Friday, December 23, 2005

Signing off for the year

With the holidays here, I am off travelling until the start of the New Year. So until then, best wishes to everyone.

Early next year many exciting astronomy events are going to happen -- the launch of a probe to Pluto, the return of pieces of a comet to Earth, and a large meeting of the American Astronomical Society. So stay tuned for exciting news in 2006!

Tuesday, December 20, 2005

New Horizons launch on the horizon

Of the nine planets in the Solar System (Okay, maybe there are ten. But since no official decision has been made by the Powers That Be, I'll stick to nine), only one has not been visited by a robotic probe, and that is Pluto. That will soon change, however.

Earlier this week, the New Horizons spacecraft was moved to a launch pad in Florida, preparing for a launch in late January. Despite the large rocket being used to launch this relatively lightweight (1000 pound) probe and despite a gravitational boost from Jupiter, the probe will still take 10 years to reach Pluto! And this probe will be racing along, taking only eight hours to pass the moon on its way out -- the Apollo moon missions took three days to cover that distance!

The New Horizons probe will also study at least one other of the strange Kuiper Belt objects, trying to figure out exactly where these big balls of ice formed in the early Solar System.

So, stay tuned for news of the launch, and then settle back and wait ten years to see a close-up view of Pluto!

Thursday, December 15, 2005

Practice makes perfect!

Last night I spent several hours at Kitt Peak learning how to use a new camera built by Ed Olszewski, an astronomer at Steward Observatory. This camera is on Steward's 90-inch Bok Telescope. This camera is huge by astronomy standards -- over a one-degree field-of-view. In other words, four full moons could fit in a single picture!

I will be using this camera for the first time on New Year's Day as part of an ambitious new survey my collaborators and I are doing. So, we figured we had better go up to learn how to use the camera. Each astronomy camera is different, with its own strengths and weaknesses. And since telescope time is precious, we donn't want to waste our own time trying to learn how to use the camera and then using it wrongly.

Last night, astronomer Richard Cool was kind enough to take time out of his work on the camera to teach my colleagues and I how to use it. We learned a lot, and I think we'll be able to make good use of the telescope now! We probably will struggle some our first night trying to remember everything, but as time goes on we will get better and more efficient.

Just like playing a musical instrument requires a patient teacher, time to practice, and just as you can expect mistakes when you first start playing, using an astronomical instrument requires a patient teacher and lots of hands-on use, with a few missteps along the way.

Wednesday, December 14, 2005

The Christmas Star

This time of year, a popular question astronomers get asked is, "What was the Star of Bethlehem?" This blog normally steers clear of religious issues altogether. After all, (1) I am an astronomer, not a theologian, (2) I would hope that this blog can reach to any person, regardless of their beliefs, and (3) my beliefs are just that -- mine -- and not necessarily yours. But, since the question comes up and since the Star of Bethlehem is central to many people's celebrations this time of year, I thought I would at least touch on the issue.

The fact is that astronomers have no good explanation for the Star of Bethlehem as described in the Gospel of Matthew. Different ideas have been put forth: a conjunction of the planets Mars, Jupiter and/or Saturn in 7/6 B.C., a comet, a supernova, and even more exotic astronomical phenomena. A search for "Star of Bethlehem explanation" on Google or your favorite search engine will being up a plethora of pages with highly-variable quality of scholarly explanations for each of these. In spite of this, none of the proposed explanations fit all of the passages from the Bible. Perhaps in the years between the Nativity and the writing of the Gospels the event became a little garbled or exaggerated, or perhaps the narrative was invented, or perhaps there is no physical explanation for what appeared in the sky.

So, I have no definitive answer to what the "Star of Bethlehem" might have been, and anybody who claims to know a definitive physical explanation is probably overstating their case. If you are interested in this, I would suggest that you read some of the materials on the web or elsewhere and form your own opinion. Like many religious matters, the Star of Bethlehem must remain an issue of faith, not of science.

Tuesday, December 13, 2005

Back in the swing of things

It took a week, but I think I am finally over my "telescope lag" (or "astral temporal disruption fatigue," as a friend suggested) and back on a pretty normal day schedule. These long nights are very difficult to work through. But I did get some fabulous images at the telescope, leaving me with lots of work to do for the coming months!

Now I must get ready for our January national astronomy conference, the winter meeting of the American Astronomical Society. Over a thousand astronomers from across North America (and some from the rest of the world) will be converging on Washington, D.C. for a grand meeting. I will be giving a short talk myself on my research. I only have five minutes to talk, so I have to boil down months of work into just a few paragraphs. I also hope to have a job interview or two there!

Wednesday, December 07, 2005

Last night!

It has been a long few weeks, but tonight is my last night of observing for the year of 2005. (I start up again on January 1!) I always have mixed feelings at the end of an observing run. I am always quite happy to go back home and get back to a typical routine. But there is always more data I wish I had been able to collect. I guess that gives me something to do for next year.

Most of my night at the telescope is spent waiting for exposures to finish. We open the shutter on the camera for ten minutes to half an hour, and then sit back and wait for it to finish. What I do while waiting depends quite a bit on the camera I am using. For taking pictures, like tonight, I just do a quick check to make sure the image quality is okay (and figure out what is wrong if the quality isn't high); otherwise I wait to work on the images when I get back to Tucson.

If I am taking spectra (splitting the light up into its component colors), I need to work on the data to figure out if the object we are looking at is "interesting." Of course, the definition of "interesting" depends on what we want to do. For instance, when I am looking for white dwarfs (the remains of dead stars), we find a lot of quasars (bright black holes halfway across the universe). Although quasars are quite cool objects, we aren't looking for them, so we move on to another object. If the star is a white dwarf, though, we need to stay and take more observations. Clear as mud? Probably.

Monday, December 05, 2005

A pretty picture

Last night was a gorgeous night on Kitt Peak. In the corner of one of the pictures we took at the end of the night, we spotted this galaxy, much bigger and brighter than the "faint fuzzies" we were looking at. This galaxy is NGC 3079, a spiral galaxy in the constellation Ursa Major (the "Big Dipper"). It is located about 50 million light-years away; the galaxies I am looking at for my work are about 3 billion light-years away.

NGC 3079 has also been looked at by the Hubble Space Telescope, as seen in this picture. Why is the Hubble picture much more colorful than mine? Two major reasons -- Hubble has graphics artists to help them bring out the colors, while yours truly has limited artistic ability, and the Hubble Telescope took pictures in more colors than I did (I stuck to red, green and blue).

This galaxy is also known as a "starburst" galaxy. Lots of stars are being formed very quickly, mostly hidden from view by thick clouds of dust. This galaxy also has a large black hole at its center that is gobbling down lots of the gas and dust in the galaxy.

It's been a hard day's night

I should be sleeping like a log! From sunset to sunrise tonight is thirteen and a half hours. For the astronomer, that is a long workday, especially to do five nights in a row. Ugh!

But, here on top of Kitt Peak, we have been working hard all night and getting some good data. It has been a crystal clear night with very steady skies.

I haven't had the time to put together a pretty picture yet, but I should have one tomorrow.

Saturday, December 03, 2005

From one telescope to another

Well, I "survived" a rather pleasant trip to use the Keck I Telescope on the Big Island of Hawaii. have since returned to Arizona and driven up to Kitt Peak, a telescope about 60 miles west of Tucson. I'm already worn out, and I still have four nights to go!

At the Keck Observatory, I was looking for white dwarfs, the remains of stars that have run out of nuclear fuel. These dwarfs are a lot like the glowing embers in a dying fire -- they are hot from the heat of the nuclear engine of the parent star, but they make no new energy. So, like the embers of a fire, white dwarfs slowly cool off, getting fainter and fainter. My fellow scientists and I are using this property to figure out how old the white dwarfs are. By finding the faintest white dwarfs in a group of stars, we have a pretty good idea how old those stars are!

Anyway, we found lots of white dwarfs during our stay, including some that are very mysterious -- they look different than most of the white dwarfs we found. Now I just have to figure out what that means!

Here at Kitt Peak, I'm looking at something completely different -- I'm looking at groups of galaxies far, far away. Where the white dwarfs above are all "only" 3000 light-years from Earth, these galaxies are a few billion light-years a way! With a little clear weather, I'll try to get a picture up within the next day or two.

Monday, November 21, 2005

On vacation

The Professor will not be blogging this week, as he takes a vacation and will attempt to overdose on tryptophan on Thursday. However, he should be back this weekend with a report on some difficult observing from the Big Island of Hawaii.

Wednesday, November 16, 2005

Jobs in astronomy

You haven't seen much from me recently, as it is time for me to hunt for jobs. Many parts of applying for astronomy jobs are the same as applying for jobs in the "real" world. We put together our resumes, write cover letters, and scour specific magazines and web sites for job advertisements. Most people apply to a whole slew of openings, hoping to get a couple of nibbles.

But there are major differences, too. First, most job openings are announced in the fall for work starting the following summer or fall. This is driven by the academic calendar, as most jobs are affiliated with universities. This also means the hiring process is quite slow, as job hires have to go through several layers of bureaucracy.

Applications are read by a committee in the department. This committee pares down the list to a select few for interviews. Then the list has to be approved by a higher official, such as the college dean. After the dean gives the list approval, people on the list are invited for interviews and to give talks on their research to the entire department. After the interviews, the committee will rank the applicants, and the entire faculty of the department select their nominee. Once again the dean has to approve, and then the compensation package must be drawn up, usually by some other part of university bureaucracy. What fun! And it takes months to finish!

So, for now, I'm busy writing all those cover letters. We'll see how things turn out.

Monday, November 07, 2005

UFOs from Taurus!

News reports from Germany and Alaska have mentioned an abundance of "UFOs" seen in the sky in the past few weeks. Is Earth being invaded? Is it time to break out your Klingon-English dictionary in the hopes that you can save yourself with some friendly banter?

Whoa, slow down. Let's approach this thing scientifically, which means that, before invoking the Borg Cube to explain these events, we need to rule out more likely explanations. What are things that people commonly mistake for UFOs?

  • Planets: Planets, especially Venus and Mars, are often mistaken for UFOs. Right now Venus is dazzlingly bright in the west after sunset, and Mars is bright and orange in the east during the evening. When low in the sky, planets can look like they are "hovering" over the ground, and they can appear to be flashing colors due to the atmosphere. I once had a TV crew try to convince me that they had a UFO slowly landing in the Pacific on video tape. I recognized where their tape had been made, and their tape had a time stamp. A little playing around with a planetarium program showed that they had just seen Venus setting in the ocean. But, the German and Alaskan witnesses said the lights were moving in the sky, whereas the planets move much more slowly. So they didn't see planets.
  • Airplanes: Airplanes move across the sky, and when they have their landing lights on, they appear very bright. A surprising number of people don't recognize airplanes in the sky. But airplanes take several minutes to cross the sky, and the lights in Germany move across the sky in seconds.
  • Satellites: Low-earth orbiting satellites move across the sky in only a couple of minutes, and some can be very bright (the Space Station and Space Shuttle can be brighter than the brightest star in the sky). Satellites can also appear to do sudden changes in direction. This is an optical illusion, but I've seen this illusion with my own eyes many times. Satellites can also appear to flash if they are tumbling out of control or if the sun mirrors off of odd-shaped corners. However, the bright things in Germany and Alaska crossed the sky in seconds, not minutes.
  • Meteors: Meteors ("shooting stars") can be very bright (these are called "fireballs"), and they can cross the entire sky in seconds. They can also leave behind glowing trails, called "trains", which can last up to a minute or more! The descriptions of the eyewitnesses to these "UFOs" match meteors exactly. So, I think it is safe to say that space dust, and not aliens, are the cause of the ruckus.

So, why so many sightings all at once? This time of year the Earth moves through the orbit of Comet Encke. Comet Encke orbits the sun every three years, but rarely comes close to Earth. However, every time the comet comes close to the sun, little bits of dust and rock come off of it. These bits of dust and rock continue to orbit the sun, but slowly get spread over the comet's entire orbit. Every November, when the Earth passes through the comet's orbit, we sweep up some of the dust and rocks, making for a meteor shower. The meteors from Encke appear to come from the constellation Taurus, and so the meteor shower is called the "Taurids."

Normally the Taurids are a pretty weak stream, with fewer than 10 meteors per hour visible from any one spot. This year the Earth seems to be passing through a denser part of the comet's debris, so we are seeing more meteors than normal. The Taurids have a history of sometimes producing many fireballs, and this seems to be one of those years!

Thursday, November 03, 2005

A smaller black hole?

I saw on the news today that the Milky Way's black hole is smaller than previously thought. This made me perk up, because the word "smaller" can mean physical size (like a foot is smaller than a mile), or it can mean mass (like a pound of brick is smaller than a ton of brick).

My first reaction was that the word "smaller" meant "less massive," especially since the physical size of a black hole is kind of a fuzzy comment. This is why I perked up. Astronomers have been able to make some very accurate measurements of the mass of our galaxy's black hole: about 2 million times the mass of the sun. These measurements are based on the movement of stars around the black hole, and physics from Isaac Newton in the 17th century is sufficient to figure out the mass of the black hole. So if its mass were smaller, this would be quite surprising.

But it is not the mass that is smaller, it is the physical size. Astronomers using radio telescopes on Earth were able to make the sharpest picture of the gas around the black hole yet made. They were able to resolve details only 93 million miles across, or the size of Earth's orbit around the sun. Not bad for taking this picture from 24,000 light-years away!

We are still fairly far outside the edge of the black hole, though. The black hole's event horizon is still at least 12 times smaller than this picture. So we still haven't "seen" the black hole, but we are pretty close!

Wednesday, November 02, 2005

Pluto and its Moons

Pluto, the most distant planet in the solar system, was discovered in 1930 by Clyde Tombaugh. It was not until 1978 that astronomer James Christy discovered Pluto's moon Charon while observing at the U.S. Naval Observatory in Flagstaff, Arizona. Charon orbits Pluto every 6.4 days. Astronomers like to study Charon, because its orbit around Pluto helps us to learn more about Pluto, like its mass, actual size, and composition.

As part of these studies, Pluto and Charon were imaged by the Hubble Space telescope in May 2005. A team led by Alan Stern of the Southwest Research Institute and Hal Weaver of Johns Hopkins University saw two "stars" that moved with Pluto and also appeared to be orbiting it. There is only one explanation for this -- these "stars" are really two new moons of Pluto!

Moons are very common in the solar system. The only planets without moons are Venus and Mercury. Even many asteroids and other icy objects in the Kuiper Belt have moons.

So congratulations to Pluto on its new moons. The International Astronomical Union will be considering names for the moons (the discovery team gets first crack at appropriate names) in the near future.

Monday, October 31, 2005

Happy Halloween!

It is a spooky day here at Steward Observatory. So far I have seen a devil prowling the hallways, and the business office has been taken over by the Cirque So Lame (pictures if/when they become available). Even my daughter's guinea pigs Dexter and Cloud have joined in the fun.

Did you know that Halloween, also known as All Hallow's Eve, is an astronomical holiday? Tomorrow, All Saints Day, is a cross-quarter day, or the day halfway between the fall equinox (first day of fall) and the winter solstice (first day of winter). Two of the other three cross-quarter days are still holidays in western culture: Groundhog Day and May Day. The other one (August 1), was known as "Lammas," but Lammas is rarely known outside of religious circles.

Thursday, October 27, 2005

Here's Mars!

Have you noticed a bright orange "star" in the east after dark? It's hard to miss, so go look for it. This "star" is by far the brightest thing in the east. But this is no star, it is the planet Mars. On Saturday, Mars will make it's closest approach to Earth in over two years, and it will be another 13 years until Mars is this close to Earth, "only" 43 million miles away. Here's a Halloween experiment to help you imagine this scale. Start with the pumpkin on your doorstep. That represents the sun. On this scale, the Earth is a pea located about 150 feet away. Mars would be a half pea located another 70 feet away from the Earth.

So why will it be another 15 years until Mars is this close to Earth, if it were this close just two years ago? This online simulator shows the position of the Earth and Mars as both planets orbit the sun. It takes the Earth one year to orbit the sun, and it takes Mars almost 2 years to finish an orbit. So, the Earth passes Mars about every two years.

But Mars's orbit around the sun isn't a perfect circle. At its closest approach to the sun, Mars is 130 million miles (206 million km) away from the sun, and at its furthest, Mars is 156 million miles (249 million km) away. So, sometimes when the Earth passes Mars, Mars is close to the sun, and therefore closer to the Earth. At other times, Mars is further from the sun (and further from the Earth).

Two years ago, the Earth passed Mars just as Mars was at its nearest point to the sun, and Mars was closer to the Earth (only 35 million miles away) than it had been in 50,000 years! This year, Mars is a little further away from the sun, and so further from us. Again, watch the little simulation I linked to above.

So, how would the Earth look from Mars right now? Would it be a bright blue dot in the sky? Would you be able to see continents with a telescope? No. Although the Earth is close to Mars, we almost directly between Mars and the sun. The Earth would be too close to the sun to see safely! And, even if you could look safely at the Earth, you'd be looking at the Earth's night side, and it would be dark!

Would you like a chance to see Mars through a telescope? Over the next few weeks, your local astronomy club will certainly be having some sort of "Mars party." They always welcome newcomers to look through their telescopes at the Red Planet! You can find the astronomy club nearest to you from this Sky & Telescope directory. Don't wait! In a few more weeks, the best views will be gone for 15 years (though we'll get another, less favorable view in two years).

Want to see pictures taken through telescopes in the last few days? Look here!

Wednesday, October 26, 2005

First Light!

The Large Binocular Telescope, a pair of 8.4-meter (27-foot) diameter telescopes being built here in Arizona, has seen first light! The above picture is the first official picture taken by the telescope, and it shows the edge-on galaxy NGC 891, a spiral galaxy viewed from the side. The galaxy is in the constellation Andromeda and about 24 million light-years away. When the light in this picture started its journey, the first elephants had just evolved, and the first early monkeys were evolving.

First Light marks an important step for any new telescope. It marks the first time that all of the telescope systems work together, including pointing, tracking (following objects in the sky), a polished and coated mirror, and a camera. While there often is still a lot of work to be done, first light means that the telescope construction is almost done, and that science can soon begin!

More versions of the above picture, as well as more detailed explanations of the photo and how it was taken, can be found here.

Tuesday, October 25, 2005

Dreaming of telescope time

It must be getting close to apply for more telescope time. Last night I dreamed that I had been appointed to the committee that assigns telescope time. It wasn't that exciting of a dream, to be honest.

Most people outside of astronomy have little idea how telescope time is assigned and used. Contrary to popular fiction, astronomers generally do not live on mountain tops, sleeping all day and working all night by staring through the eyepiece of a telescope. Except for the few astronomers hired to run telescopes, most of us work fairly normal hours at universities. We teach classes and do our research on computers, only rarely travelling to the mountains to use telescopes.

So, how do we get telescope time? The first part involves writing a proposal. We have to answer several questions. What science do we want to do? What star or galaxy do we want to look at? Why do we want to use this particular telescope? What cameras will we be using? How much time do we need to finish the science? What are the acceptable dates and times to use the telescope? And can we back all of this up with calculations?

Once each astronomer has written her/his proposal(s), the proposals are collected and sent to a "Time Allocation Committee," or TAC. The TAC must then read through the proposals and rank them. The rankings include a mix of how important the science is and how likely the project is to succeed. There are always proposals with great scientific ideas, but the proposed observations seem quite unlikely to succeed. Sometimes a project will definitely work, but the science isn't that exciting.

The TAC's job is a thankless task, because usually there are two to ten times more time requested than actually exists. So many good projects that are likely to succeed won't get time just because there isn't enough to go around. And how do you decide who gets time and who doesn't? It's pretty arbitrary a lot of the time.

Once the TAC is done, there is one last step -- the actual scheduling. The people who schedule the telescope use the TAC's rankings to guide their work. Often they can't schedule all of the highest-ranked proposals, though. Suppose there are two highly-ranked projects that will only succeed on May 23. Then the scheduler has to make a tough choice!

Anyway, that's how we get our time. It's a hard process, and even the best astronomers won't get all the time they want. But it pushes us to think hard about our projects and what we need to succeed.

Monday, October 24, 2005

Telescopes on the Moon? Part 2

The idea for a telescope on the moon is not new. There are advantages to a telescope on the moon. First, there is gravity, which makes the telescope design much cheaper than for space. Second, the moon is a stable platform. The gyroscopes that have caused headaches for the Hubble Telescope would not be needed -- a lunar telescope can point at a given point in space for years without needing any power or pointing at all. Finally, the lunar telescope will give our astronauts exploring the moon as part of NASA's Moon-Mars project something to do on the moon.

A lunar telescope would likely not have a glass mirror, like most telescopes on Earth, but a liquid mirror, like the Large Zenith Telescope in British Columbia, Canada. This mirror works by spinning liquid mercury in a large dish to make a thin layer in an exact parabolic shape. Many of the problems of such telescopes on Earth, such as the wind distorting the mirror, will not be a problem on the moon.

There are a few potential deal-breakers on a lunar telescope. First, the moon is a dusty place. There is some evidence that the moon may actually have an atmosphere made of dust. Obviously, you don't want dust landing in your liquid mirror, because you'll have to clean it! Second, a liquid-mirror telescope can only look in one direction -- up. If we build a telescope near the moon's north pole, we can always look at almost the same patch of sky. There are advantages to this, but if there is something we want to look at elsewhere in the sky, too bad!

With NASA's decision to go back to the moon and to Mars, the idea of a lunar telescope is being revived. Stay tuned!

Tuesday, October 18, 2005

A telescope on the moon?

This week Steward Observatory is having our annual "Internal Symposium." This is a two-day informal meeting where many of the astronomers, students, and other people associated with Steward come and give talks so we all know what each other is working on. It's a lot of fun, and we get a lot of talks on quite unrelated science.

Yesterday's highlights included a faculty member who is working on a design for a telescope on the moon, a talk about the International Dark Sky Association, discussions of the progress on building the Large Binocular Telescope, and even research into variations of Einstein's Relativity.

Later I'll talk more about the lunar observatory -- it's way cool.

Monday, October 10, 2005

Milky Way Bar

In the last few weeks, I got a question emailed from a reader of this blog (wow, I actually have a reader!). The question dealt with a new science report that the Milky Way has a larger bar than previously thought, and the reader wanted to know my opinion on the issue. Well, it's really quite simple. In order to raise flagging sales, the Mars Corporation has increased the size of a Milky Way chocolate bar from 1.2 ounces to 1.44 ounces net weight. (Just kidding!)

Spiral galaxies come in two basic flavors: "barred" and "non-barred." See if you can guess from these two images which is which:

It is hard to know the exact shape of the Milky Way, the galaxy our sun lives in, because we are in it. It is much like being in the middle of a dense forest and trying to figure out what its boundaries look like. In our galaxy, thick dust clouds block our view of the far parts of the galaxy. However, astronomers were able to use some clever techniques of measuring how fast stars are moving through space to deduce that our galaxy had at least a weak bar; perhaps something like this galaxy:

However, infrared light can go through much of this dust. The technology for studying large numbers of stars in the infrared has impoved dramatically over the last decade. Using this infrared light, astronomers were able to determine that our bar is in fact quite significant, perhaps something like this:

In this picture, our sun would be located about halfway between the center of the galaxy and the bright star near the lower right.

Friday, October 07, 2005

The Ig Nobel Prizes

Alas, blogging must be short today as I am in danger of missing deadlines.

As you know, every year the Nobel Prizes are awarded to scientists and scholars who have made extraordinary contributions to their fields. For 15 years, the Annals of Improbable Research has also awarded a prize, the Ig Nobel award, to scientists for research that cannot or should not be repeated. Sometimes this research is funny, sometimes it is just plain bizarre.

This year's winners and their achievements will soon be posted here. If you get a chance to watch the video of the prize ceremony, be sure to be on the lookout for real Nobel prize winners who often debase themselves by appearing at

Thursday, October 06, 2005

A visit to the Naval Observatory

Last week I had the pleasure of visiting the U.S. Naval Observatory in Flagstaff, Arizona. (Here is the Flagstaff Station website.)

The Naval Observatory was created for the purpose of doing astronomy and astronomical measurements that are vital for the Navy. This includes the positions of stars (for navigation), the exact time, and positions of the sun, moon and planets. Their mission statement outlines this, though I find the second part of point four to be darkly humorous. It reminds us that, although the USNO hires astronomers, it is still a branch of the military.

Most of the people at the Flagstaff station work on the positions, distances, and motions of stars. Yes, stars move, albeit usually much too slowly for people to detect. The "fastest" moving stars still take a thousand years to move a distance the size of the full moon through the sky. Still, these motions are important for understanding the structure of the Milky Way galaxy.

My thanks to the staff at the USNO for being such gracious hosts!

Friday, September 23, 2005

It's the time of the season...

Ah, fall is in the air, as yesterday afternoon the sun crossed the celestial equator to head south for the winter. Now it is officially autumn. Here in Tucson it feels like fall, as the temperature is only 99 degrees today.

By far the number one mistake the general population makes about astronomy is the cause of the seasons. A lot of people believe that the cause of the seasons is that the Earth is farther from the sun in the winter than in the summer, but that is wrong. In fact, the Earth is a million miles closer to the sun in the winter than in the summer. So what causes the Earth's seasons? It is the Earth's tilt.

Let's say it is a sunny but cold winter day, and you are outside and want to warm your face up a bit. What do you naturally do? You close your eyes and tilt your face so you are looking directly at the sun. When your face is pointed toward the sun, you are warmest. Likewise, the Earth is warmest when it is pointed toward the sun. The Earth is coldest when it is pointed away from the sun.

During winter here north of the equator, the North Pole is pointed as far away from the sun as it ever gets. At the same time, the South Pole is pointed toward the sun, so those lucky Aussies and Kiwis get summer. But by June, the North Pole is pointed as much toward the sun as it gets, and we northerners get to enjoy summer, while the southern hemisphere is plunged into the cold of winter.

So, keep this fact straight: The Earth's seasons are caused by the Earth's tilt, nothing else.

Wednesday, September 21, 2005

Mars is a changin'

In astronomy we are used to things not changing. There is the occasional comet or supernova or gamma-ray burst to liven things up, but most of the time a galaxy or star looks the same today as it did over 100 years ago. Most things just don't change over human lifetimes.

A recent press release from NASA's Mars Global Surveyor team reveals changes on Mars that have occurred just over the last few years. Gullies carved by evaporating dry ice appear in sand dunes, the southern polar ice cap changes shape from winter to winter, and even a meteor crater appears out of nowhere and then fades from view.

These pictures tell us that Mars is an active planet like the Earth, not a slow-changing world like the moon. This isn't surprising, as humans have seen huge dust storms appear on Mars and observed the changing polar caps for centuries. But to see the changes up close is, in scientific parlance, wicked cool.

Tuesday, September 20, 2005

Bad timing?

Yesterday NASA announced its plans for returning humans to the moon and later to Mars. This is an ambitious program, and it builds on our combined knowledge of space travel. There are also some ambitious plans that may or may not work, such as using ice that is thought to exist at the moon's south pole as water so moon crews can stay for months at a time. The cost for the return to the moon: $104 billion dollars between now and 2018.

That sounds like a lot of money, and it is, though probably not as much as people think. This adds up to about $9 billion per year. Compare this to costs in this year's federal budget: $31 billion for veteran's benefits, $40 billion for "administration of justice," $31 billion on environmental spending, $80 billion on education. So, the cost of a return to the moon is significantly less than these important costs.

I think NASA's in trouble, though, because of their timing. This announcement was made just days after the president requested another $60 billion for Katrina relief on top of a $400 billion federal deficit. Plus, we have two major military conflicts to pay for. So it is difficult to ask for even more spending to go to the moon.

The reason for the bad timing has to do with the federal budget process. This is the time of year when the 2007 budget is being prepared by the president for submission to Congress, so government agencies have to figure out what they want and need and justify those figures. It is just bad luck on NASA's part to time the announcement of the moon program right as unexpected major spending becomes necessary.

Thursday, September 15, 2005

Astronomy Ethics

Clay Bennett, The Christian Science Monitor

As mentioned in the last post, a huge ethical swarm is swirling around astronomy right now, centered on the recent discovery of large objects (maybe even planets) in the outer reaches of our Solar System. The issue is fairly complex, and I'll let the NY Times article speak for itself.

However, an interesting point is raised on when data should be released. Did the american team "hide" their discovery? Well, yes and no. They knew they had found a new object far out in the solar system, and from its brightness they knew it was quite big. So the find was very interesting, and lots of astronomers would be chomping at the bit to explore it. Understandably, the discoverers wanted to wait before announcing their find so that they could do some of the most obvious follow-up work themselves.

While this sounds selfish, I don't personally feel that it is selfish or unethical. Too many times I have seen press releases on discoveries that a little basic follow-up work found to be completely wrong or completely misinterpreted. Therefore I think it is scientifically responsible to do the first bit of follow-up work yourself, as long as, once you are confident in your find, you make appropriate announcements.

Currently I am working on several research projects with results that other astronomers will (hopefully!) find interesting, but I have not yet announced them. I want to make sure that I haven't made a big mistake first. I want to be correct as well as first. And these galaxies and planets will be around for thousands of years for further study. So am I being selfish or just responsible? I'll leave that up to you.

Tuesday, September 13, 2005

Scientific ethics

This article from the New York Times reports on an ethical brawl that has erupted in astronomy. I'm still trying to digest my thoughts on this, and will give my opinion tomorrow. In the meantime, it shows that even "pure science" is not immune from politics. How sad.

Monday, September 12, 2005

Solar Storms

The sun has been very active this week, causing major geomagnetic storms as a large sunspot group crosses the sun's face.

In the past several years the study of solar weather (more importantly, "Space weather" in the region of space around the Earth) has been recognized as an important area of study. Storms on the sun release large amounts of radiation and energetic particles, both of which can and have damaged satellites. With our growing use (and, dare I say, dependence) on satellites, from weather to GPS to phone calls, it is clearly important to learn to predict "space weather."

Space weather is also important for astronauts and cosmonauts on the International Space Station. Inside the station they are safe, but they cannot safely go outside during these storms. The radiation also affects Earth's upper atmosphere, making radio communications (such as military and jet aircraft radios) difficult if not impossible, especially near the poles. On the good side, solar storms make aurora (the "Northern Lights"), which are quite beautiful.

If you'd like to follow space weather, the Space Environment Center has more information than you could care to find!

Thursday, September 01, 2005

Clear Skies and Star Trails

We never did get to work last night because of ice on the domes, but it did clear off. My colleague, Ivelina Momcheva, took the following pictures with her digital camera last night. Great photography, Iva! Captions are above each photo; click on each photo for a better view!

This picture shows the Magellan Telescopes with the backdrop of the northern sky. The star trails here represent a one-hour exposure. What you are seeing is the rotation of the Earth, apparently causing the stars to move!

Now we swing around 180 degrees for a view of star trails near the South Celestial Pole. Notice that, unlike in the Northern Hemisphere, there is no bright "Southern Star" to mark due south, just a few faint stars. Notice also the beautiful colors of the stars. Our eyes only detect colors of the brightest stars, but they range the spectrum from red to yellow to blue.

This is another picture of the South Pole, but shorter. Two nearby galaxies are visible in this image. The large fuzzy one, just above the roof of the Commons Building, is the Large Magellanic Cloud, and the smaller fuzzy patch near the top of the image is the Small Magellanic Cloud. These galaxies are 200,000 light years away, yet easily visible to the naked eye in dark skies!

This picture shows the southern sky, along with the glow of the Milky Way, the galaxy we live in. The yellow glow low in the sky are street lights in the city of La Serena, about 150 km (100 miles) to the south.

What could have been much worse

Ah, it is a beautiful night here. The Milky Way arches majestically overhead, the Southern Cross is low in the south, and the Magellenic Clouds are climbing upward in the sky. Alas, we are not working here at Las Campanas this evening. Last night we received 4-6 inches of snow, and while much of it melted today, the melt water froze on the domes at nightfall, and it is not safe to open up the domes or operate the telescopes. This happens, unfortunately!

With some time on my hands, I've been closely following the news about the aftermath of Hurricane Katrina. It is truly a horrendous national disaster, and I'd urge everyone to help out the best that they can, even if it is just donating money to relief efforts.

In spite of the horrible distruction and loss of life in Louisiana, Mississippi and Alabama, things could have been much worse. Thanks in large part to weather satellites, plenty of warning was available to help evacuate hundreds of thousands of people out of New Orleans and other affected areas. Imagine how extreme the loss of life would have been without such warning. Tens of thousands could have died, much like in the Galveston Hurricane of 1900. These satellites, along with many others studying the Earth and its environs, are direct benefits from our space program and space research. These benefits were not all that apparent in the early part of the space race, when the largest concerns were the potential militarization of space. So, while much of today's space research may seem like it has no direct bearing on us (how many times have I heard the comment, "Wouldn't we be better off if that money were spent here on Earth?"), we need to remember the tens to hundreds of thousands of lives that space exploration saved this week, even as we mourn the hundreds who perished.

Tuesday, August 30, 2005

Arrived at the telescope

After 24 hours of travel, I have arrived at the Las Campanas Observatory in the mountains north of La Serena, Chile (actually about halfway between La Serena and CopiapĆ³ on this map, just north of Santiago).

I am glad that I have a night of rest tonight, because the weather is quite bad. The temperature (at 5pm local time) is 25 degrees F (-4 C), and thick clouds are slowly drifting just overhead. Over the past few nights they've had some ice here, and a thick layer of ice is on most of the plants. We'll have to see what things are like tomorrow!

Monday, August 29, 2005

on the road again...

Blogging has been light because of a few days' vacation. Today I am starting the 24-hour trip to Las Campanas Observatory in Chile, where I will have four nights on the telescope. Hopefully I'll get some neat observations to share!

Tuesday, August 23, 2005

Asteroids!

Although I like to read a lot about studies of our solar system, my research focuses on stars and distant galaxies. So, despite havng done astronomy research for over a decade, today I submitted my first ever observations of asteroids.

I did not set out to find asteroids. My collaborators and I took many deep images of the star cluster M67 in order to find white dwarfs. But when I was comparing images, I noticed something moving slowly through the cluster. The stars are all much too far away to move noticeably in a night, so it had to be something in our solar system. So, for fun, I went to the Minor Planet Center website and entered the coordinates of the object. Yes, it was a known asteroid, but they wanted more data! So, I prepared my observations and sent them in. I'm still waiting for a reply, but this could take a few days.

I have discovered two asteroids in my images, and pictures of them are below. I've reversed the colors, so stars are black and the night sky is light (it is easier to see faint objects as black on white rather than white on black). The white bars are spaces between the silicon chips used to take the pictures. In each frame, north is to the right and east is up. These images were taken 45 minutes apart. The asteroids are the objects that move! The names are temporary designations used until the orbits are known well enough for the asteroid to get an official name. Hopefully my chance observations will help with that!

My asteroid pictures:

(Just kidding!)

2002 TF71

2004 BU85

Monday, August 22, 2005

1,000,000,000 and counting

This last weekend I passed through my one billionth second since birth. While this is, admittedly, a fairly nerdy milestone to celebrate, you too can calculate other semi-useless anniversaries since your birthday using this calendar. (Note that this calendar is only accurate to 30 seconds or so, due to round-off errors. But if you really want to be exact, then you can probably think of other ways to calculate your billionth second. Don't forget to account for leap seconds!)

Numbers like this actually allow people to get some handle on big numbers, which astronomers love to throw around. Here are more commonly-used amounts of time related to seconds:

  • 100 seconds = 1 2/3 minutes
  • 1000 seconds = 16 2/3 minutes
  • 10,000 seconds = 2 hours, 46 2/3 minutes
  • 100,000 seconds = 1 day, 3 hours, 46 2/3 minutes
  • 1 million seconds = 11.5 days (I'm rounding off from here on)
  • 10 million seconds = 115.7 days
  • 100 million seconds = 3 years, 2 months
  • 1 billion seconds = 31 years, 8 months
  • 10 billion seconds = 317 years
  • 1 trillion seconds = 31,688 years

How does this compare to astronomical times and distances?

  • Time it would take to travel to the sun at a rate of one mile per second (3600 miles per hour, or about 6 times faster than a typical commercial jet airplane) = 93 million seconds = 2 years, 11 months (light takes just 8 minutes!)
  • Time it would take to travel to the the nearest star, Proxima Centauri (4.2 light-years away), at a rate of one mile per second = 25 trillion seconds = 800,000 years
  • Time it would take to travel to the nearest big galaxy, the Andromeda Galaxy (about 2 million light-years away) at one mile per second = 380 billion years, or nearly 30 times longer than the Universe has been around!

Thus ends your daily dose of useless trivia. :)

Thursday, August 18, 2005

Passing of astronomer John Bahcall

We learned today that astronomer Professor John Bahcall died Wednesday, August 17 due to a blood disorder. His obituary is given here.

John Bahcall was famous for helping in our understanding of how the sun works, especially in regard to the mystery of neutrinos, nearly-massless particles that are created during nuclear reactions. The detection of neutrinos coming from the sun proved that nuclear reactions provide the sun's power. But, under the early thought that neutrinos were massless particles, we only detected 1/3 the expected number. Recently it has been shown that neutrinos do have a small mass, and complex physics then explains why we only see 1/3 the number (in short, neutrinos can change into other types of neutrinos due to quantum mechanics).

Due in a large part to Professor Bahcall's work, we now understand the interior of the sun to very high precision. His contributions are enormous, and he and his mind will be missed greatly.

Wednesday, August 17, 2005

1,000 comets later...

Today, NASA announced that the SOHO spacecraft has discovered it's 1000th comet! What is even more amazing is that the majority of these were discovered by amateurs, more or less looking for fun and the excitement of discovering a comet.

SOHO is a satellite jointly operated by the European Space Agency and NASA, launched for the purpose of monitoring the sun around the clock. One of the cameras, called "LASCO," uses a disk to block out the sun, allowing the faint tendrils of the solar corona (the sun's outermost atmosphere) to be seen (see picture below, courtesy the Jet Propulsion Laboratory).

Most of the comets are known as "sungrazers," or comets that approach extremely close to the sun. These comets are probably the pieces of a few large comets that broke up on a previous trip around the sun. Most of the SOHO comets are only a few yards (few meters) across, and they are completely destroyed after they pass the sun. This tells us that the comets are very loosely packed, and easily pulled apart.

Before SOHO, only a couple of dozen sungrazing comets were known, and now we know of over 1000! Congratulations to all of the people working with SOHO to find comets!

Wednesday, August 10, 2005

What's in a name?

I've spent time over the last few days trying to develop a naming scheme for galaxies my collaborators and I have discovered as a part of one of our projects. Unforunately, it's not quite as easy as picking out family members and pets to name the galaxies after. First and foremost, it's not allowed, and second, those names hinder our research work.

The International Astronomical Union is, by agreement, the astronomical organization that officially names all objects. Most objects are designated by a catalog name and catalog number, but sometimes instead of a catalog number, the objects are numbered by there coordinates. For example, the Andromeda Galaxy is also known as M 31 (for the 31st entry in Charles Messier's catalog) and, much much much less commonly, as RX J0042.6+4115, for the ROSAT X-ray source at coordinates 00:42.6, +41:15. Our finished galaxy catalog may have 10,000 or more galaxies, far too many to name after all of our friends, family, pets, co-workers, competitors, and enemies. So, we'll be using catalog numbers, and naming the catalog after ourselves. (This is standard practice so that other people can find our papers talking about our search later, not so that we are immortalized.) As soon as the IAU approves our names, we'll be able to chug along!

There are companies that, for a fee, claim to "name a star" after you or anyone else. Many people think that this makes a cool gift, which is fine. Just be aware that these names are not "official;" they are not recognized by the International Astronomical Union. So just be aware that if you do "buy a star" to name, you do not either own the star or get to officially name it. In fact, one person bought me one of these stars, and there was no star at the coordinates they sent me! But, since I also received a star map, I was able to find the right star in a real catalog and learn its real name, which was a boring catalog number.

Thursday, August 04, 2005

Close to my heart...

Today's Astronomy Picture of the Day was interesting for me, because it contains objects similar to those I study in my research: young open star clusters. My work involves looking for the remains of dead stars, stars that have burnt all of their fuel, called white dwarfs. White dwarfs are small, incredibly dense objects. Imagine taking the sun, which is almost one million miles across, and squeezing it into a ball the size of the Earth, which is only 8000 miles across! In the picture, toward the upper left, you can see a white dwarf in the process of forming. The small, green circle is a planetary nebula, or a star in the process of dying. A star which has used up all its fuel sheds it outer layers, leaving behind the hot, now-defunct nuclear reactor at its core behind. This core will quickly shrink to form the white dwarf, while the outer parts of the star slowly drift away into deep space.

Tuesday, August 02, 2005

What makes a planet, part 2

In addition to the question about small things in our solar system (see yesterday), the question of the definition of "planet" also extends to things larger than Jupiter orbiting other stars.

The smallest "stars" are called "brown dwarfs," which are heavier than about 13 times the mass of Jupiter. Early in their lives, brown dwarfs do a little bit of nuclear fusion, burning deuterium (hydrogen with an extra proton) to make helium. But brown dwarfs are too wimpy to keep up nuclear fusion, and once all the deuterium is gone, the slowly cool off and fade away. Stars like the sun, on the other hand, get hot enough in their centers to continue nuclear fusion by burning normal hydrogen into helium steadily for millions, even billions of years.

For things smaller than 13 times the mass of Jupiter, no nuclear fusion will ever happen. For this reason, some astronomers think anything this small or smaller should be called a planet.

However, other people disagree. There are two ways to form objects this small. One is to form them like we think the planets of our solar system formed -- rocks and gas in a disk surrounding the parent star slowly build up to make planets. Some, like the Earth, would be pure rock, while others, like Jupiter, would have a rocky core with a very thick, massive atmosphere on top. Things that form this way would definitely be called "planets" by most every astronomer.

The other way to form giant planets is similar to the way stars form -- a large cloud of gas breaks up and shrinks under gravity. This could happen in isolation, or in orbit around another star (this is how multiple star systems are formed). "Planets" formed this way do not have rocks at their center, but are just large clouds of gas. They would not even need to be in orbit around another star, but floating freely in space. So, are these "planets?" I think most people would say "no," but astronomers are split on the issue.

The problem is that it is not possible to tell in which way a massive object formed. A 5-Jupiter-mass object detected around a star could have formed by either way, but it is virtually, if not fully, impossible to tell how it formed. For this reason, most atronomers lean toward a definition based purely on a planet's mass, not how it was formed.

I read this morning that the Internation Astronomical Union (IAU), which by agreement among astronomers has the power to define and to name all objects in space, is finally going to decide on all of these issues. The IAU has been talking about this for years, but the discovery by Mike Brown and collaborators is finally pushing them to come to a decision. It seems to be typical politics that now a decision has to be rushed, especially since astronomers have suspected for years that the Kuiper Belt had objects larger than Pluto, and since many objects more massive than Jupiter have been found around other stars and floating free in space.

The definition of a planet is likely to be an object that is too small to have ever undergone nuclear fusion, is large enough that gravity makes it round (instead of the potato shape of asteroids and comets), and that orbits another star. While I personally would like to include the way an objects is formed, I seriously doubt that can be part of a viable definition. With this definition, though, there would suddenly be many more "planets" in our own solar system, including a a handful of large asteroids and several objects in the Kuiper Belt -- as many as 23! Astronomers may just have to wait for pop culture to decide what a planet is.

Monday, August 01, 2005

What is a planet?

The discovery of a new object in our solar system larger than Pluto will once again re-open the debate, "What is a planet?" This question is especially tricky because the definition of the word "planet" is unclear on two ends, both the Juptier-sized objects being found around other stars, and large, icy bodies being found in our own Solar System. A big part of the problem, as articulated by Mike Brown, the co-discoverer of the new "planet," is that the word "planet" is not owned by scientists. Rather, the term "planet" also has cultural definitions that scientists cannot and should not control.

Let's start with the nine (ten? more?) planets in our own Solar System. Nobody would claim that the Moon is a planet, but the Moon is larger than Pluto! So size is not the sole criterion. So you might say that a planet has to orbit the sun and not another body, but since nobody would call asteroids and comets "planets," this definition is not enough either.

Finally, looking at the nine planets (Mercury through Pluto), Pluto is clearly the odd man out. Pluto is far smaller than any other planet; its composition is very different from any other planet; its orbit is not nearly circular, and its orbit rises out of the plane that all the other planets lie in. But Pluto's orbit and chemical makeup are very similar to the dozens of smaller "Kuiper Belt Objects" that orbit the sun beyond Neptune.

Because of this, many astronomers want to "de-list" Pluto as a planet. But when astronomers try to do this, there is a huge cry from the public. In your eyes, Pluto is a planet. My suspicion is that, in time, astronomers will learn to live with the dichotomy between what astronomers call a planet and what the public calls a planet. Also, only time will tell whether the public will accept this new object and any more objects larger than Pluto as "planets." Stay tuned!

Tomorrow we'll discuss the other side of the definition of "planet," the large objects around other stars.

Friday, July 29, 2005

Is it "Planet X"?

Well, probably not, but a team of astronomers has discovered a distant icy body larger than Pluto, long regarded as the ninth planet of the solar system. Like Pluto, this new discovery (which as of yet has the boring name of "2003 UB313") belongs to the Kuiper Belt, a collection of icy remains from the formation of the Solar System.

While most planets orbit the sun in a flat disk called the ecliptic, this new Kuiper Belt Object is at quite an angle, nearly 45 degrees out line! It is also quite far away, nearly 100 times the Earth-sun distance, and twice as far from the sun as Pluto.

This discovery is sure to re-open the whole "is Pluto a planet?" debate. But, at the very least, Clyde Tombaugh, the discoverer of Pluto, can be said to have discovered the first object in the Kuiper Belt 21 years before Gerard Kuiper hypothesized its existance!

More information on 2003 UB313 can be found here.

Wednesday, July 27, 2005

Back from vacation, having missed all the fun

Well, I'm back from a week's vacation, well-rested and ready to get back to work. While I was out of town, though, I missed a lot of the fun here at Steward Observatory.

Steward is one of the observatories joining together to build what is known as the Giant Magellan Telescope, or GMT. The GMT will be made of seven round mirrors for a total collecting area equal to a single mirror 21.4 meters in diameter, or about 71 feet across. This is over four times larger than the Keck Telescopes, currently the world's largest.

The design of the GMT requires making mirrors in a novel design, called "off-axis" design. This is because six of the seven mirrors are not at the center of the telescope, but rather away from it. A big step toward proving the required technology was taken this last weekend, when the first mirror 8.4 meters (28 feet) across was cast. This involved melting twenty tons of glass to 2150 degrees, and spinning the melted glass at 4.8 RPM. VIPs and Observatory staff were invited to watch this past weekend (though, like I said, I was out of town).

So far, everything has gone well! Now the glass will be allowed to slowly cool over a period of a few months, then the mirror will be examined and ground to its final shape.

Monday, July 18, 2005

We can start breathing again...

Although I don't want to be too premature, it looks like the MMT Observatory has dodged a bullet. Saturday a thunderstorm dropped up to an inch of rain on the Florida Fire, slowing its progress. In addition, the humidity has gone up, which also slows the fire. And by Wednesday it looks like the summer monsoon will finally start, and the rains should put out the fire. Although the fire could still flare up, it appears unlikely, and some fire crews are moving to other fires in the west that are more dangerous.

Friday, July 15, 2005

More Fire News

Today the Florida (flor - EE - da) is a little closer to the MMT Observatory, but things are looking up. The summer monsoons are trying to get started, so the air isn't as dry, which is slowing the fire down. The picture to the right shows the fire as viewed from the MMT yesterday, an image provided by Emilio Falco. The buildings are likely safe, because trees near the buildings were cut back, sprinklers were put in place, and slurry has been dropped everywhere (some pictures of the road show a pink road from all the retardant!). However, the fire is 40% contained, much better than yesterday, and back-burns have been set to help contain the fire. And, luckily, most of the burning is still more beneficial than harmful to the environment in the area.

Thursday, July 14, 2005

Creeping closer...

The Florida Fire outside of Tucson continues to menace the MMT telescope and the telescopes of the Fred L. Whipple Observatory south of Tucson.

According to Barbara Russ (MMT staff) and Gary Schmidt (former director of the MMT), the mountain has been evacuated. Small groups were allowed up today wearing protective equipment to secure equipment away from windows and other vunerable spots. Because the fire is getting close, the fire crews have been moved out, as they could quickly get trapped on the mountain top if the fire comes through.

The MMT itself is likely safe from any fire, because it is located on a large rock far from trees (see some of my pictures from last September). However, many of the smaller telescopes and the astronomer's sleeping and eating quarters are in the forest and could be destroyed by the fire.

Yesterday it looked like it might rain, but the big clouds only produced wind, which made matters worse rather than better. It looks like there won't be any rain today, but tomorrow is looking quite promising. Here's hoping the Observatory and its neighbors living in Madera Canyon (also threatened by the fire) stay safe and secure until the rains come!

Wednesday, July 13, 2005

Wildfires lurking again!

For the third year in a row, a telescope owned by the University of Arizona is being threatened by a wildfire. Two years ago, two small telescopes on Mt. Lemmon just north of Tucson were threatened by the horrible Aspen Fire, which destroyed the small town of Summerhaven. Last summer, the Nuttall wildfire threatened the Vatican Advanced Technology Telescope (VATT) and the under-construction Large Binocular Telescope (LBT) on Mt. Graham, between Tucson and New Mexico (Click here for a dramatic movie of the fire passing the LBT on July 6, 2004.)

This year, a fire in the Santa Rita mountains just south of Tucson are approaching the MMT Observatory, part of a complex of telescopes on Mount Hopkins. Yesterday the fire jumped containment lines and is threatening homes in Madera Canyon, a popular recreation site. While the fire is still miles away from the telescopes, the mountain has been evacuated. An unexpected change of wind could bring the fire toward the observatory and trap people. A photo taken yesterday from the administrative offices at the base of Mt. Hopkins is below (Image courtesy Stephen Criswell, FLWO).

Fires are a part of life in the western US, and part of the natural cycle. The Florida Fire now burning was started by lightning, and mostly has been burning out brush and dead wood, which is a good thing. And, luckily, to date no people have been hurt or property damaged by this fire. Astronomical observatories get the best data when located on mountain tops far from human habitation. Unfortunately, this often puts observatories in prime wildfire areas. In January 2003, a fire near Canburra, Australia destroyed the Mt. Stromlo Observatory (Click here for an example photograph taken by Matthew Colless three days after the fire). Even worse, this fire claimed many human lives as well, and I have heard amazing stories from astronomers who barely survived the conflagration. Here's hoping that the observatory and its neighbors come through this fire safely!

Monday, July 11, 2005

Writing it all down...

One of the most important, but most boring, parts of astronomical research is writing up what you have learned and publishing it in a professional journal (these are akin to the "New England Journal of Medicine"; if you aren't a professional in the field, you probably won't understand a word).

I've been working for a while nowon writing a couple of pretty long papers. It takes longer than you might think. For example, making a single graph can take most of a day. How can I convey as much relevant information as possible without making things too cluttered? Should I use color? Would a bar graph work better? When the graph goes on the page, will I still be able to tell the difference between triangles and squares?

Although this sounds boring (and it is!), it is vital to scientific research. If I discover new galaxies or a new type of star, what does it matter if I cannot both tell other people about it and convince them that my work is correct? That latter part is often the hardest. We spend more time testing and re-testing our data than we do at the telescope taking more pictures. And when we finish a paper, it has to get approved by one or more fellow astronomers who weren't involved with the work in the paper. If they aren't convinced, the paper doesn't get published. Often just a little tweaking is necessary; sometimes substantial work is needed. Rarely a paper just will not get published because it is wrong.

Once my papers are done, I will feel quite good about all the work I've put in. In the short term, though, it's back to the grindstone...

Friday, July 08, 2005

Back in town / Deep Impact

I'm back in town after a family emergency called me out for a week. Because of that, I also didn't get to observe NASA's Deep Impact success with the MMT telescope.

Wasn't the comet mission a smashing success? My concern was that the impact would create few fireworks, but instead we are still seeing the effects several days later.

Events like Deep Impact make professional astronomers look like little kids. We've been sitting around in the office, looking at movies from the spacecraft. Remarks like "Whoa, cool!" and "Dude, did you see that!" arise from the supposedly professional audience. It's what we got into the buisiness for. :)

Monday, June 27, 2005

Preparing for fireworks

On Sunday night, July 3 2005, NASA's Deep Impact spacecraft will crash into comet Tempel 1. The point of this mission is to see what comets are made of and how they are constructed. Telescopes across the western hemisphere will be pointing at the comet to try and observe the celestial fireworks and see what happens.

Before the exact timing of the event was scheduled, I was awarded time at the MMT telescope outside of Tucson, Arizona. I'll be looking at distant galaxies during most of my time, but I was more than happy to volunteer a few hours of my time to try and study the comet before Earth's rotation takes it below the horizon.

So now I get to spend time this week learning about comets and trying to figure out how best to observe the Deep Impact mission. I'll be asking the instrument on the telescope to do things it wasn't designed to do, so I hope it all works out! There will be a TV crew up on the mountains, and I'll be sure to report here what is going on as it happens. Stay tuned!

Thursday, June 23, 2005

Evening Planets

The planets Venus, Mercury and Saturn are currently putting on a great show in the early evening sky. From our view on Earth, the planets are the closest they'll be until 2030 (though in reality they are tens to hundreds of millions of miles apart).

Tomorrow night, the 24th, the planets will appear to be only 2 1/2 degrees apart, or about 5 times the width of the full moon. Venus is the brightest of the three. If you watch the planets over a few days, it will be easy to see them move relative to one another as their orbits carry them around the sun. Saturn will appear to sink closer to the sun, while Venus and Mercury are climbing higher in the sky.

Take a few minutes over the next few days and take in the spectacle. More detailed explanations and graphs can be found from the Sky & Telescope website.

Wednesday, June 22, 2005

Solar Sail Sinks

Yesterday, the Planetary Society, a private group interested in fostering space travel, attempted to launch a $4 million solar sail called "Cosmos 1" from a Russian submarine. Unfortunately the booster rocket failed, and the satellite never had a chance. So what is a solar sail? The idea is to use sunlight as a "wind" to push a spaceship through the solar system. Light, like wind, exerts pressure and pushes on objects. For us on Earth, this pressure is much, much, much smaller than the forces of gravity and friction that control our movement, so we don't notice it. But in space, this pressure can push objects around. (Just note that this is not the solar wind that causes aurora here on Earth.) A solar sail is a very large piece of light-weight material (just like a boat sail) that has a large area for sunlight to push on. The sunlight will slowly accelerate the spacecraft, allowing it to move around the solar system without the need for a rocket engine. Changes in the spacecraft's speed are slow, but they add up over time. And spacecraft can be made lightweight, since most of the weight of any spacecraft is its engine and fuel. This launch was an experiment to see if a solar sail can really work, and it is a shame that the sail never even had a chance to unfurl. I suspect that the Planetary Society will try again before too much longer to prove this fanciful technology!

Tuesday, June 14, 2005

Earth-like planet discovery

Yesterday the planet-finding team of Paul Butler, Geoff Marcy and Debra Fischer (among many others) announced the discovery of a planet with a mass of 6-8 times the mass of the earth orbiting a nearby star. The work, headed by team member Eugenio Rivera of Lick Observatory, has been submitted for publication in The Astrophysical Journal, one of the top astronomy journals.

Here's an FAQ about the new planet:

  • How far away is the planet? The planet orbits a star, Gliese 876, which is 15 light-years (90 trillion miles, or 150 trillion km) away.
  • How do we know the planet is there? The discoverers detected a wobble in the parent star caused by the planet's gravity.
  • Are there any other planets around this star? Previously, two Juptier-sized planets were known to exist around this star.
  • Is there any chance of life on this planet? Almost certainly not. The planet orbits very close to the parent star, about ten times closer than Mercury is to the sun. It's surface temperature is likely between 400 and 800 degrees Fahrenheit, or almost as hot as Venus!
  • Why is this planet exciting? This planet is hot enough that it very likely could not hold on to a large atmosphere. Most of the mass of Jupiter, Saturn, Uranus and Neptune resides in the atmosphere. For the new planet, most if not all of the mass is probably pure rock, like the Earth, Venus, Mercury and Mars. This would be the first planet outside the solar system known to be made of rock.

A caveat, though, is that the Geneva planet search team claimed to find a rocky planet last year (see my blog post on the "super Earth"). So one could argue (and I'm sure astronomers are!) whether this is the first discovery of a rocky planet around another star. The reality is that we really don't know what these two planets look like or are made of. Future space missions that will actually be able to take pictures of these planets will help us to tell how big the planets are, allowing us to tell if they are made of rocks or gas.

Monday, June 13, 2005

Am I blue?

A story posted on space.com talks about the "discovery" of blue galaxies in voids, or large regions of the universe that have few galaxies. The result itself, which you can read about in the article, isn't unexpected, but it makes for a good lesson on the structure of the universe.

Shortly after the Big Bang, the Universe was almost perfectly smooth, with "almost" being the key word. Some parts had slightly more matter than others, some had slightly less. Over the 13 billion years the Universe has been around, the extra pull of gravity in the slightly denser areas pulled much of the material in the universe over, creating a pattern of galaxies that looks like the foam in a bubble bath. "Voids" are the spaces in the middle of these bubbles -- there isn't much there!

Since galaxies in voids are alone and mainly untouched since they formed, studying these galaxies helps astronomers to understand how galaxies grow, form stars, and change when nothing else is around. Since most galaxies are not in voids, but live near other galaxies in groups (a handful of big galaxies) or clusters (a swarm of hundreds of galaxies), any differences between the galaxies in voids and all other galaxies are likely due to interactions between galaxies. This includes galaxy harassment and galaxy collisions.

Thursday, June 09, 2005

Albert Einstein Action Figure

This past weekend, I had family visiting from around the country. Why they came to the desert in the middle of summer is a question I can't answer. At any rate, I was given an Albert Einstein Action Figure. While I doubt kids are going to start playing "mad scientist" with these figures anytime soon, it is a cool addition to my office.

This year marks the 100th anniversary of Einstein's "Year of Miracles," when he published landmark papers on three fundamental areas of physics. For that reason, 2005 has been declared the "World Year of Physics". So feel free to celebrate appropriately; just remember Einstein's admonition not to drink and derive.

So what were Einstein's three big breakthroughs that year? The most famous is the theory of Special Relativity, which describes how the laws of physics seem to change as you get close to the speed of light, including his famous E=mc^2 equation. This is different from his theory of General Relativity, which deals with the warping of space time, black holes, etc. That theory came 10 years later.

Einstein's second big idea was on the "photoelectric effect." In short, Einstein discovered that light acted like a particle, called the photon. Scientists already knew that light also acted like a wave. Einstein's thoughts on the photoelectric effect helped lead to the theory of quantum mechanics, or how subatomic particles actually work.

Einstein's third big concept involved "Brownian motion." If you watch a speck of dust in a drop of water, you'll notice the dust move around randomly, even though the water appears still. Einstein suggested that this was due to the water molecules jiggling around, randomly pushing the dust in different directions. Einstein was able to calculate the size of water molecules from this information, and it proved that substances were made of atoms long before electron microscopes allowed us to see individual atoms.

You can read more about Einstein's Miracle Year at this site.

Tuesday, June 07, 2005

Snippits & Factoids

I took a nice long weekend, as family was visiting in town. So below are little facts and snippets I picked up over the last few days.

  • Unstuck! The Martian rover Opportunity finally freed itself from its sand trap. Look for more cool science from this sturdy explorer!
  • Icy lava -- Yesterday's Astronomy Picture of the Day shows a picture of Saturn's moon Enceladus (not to be confused with enchiladas, a tasty treat.) This moon may have volcanos that spew water ice as lava! I like this idea, as I have a minor interest in volcanology. For some reason, many astronomers seem to have additional interest in geology, and many geologists have an interest in astronomy. There must be some similarity between the fields that draws similar people.

Thursday, June 02, 2005

New Pictures From Mars

Today I found two new pictures from our intrepid explorers on Mars, the rovers Spirit and Opportunity. From it's vantage point mired in a sand dune on the plains of Meridiani Planum, Opportunity snapped this picture of our home, the Earth. On the date the picture was taken, April 29, the Earth was about 130 million miles away. Meanwhile, Opportunity's twin sister, Spirit, sent this movie of a dust devil crossing the floor of Gusev Crater. As a resident of the Sonoran Desert, I see quite a few dust devils, especially this time of year. Spirit and Opportunity have benefitted from the dust devils, which clean dust off of the rovers' solar panels and have helped the rovers to survive over one year longer than planned in the harsh Martian climate.

Wednesday, June 01, 2005

Astronomy in the news

See any news stories on astronomy in the paper or on TV this week? This week in Minneapolis, many astronomers from across the continent are gathered for the summer meeting of the American Astronomical Society (AAS). These meetings are held twice a year, usually in early January and early June. Astronomers at the meeting give short talks on their research, display posters with new results from their projects, renew friendships and collaborations, and live, sleep and breathe astronomy. The AAS also takes this opportunity to issue press releases on cool new research.

If any interesting news comes out, I'll be sure to comment!

Tuesday, May 31, 2005

The future of the Hubble Telescope -- Part III

So now that we've seen some reasons that people espouse for not servicing the Hubble Space Telescope, I'll present my arguments why we should service Hubble. (Let me state for the record that these are personal opinions, not necessarily those of my employer or anybody else, etc., etc., etc.) Some of these were hinted at before, but I'll spell it out explicitly here. :)
  1. The Hubble Telescope can be completely repaired. With new batteries, new gyroscopes, and two new cameras, the Hubble Space Telescope could last up to ten more years. Without repair, it will not last more than two.
  2. The Hubble Telescope has unique capabilities that will not be replaced any time soon. Hubble's power to see blue light sharper than from the ground and its power to see ultraviolet light invisible from the ground have no planned replacement. It would hurt astronomy to lose these abilities.
  3. Hubble has two brand new cameras ready to be installed. Two new cameras, one replacing a broken camera on Hubble, and the other replacing an aging instrument that's still working, have already been built. It would waste millions of dollars not to use these instruments. There has been talk that these two cameras could be put on a "Hubble Lite" telescope, but as of now no such design exists, and more importantly no money exists to build such a telescope.
  4. It will be at least 7 years before the next space telescope is ready to fly. Not much more to say there, other than, knowing NASA, it could easily be 15 years or more before the actual launch.
  5. Hubble has captured the hearts of people around the world. NASA and astronomers have done an outstanding job showing off Hubble's accomplishments. Many people forget that the Hubble Telescope started off with blurry vision that was fixed by astronauts a couple of years later. Since that time, we have gotten amazing pictures of the distant universe, detailed looks at nearby galaxies, and fantastic shots of amazing things in our own galaxy.

So, there you go. Make up your own mind about what you think should happen to Hubble, and let your representatives and senators in Congress know. They control the purse strings in all of this!

Monday, May 30, 2005

The future of the Hubble Telescope -- Part II

So, as promised, here are some arguments people have used against servicing the Hubble Space Telescop which I consider somewhat suspect. Some of these arguments have been put forward by people who should know better, such as high-level NASA people.
  1. Hubble is dying. This is a partial truth. If left alone, the Hubble telescope will die. But the Hubble was designed to be repaired -- many of its parts, such as the failing gyroscopes that are threatening Hubble now, have been replaced many times already. Although Hubble is sick right now, a successful repair mission will make it as good as new, and ready to serve out another 5-10 years before retiring.
  2. Hubble's replacement is being built right now, so there is no need to repair Hubble. This refers to the "James Webb Space Telescope" (JWST), which is a larger telescope than Hubble with a planned launch no earlier than 2012. The JWST will be a great telescope, but it does not replace Hubble. To save money, the JWST is being built for a narrower purpose than Hubble -- to look at red light and near-infrared light (heat). This makes the JWST perfect for researching the furthest galaxies in the Universe, because the expansion of the Universe shifts their light into the red and near infrared. But Hubble is also very capable of taking data in the blue and ultraviolet light, which is important for studying nearby stars and galaxies. When Hubble dies, no space telescope in orbit, being built, or even planned, will be able to study. Even more, ultraviolet light is blocked by the atmosphere, so telescopes on Earth won't be able to study this light either. Hubble has unique capabilities that its "replacement" won't have.
  3. Ground-based telescopes can now see just as sharp as Hubble. This is true in the infrared light, because ground-based telescopes now have "adaptive optics," which allow them to correct the blurring caused by Earth's atmosphere. But these systems don't yet work in visible light, so Hubble still beats Earth-based telescopes for clarity of vision!
  4. Robots can do the job cheaper and without risk to humans. I wish this were true! But to date, no robot has been tested successfully in space. In fact, a NASA experiment to show that a robotic spacecraft can successfully meet up with another satellite, DART, experienced several problems that have yet to be understood. The chances that a robot could be ready in the two years or so Hubble has left to be serviced before it would die from being left alone are very small, and the costs are not well constrained at this point.
So next time I'll explain why I think it is worthwhile to try and service the Hubble with a space shuttle mission.

Friday, May 27, 2005

The future of the Hubble Telescope -- Part 1

Over the past several months there has been quite a bit of talk about the future of the Hubble Space Telescope. The previous NASA administrator, Sean O'Keefe, announced a while ago that there would be no more missions to service Hubble. Then, after an outcry from scientists and the public, he decided to consider alternatives, such as a robotic servicing mission. Recently, the new NASA administrator, Michael Griffin, announced that he was more seriously considering a manned servicing mission to fix Hubble.

Several of the arguments used agains fixing Hubble are not very good arguments, but some are very good. Let's start with the good arguments against fixing Hubble:

  1. A repair mission is expensive -- The total cost of a mission would be over a billion dollars. That money would have to come from other NASA programs, such as future space telescopes.
  2. If the shuttle were to lose part of its protective shielding, there would not be enough time for a rescue mission -- This is true unless a second shuttle happened to be put on the launch pad, ready to go on a rescue mission at a few days' notice. This would raise the cost of the mission a lot.
  3. Hubble has outlived its planned lifetime -- Also true; it was hoped that Hubble would last 5 years, maybe 10. And its up to 15 years!

Next time I'll talk a bit about some of the flimsier arguments used against a servicing mission, and then in the last of three parts, I'll give what I feel are good arguments for servicing Hubble.

Wednesday, May 25, 2005

Nearing the edge of the Solar System

Voyager 1, that intrepid spacecraft launched in 1977, has entered the last reaches of the solar system (depending on how you define the solar system). What does this mean?

The sun blows a wind of charged particles at speeds of up to 500 miles per second. This solar wind is created by the sun's magnetic field and is responsible for the Earth's auroras. Even out beyond the orbit of Pluto, the solar wind essentially controls all of the magnetic and electric dynamics of the solar system.

As the wind moves outward, it thins out because it needs to fill more space. Eventually the solar wind runs into the winds of other stars and of our galaxy itself. The solar wind abruptly slows way down in a termination shock, which also heats up the wind. The wind piles up, becoming denser (though it is still a far better vacuum than humans can make on Earth!).

Voyager 1 has now definitely crossed this termination shock and entered the heliosheath, a region where the solar wind continues to dominate, but moves more slowly. Eventually, the Voyager probe will cross the "heliopause," where the solar wind will end and the interstellar gases of the Milky Way galaxy will rule.

So, how far away are all these things? Right now, Voyager 1 is about 9 billion miles from the sun, or 94 times the distance from the Earth to the Sun. For reference, Pluto is, on average, 40 times further away from the sun than the Earth. The distance to the heliopause is uncertain, but is thought to be around 110 times the Earth-Sun distance. Voyager 1 should have enough electricity and fuel to communicate with the Earth until the year 2020, at which point it should be almost 150 times the Earth-Sun distance away, or almost 14 billion miles!

But does the heliopause really mark the edge of the Solar System? The heliopause marks the limits of the sun's magnetic influence, but the sun's gravitational pull extends further yet. The Oort Cloud, comets in giant orbits around the sun, may extend out nearly one light year, or six trillion miles. That's over 550 times the distance to the heliopause! Voyager 1, at its current rate of speed, will take almost 18,000 years to reach this distance and become a true interstellar spaceship.