a planet is, many people will be unhappy.

Sunday, August 13, 2006

A once-in-3000-year view of the "Eye of God?"

A cousin of mine forwarded me an email with the above picture and the following text:

Dear All:
This photo is a very rare one, taken by NASA. This kind of event occurs once in 3000 years. This photo has done miracles in many lives. Make a wish .. you have looked at the eye of God. Surely you will see the changes in your life within a day. Whether you believe it or not, don't keep this mail with you. Pass this at least to 7 persons. This is a picture NASA took with the Hubbell telescope. Called "The Eye of God."

First, this is not a once-in-3000-year occurrence. This is a picture of the Helix Nebula, which was discovered sometime before 1825 and has been visible ever since. The nebula is what is known as a "planetary nebula," and is formed when a star like the sun runs out of nuclear fuel and sheds its outer layers. The hot furnace of the dying star lights up the shed gas, producing a planetary nebula. Other famous planetary nebula include the Ring Nebula, the dumbbell Nebula, and the Cat's Eye Nebula.

And, as far as I can tell, no astronomer has ever referred to this as the "Eye of God." Everyone I know calls this the "Helix Nebula," it's proper name. In fact, if you do a search for images of the "Eye of God," several different planetary nebulae show up.

This is just further evidence that you need to be careful when someone asks you to forward an email to everybody you know -- I'm glad my cousin asked before forwarding it to her whole email list. Likewise, if you ever have a question about an email you've received talking about something astronomical, feel free to ask!

Friday, August 11, 2006

Science and chaos

Our conference in Leicester, England, is continuing. Most of the talks are on more specialized projects, and it can be hard to stay awake. But there are nuggets of science important for my work hidden among the rest.

The biggest topic is the terror alert due to the foiling of a plot to bomb airplanes bound for the US. As someone who will be on a flight from the UK to the US on Saturday, I am quite happy they caught the plotters. But it does mean that travel will be even less fun, as we cannot bring anything on board beyond essential medicines -- not books, soduku puzzles, iPods, etc. So, I will be forced to watch the airplane movie (probably Ishtar 2, with by luck).

The above picture, taken from the Sydney Herald web site, is Heathrow Airport yesterday. We'll see what it is like at Gatwick tomorrow.