Telescopes on the moon

Image Credit: NASA

We're going back to the moon. It may be 15 or 20 years until we get there, but NASA is headed that direction. Many people, including a lot of astronomers, are opposed to this new lunar exploration. It will be very expensive, and we aren't sure what the point of the exploration is.

A colleague of mine once argued that we astronomers should be pushing NASA to build a telescope on the moon once we return. His idea, a liquid-mirror telescope, is pictured above. Such a telescope would be quite expensive, and the science it could do may be able to be done more cheaply with orbiting telescopes. But the point was that NASA is much more likely to spend a lot of money on the moon, not on new space telescopes, and if astronomers want a piece of that money, the time to start lobbying is now. Otherwise, we could find ourselves out in the cold once lunar exploration ramps up.

It's sort of like a parent shopping at a high-end luxury store asking their thrifty teenager, "Hey, should we buy you this 2nd-generation iPhone for $500?" The teenager responds, "But we can go to the Apple Store and buy the new iPhone 3G, which is more functional and less then half the price!" To which the parent responds, "You're getting this phone or you're getting nothing." What should the kid do? I think most of us would be tempted to take the phone.

Today, Space.com posted an article on a new design for a lunar telescope that has been proposed. This telescope could be built from materials on the moon. I have no doubt that the cost would be very high and the design technologically challenging to build (as would be the liquid-mirror telescope my colleague proposed). I know very little about the new proposal, such as what wavelengths of light it would be best suited for, or what instruments would go on it, or what scientific question(s) it would address. And, no doubt, NASA would make sure it is a very nice telescope, in terms of these capabilities.

But I wonder if we astronomers need to start thinking much harder about this. Do we want to push for a telescope on the moon? If there is a trade-off between a lunar telescope and a more functional, less-expensive space-based telescope, then let's by all means choose the latter. But I do think it is likely that we might be given the choice of a big lunar telescope, or no big telescope at all. And if we wait 15 years to make up our minds, it will be too late. Who knows what the astronauts will be doing on the moon science-wise, but it certainly won't be astronomy. And we'll have missed out.

There is good astronomy that can be done on the moon. One of the most convincing ideas I've heard is to put a radio telescope on the far side of the moon; the moon will block out radio signals from Earth, allowing us to study signals from space that are currently swamped by our FM radios, our iPhones, our satellite TV, and most every other modern bit of wireless communication. Some types of astronomy, like optical astronomy and, perhaps, infrared astronomy, are better done in orbit so that we don't have to worry about astronaut dust and other activity upsetting the instruments. But both of these fields would not suffer from a lunar telescope.

Astronomers are beginning to assemble our "decadal survey," a 10-year look into the future needs and desires of astronomy. This survey is cited in our funding requests to Congress and NASA. Maybe this time around we should debate the various possibilities of lunar telescopes. If we wait until 2020 to ask, it may be too late.

Wildfire near McDonald Observatory

We've just heard that there is a grass fire that has consumed 20,000 acres about 15 miles away from McDonald Observatory. I haven't heard if the observatory is threatened or not, but I suspect I would hear if they were worried.

However, there is a lot of very dry grass and tinder around the area, because it rained a lot last year, but has been very dry ever since. The telescopes worked last night, so the smoke can't be too bad. (Smoke is very bad for telescope mirrors, because it contains corrosive chemicals. So we close up tight when smoke is around.)

I'll write more if I hear more. In the meantime, here is a news story about the fires.

Proposing to use Hubble

Today, optical and ultraviolet astronomers around the world are scrambling to finish proposals for the Hubble Space Telescope. Tonight, at 8pm Eastern Time, proposals are due for the Hubble's 17th Cycle (each cycle is roughly a year) of operation.

This time around, there are two new instruments that astronomers hope to use, if the Space Shuttle's servicing mission works as planned. One is a spectrograph for analyzing ultraviolet light, that high-energy light that can be harmful to humans, but which contains a wealth of information about stars and distant galaxies. This spectrograph is called the "Cosmic Origins Spectrograph," because it will be useful for interpreting light from the earliest galaxies. More to the point, the light that we detect on Earth from the earliest galaxies is ultraviolet light that the expansion of the Universe has stretched into visible and optical light. So the Hubble's spectrograph will be used to explore more nearby galaxies (where we think we understand what is going on), and that information used to interpret the light from more distant galaxies.

Another new instrument will be a new imaging camera, more sensitive than the current one on Hubble. Like other cameras, this one will be able to take pictures in ultraviolet and visible light for studies of just about anything.

So, although these cameras are still on Earth, waiting to be launched by the space shuttle, we are starting preparations to use the cameras. It takes months for people to sort through the hundreds of proposed projects, select the very best ones (and some back-up plans in case one of the instruments fails or repairs don't work), and plan out an observing schedule. By the time that is done, we hope that the space shuttle will have safely traveled to Hubble and gotten back in tip-top shape.

Still, it is a little nerve-wracking to write proposals for broken cameras that we hope to fix, but may not get fixed, or for cameras that are not yet there and may not function exactly as advertised. And, since each proposal takes a lot of time if you want to do it properly, we hope that we are not wasting that time.

Looking for proper motions

Image Credit: Sebastien Lepine/SUPERBLINK

Yesterday I mentioned that I am here at Kitt Peak outside of Tucson, Arizona, working on a project to image a large fraction of the sky.  So, why are my collaborators and I trying to image 1/4 of the entire sky visible from Kitt Peak?

The part of the sky we were looking at was imaged between 1999 and 2005 as part of the Sloan Digital Sky Survey, which mapped a large fraction of the Northern Hemisphere sky in five colors.  So, at first glance it may sound silly that we are getting new images of part of the sky that was just mapped within the last decade.

While the stars in the sky appear to be fixed, with constellations staying the same from year to year, generation to generation, and even millennium to millennium, all stars are slowly moving around the Milky Way galaxy.  It takes stars like the sun 250 million years to orbit the Milky Way, so in a human lifetime, we don't cover much of that orbit!  

But, with precise measurements, it is possible to see that the stars are slowly moving in the sky.  If you brought an ancient Greek to modern times, he or she would notice that a few bright stars have moved noticeably in 2300 years.  But with more accurate measurements, we can use ground-based telescopes to measure changes in position as small as about one hundred thousandth of a degree, or about the size of a bacteria seen from 30 feet away.  These star motions are called proper motions.  

The closer a star is to us, the larger its proper motion, on average.  Some nearby stars can move quite a bit, as in the picture above, which shows one red dwarf star moving a large distance (still only the tiniest fraction of a degree!) 45 years, while the other stars appear to stay still.  This particular star is only about 35 light-years away from the sun, while the other stars in the image are probably hundreds of light-years away.

We are looking for the faintest white dwarfs, the remains of dead stars that are slowly cooling off and fading away.  The faintest white dwarfs we can find are therefore some of the oldest stars in our Galaxy, and we hope to use these white dwarfs to tell us how old various parts of the galaxy are. (If we know how faint they are and how fast these stars fade, we can estimate how old they are).  Like the red dwarf in the picture above, faint white dwarfs tend to have relatively large proper motions.  So, although only five years have passed since the first images were taken, the stars have moved enough that we can measure the movement. 

If we showed you most of the stars that have measured motions, you probably wouldn't believe it.  The motions are very tiny, smaller than the spot size of the star.  But my collaborators can still measure a slight shift in the center of that spot!

So, that's why we're here -- searching 1/4 of the visible sky for maybe a fifty or a hundred of the oldest stars in our galaxy, out of millions of stars we'll be imaging.  Hard? Yes!  But the science result will be worth the work.

"You may wish to consider closing the dome."

Today was my class's fourth night at McDonald Observatory. Most of the students are now on a night schedule, so they barely woke up in time for our 4pm field trip to see the Hobby-Eberly Telescope, the largest telescope in the continental United States. After that field trip, Casey Deen (pictured above) mugged for a few pictures as we prepared the telescopes for the night.

Our night started well, though we did see thunderstorms on the distant horizon. About 1 in the morning, we stopped due to clouds, but we kept the telescope pointed at the sky in case the clouds blew over. After 20 minutes or so, the telephone rang. Professor David Lambert, Director of the McDonald Observatory, was calling from a neighboring telescope. Professor Lambert very calmly and politely said, "You may wish to consider closing the dome." So, I sent the students to close the dome just as the skies opened and it began to rain. And then we all had a good laugh about the very cordial tone of Professor Lambert in the face of impending disaster.

It continued to storm and rain all night, and at 4am, after several games of Scrabble, we called it a night. And so here I sit, writing and trying to stay up just a little longer and keep on the night schedule. So now you know what astronomers do when it rains -- wait up as late as possible to see if it is going to clear off. And, if not, we stay up later just to stay on our schedule.

Doing the tourist thing

As I mentioned yesterday, I have my summer observing class at McDonald Observatory in west Texas for the next week. Since many of the students have not been here before, I am taking the students around to many of the telescopes here at the observatory. Today we visited the 2.7-meter telescope, where astronomer Gary Hill took time to show off his baby, a spectrograph called VIRUS-p.

VIRUS-p is an instrument that is a prototype for a new camera being designed for the Hobby-Eberly Telescope. This camera will take spectroscopic images of over a million galaxies in just a few years of operation, and allow astronomers to map out the universe and, hopefully, understand a little bit about "Dark Energy," the mysterious force that is causing the Universe to expand at ever-increasing speeds.

In order to get information on millions of galaxies in a short amount of time, lots of new technology is being used, so we want to test it before spending 35 million dollars on an unproven concept. And VIRUS-p is working extraordinarily well.

Today we also survived several thunderstorms with a lot of lightning. It's always a little scary to be on top of a mountain during a thunderstorm. Lightning likes to hit the tallest thing around, and when we are in a large metal building on top of a mountain, we're that tallest object! But the thunderstorms passed, and now it is a very clear night for the students to gather data.

Road trip!

Yesterday, I drove eight hours from Austin to McDonald Observatory, located in western Texas near the town of Fort Davis. My reason for coming out here is to bring the graduate student class I am teaching to the observatory for a week of time on the telescopes. The class is on their way out today, but I came out last night so that I could learn to use a new camera on one of the telescopes before I try and show the students how to use it.

This should be a lot of fun. I'll have my hands full the first couple of nights, but hopefully after that the students will know how to use each telescope, and will be able to take their own data. Then I'll be able to step back from teaching and just supervise.

Over the coming days, I'll take some pictures to share; hopefully one of them won't be a tangled mass of metal that used to be a telescope.

Is all the romance gone from astronomy?

In this article from CNN, astronomer and planet-hunter Geoff Marcy, nearing the end of a night on the Keck Observatory, laments:

"There are no eyepieces anywhere. In fact, we don't have an eyepiece for the Keck telescope. Some of the romance of astronomy is gone."

Is this true? Is technology removing the "romance" from astronomy?

Most people have the picture of the astronomer as a lone man on a mountain top, looking night after night through an eyepiece on the back of a giant telescope, somehow making measurements of other worlds and other galaxies. There was a time when this was true, but over the past 75 years, astronomy has been transformed by technology. Believe it or not, it was the phtographic plate, invented in the late 1800s, and not computers or digital cameras, that "doomed" the romantic view of astronomy. For, with a photographic plate, astronomers could see fainter than ever before and could take information home to study over long periods of time. By taking information home, more accurate measurements could be made, and more careful analysis performed. Suddenly, an astronomer didn't need months of time to gather all the information he wanted; he could gather a lot of information in a few nights and work on it for months to come.

With computers and digital technology, the science of astronomy has changed even more. Some astronomers don't go to the telescope at all -- some telescopes will take data for the scientist and send it over the internet. There are good points and bad points to this method of observing. I find the quality of my science data isn't as reliable when somebody else takes it, but for some telescopes, like the Hubble Space Telescope, there is no choice!

Modern technology has also opened up new fields that were impossible before. Planets around other stars, Geoff Marcy's main point of study, can only be detected with modern instruments. Yet now, as we find a wide variety of planets around all sorts of stars, our imaginations can run wild with ideas of what we may find. The Hubble Space Telescope has taken amazing pictures of everything from nearby stars and nebulae to the most distant galaxies in the Universe. Due to modern technology, we have discovered black holes a billion times more massive than the sun and watched stars exploding halfway across the Universe.

So, if you consider the "romance" of astronomy to be a lone man on a mountain top struggling to comprehend the Universe, then that romance is lost. But if you, like I, consider the romance of astronomy to be the exotic nature of the Universe around us, then modern technology only serves to open entire new worlds to the power of the human mind and imagination. (Note also that, due to positive changes in society, astronomers are no longer just males; an ever-increasing number of women are contributing to every aspect of the science.)

A News Note: This week, astronomers from around the country have congregated in Honolulu for the summer meeting of the American Astronomical Society. I am not there due to teaching commitments, but you will probably see lots of astronomy news in the coming days as new results are announced!

Will Astronauts visit Hubble's replacement?

If next fall's visit by astronauts is successful, the Hubble Space Telescope will be with us for at least another five years. But plans are already in place to launch NASA's next large space telescope, the James Webb Space Telescope, in 2013 (although I'd be surprised to see it launched that year).

Although the Hubble has been well-served by four (and soon a fifth) servicing missions by astronauts, we've always assumed that JWST would not be able to be visited by astronauts. Hubble is in low Earth orbit (just a few hundred miles up), where the Space Shuttle can easily fly. But the JWST is going to be at the second Lagrange point, a spot about 1 million miles away from the Earth where the Earth and the Sun's gravity balance perfectly. The main reason for this distance is to get the telescope, which will look at infrared light, far from the heat of Earth. But none of our current rockets can carry humans to this Lagrange point, so it seems that repair of the telescope is out.

So I was surprised today when NASA announced that it was going to add a docking port to JWST in case future astronauts ever visit the spacecraft. Their reasoning is that if this expensive telescope fails to work, their new Orion rockets might be able to take astronauts to the Lagrange point to try and salvage the telescope.

If astronauts were to go to the JWST, it would mark the furthest humans had ever ventured away from the Earth -- it is nearly four times further from the Earth than the moon. It would also be a very risky and very expensive mission. Would it be worth the trouble? I don't know. Certainly astronauts would probably like to try if the chance of success seemed reasonable, and I don't doubt their ability to fix the spacecraft.

But adding a docking ring adds weight and complexity to the telescope, two things that are not always desirable. I am not a space engineer, so I really do not know how much the docking ring affects the spacecraft. But it could also mean that some science may need to be scaled back to reduce the weight of the telescope. Again, this is just my guess, I don't know.

So, I have mixed feelings about the announcement. In some ways, I am glad NASA is thinking ahead and allowing for new possibilities we hadn't previously dreamed of. But I have reservations, and until I know more about the plans, I'll remain skeptical.

Looking through Hubble

Friday was a day that many observational astronomers dread. It was the day that the time allocations on the Hubble Space Telescope were announced. Some of you may remember my writing about this proposal back in January. I submitted a proposal, and 12 hours later, Hubble's camera that I had asked to use quit working. Because so much of the time astronomers asked for used this camera, and because the deadline had just passed, NASA extended the deadline for a couple of weeks.

Two weeks ago, while I was learning about exploding white dwarfs, dozens of astronomers met in Washington, DC to choose which of the proposals would get time on the Hubble telescope. It was a tough job, as astronomers asked for over five times more time than was available. And this was after some large programs were knocked out because they required the now-defunct camera!

When so much time is requested, it is inevitable that perfectly good requests are denied. So, I felt absolutely ecstatic when I learned that I was granted Hubble time. For the first time ever. And I was worried that I was asking for a lot of time, which can hurt a proposal.

It may be 15 months before my images are taken, and I have to keep my fingers crossed that nothing else breaks before I get my data. On the good side, at the end of the next 15 months, astronauts should be up fixing the Hubble one last time.

Curses! Foiled again.

If you remember from a the few posts ago, I spent much of the past 2 weeks writing proposals to use the Hubble Space Telescope. So, you can imagine the foul mood I was in yesterday when NASA announced that Hubble's main camera quit working Saturday morning, only 11 hours and 26 minutes after the deadline on proposals. And, of course, this is the camera I was proposing to use in my work.

The camera is almost fully dead due to problems with the electronics. It may (or may not) be possible to fix it when astronauts come to repair the Hubble in about 18 months, but they have a long list of things to do already, and the astronauts will be installing a camera that is almost as good as the dead camera in some respects, and better than the dead camera in other respects.

The camera that died, the Advanced Camera for Surveys (ACS), was truly the workhorse instrument of Hubble. At the end of the day on Friday, there were 747 proposals to use the Hubble over the next year; 498 of those were to use ACS.

NASA has decided to re-open the system to proposals in order to try and fill the gap left by the loss of ACS. I might be able to change my proposal to use another, older camera that isn't as powerful as ACS. It has a smaller field of view, and is much less efficient at detecting light. But, given the choice between that and none, I'll take the older camera.

Proposing to use telescopes

Whew! I have worked harder this week than for a long time, all trying to get some different proposals to use the Hubble Space Telescope done. I sent one in a few minutes ago, and other collaborators at other institutions are putting finishing touches on others, so I can finally relax.

Many of you probably are wondering, "What the heck is this proposal he's talking about, anyway?" So let me explain.

The vast majority of professional astronomers do not work in front of a telescope. We spend most of our time in an office in front of a computer to do our work. Professional astronomers share all of our large telescopes with other astronomers at our institutions, at other schools, and around the world. So if I learn of a neat object I want to study, I can't just jump in my car, drive to the mountain top, open up the dome and start looking. Somebody else is probably already using the telescope, and they won't be too happy if I force my way in to the dome and try to take over for the night.

In order to get the telescope, I must start by writing a proposal. A proposal has two jobs. First, I have to show that the science I want to do is interesting. If I say I want to see what phase the moon is, people will say that is boring and stupid, and they won't waste time on my project. But if I say I want to look for new moons around Pluto because any such moons would help to tell us how Pluto formed, then people might start to think it was interesting.

Second, I have to prove that my project is suited to the telescope I am asking to use. If I try to take a picture of Venus with the Keck 10-meter-wide telescope in Hawaii, there will be so much light I will hurt the cameras, which will make a lot of people mad. Likewise, if I say I want to take a detailed look at super faint galaxies with a tiny telescope, I won't get anything useful, because small telescopes can't see really faint things.

So, observatories ask for proposals to use their telescopes one to four times a year. A group will then get together to evaluate the proposals. Is the science worthwhile? Is the telescope the right one for the job? If so, they'll put me in a schedule to use the telescope. If not, then they'll say "sorry, better luck next time," and I won't get to use the telescope.

As you can guess, being able to write a good proposal is an important skill for astronomers. I've spent several days (most of the last week and many partial days over the past month) working on my proposals to use the Hubble Space Telescope. But my proposal only has about 5 pages of text, plus a couple of graphs. They won't take anything longer, or else the committee that assigns time will have to sift through tens of thousands of pages, as there are often more than 1000 proposals to use the Hubble! That's a lot of reading.

For fun, I'm putting a PDF version an old proposal from 2004. The project got time on the Keck Telescope that fall. You can try and read it if you want, though I will warn you it is technical and quite boring. And you will find a few grammatical mistakes, typos, and stylistic problems. It's amazing how much of that can sneak through even though you've been staring at the same 5 pages for days.

And to those who have sent me emails in the last month, I will get around to answering them now that I am both home and finished with deadlines. I'm sorry it is taking so long.