Friday, June 30, 2006

Back in business

The Hubble Space Telescope's Advanced Camera for Surveys, which shut down last week after some strange power fluctuations, is back in business. Today engineers turned on the backup power system, and all seems to be working better than before the incident. So, back to work with Hubble!

Post-Doc Skip Day

Today will be a quick note, as it is the Steward Observatory's annual Postdoc Skip Day (PDSD), a day when we throw astronomy up in the air and rush off to the cool Lake Patagonia.

Happy PDSD to you all!

Thursday, June 29, 2006

Arizona Astronomy Shutdown

Click on the picture to see a video of a stormy day in Tucson!

Astronomy observations will be sparse in Arizona for the next two or three months. While it would be nice to blame it on a lack of government funding for science, it is really due to the weather. Every summer, the Sonoran Desert experiences the monsoon season, marked by almost daily thunderstorms delivering, on average, about half of our annual rainfall. Given that we had almost no rain in our winter rainy season, many Arizonans are hoping for a very strong monsoon this year. We've already seen many thunderstorms, but not too much rain has reached the ground yet.

Because the monsoon is fairly reliable, as it comes every year, most telescopes shut down for the month of August, and many also shut down for the month of July as well. During these shutdowns, a lot of telescope maintenance is done, new computer programs are tested, new observing techniques are tested, and so on.

Often the mirrors are re-coated during this time, too. Over the year, mirrors pick up a lot of dust and grime, which reduces the amount of light making it through the telescope. It takes several days to carefully remove all of grime and the old metallic coating. The mirror is then placed in a giant vacuum chamber, and all the air is pumped out. Evaporated metals are then put in the chamber, and the settle on the mirror to make an even, shiny coating. The mirror is then removed from the chamber and put back on the telescope, giving September's observers a nice, shiny, clean mirror! Some pictures of this process are at the bottom of this page.

Some telescopes do remain open through part or all of the monsoon. Although you don't want to run the telescope during a thunderstorm, after the storms leave and the dome dries, you can open up and work for a couple of hours. I've been told that the air is remarkably clear and steady!

Saturday, June 24, 2006

Hubble Trouble

You may have heard that the Hubble Space Telescope has had an instrument glitch (CNN called Hubble "blind in one eye.") So, what's up?

Hubble, like most ground-based telescopes, has multiple cameras. Each of those cameras has a specialty. The camera that is having trouble is the "Advanced Camera for Surveys," or ACS. ACS was placed on Hubble by astronauts during the last servicing mission in 2002. It has taken most of the pretty pictures that have come out since then. Another camera, the WFPC2, is still operating, and it was responsible for many of the pictures prior to 2002. A third camera, NICMOS, is working fine. It looks at infrared light. While we try and figure out exactly what happened to ACS, these two cameras will be doing much of the work on Hubble.

What happened to ACS? That is uncertain. The gossip I hear is that most likely the power circuitry went bad. This happened to another Hubble instrument, the Space Telescope Imaging Spectrograph (STIS), several years ago. Both STIS and ACS were built with a second power supply. In the case of STIS, this backup was turned on, and the camera worked for many years before finally dying a year or so ago.

In this case, all that must be done is to change some software to startup the second power supply on ACS, and we'll remotely "flip the switch" and turn the camera on.

Doing this takes some time. The camera sent down it's telemetry (kind of like an instrumental weather report) before it automatically shut down. Engineers are looking through this to see exactly what caused the problem. If something else other than the power supply is wrong, say, a wire came loose and shorted the camera out, then turning on the second power supply could damage the telescope.

The news I hear gives the camera a better than 80% chance of coming back online in the next few weeks. If the problem is more serious, though, it may be much longer.

Thursday, June 22, 2006

Another sense of scale

Today's Astronomy Picture of the Day (click on the picture for the large version) is another great sense of astronomical scale. The two bright "stars" are really the planets Mars (upper right) and Saturn (lower left). At the time of the picture, Mars was about 214 million miles away, and Saturn was 920 million miles away. Saturn looks much brighter because it is much bigger, and because its rings (lost in the planet's glare) reflect a lot of light.

Most of the stars belong to the Praesepe star cluster, a group of stars about 600 million years old and 580 light-years away (that is 3500 trillion miles, or sixteen million times further away than Mars! Too faint to see in this image are (at least) three quasars that I discovered in 2004. These giant black holes are over nine billion light years away, or 16 million times further than Praesepe!

On a clear night, you can see forever...

Wednesday, June 21, 2006

Happy summer solstice!

This morning, at 8:26am EDT, 5:26am PDT, or 12:26 Greenwich Mean Time, the sun reached its most northern part in the sky for the year, marking the summer solstice and the beginning of summer for the northern hemisphere. And our poor friends in the southern hemisphere are now looking at the start of winter. (They'll get their laughs in six months.)

This means it is also time for me to harp on one of the largest misconceptions in public astronomy knowledge -- the cause of the seasons. The cause of summer is not that the Earth is closer to the sun in the summer. In fact, the Earth is getting further away from the sun for the next few weeks yet, and reaches its closest point to the sun in January. The Earth's distance from the sun has nothing to do with the seasons!

The cause of summer is that, right now, the North Pole is tilted toward the sun, so the sunlight hits us more directly. The southern hemisphere is having winter because the South Pole is tilted away from the sun. Think about a nice cold day (a pleasant thought in this heat!). If it is sunny and you want to warm your face, you naturally tilt your head so the sun is shining directly on your face. Now that it is summer, you naturally tilt your face away from the sun and run for shade or air conditioning. It works the same for the Earth. When it is warm, we are tilted toward the sun, when it is cold, we are tilted away from the sun.

Another experiment -- Go out at lunchtime in the next few days and look at your shadow. If you are in the Northern Hemisphere, you notice your shadow is short, because the sun is nearly overhead. Now, this winter, look at your shadow again at noon, and you'll notice it is much larger. That's because the sun will no longer be overhead.

So, promise to remember -- the tilt of the Earth causes seasons. And I promise not to harp on this issue for another six months.

Tuesday, June 20, 2006

Not much to say

I know it would surprise my family, but I really am at a loss for words today. In the last 24 hours, I have read five nights worth of data off of DVDs, started a day-long program running, and looked for airplane tickets to England. Plus my computer decided to crash overnight, so I had to go into recovery mode.

Even astronomers have boring days!

Monday, June 19, 2006

It's quiet... too quiet

Here at the university we often joke that things go so much better once the students leave. This is partially true -- parking is easy to find, lunchtime lines are smaller, and since there are no classes to prepare for, many professors can devote most of their time to research.

But if pressed, I would admit that I doubt more work gets done. Due to the lack of classroom responsibilities in the summer, the summer months tend to be when most astronomical conferences are held. At the present, my supervisor and one office mate are at a month-long workshop in Aspen, Colorado, and my other office mate is meeting collaborators in Hawaii. A couple of weeks ago, the summer meeting of the American Astronomical Society was held in Calgary. I will be traveling to England in early August for a meeting dealing with white dwarfs (my research), and the triennial meeting of the International Astronomical Union will be held in Prague in mid-August. And this is just a small sampling of the meetings this summer.

So, due to these meetings, my office and the hallways are very quiet, almost eerily so. It is nice to have the office to myself, though!

Friday, June 16, 2006

Meteorites and lutefisk

One day my wife was talking with a doctor who inquired if she was part Norwegian due to her light-colored hair. When my wife answered, "yes," the doctor said he, too, had Norwegian blood in his veins, and he pulled out a book of Norwegian jokes, most of which involved lutefisk. Being good-natured, my wife laughed politely at each joke, even though she had no clue what lutefisk is (it's fish pickled in lye).

Anyway, make up your own joke about lutefisk and the Norwegian meteorite. According to this story from Sky and Telescope, a fireball (extrememly bright meteor) was seen in Norway early this month, and it evidently impacted the Earth, as seismic detectors recorded the hit as a small earthquake. Initial reports put the explosion at about 10 kilotons of TNT, or similar to the atomic bombs dropped on Japan. Revised data, though, show it was much smaller -- maybe only 100 tons. Still, that is a lot of energy!

Meteorites with this energy hit the Earth several times a year. Most hit in the ocean and are only detected as a bright heat signal by military satellites. Most of the rest of these meteorites hit ground far from civilization. So to have one hit near civilzation is a rare event.

No pieces of the meteorite have been found yet, as the area of the impact is heavily wooded. But if you happen to be in Norway and have a spare week or so, why not go meteor hunting? If you find the meteor, it could be worth your while.

Wednesday, June 14, 2006

Cool new Hubble picture

This weekend, while looking at the Astronomy Picture of the Day, I saw this picture of the galaxy NGC 5866, an edge-on spiral galaxy in the constellation Draco. (Click on the picture to get to the NASA site with larger images).

If you look at the large version of this picture, you can see some really neat things. First, if you look at the dark lane of dust crossing the galaxy, you can see thin tendrils of dust silhouetted against the starlight from the galaxy. You can also notice that the dust is very slightly askew compared to the edge-on disk of stars. And you can tell that the disk of stars is bluer than the rest of the galaxy, meaning that these stars are younger. Like in our Milky Way galaxy, stars in this galaxy are only formed in the thin disk. The outer halo of stars is much, much older, and no new stars are being made there. Finally, you can see many more distant galaxies (orangish in color, as the expansion of the Universe stretches the light from blue to red). Some of these can even be seen right through the light from the big galaxy!

Tuesday, June 13, 2006

Finishing my thesis

In December 2002, I finished my doctoral thesis. And now that it is June 2006, I am finally going to get around to publishing it.

While my dissertation was printed out on nice, expensive paper and is safely enshrined in the library at the University of California, Santa Cruz, it is difficult for other astronomers to access it. Since one of the main points of science is to disseminate what we learn, it is considered good form to publish papers based on your thesis in a professional journal.

These days, it is quite common for a student to publish papers before she finishes her thesis. In this case, the thesis is often just a collection of published papers stapled together. Well, okay, it is not actually stapled. Students still have to reformat their papers according to a fairly stringent (ridiculously so) set of rules, so published papers act more like chapters. And we still have to print it on 100% cotton heavy paper.

However, I did my dissertation the "traditional" way. And then I moved on to other projects before writing it up for a journal. In some sense I am glad to have procrastinated, though. I learned a lot more about my research subject in the past three years, and so I was able to make a few connections I might not otherwise have been able to make. But it is time to finish the paper. Today I finished a draft and sent it to my collaborators for their opinions. I hope they like it!

Monday, June 12, 2006

Miniature black holes

I was surprised to pick up Sunday's newspaper and read an article about miniature black holes that may be swimming through our solar system. I wasn't surprised by the idea, as I've heard various versions before, but I recognized one of the scientists' names. Charles Keeton is a collaborator of mine; we work on gravitational lensing together. This is where some source of gravity, like a galaxy, bends the light from a galaxy or quasar in the background.

Anyway, the idea is this. Many people have suggested that dark matter, which makes up 30% of the universe, could be miniature black holes formed during the Big Bang. The problem with this theory is that black holes actually radiate light and particles (this is the "Hawking Radiation" that Stephen Hawking determined). The smallest black holes would by now have radiated all of their mass away into space, and we should see these events as miniature nuclear explosions throughout space. We don't see such explosions. So, it seemed that this theory was dead.

Now we go from the bizarre to the realm of pure speculation. There is a currently-popular hypothesis called the "braneworld theory." The idea is that there are many more dimensions than the four we live in (three space dimensions, plus time). If the theory is true, then our Universe is just part of a larger "braneworld" existing in multiple dimensions, though we are stuck in our four. Are you lost yet? I sure am, so don't ask me to try and explain this further! :)

Keeton and his collaborator, Arlie Petters of Duke University, calculated that, in braneworld theory, black holes may survive much longer than Hawking radiation would suggest, and that the Universe might be full of black holes that have about 200 million metric tons of mass each (if I did my math right, this is about the mass of a cube of granite one quarter of a mile on a side, or the weight of a small hill), but are only about three millionths the size of an atom!

While these sound giant, these are really tiny black holes. They could pass through you and not do anything to you! This is because black holes are not cosmic vacuum cleaners -- they only can eat what they pull in by gravity. And the gravity of a small hill is pretty weak, or else we would all be pulled off of our feet anytime we walked past a mound of dirt. Just remember -- black holes are cool; they don't suck. And imagine trying to find something the size of an atom in the solar system!

Anyway, Keeton and Petters figured out that a new satellite about to be launched to look at giant cosmic explosions, the GLAST satellite, might be able to detect such black holes, if they even exist.

Personally, I remain unconvinced that these little black holes exist. But this is why astronomers keep physics theorists around -- they come up with many ideas, many of which are wrong, but some of which prove correct. And it would be really neat if a co-worker ends up predicting what would be a very exciting discovery -- miniature black holes!

Sunday, June 11, 2006

Slacker Astronomy

This weekend I learned of group of professional astronomers who put together the occasional podcast describing astronomy. I listened to a few back episodes and was duly impressed.

So, why not check out Slacker Astronomy and sign up for their podcast?

Tuesday, June 06, 2006


The hypothesis of Panspermia is that the Universe is full of the seeds of life, such as hardy bacteria, and that life forms on any hospitable planet where these bacteria land. Under this scenario, the origins of life can be pushed off to some distant planet, so we don't need to worry that the early Earth may have been inhospitable in the past. If true, this idea would also mean that we are closely related to any aliens in space.

Some of the proponents of panspermia claim that a constant "seeding" of the Earth by these alien bacteria and/or viruses could be responsible for the emergence of new diseases on Earth, such as HIV or bird flu.

Panspermia does have some severe problems that have yet to be tested. Space is a very, very harsh environment, and the distance between planets is further than our minds can comprehend. Can bacteria survive the millions or billions of years it takes to travel between planets? Can bacteria survive the impacts necessary to loft a chunk of rock into space? Can bacteria survive the fiery re-entry of a rock into a planet's atmosphere? And where did life originally come from?

I will admit that I am a doubter of Panspermia. Note that I do not claim that Panspermia is wrong, but I will claim that I think it to be wrong. This is a hallmark of science. Ideas can be proven to be wrong, but no proof has yet emerged for or against Panspermia. Time will tell.

Monday, June 05, 2006

Aliens? I doubt it...

This weekend, two news stories talked about aliens. One, involving the picture above, is more of a joke. Unless a duck both became carnivorous and swallows food larger than its mouth whole, this is just an illusion (and an excellent illustration of our human ability to see faces in just about everything).

This story, on the other hand, is not meant to be humorous. The story involves a mysterious red rain that fell over parts of India five years ago. One group testing the rain claims that the particles that made the rain red multiply (a sign of life) yet have no DNA. This could imply that the particles are extraterrestrial, in other words, aliens!

Now I seriously doubt this is true. Other labs are testing the result and finding evidence of DNA. Besides, there is life on Earth that does not have DNA (many viruses have only RNA), and there are replicating particles that are not alive and do not have DNA or RNA (prions).

Maybe tomorrow I will talk about the connection of this story with the hypothesis of "Panspermia"

Aliens? I doubt it...

This weekend, two news stories talked about aliens. One, involving the picture above, is more of a joke. Unless a duck both became carnivorous and swallows food larger than its mouth whole, this is just an illusion (and an excellent illustration of our human ability to see faces in just about everything).

This story, on the other hand, is not meant to be humorous. The story involves a mysterious red rain that fell over parts of India five years ago. One group testing the rain claims that the particles that made the rain red multiply (a sign of life) yet have no DNA. This could imply that the particles are extraterrestial, in other words, aliens!

Now I seriously doubt this is true. Other labs are testing the result and finding evidence of DNA. Besides, there is life on Earth that does not have DNA (many viruses have only RNA), and there are replicating particles that are not alive and do not have DNA or RNA (prions).

Maybe tomorrow I will talk about the connection of this story with the hypothesis of "Panspermia"

Thursday, June 01, 2006

Back to the telescope

I am back at Kitt Peak, west of Tucson, for a few nights of observing. It is kind of nice to get here. Due to the 7000-foot elevation, it is much cooler up here than in Tucson, where the temperatures are over 100 degrees Fahrenheit.

Observing in the summer is, in many ways, much nicer than observing in the winter. The nights are shorter, so it isn't as hard to stay up all night. For example, tonight it is fully dark for about 7 hours, while in December it can be dark for over 13 hours. That's quite a difference! In the winter, we wake up, make sure the telescope is ready for the night, eat dinner, start observing, and go to bed. In the summer, we wake up in the afternoon, play around for a while, go hiking, answer email, eat dinner, shoot some pool, have some coffee, and then go to work for a short night. Now THAT'S working! :)