Thursday, July 30, 2009

Pobody's Nerfect: Errors in an Age of Open Source Data

There's a saying in astronomy that you've never really reduced your data until you've reduced at least 3 (or 4 or 5) times. Data reduction is a fairly tedious task that takes astronomy images from the raw digital files obtained at a telescope and turns them into calibrated, quantifiable (number-based) results. It's absolutely crucial, but it is a pain. When we get to the end, we often find some unexpected feature in the data that makes us go back and re-examine every step of the reduction. And then we do it again to make sure we get the same answer again.

This process can be relatively fast, if we used the telescope in a fairly standard way and the instrument is well-understood, or it can take a long time if we were pushing the telescope or using a new instrument. Even then, problems crop up. I had to throw out one entire night's worth of beautiful-looking from the Lick Observatory because there was an odd instrumental problem that I couldn't solve (stars that were known to be twice as bright as other stars did not have twice as many detected photons), and the problem seemed to come and go through the night. Rather than risk making claims based on those data, I had to start over. Of course, I didn't discover the problem until months later when I was trying to interpret results, so I had to wait an entire year for the Earth to swing back to the proper side of the sun for viewing those stars.

So, it is well-established among scientists that raw data and normally-reduced data often have errors, sometimes serious and hidden ones. The scientific process seeks to identify and correct those errors, preferably sooner rather than later, but sometimes we even have to change results once we've published them. After all, we want to be right when we are probing the secrets of the Universe. Nobody wants to be remembered as the one who claimed to see irrigation canals on Mars ("Yeah, he founded a world-class observatory and started the program that discovered Pluto, but he saw canals on Mars"); we would rather our name be thrown in with the people like Hubble and Zwicky and Schmidt, whose then-radical conclusions based on careful analysis of observations were proven correct.

With the ascendancy of the Internet, many science programs (especially NASA programs) now publish their images and data online as soon as the pictures come in. Satellite weather maps have been transmitted live for years, and I remember watching live on CNN as Voyager 2's pictures from Uranus (I think, maybe it was Neptune) were sent back to Earth. But recently more and more space missions are dumping data directly to the Internet. The Mars Exploration Rovers Spirit and Opportunity are perhaps the most well-known, but NASA's flotilla of Earth-watching satellites such as the MODIS Aqua and Terra satellites post images of the Earth updated after every data dump (and, if you have a satellite receiver, you can even tune in and capture the data yourself in real time!).

These nearly-live data streams are quickly processed, but errors do happen. When they are noticed, the errors are corrected as quickly as possible, but sometimes this takes a while. For example, many of the Mars images you will see are partial because the data stream was interrupted; these images will be re-sent by the rover during the next data relay, but that can be a day or two away. For other missions, the time to correct data can be even longer -- it depends on how fast the problem is noted, how easy it is to correct, and how busy the scientists dealing with the data are. Sometimes the data corrections are minor, and sometimes the adjustments are major.

Again, we scientists are cool with this. We assume all results are preliminary and subject to change, though we hope it is correct by the time it is published in a peer-review journal (often years later).

In August's issue of Scientific American, an article points out a problem with this open access to data. In at least three recorded instances (I'm sure there are more!), data measuring Earth's climate was incorrectly reduced and analyzed. In these cases, the errors resulted in a slightly warmer climate than in reality, and in one case saw the "disappearance" of millions of square kilometers of sea ice overnight. When these errors were recognized, they were corrected. My reaction as a scientist is, "I'm glad they caught and fixed the errors."

But as these data were openly available to everyone, many lay people watching these data on the Internet saw these mistakes as, at best, incompetence, and at worst, evidence of a conspiracy to inflate the effects of global warming.

It's unfortunate that such public errors happened in a very politically-charged subject, but I don't believe that the scientists are incompetent nor that there is a conspiracy to cook the data. Rather, I think the public is seeing the truth behind how observational science, whether astronomy, climatology, geology, or any other such science works.

Scientific observation is not a nice and clean process where every data point is sacrosanct and set in stone as soon as it comes out of an instrument. It's a drawn out process of analysis, interpretation, re-analysis, and re-interpretation. Sometimes we learn that our calibration was wrong. Sometimes we learn that our instrument was broken right when the most exciting part of an event was going on. Sometimes we find out months later that, although we thought we had great information, it's really unsalvageable garbage. The hardest part of data reduction is coming out confident that we haven't made a mistake, and that's why we are forgiving (to a reasonable extent) when changes are made to data.

Our problem is that, as we do science out in the open (which I think is generally a good thing), the public gets to see the uglier parts of the process. Much, if not a vast majority, of the public is unaware of how complicated the process really is. That ignorance makes the public susceptible to people who come along and say, "Look, the number changed! Either they were lying before, they are lying now, or they are incompetent buffoons." This is a false choice, and this casts an unwarranted shadow over otherwise good science.

So, should science be done out in the open? Almost certainly! But perhaps the open source paradigm of instantaneous access of all people to all data is not the best model. I find the idea very appealing, but if such access is going to harm the scientific process, then I think we had better continue to discuss the issue and not be afraid to refine the idea.

Monday, July 27, 2009

Whats in a name

Galaxy Zoos so-called Green Pea galaxies


Image Credit: Galaxy Zoo / SDSS

Today, on both the arXiv astro-ph preprint server (where many astronomers post papers accepted for publication in our professional journals) and at Universe Today, articles announced the discovery of "Green Pea" galaxies by researchers analyzing results from the citizen science project Galaxy Zoo. These galaxies are a type of small, compact galaxy rapidly forming stars. They are green in color because of light emission from oxygen, which is very common in star-forming regions. (Many of the Hubble pictures of star-forming clouds in our galaxy have this same greenish glow.) It's a neat discovery; read the Universe Today article or the Galaxy Zoo blog post on these objects.

Alas, I think the name "Green Pea" is too cute to last. Original names for types of astronomical objects do not have a good track record. For example, a type of faint blue galaxy was once called boojums, short for "blue objects observed just undergoing moderate starburst" and based on a creature from the Lewis Carroll poem The Hunting of the Snark. That moniker failed to catch on.

No, we astronomers tend to give things much more boring, though perhaps more scientifically descriptive, names. Spiral galaxies are galaxies that look like spirals. Elliptical galaxies are, well, elliptical. "E+A" galaxies are galaxies that look elliptical ("E") but have spectra indicating the presence of stars of spectral class "A" (which are normally absent in elliptical galaxies). Even slightly fanciful sounding names like "planetary nebulae" just mean nebulae (gas clouds) that look kind of like planets in small telescopes. The more imaginative term "Big Bang" was coined by British astronomer Sir Fred Hoyle on a BBC radio show in 1949; some people claim this was to disparage a theory Hoyle didn't believe, although Hoyle claimed he was just being descriptive. But even this rare piece of originality has detractors; in the comic strip Calvin and Hobbes, Calvin wants to rename the Big Bang the "Horrendous Space Kablooey." (Some astronomers have tried to latch on to this term, but the "Big Bang" is sticking.)

In astronomy, originality in names just isn't appreciated nor adopted. William Herschel wanted to name the planet he discovered Georgium Sidus ("George's Star") after King George III, but the planet eventually became known as Uranus, named after the mythical father of Saturn, who was the father of Jupiter. Of course, that name doesn't permit any schoolchildren to take the planet seriously, so maybe we should have stuck with Herschel's idea.

While the names of specific objects (like planets and stars and galaxies) have to be approved by the International Astronomical Union, names of types of objects do not. The names that get accepted over time tend to be names that are fairly conservative, perhaps because we unconsciously feel that the primary point of the name is to convey a clear picture of the object in question, especially to people who work in different parts of the field. If we stand up in front of a group of astronomers who we don't know and say, "I'm going to talk about Green Pea galaxies," 90% of them won't have any clue what you are talking about, and many of those therefore won't take you seriously. But if you stand up and say, "I'm going to talk about star-forming ultra-compact dwarf galaxies," even astronomers who don't work on galaxies will be able to guess what you are talking about. I'm not saying that this cultural phenomenon is right or fair (see chapter IV of "The Little Prince"); it's the way things are and probably will remain.

So, I fear that Green Pea galaxies are likely doomed to get a boring name like "compact extremely star-forming galaxies" (the subtitle to the green pea paper). More likely, I suspect they'll be known as star-forming ultra-compact dwarf galaxies, since "ultra-compact dwarfs" are an already-accepted type of galaxy (guess what -- ultra-compact dwarf galaxies are small, very compact galaxies), and the Green Peas seem to be related to the UCDs in many ways. This is too bad, as it would be cool to create a computer animation of the in-spiral and merger of two Green Pea galaxies; the paper could be called "Visualizing Whirled Peas".

Friday, July 24, 2009

New Pictures from Repaired Hubble!

Hubble Space Telescope image of the impact scar on Jupiter
Image Credit: NASA, ESA, and H. Hammel (Space Science Institute, Boulder, Colo.), and the Jupiter Impact Team

Hubble took time out of its recovery from the repair mission to take pictures of the scar on Jupiter from the giant planet's recent collision with a comet or asteroid. The images were taken by the brand new Wide Field 3 camera and were just released. Hubble now will return to its verification and check-out phase (probably snapping occasional images of Jupiter now and then) as it prepares to return to full-time science.

Thursday, July 23, 2009

When it absolutely, positively has to be observed overnight

Impact scar on Jupiter
Image source and credit: Anthony Wesley / Image originally hosted on jupiter.samba.org

Last weekend, Australian amateur astronomer Anthony Wesley snapped pictures of a dark spot on the face of Jupiter, which turned out to be the scar of the impact of an unknown asteroid or comet into the planet. This conclusion came after rapid follow-up of Wesley's discovery by professional astronomy telescopes around the planet.

Getting professional telescopes to follow up an event like this is no easy task. Telescopes are scheduled six months or more in advance, and an astronomer who has waited six months for a night or two at the telescope is not going to always willingly turn the telescope and look at something that other people think is cool, but is outside the astronomer's research area. But data on unexpected short-lived events, such as unexpected whackings of Jupiter, or supernovae or gamma-ray bursts are obtained. The story of how is a bit illuminating of the many forces that go into scheduling telescope time.

As I blogged last week, telescopes are primarily scheduled in one of two methods: classical observing, where the astronomer has a block of nights at the telescope and has to travel to the telescope to take the observations, and queue observing, where all of the approved programs are ranked and a staff scientist takes data depending on which objects are up, which instrument is available, what the weather is like, and which project meeting these criteria is most highly ranked.

As you might be able to guess, it is often easier to get data on an unexpected event on a queue scheduled telescope than on a classically-scheduled telescope. In the case of the recent impact on Jupiter, teams interested in getting observations can call the head of the observatory and ask for what is often called director's discretionary time. The director of the observatory can then call the staff astronomers and say, "When Jupiter rises more than 30 degrees above the horizon, take the following observations for Astronomers X, Y and Z." And that trumps whatever the queue says to do.

There are two major complications. First, if a really neat event (like the Jupiter impact, or like a supernova in the Milky Way galaxy) happens, more than one group will call the director and ask for observations. Then the director has to choose which group will get the data (or perhaps she'll decide to let each group get all of the data, and require them to work together, or decide to divvy up certain observations). This is hard to do, and often must be done with only a few hours to make a choice.

Second, time-critical events like gamma ray bursts and supernovae are discovered somewhere in the sky every few days. While it isn't possible to predict where a supernova or gamma-ray burst will happen, we can predict that some will happen. In these cases, the astronomers are often required to propose observations in the normal six-month cycle, saying something like "I want to observe six supernovae to be named later, getting a spectrum 1 day, 5 days, 10 days, and 30 days after the explosion." If such a project is approved, when a supernova is discovered, the astronomer uploads the coordinates to the queue-scheduling computer, which then gives the observations highest priority the next night that the weather is clear. This process keeps an observatory director from getting several phone calls a day from ten groups asking for observations of a gamma-ray burst just discovered. It also forces the astronomer to think about which supernovae or gamma-ray burst to observe. If the astronomer has approval for six supernovae, and uses that on the first six supernovae discovered in a semester, he'll miss out later in the semester when that once-in-a-lifetime supernova happens in the Andromeda Galaxy.

On classically-scheduled telescopes, it is often trickier to get time-critical observations. If something really important has happened, the astronomer at the telescope can often choose to look at the object herself and collect and use the data. Often the observer will also get emails from colleagues begging for some quick data on an interesting event, and it then is the observer's prerogative whether or not she gets data for her colleague. For cases like this, there is often a you-scratch-my-back-I'll-scratch-yours mentality. If I get data for you, and a year later I ask you for data and you don't make any effort to take it, fat chance at me ever taking more data for you.

The director can also preempt the observing astronomer and force observations to be taken of interesting events. This is pretty rare, because it ruffles a lot of feathers and causes nightmarish headaches and inquiries for the director. The event had better be pretty darn important for this to happen, like a supernova in our own galaxy.

Many classically-scheduled observatories also have some version of Director's Discretionary Time. At national observatories like Kitt Peak, projects can be awarded time for transient events, and the observing astronomer can be required to take up to one hour of the night to take such observations. That happened to me once, and it really upset me. I'd travelled to Chile and sat through three nights of winter storms and clouds. On my fourth and final night, the sky was clear and steady, and I prepared to take as much data as quickly as I could. Then my phone rang, and one observer who had a project for gamma ray bursts pulled the trigger on their discretionary time. So I was required to do their observations for one hour of my only clear night. Not only that, but they'd made a poor choice of gamma ray burst -- if they'd consulted a star chart, they'd have seen that the burst was happening almost directly behind the center of the Milky Way, and so it was hidden by thousands of light years of dust, and we saw absolutely nothing. But since it was an approved program, I got no compensation for the lost time. That still makes my blood boil.

In general, though, most astronomers are very good about only asking for discretionary time when it is really important and really useful. And most classical observers will take a half hour or so to go and get important, time-sensitive data for a colleague, especially if the colleague has a good reputation and pays back the favor.

In short, getting data on a time-sensitive astronomical event is difficult to arrange and requires dabbling in politics and interpersonal relationships as well as simply science. So, when you see pictures of a new supernova or an impact on Jupiter, remember that a lot more effort went into getting that image then just pointing the telescope and clicking the shutter. In my opinion, getting large volumes of data quickly is almost as impressive as the events themselves.

Wednesday, July 22, 2009

What good is astronomy research?

One of the most common questions we astronomers are asked about our research is, "What good is it?" What will we learn from our research that will impact those of us here on the Earth? How can studying black holes help to cure cancer or reduce poverty? These questions are, in some sense, trick questions. The questioner thinks they know the answer, which makes constructing a cogent answer all the harder.

The truth is that "pure" research rarely has an immediate return. But even the most esoteric research can pay off in ways that the researchers could never have imagined. During last weekend's Board of Visitors meeting at McDonald Observatory, Development Officer Joel Barna talked about a few of these unexpected payoffs.

Perhaps the most profound, in my opinion, is that of electricity. Humans had studied electricity for thousands of years, but it wasn't until the 18th and 19th centuries that the studies of electricity became quite intense. Electrical researchers such as Franklin, Faraday, Volta, Ohm, and many other familiar names worked on electrical theory and experiments, culminating in Maxwell's Equations, four equations that describe the properties of electricity and magnetism that are still used today. These equations were settled in their current form in 1873.

Along the way to the production of Maxwell's Equations, batteries, electrical circuits, and even electrical motors were invented, but these found little practical use. Electricity was an esoteric, albeit fertile, area of physics research, but it had almost no impact on the average human until the 1850s, when Samuel Morse perfected an invention known as the telegraph, which allowed information to be sent over wires. Within 10 years, telegraph wires criss-crossed the continent. In 1876, Alexander Graham Bell received a patent for a telephone. A few years later, Edison invented the light bulb. The rest, as they say, is history. For nearly two hundred years, the science of electricity had been highly esoteric, and over a short two decades it made the leap to the most practical of physical sciences.

Another example involves Albert Einstein. His General Theory of Relativity remains one of the most enigmatic and obscure physical theories, with only a handful of people who seem to be able to grasp its full import. Tests of General Relativity still win Nobel Prizes. One test of General Relativity in 1977 involved the launch of a satellite called Navigation Technology Satellite 2, which was a forerunner of the modern Global Positioning Satellite system. This satellite had an atomic (cesium) clock that was observed to record a slightly different time than an Earth-bound clock, proving general relativity's predictions for the change of time in a gravitational field. The test also showed that general relativity had to be taken into account in navigational systems like the GPS. Without it, after one day positional errors would be as large as two kilometers! So, though Einstein never worked on satellite navigation, without his research into general relativity, our modern GPS systems would not function.

A last example Barna gave involved the research into quantum mechanics by Paul Dirac in 1928. Dirac's equations predicted the existence of a particle with the mass of an electron but with the opposite charge, what we now call a positron. In fact, Dirac's equations show that every particle has an "opposite" particle, what we now call antimatter. Although science fiction has made plenty of use of antimatter, it appeared to have little practical use at first. But, in the 1950s, several groups of scientists learned how to create and use positrons for medical imaging. Positron Emission Tomography (or PET scans) are now used quite commonly for diagnosing cancers and studying brain functions. I suspect that none of the quantum physicists of the 1920s and 1930s considered any such application of their work.

The point is that research, like astronomy research, doesn't always pay off right away. It can be decades, even generations, before applications of what seems to be "pure" research can be found. And those applications are often vastly different from what the original scientists could ever have imagined. Do you think that Volta ever thought that his pile of zinc and copper disks separated by brine-soaked strips of cloth would eventually lead to the modern batteries that allow humans to speak to each other over thousands of miles via wireless cellphones? Or Isaac Newton imagining how his work on optics could lead to modern semiconductor lithography?

I cannot promise that my work on white dwarfs will ever lead to a stunning advance in food production, or to a new source of green energy. But after 200 years of brewing, who can say what today's astronomy research may lead to? So, before you lambast your friendly neighborhood astronomer for not being able to solve all the world's ills, consider where we as a species may be a few centuries down the road, and consider if astronomical science may have any bearing on that future. I cannot predict which of today's discoveries will impact that future, but I'm willing to bet that some astronomer's work will.

Tuesday, July 21, 2009

News bites of July 2009

Sometimes the news rolls in just too fast to comment on. Add in two trips to west Texas in two weeks, a bout with a stomach bug resulting in an Urgent Care visit in Ozona, Texas, and telescope deadlines, and it becomes even worse. Here is the cool news of the past several days that I haven't had any time to blog about:

  • Jupiter 2, Comets 0 On the morning of Sunday, July 19, Australian amateur astronomer Anthony Wesley was taking images of the planet Jupiter when he noticed a black spot near the planet's south pole. Subsequent observations found pretty conclusive evidence that the spot was the debris left from the collision of a small body, like a comet or asteroid, with Jupiter. Precisely 15 years before (July 16-22, 1994), Jupiter was hit by several fragments of the Comet Shoemaker-Levy 9, which created similar dark spots. As of yet, we don't know what the impacting body was, how big it was, or where it came from. We may never know. But detecting this impact and future impacts is crucial to helping to determine the rate of impacts on Solar System objects.
  • The longest total solar eclipse of the century. Today (right now, in fact), the sun is being eclipsed by the moon over India, Nepal, Bhutan, Bangledesh, China, and the Eastern Pacific Ocean. During a total eclipse, the Moon completely covers the disk of the sun as seen from a narrow path on the Earth. The length of the Moon's covering of the sun depends on geometry, including how close the Moon is to the Earth. Since the Moon's orbit is elliptical, it is closer to the Earth at some eclipses and further away for others. In fact, if the Moon is near its furthest point, it will fail to completely cover the sun, and observers see a ring around the sun (called an "annular eclipse"). For this eclipse, the moon was at its closest point to the Earth just 6 hours before the eclipse! At the point of greatest eclipse, totality will last 6 minutes and 39 seconds. Be sure to use Google tomorrow to find some neat pictures of the eclipse. Those of us waiting for the next total eclipse in the continental USA still have another 8 years to wait.
  • Hubble is coming along nicely. A nice, detailed report from the Hubble Servicing Team shows that commissioning of the repaired instruments is going well and nearly finished, with the exception of the repaired Space Telescope Imaging Spectrograph (STIS). It's having major memory problems. I presume the engineers will find their way around that issue, though it may take a while.
  • The Thirty Meter Telescope finds a home. The Thirty Meter Telescope (TMT) Corporation, a collaboration including the Association of Canadian Universities for Research in Astronomy, the University of California, and the California Institute of Technology, announced today that they will build what would be the world's largest telescope at the summit of Mauna Kea on the island of Hawai'i. The site selection allows the telescope to move from planning phases into construction. Mauna Kea, according to the TMT, is the best site available, and it also ensures that the TMT will be the only next-generation large telescope able to view the skies of the northern hemisphere. There are cultural and environmental challenges to building on Mauna Kea, but it is possible to build in a culturally- and environmentally-friendly way.

Apollo plus 40.00274

Bootprint on the moon
Image Credit: NASA/Courtesy of nasaimages.org

Yesterday, as you all probably know, was the 40th anniversary of Neil Armstrong and Buzz Aldrin's moonwalk, the first steps by humans on the Moon. Other news outlets and blogs are giving their opinions of the meaning of the Apollo landings for the world. Others are giving their recollections of where they were and how they felt when men from Earth landed on the Moon. I have little to add to the former, and nothing to say at all on the latter, as I was not born until a year after Apollo 17's first day of moonwalking. So, let me look forward instead. NASA is planning on a return to the Moon, and many people are wondering if this is a good idea, and what we'll do if we go back. What would we do on the Moon if we returned?

Astronomy. The Moon offers some unique opportunities for astronomy research. The far side of the Moon is a wonderful place to do radio astronomy. The Earth is a noisy place for radio astronomy. All of our radio and TV broadcasts, cell phones, wi-fi, satellite transmissions, and even electric transmissions create radio noise that make it difficult to study astronomical objects in the radio from Earth. In addition, Earth's ionosphere reflects many wavelengths of radio waves. This is great for shortwave radio operators, who can talk with other radios on the distant parts of the planet as radio waves are bounced around the curvature of the Earth, but bad for astronomy, since those waves are reflected back into space. The Moon has no ionosphere, and the 3500 kilometer-thick ball of rock that the Moon provides is great for blocking all radio signals from the Earth. The only problem with radio astronomy on the Moon is that the moment we have people on the Moon, we are going to want communications satellites in place that bathe the far side of the Moon in radio waves. With smart planning, though, such as using radio wavelengths that we can already study perfectly well from Earth, this may not be a huge problem.

All other types of astronomy are possible from the Moon, including infrared, optical, X-ray, and gamma-ray astronomy. Here, though, the general consensus is that satellites are better. The Moon's gravity attracts micrometeoroids (what we would see as meteors on the Earth) that would slowly pit and degrade lunar mirrors. The temperature swings are also quite high (except in permanently shadowed craters near the lunar poles, which limit the amount of sky we could look at); such temperature swings are hard on equipment. Telescope repairs and new instrumentation would be easier on the Moon than in space. I think most astronomers feel that non-radio astronomy is probably best done with orbiting telescopes, and it's probably cheaper with orbiting telescopes. But, if we humans are going to the Moon anyway, and if more and more NASA funds are going be funnelled toward the manned program, a lunar telescope may be astronomy's safest bet to continue to have large space-based telescopes in the near future. I think this last sentence is a point most of us astronomers should pound into our thick skulls as we plan future space telescopes.

Geology. I guess the proper term is selenology. While the Apollo astronauts brought back hundreds of pounds of moon rocks, only one Apollo astronaut (Harrison Schmitt) was a geologist by training. Having participated in a couple of paleontological expeditions in the past, I feel confident saying that the trained geologist will always have a faster and sharper eye than a non-geologist when it comes to selecting interesting rock formations for sampling. Selenology would not only consist of understanding the formation and subsequent evolution of the Moon, but also collection of meteorites that are far-better preserved than those found on the Earth. This helps with understanding the formation and evolution of the Solar System.

Could robotic rovers driven by geologists explore the Moon more cheaply and select samples for return to Earth for study? Perhaps, though I suspect a geologist on the Moon would be faster and more reliable. This would be a point for planetary scientists to argue over.

Biology. The Moon would probably be a great place to study some of the hazards of space travel, such as long-term exposure to radiation. Some of this can be done on the International Space Station, but the Moon mostly stays outside of Earth's protective magnetic field. If we have aspirations of human travel to Mars, we must better understand how to protect the astronauts from radiation hazards, and the Moon provides a more typical space radiation environment than Earth orbit. Here the problem is that space biology is not quite as sexy for the Earth-bound taxpayers who fund the research, though this is perhaps the most pressing research needed for future space exploration. ("Moon Mice do/don't get tumors as fast as we feared" versus "3-pound chunk of Venus found at center of crater" versus "Magnetic anomaly in Tycho crater leads to discovery of a black monolith") This research could also shed light on some controversial ideas such as panspermia, the idea that life routinely travels between habitable planets in the Galaxy by hitching rides on meteoroids.

Other reasons for returning to the Moon, such as national pride, international cooperation, or some sort of space Manifest Destiny are not nearly as compelling to me, though they are compelling to other people.

If we as a species do decide to return to the Moon, then we need to meet one challenge that we have only accomplished once (through Apollo) in space exploration: to make a decision and stick with it, through thick and thin. In space exploration, we tend to set goals, then revisit them, then cut funding, then restore funding, then redesign, then cut some funding, then restore a fraction of the funding, then redesign again, then start the project, then revisit and redesign it, then tinker with the budget yet more. To make a return to the Moon worthwhile, we need to make a commitment that we realize will last longer than any one career, or than any one economic cycle. For if we only go for another six short visits, then we will not have advanced at all, which would be a shame.

Saturday, July 18, 2009

The McDonald Observatory Board of Visitors

This weekend, I am back in West Texas at the McDonald Observatory for a meeting of the Board of Visitors, or BoV for short.

The BoV is a group of donors to the observatory, and it is a veritable Who's Who of Texans. At this meeting I have seen Former Bush advisor Karl Rove, Chief Justice of the Texas Supreme Court Wallace Jefferson, and University of Texas Chancellor Dr. Francisco Cigarro, among others. The BoV has two meetings a year, a summer meeting here at the observatory, and a winter meeting in Austin.

This is the first meeting of the BoV I've attended; I was asked to give a short talk about my white dwarf discoveries I've made here at the Observatory. A graduate student, Amanda Bayless, gave a good talk about her work on black holes, and research scientist Mike Endl talked about finding planets around other stars with the McDonald telescopes. This afternoon the BoV members are watching demonstrations on the telescopes, touring some of the natural wonders of West Texas, or shopping in Marfa. And most of us astronomers are sitting in the astronomer's lodge over cups of strong coffee, admiring the freshly-painted dome of the Harlan J Smith telescope.

The BoV is really a marvellous group. They donate their money and time to support astronomy research, and they really care about the scientists as well as the science. (This used to be somewhat surprising to me, given the personal politics of some BoV members, but in spite of political differences I may have with individuals, I appreciate their support.) The BoV donations are helping to build new instruments for the telescopes, they support scholarships and endowed professorships, they support scientific meetings, and they use their influence to encourage the Texas legislature to support the University and the Observatory. Every member I've talked to is deeply interested in the science of astronomy, and they have very insightful questions about the Universe and our place in it. The BoV is the lifeblood of Texan astronomy.

Tonight there are a few more talks and a wonderful dinner prepared by the Observatory staff, followed by star gazing and telescope viewing. It should be a blast!

Thursday, July 16, 2009

Getting my white dwarfs in a row

Hobby-Eberly Telescope at McDonald Observatory
Image Credit: McDonald Observatory

Since returning from last weekend's teacher workshop, I've been working on planning observations with the Hobby-Eberly Telescope, the largest telescope at McDonald Observatory and one of the largest telescopes in the world.

Observing with the Hobby-Eberly Telescope works differently from the way astronomy has been done classically. Instead of going to the telescope and staying up all night taking data, we submit a list of observations we want to do over the web, and those data are taken by a staff astronomer in what we call "queue observing".

In queue observing, all of the requested observations are thrown into a single big list. These observing requests include coordinates of objects, the scientific instrument we want the data taken with, the weather conditions that we need (some observations can be done through thin clouds while others need clear skies; some need steady skies, while others can be done through slightly blurry skies; etc.), and the rankings that a project review committee gave each project. At night, the staff astronomer asks the computer for the next target, and a computer program looks at the current weather and which objects are currently observable, and then it picks the highest-ranked project and gives the staff astronomer the target information. The telescope is moved, the pictures are taken, and then the computer tells the astronomer where to go next.

This method of observing makes efficient use of the telescope. This is necessary at telescopes like the Hobby-Eberly Telescope, as its unique design severely limits where it can look and how long it can follow any one star or galaxy.

The drawback to this observing is that I'm not the one doing it. So I have to try and put together enough information that the staff astronomer knows exactly which star I want to look at and exactly how to do the observations. And I have to give them all of this information now, several weeks before the observations start, so the staff astronomers can feed all of the information into the computer, make sure they have all of the charts they need, and look for any holes in the sky where nobody asked for observations.

Last week, I learned that a project I proposed to use the Hobby-Eberly Telescope to look at white dwarfs was awarded time, and that the observing materials are due this weekend. I have about 40 targets, though probably only 10 or so will get looked at. But I don't care which of the 40 get looked at, so I send them all and hope that some of them fall into cracks where nobody else with a higher-ranked proposal is looking, and maybe I'll be able to get some extra observations.

So, I've been queuing up my white dwarfs. I filled out all of the paperwork, but I still need to make charts showing the staff astronomers which stars are mine. I'm going to try and get that done this evening so I can enjoy the weekend (which involves a special event at the observatory, which I'll talk about another day).

Wednesday, July 15, 2009

Cannibalizing education

I hope you'll forgive yet another digression from astronomy, but I'm ticked off.

For a country that claims to value education, we've been very good at gutting it right and left at all levels. Now that we are in the midst of a severe economic crisis, this is coming to the fore, and institutions right and left are fighting for their survival, sometimes by offering to sacrifice the school next to them, and sometimes by cutting so deeply that one is left to wonder how those in charge of the purse strings can sleep at night.

In 2004, Pennsylvania Governor Ed Rendell celebrated the 150th anniversary of the founding of Penn State University, the state's largest public institution, with the following words:

"At the height of the Civil War, when our continued existence as a nation was in question, our state and national leaders turned their attention to higher education, and to the future. It should serve as a lesson to us today that, no matter how difficult the times, it is never too bleak to justify deferring our attention from the needs of the people. It is always the right time to invest in the future."
(emphasis mine). Last week, the exact same governor tried to declare that four storied Pennsylvania state universities, Penn State, Pitt, Temple, and Lincoln, were not truly public institutions, and therefore did not qualify for federal stimulus money earmarked for higher education, claiming that times were unprecedented. Again, I realize that times are really bad, but I think the Civil War was worse... This move led Penn State to temporarily approve a monstrous tuition hike to cover the loss of funds. Thankfully, the U.S. Department of Education prohibited this change in status, but the cards are now out on the table, so to speak, and I suspect that the fight to retain public university status will now be much more common.

In California, where the word "crisis" doesn't begin to cover the depth of economic woes, 22 department chairs at the University of California San Diego wrote a letter to the president of UC suggesting that three campuses (UC Santa Cruz, UC Riverside, and UC Merced) be closed, because these "teaching institutions" are not profitable, and "corporations faced with similar problems eliminate or sell off their least profitable, least promising divisions." Frankly, I am shocked and horrified that any university professor worthy of the title would consider that teaching is not profitable nor promising, especially since teaching is and should be the primary goal of institutes of higher learning. They aren't called "institutes of higher research." Further, as a graduate of UC Santa Cruz, I can say based on experience that there is a large amount of "profitable" research that goes on at Santa Cruz and Riverside. (UC Merced opened after I graduated, and I strongly suspect that it is no slouch, either.) And, lastly, education is NOT a commodity to be bought and sold, but a fundamental right of human beings.

Other universities are also struggling with crippling budget cuts, and they are all trying to maintain educational services while cutting costs. Staff (including administrative assistants, janitorial staff, etc., not just faculty) are going without raises and often are receiving pay cuts. Universities are closing departments, not filling positions, and letting basic maintenance go.

In the meantime, public education is also suffering. My high school recently effectively cut the orchestra out of the school. They didn't cut it completely, but didn't fill the teaching position, either. Many other public schools nationwide have already completely cut music, arts and sports programs, libraries, lunch rooms, and so on, often because the administration deems that these are not part of an essential education; these cuts were often made before the current budget crisis. I strongly disagree with the notion that music, sports and arts are not crucial parts of education (and libraries! How can you possibly claim that a modern library does not enhance education?!). It's a lot like cutting two fingers off of each hand, removing an eye and an ear because they are redundant and not necessary to functioning as a human.

At the start of every school year, my daughter comes home with a "wish list" of supplies for the teachers. These supplies are not luxuries like high-definition computer monitors or surround-sound systems for auditoriums, but absolute necessities like paper and pens and Kleenex. If the students don't bring these in, then the teachers have to purchase these supplies out of their already barely-living-wage salaries. Our society claims that we value education, but we are too cheap to buy pens and paper for our students?

I realize we are in a severe economic crisis. But the students currently in school or in college cannot wait two or three years for state budgets to recover. They can't put their lives and growth on "pause" for more favorable times. By slashing education budgets and pushing schools to try and cannibalize each other for funding, we are condemning students who had the unfortunate luck of growing up during a crisis of our making (not theirs) to a substandard education.

Growing up, I heard stories of how my great-grandparents would forgo comforts and even meals to make sure that my grandparents could go to school during the Great Depression. My parents and many parents of their generation went deep into debt to give my sister and I a decent college education. Now it's my generation's turn to sacrifice to make sure that our kids do not get left behind. Shall we step up to the plate? Will we make the vow that it is "never too bleak to justify deferring our attention from the needs of the people?" Or will we let our society turn on itself and consume the very institutions that gave us the luxuries we are all too unwilling to part with?

Monday, July 13, 2009

Getting a little giddy

Our last night of the teacher workshop is winding down; we managed to smooth out some of our computer problems, and we have our fourth clear night out of four nights -- not too shabby!

The photo above shows some of our group goofing off while waiting for a tour of the McDonald Laser Ranging Station. Or perhaps they were trying to stop our head facilitator, Kyle Fricke, from jumping off a cliff due to the stress of putting on a successful workshop.

Sunday, July 12, 2009

Clear weather and cloudy computers

Our high school science teacher professional development workshop continues here at McDonald Observatory. We've got 19 teachers who have been learning about the lives of stars and white dwarfs. Right now, they are all sitting around styrofoam cups full of hot water, measuring how fast it cools. We'll then relate this to white dwarf, which emerge from planetary nebulae with surface temperatures of a hundred thousand degrees, and cool down to a few thousand degrees over several billion years.

Below are some pictures of the night sky at McDonald taken by one of our participants, Leslie Howell, a science teacher from the Ft. Worth area. If you look at the large versions of the images (click on an image to enlarge it), you can see both the colors of the stars and their trails, created as the Earth rotates about its axis. You can also see the Milky Way, the band of starlight caused by the billions of stars in our own galaxy. The picture with a telescope dome is of the Harlan J. Smith 2.7-meter telescope; the yellow glow on the lower parts of the dome is a reflection of the rising gibbous moon. In this picture, you'll notice that the star trails are wider on the right of the image than on the left. That's because the North Pole is behind the dome, and stars further from the pole have to make larger arcs to circle the pole.

These images were taken with a Nikon D70s digital camera; the image of the Milky Way was a 45-second exposure, and the image including the telescope dome was a 105-sec exposure. The Milky Way seen from McDonald Observatory

The Milky Way behind the Harlan J. Smith Telescope

Alas, although the weather has been great, we've had no end of problems with computers. We are trying to perform an activity where the teachers measure the brightnesses and colors of stars in star clusters; we've done this activity for many years and thought we finally had all the wrinkles ironed out. Unfortunately, we are having buggy problems with the computer program we use to analyze the data, bugs we've never seen before. And, worse, the bugs are intermittant, and don't affect everyone. So, the teachers are getting pretty frustrated with the activity. Tonight I need to try and smooth things over, and I'm still debating how to do that.

Friday, July 10, 2009

McDonald Teacher Workshop, Day 1.5

I'm out at McDonald Observatory again for our summer teacher workshop on white dwarfs and the age of the Milky Way galaxy. This is my fourth year of participating in the workshops (look in the blog archive for June or July of previous years to see entries from those visits).

This year we have 19 teachers, a larger group than in the past. They come from as far away as Minnesota and New York, and seem quite excited to be here. The weather is great, so we spent several hours last night looking through small telescopes, eyepiece observing through the 36-inch diameter professional telescope, and taking images with the 30-inch professional telescope. Saturn was just gorgeous, and we had many "Oh, wow!"s and "Holy &%^$*#!" comments looking at the Whirlpool Galaxy.

I've been very busy here the first couple of days; in addition to being the resident scientists for the teachers, I gave a talk on my research for the observatory employees and summer undergraduate research students. So, my voice is mostly shot. As I type this, the teachers are playing with the colors of light using colored light bulbs; it's a simple experiment, but always one of the favorites (picture above).

Tonight we are giving the teachers a science experiment to perform based on the pictures they take with the 30" telescope. The weather is looking great, so here's hoping the telescopes keep working!

Tuesday, July 07, 2009

Talk talk talk talk

Tomorrow I head out to west Texas for our annual high school science teacher professional development workshop. I hope to be able to write about all the fun we have, and maybe even snag an guest author blog entry from one or two of our teachers.

In the meantime, I busily preparing talks for the workshop. I'm the senior scientist for this week's workshop. My role is to field any science questions that the teachers may have, and to talk about the current research behind the many activities our teachers participate in. Last year these research talks were given by a good friend and colleague, Dr. Jim Liebert of the University of Arizona Department of Astronomy. Professor Liebert is ill and unable to attend this year. We'll sorely miss him, and wish him a speedy and full recovery.

This means that I have three more talks to prepare by tomorrow, so I'd better get cracking. In the meantime, if you have any suggestions of neat things our teachers should look at through our professional telescopes, please let me know. Details of ideas we're looking for are here.

Thursday, July 02, 2009

"Discovery" of a new class of black holes

Illustration of the possible mid-sized black hole HLX-1


Illustration credit: Heidi Sagerud

When reading about scientific discoveries, it is always important to remember Professor Astronomy's Discovery Law: The last person to discover something gets the credit.

Yesterday, a news story was released on a nice bit of research that is "the first solid evidence of a new class of medium-sized black holes." Only many other astronomers who have claimed to discover medium-sized black holes would argue that they had already discovered the first solid evidence of such things. Now, let me make it clear. The authors do not claim in their paper to have discovered mid-sized black holes; that claim is made in the European Space Agency's press release. And such hyped claims are often made by NASA and other US agencies, so ESA is not doing anything unusual. But this is not the first claim of a mid-sized black hole, and it won't be the final word, either.

An artist's conception of how the black hole, called HLX-1, might look if our eyes could see both X-rays and optical light is at the top of this post. It looks like a photo, but it is just an illustration.

So, forgetting the cultural aspects of the story, let's look at the science. Stories like this always raise the questions, "How can we see a black hole if light cannot escape it?" and "How do we know how big a black hole is?" These two questions are actually very closely related.

It is true that light cannot escape a black hole, if the light gets too close. How close is too close? For a black hole with the mass of the sun, the light would have to come within about 2 miles of the center of the black hole to be captured. The further away from the black hole you go, the more "normal" things are. If we replaced the sun by a black hole with a mass the same as the sun, the Earth and all the planets would orbit exactly the same as they do now, and we would still see all the stars in the heavens, except for those appearing the tiniest fraction of a degree away from the black hole in the sky.

So, stuff in orbit around a black hole will move in almost perfect ellipses around the black hole, just like it would around a normal star. They obey what we call "Kepler's Laws of Planetary Motion" first described by astronomer Johannes Kepler in the first decade of the 17th century. Kepler's Laws provided some of the first evidence for "small" black holes, those just a few times the mass of the sun. An example is the star system Cygnus X-1 (meaning the first X-ray source discovered in the constellation Cygnus). In that star system, a star with about 30 times the mass of the sun is losing some of its outer layers to a nearby unseen companion.

Now this invisible companion to Cygnus X-1 could have been a normal star, a white dwarf, a neutron star, or a black hole; all three would be impossible to see next to the very bright star. However, we can measure the movement of the bright star due to the gravitational pull of the companion star, much in the same way we find planets. The mass of the unseen companion is roughly nine times the mass of the sun. A normal star of that mass would be visible in optical light, but we don't see it. White dwarfs explode if they get bigger than 1.4 times the mass of the sun, so we know it's not a white dwarf. We aren't positive how big neutron stars can get before they collapse under their own gravity; but we know that limit is somewhere between 2 and 5 times the mass of the sun. So the invisible companion in Cygnus X-1 must be a black hole, and that black hole is about nine times the mass of the sun (but only about 30 miles in diameter!). Dozens of systems like Cygnus X-1 are known, and all the black holes have masses of a few times the mass of the sun to a few tens of solar masses.

Astronomers have also used Kepler's Laws in interpreting the movements of stars in the center of the Milky Way galaxy. They are able to determine that there must be something about 2 million times the mass of the sun in a volume no larger than the size of our Solar System at the very center of our galaxy. But we don't see any infrared light from that spot, even though we can see individual stars moving around that spot! That is some of the best evidence we have of a giant black hole at the center of the Milky Way.

Astronomers can also use the motions of stars to get the masses of black holes in other galaxies. This is harder to do, because we can't see the individual stars in the centers of most other galaxies. But we can measure average velocities of these stars, and we find that most galaxies have "supermassive" black holes at their centers, with masses of a million to over a billion times the mass of the sun!

So, we have lots of little black holes (ten times the mass of the sun, probably hundreds in each galaxy), and we have lots of ginormous black holes (millions of times the mass of the sun, but seemingly limited to one or two per galaxy). The first thing that pops into my mind would be that we probably have to build supermassive black holes out of sun-sized black holes, so I think it's natural to assume that there must be black holes with sizes in between, say maybe a few hundred times the mass of the sun to ten thousand times the mass of the sun, and there would be several of those in each galaxy.

But it's been hard to find candidate black holes of these intermediate masses. Some candidates have been claimed. One group, led by astronomer Karl Gebhardt here at the University of Texas, has found evidence of intermediate-mass black holes at the centers of some globular star clusters. Their evidence is from measuring the motions of individual stars, much like in Cygnus X-1 and in the center of the Milky Way.

Another way to find intermediate-mass (mid-size) black holes is to look in with X-ray telescopes. As gas and dust orbit around a black hole, they heat up due to friction. And, since they are moving so fast in their orbits, the gas and dust glow in energetic radiation, including ultraviolet light, X-ray light, and even gamma rays. Numerous studies (like this one) of X-ray sources have suggested that intermediate-mass black holes exist, and yesterday's press release on HLX-1 falls into that category.

The main difference of the HLX-1 black hole with other mid-size black hole candidates is that it is brighter in the X-rays than the earlier candidates. A brighter X-ray source means that it cannot be a stellar-mass black hole, because if those smaller black holes produced as much X-ray light as HLX-1, the X-rays would push all the gas away from the black hole, and it would stop emitting light. The astronomers studying HLX-1 also rule out that the X-rays come from a distant galaxy, because they don't detect any radio or optical light; supermassive black holes often (but not always) emit light in one or both of these kinds of light.

But I think the jury is still out on whether HLX-1 is any more convincing of a mid-sized black hole than any previous candidate. I won't list off the many questions I have. Frankly, solid evidence is very difficult to come by, and we may just not yet have the necessary tools to convince ourselves that mid-sized black holes exist. Future X-ray and optical telescopes may help a lot by allowing us to see fainter and get better data.

Finally, it may not be true that supermassive black holes are made out of coagulations of small black holes; some people argue that they are formed in completely different ways. I think that this idea is intriguing and could explain the apparent paucity of mid-sized black holes. But the lack of known intermediate-mass black holes may just mean that, in most cases, these black holes don't have any gas or dust to eat. If gas and dust are not falling into a black hole, they are virtually invisible and nearly impossible to detect.

In short, mid-sized black holes may exist and be hard to prove, or maybe they are very rare or even absent. HLX-1 is another important piece in the puzzle, but it is not convincing proof of mid-sized black holes nor the first evidence of mid-sized black holes.

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