Saturday, August 30, 2008

Changes afoot

While I sit in the clouds and rain over the next couple of days, I'm going to try some upgrades to this blog.  So, if you were trying to read this and getting errors, or if there are several broken links, or if things look ugly, I apologize.  Hopefully all will be well by the end of the weekend.

Friday, August 29, 2008

On top of Mount Locke

Clouds float by Mt Locke

Yesterday I drove across Texas to McDonald Observatory.  As always, it was a long drive.  I think there must be a buzzard convention in the area, because many times I came around a corner to see a flock of buzzards just sitting in the road, even though there was no roadkill for them to eat.  Or maybe they were hoping to cause me to wreck, thereby getting an easy meal.  Either way, it was a little odd.  I also saw a tarantula crossing the road, as well as what used to be several armadillos.  And, these days, no trip across West Texas is complete without seeing a truck or two carrying parts for the construction of wind farms.  Yesterday I saw two semis, each carrying a single blade for a windmill.  It's eye-opening to see how big the windmills are, when it takes an extra-long semi to carry a single blade.

Starting tonight I have seven nights on the 82-inch telescope.  Unfortunately, as you can see above, the weather is not very favorable.  It rained overnight, and will probably rain again this afternoon and tomorrow and Sunday.  Thick clouds are drifting overhead, with delicate tendrils reaching down toward the mountain tops.  Occasional bursts of brilliant blue sky appear behind the clouds.  Some of the mountainsides have long-dormant waterfalls cascading down into the desert floor.  It's gorgeous, but not conducive to astronomical research.

Still, I'll prepare this afternoon as if it is going to be a clear night.  One never knows; the clouds could magically part, and if I'm not ready to go, I could miss the only clear weather of the week.  Most likely, though, we're going to be socked in until at least Monday.

In the coming days I'll blog about what I'm looking at, and maybe make a few changes to the website along the way.  These cloudy observing runs are good for that sort of thing.

Wednesday, August 27, 2008

The students are back

PhD Comics Image Credit: Jorge Cham

Today is the first day of classes here at the University of Texas. In the past few days, this campus has transitioned from its sleepy summertime state to a bustling hive of educational activity. Monday, things were very quiet, with the exception of some large tents being put up. But coffee carts were closed, lines at restaurants were short, and there were plenty of seats on the bus. Yesterday, the coffee carts were still closed, but the sidewalks were a steady stream of students carrying burnt-orange bags filled with overly-expensive text books, and the smell of barbecue wafted from the large tents, welcoming students back to campus. And today, the buses are overflowing, the sidewalks are full of students trying to find their way around campus, Gideons on every street corner trying to pass out New Testaments, lines for coffee are spilling out of buildings, and new students are riding the elevators up and down, wondering why it won't stop on the second floor (despite the signs saying that the elevator doesn't stop there).

Education is our primary purpose for existence here at the university, so it is hard to complain about the inconveniences when they simply mean it is time to get back to work. But academics and astronomy are an odd mix. Success in our careers is most often defined by the impact we have on astronomy research, not on how many students we teach or how well we teach them. But teaching a course requires much more than the 4 hours a week spent in the lecture hall; trying to teach multiple courses means foregoing almost all research for a semester. So it is in the summer that most research gets accomplished. With the start of the school year, as we re-enter our primary mission, our productivity will now decline. To me, that's a bit perverse. But it's the way of the world, I guess.

Tuesday, August 26, 2008

When the refereed becomes the referee...

Last week I talked about how much fun I was having (NOT!) responding to a peer review of one of my papers. Well, now the tables are turned, and I am working on a review of someone else's paper.

It's a bit nerve-wracking. I am supposed to look over the science and make judgements on the quality of another person's work. But more than that, the author usually knows more about what she/he is writing about than I do. So, if I want to do a good job as a peer reviewer, I need to read not only the paper that I'm reviewing, but a lot of background literature.

There are lots of things that need to be considered in a peer review. These include:

  • Is the research new and useful? It doesn't need to be the most exciting astronomy ever, but if a paper has little use to anybody else, then the big astronomy journals tend not to want it.
  • Is the research convincing? Do I believe the results? Even if I don't believe the conclusions, do I at least believe that the data and the methods are sound?
  • Have the authors references enough of the literature? When we write a paper, we don't need to re-derive all of 500 years of astronomical research. It is okay to use the results of other people (like Newton did in his famous quote about "standing on the shoulders of giants."), but we have to give those people credit. And, as a referee, I need to make sure that the paper is not based on old results that have been discredited.
  • Did the authors do the math right? Astronomy involves a lot of math. If I were to be a super referee, I would re-calculate their numbers and re-derive their equations to make sure I get the same answers. I tend not to do that. Instead, I spot check numbers and see if the results make sense. This is not an ideal method! I'm being a bit lazy here, and I am giving the referee the benefit of the doubt, assuming that they've checked their own work for mistakes. But, generally, the only way to truly check the work would be for me to re-do their project. That would take time, and delay the publication of the paper. If I suspect a problem, it is okay for me to tell the authors that I think there may be an error, and for them to check the results.
  • Does the organization of the paper make sense?
  • Do tables and graphs and figures convey the information the authors claim, and do so in a clear manner?

In the end, as a reviewer I get large sway over whether or not a paper eventually gets published. If I reject a paper, the authors can ask the editor of the journal to send the paper to another reviewer, and that decision lies with the editor. If I say a paper is fine, it will almost always appear in print, but the editor would have the power to request changes or even send it to another reviewer, if he/she had reason to doubt the quality of my report. So far, I have never suggested that a paper be rejected.

I do feel a little bad for the people who get my reports. I tend to be long-winded, ask lots of questions, and make lots of suggestions. I just hope that the authors on the receiving end of my reports find my long litany of comments useful. After all, it is science that needs to be served, not my whims or the authors' own desires.

Friday, August 22, 2008

Heart of Darkness

I've noticed that, when we astronomers are attacking a problem or question, we tend to attack from many different angles. Some work, some don't, and eventually the picture becomes clearer. But we have a memory of the mess that existed during the highest frenzy of research, and we tend not to see how nicely all the pieces fit together into an overwhelmingly convincing argument. It is only when someone comes along and organizes all the evidence in a linear fashion that we can admire the result.

This week on our preprint server (the webpage where astronomers can post their research before the journal containing the paper arrives in the mail), Mark Reid of the Harvard-Smithsonian Center for Astrophysics published this article, which is a scientific review of the search for a black hole at the center of the Milky Way galaxy over the past five decades. The review starts with some of the early evidence for something big at the center of the Milky Way and other galaxies. But it quickly moves to a discussion of the strongest current evidence for a black hole in the center of the Milky Way:

  1. The orbits of stars at the center of the galaxy: Over the past decade, two groups of astronomers (one led by Andrea Ghez at UCLS, and the other by Rheinhard Genzel in Garching, Germany) have used infrared cameras on large telescopes to take pictures of the center of our galaxy. Over this time, they have been able to see stars completing orbits around the same point in space. One star even comes within 100 Astronomical Units (100 times the Earth-Sun distance) of this point, and moves at 6000 miles per second at closest approach, about 3% of the speed of light. Using the laws of gravity and orbits laid out by Johannes Kepler and Isaac Newton 300-400 years ago, we know that the object at the center of these orbits must have a mass about 4 million times that of the sun! So, we have four million times the mass of the sun in an area no larger than our Solar System. That's a lot of stuff! (You can see animations of the stars' movements here (UCLA) and here (Germany).
  2. The focus of these orbits is at the same point as a strong radio source, but this source has to emit less infrared light than a single star. The pictures used to track the stars' orbits were taken in infrared light, but there was no light coming from the center of their orbits. So, we need an object that needs to be 4 million times the mass of the sun, is smaller than our Solar System, can emit radio signals, yet emits almost no infrared light. (We don't know about visible light, because dust between us and the center of the Milky Way blocks visible light.)
  3. The size of the radio source is less than 1 Astronomical Unit across. In other words, unless only part of the object is making radio waves (which would be a very improbably feat), all of that matter, four million times the mass of the Sun, is constrained to be in an area smaller than the Earth-Sun distance. A black hole with a mass of 4 million times the mass of the sun would be about 1/8 of an astronomical unit in size, This means that the object we are looking is smaller than eight times bigger than a black hole.
  4. The object is sitting still at the exact center of the Milky Way. Those stars we see in orbit around the dark object at the center of the Milky Way are pretty big, and there are a lot of them, adding up to almost 4 million times the mass of the sun themselves . If the thing at the center of their orbits is not a single object at the exact center of the galaxy, then it should be whipping through space at speeds similar to those of the stars around it. But it is sitting almost perfectly still, moving at a speed of less than a quarter of a mile a second, or "just" 900 miles per hour. That may sound fast, but remember those nearby, massive stars are zipping through at 6000 miles per second. The sun is moving at about 150 miles per second around our galaxy. So the fact that this thing isn't moving in such a harsh environment means that it is not only pretty honking massive, but it's right at the dead center of our galaxy.
  5. Ordinary matter can't explain all the data and survive for very long. It is possible to make very dense clusters of faint stars, white dwarfs, or neutron stars that would be visible only in radio waves and have this large amount of material in a very small space. But if you somehow make a tight ball of fairly ordinary stars, the stars will collide with each other, merging to make a single black hole, or slingshot each other out of the middle of the galaxy. In either case, the cluster of stars would only live for a million years. This sounds like a long time, but it is the blink of an eye in the 13-billion year lifetime of our galaxy. How could you make such a dense ball of stars, and why would it be at the exact center of our galaxy right now? And when we look at other big galaxies, they all have something big and massive at their center. How could all big galaxies have a short-lived cluster of faint stars at their middles at this instant in time? There's no reasonable answer.

When you add all these things up, there is only one object in all of currently-understood physics that can be this massive and this small, and that is a black hole. Other explanations, like the very dense cluster of faint stars or balls of weird subatomic particles, are just too contrived to seem reasonable. In the parlance of a criminal court, the presence of a black hole at the center of the Milky Way is beyond a reasonable doubt.

The best part is, there are still more tests that we can do to continue to test and probe this black hole. Every theory should be tested and re-tested as often as novel techniques arise. But, I think we can move on with confidence and stop asking "Is there a big black hole in the center of the Milky Way?" Instead, we can start asking the even harder question of "Where did the big black hole come from?" Hopefully, in another review article 50 years from now, the evidence answering that question will be just as overwhelming.

Thursday, August 21, 2008

The referee report

In addition to my travels last weekend, another reason that I've been so quiet is because I've been working on revisions to a paper that I have submitted for publication in one of our professional journals. It's been a very intense process, and dries up all of my writing skills for the day.

In astronomy (and every science), when we submit a paper to a professional journal, it has to go through a process called "peer review," or "refereeing." The draft of the paper is sent to one or more experts in the field. These experts, who are expected take a fair and unbiased look at a paper, are given three options: (1) approve the paper, (2) send the paper back for revisions, or (3) reject the paper.

In astronomy, option (2) is by far the most common, especially if it is the first time the paper has been sent in. Very few papers are approved without any revisions. And outright rejection is rare, with only a few percent of papers never being published.

So, when I submit a paper, I usually wait a month and then get an email from the editor of the journal with the referee's report, a list of suggestions, questions, and criticisms. I am then expected to make a good faith effort to address the referee's report in my revisions. After I revise the report, I re-submit the paper to the journal, who then passes it on to the referee (almost always the same person as before). In most cases where the authors have made a good effort, the referee will accept the paper, often contingent on a few minor edits. Sometimes the referee decides it needs some more work and sends it back for more substantial revisions. And, rarely, the referee will decide the paper is just not up to snuff and reject it.

This process is designed to try and ensure that all papers published in a professional journal are scientifically rigorous and meet certain standards of quality. At least, this is the theory. The peer review process is not perfect. Sometimes bad articles get through. Sometimes the referee tries to hold up a good article for purely personal reasons. Sometimes a different or additional referee has to be brought in to resolve conflicts. But while the process isn't perfect, it generally works pretty well.

I've found that most referee's reports I get can be ranked on three scales: length, positive/negative, and helpfulness. Some reports I've received have been short and positive with a couple of useful suggestions. I've gotten reports that are short and positive, and only later did I find out that they weren't useful, because both the referee and I missed a glaring problem. I've gotten long, thoughtful reports that have really helped a paper. And I've gotten long reports that are fairly critical, with the criticisms making me wonder if the person actually read the paper. (As a fictional example, the referee's report might include the comment, "I am shocked that the authors did not discuss the price of tea in China," when the paper has a section headlined, "Our star and the price of tea in China.")

These latter types of reports are a pain. I feel I have to make at least one good-faith effort to address the report, but it is hard for me (a naturally sarcastic person) to avoid putting snarky remarks in my response. Once I had a long, negative report that, after a lot of thought, I realized came down to the referee misunderstanding a single word. I did a search and replace of that word in the paper, and the referee's report came back saying, "this paper is vastly improved." Alas, if they were all that simple.

As for my most recent paper, the revision process wasn't exactly fun. But I finished it, and, after my co-authors review the paper, I will be able to send it back in for another round with the referee.

Monday, August 18, 2008

Travel fun

Blogging's been light because I've been on the road late last week and this weekend. It's been adventurous; I've already been re-routed once due to weather, and there could be more weather problems today. With a bit of luck, I should be home tonight, and back to regular blogging tomorrow.

I must admit that, in spite of all the problems with the airlines recently, I've been treated very well by the airline. I think a big part of it is because I have flown enough to get elite status as a frequent flier. While I won't complain about getting help with travel plans, I do think it is unfair that most fliers don't get the same service. I suspect that airline travel would be much more comfortable if everyone were treated as valued customers instead of self-boarding cattle.

To any airline execs that may read this (probably none): I get that delays happen. I know you can't control the weather. And I know that jet fuel prices are high. I'm willing to pay extra for my ticket, though I won't reject the deeply-discounted fares you are offering me that don't even cover the cost of fuel, let alone operations, needed to get me from point A to point B. But I think it stinks that you want to charge me money to put my bag in the hold. And I refuse to pay for potable water. I'll travel on a competitor first, no matter how many frequent flier perks you give me. Raise fares, I'll pay. Nickel-and-dime me, and I'll walk to the next counter.

Wednesday, August 13, 2008

Why we should listen to scientists

In this blog, there are a few topics that I try hard to avoid, because they rarely serve my primary main underlying goal: trying do to-mystify the scientific process (especially with regard to astronomy). One such topic I avoid like the dickens is politics, as the best political commentary I can muster would, if I were lucky, only alienate half of my audience. But today, I can't avoid the topic. Politics often sticks its nose into science (stem cell research, global warming, and science education are a few of the big topics of recent years), and the debate over these topics is often not based in science (good or bad) at all. But at least the debate is public, and it offers us scientists a stage, however imperfect, for trying to spread what we've learned about these subjects.

Earlier this week, the Bush Administration tried to quietly announce some whopping changes to the Endangered Species Act (ESA). As far as I understand it, the basic impact is that government agencies will no longer need to seek an independent review for projects that may impact an endangered species. Of course, they could still seek a review, but given that the review often slows down and forces changes to projects, does anyone honestly think that they would?

These reviews typically include scientists who collect evidence (most provided by the agency required to seek the review) and decide if a project would have a significant negative impact on an endangered species, and if there are changes that can be made to the project to lessen that impact. Sometimes those changes may be very expensive, and sometimes these reviews can really slow down the process. And a negative review can torpedo projects.

Is the ESA perfect? No. Sometimes the delays seem silly (like a bike path in California being delayed because it crosses territory of an endangered beetle), though there are often larger issues at stake. So, if the government wants to debate the process and make changes, I can go along with that. But let's at least do it in public. The U.S. is, after all, a republic; if we can't debate laws in public and have to change them in secret, then we've lost the most important rights that millions of men and women have died for over the past 240 years.

Some argue that the scientists involved in the review care more about endangered salamanders than they do about human beings. We are called elitists who think we know more than John Q. Public, and therefore our opinions have no value. Well, frankly, when it comes to science, we do know more than John Q. Public. That's not snobbery. It would be snobbery/elitism if we thought that our extra knowledge in scientific matters made us better than other people, but we know better. If the plumbing in my apartment breaks, I call the plumber, because I know that he/she knows much more about plumbing than I do. When my car quits running, I take it to the shop, because I know the mechanic knows much more about cars than I ever will. And I think the plumber and mechanic would be within their rights to say that they know more than I do about those subjects; I wouldn't be able to argue with them. So, when it comes to ecology, how can a career bureaucrat ever claim to know as much as the career biologist? The ecologist who says, "I know more about that than the bureaucrat, so please give my opinion some consideration" is not being snobbish, but just asking for the same deference we give to experts in other walks of life. Scientists are not crazed misanthropes bent on world domination, nor do we put our own personal ambition above the needs of our fellow man. We want humankind to progress, just in a way that doesn't take down the rest of life with it. We humans are part of a very complex and interconnected biological system, and if we fail to take care in our dealings with that system, we may be asking for trouble.

I often hear or read wisecracks about how stupid scientists are being when proposed developments are delayed because of impacts on endangered salamanders or frogs. And, I would have to agree that if the question were, "us or the frogs?", I'd side with us. But the question is not that simple; there are usually larger issues at play than just the endangered species. Often, the biggest danger of a shopping mall or an interstate to a salamander is not the increase in cars running over the poor creatures, but the loss of habitat, because the wetlands in which the salamander likes to live will have to be drained or altered. And while wetlands, swamps and bogs may not seem like very desirable things for humans, they can have tremendous impacts on us. For instance, there is strong evidence that a loss of wetlands increased the damage from Hurricane Katrina. While those lost wetlands would not have prevented the devastation from the monster storm, they may well have lessened the impact.

The Bush administration has claimed that the independent scientific reviews are no longer necessary because agencies have developed sufficient expertise to conduct their own reviews without scientific input. But science is constantly changing; we are continuing to learn more about the connections between environments, species, and humans. And these connections change with time. Bald eagles and alligators don't need the same types of protection they did 30 years ago, and pacific salmon need protections that they didn't just a few years ago. Who is going to be more up to date on the current environmental needs, a Ph.D. ecologist or the manager of a road construction project? I'll believe the ecologist on the environmental issues (though I'd take the manager's advice on the bridge design).

The fact is that, despite the extensive delays sometimes caused by environmental protection laws (though egregious cases exist, they are rare), our environment is in much better shape than it used to be. And that bodes well for humans. Compare a smoggy day in LA to a smoggy day in Beijing, and ask yourself which air you'd rather breathe. Environmental laws made that difference. Or read Silent Spring and then look at the change in bald eagle population since that time. The Endangered Species Act made that difference.

I have no problem with a healthy public debate on the details of environmental law and the role of scientific reviews within that law. But silent changes gutting existing laws (that have saved many species and have improved our human quality of life) without so much as a word of public discussion is wrong. It's antithetical to democracy. It blatantly ignores the voices of scientists whose life work is directed toward improving the lives of humans, both living and in future generations. It threatens the continued (and improving) health of the ecosystem of which we are an integral part.

Monday, August 11, 2008

Around and around and around it goes...

Hubble celebrates 100000 orbits

This morning, at 7:42am EDT, the Hubble Space Telescope reached a new milestone by completing it's one hundred thousandth (100,000) orbit around the Earth.

The Hubble orbits the Earth in what is known as a "low-Earth orbit," or "only" 600 kilometers (375 miles) above Earth's surface. While this sounds very high, it's not, in space terms. The space station and space shuttle also orbit this low. In low-Earth orbit, it takes a satellite about 90 minutes to orbit the Earth. But at these altitudes, the Earth's atmosphere is still present (although very, very tenuous), and if you don't put a booster rocket on your spacecraft, it will fall back to Earth in just a few years or decades.

In order to stay in orbit, the Hubble has to move at a speed of about 7.5 kilometers per second, or almost 17,000 miles per hour. When the space shuttle goes to repair Hubble, it is also moving this fast. How can the astronauts safely catch the Hubble? It's all relative speed. Although both spaceships are moving at 17,000 miles per hour, compared to one another, they are moving only a few miles per hour (more when the shuttle is moving in to catch it, and much less when the shuttle sticks out its arm to grab Hubble). It's like passing a car going slightly slower than you on the road. Although you are both moving at 65 miles per hour, you can take several minutes to pass each other. Plenty of time to see what their kids are watching on the DVD, get a good look at the driver, and perhaps even try to pass some Grey Poupon.

In the 18 1/3 years it took Hubble to go around the Earth 100,000 times, it covered a distance of 2.7 billion miles. That sounds like a lot, especially if you are moving at 17,000 miles per hour! But, in space, 2.7 billion miles is only about the distance from the Earth to Neptune, and only 1/10000th the distance to the nearest star. We have four space probes (Pioneer 10 and 11, and Voyagers 1 and 2) that have travelled much further. And many other satellites around the Earth have been longer-lived, and have logged many more miles than Hubble.

Basically, Hubble hasn't set any records. It's just reached a nice, round number that is kinda fun to celebrate. So, in that line of celebration, NASA has released some colorful new pictures of a star-forming region in the Large Magellanic Cloud (LMC), one of the Milky Way's own satellite galaxies. And the LMC has only completed one or two orbits around the Milky Way in the 13 billion years its been around. So, our Hubble has an entire galaxy beat! (Of course, instead of an altitude of 600 kilometers, the LMC is at a distance of about 160,000 light-years, and it is travelling about 40 times faster than Hubble).

Also, NASA has a contest where you can win a nice print of a picture from the Hubble; look on the Hubble's home page for that contest (which ends after this week).

Thursday, August 07, 2008

Hanny's Voorwerp

Hanny's Voorwerp
Image Credit: Galaxy Zoo, ING, APOD

A couple of months ago, I was looking at the daily Astronomy Picture of the Day, when I saw the weird green thing near a normal galaxy in picture above. Even stranger was the object's name: "Hanny's Voorwerp" (which, it turns out, is Dutch for "Hanney's Object"). It was a cool picture of an object the likes of which hadn't been seen before. So, I stuck it in the "weird astronomy things" file in my brain and went on.

Now, a couple of months later, CNN.com has made Hanny's Voorwerp its lead story. It must be a slow news day, because while the discovery (and method of discovery) are good stories, I'm not sure it should rank above the news about the Olympics, or news from Iraq or Afghanistan, or the U.S. election. But it is a nice change.

So, what's the story? It starts with a project called Galaxy Zoo. Galaxy Zoo was set up to get people at home involved in a science project that requires human eyes and brain power to classify galaxies, but is too labor intensive for any astronomer to undertake. Basically, galaxies come in three basic shapes -- spiral, elliptical, and irregular. (That's an over-simplification; there are sub-classifications and many details that I won't go into, because they aren't important here). Computer algorithms for identifying galaxies do okay, but they aren't perfect, and they tend to miss interesting objects. In the Galaxy Zoo, pictures of millions of galaxies taken as part of the Sloan Digital Sky Survey have been looked at by volunteers around the world.

Hanny's Voorwerp is one of those interesting objects that I doubt a computer would have recognized, because it is unlike anything we've seen around other galaxies. It appears to be a large patch of gas near big galaxy, but this gas doesn't seem to have its own stars. It's just sitting there in space and glowing. It was discovered by a school teacher from the Netherlands, Hanny van Arkel.

So, what is Hanny's Voorwerp? We don't know! But that doesn't keep us from guessing. Initial data from the picture and from spectrographs indicate that this is really hot gas at the same distance as the galaxy in the picture above, and that the gas has probably been heated by a shock wave (like a blast wave from an explosion, or a collision with something). The best guess, according to astronomer Bill Keel's work, is that the galaxy above Hanny's Voorwerp harbors a big black hole at its center (as most galaxies do), and that it recently was "active," or swallowing dust and gas at a prodigious rate. When a black hole is gobbling material like this, the material tends to heat up, and some of it can get shot away from the black hole before it is swallowed in gigantic, high-energy jets (like these). And then, within the last 100,000 years or so (very recently by astronomical standards), the black hole ate everything within reach, and went into hibernation, turning off the visible light.

Hanny's Voorwerp was an innocent bystander, some gas that happened to either be passing by the galaxy, or perhaps falling into the galaxy, when the black hole turned on and blasted it with intense radiation and jets of material. The black hole then turned off, leaving behind a ghostly glow from the impact.

Congratulations to Hanny van Arkel on her unique and interesting find!

The emotions of UFOs and other fringe topics

Today I came across this excellent editorial by Seth Shostak, a researcher at the SETI Institute, about how many of the most vocal proponents of alien visitations seem to prefer uncivilized arguments to rational discussion on the issue.

Note that some scientists are guilty of the same thing, and most believers in UFOs don't engage in this behaviour. But it is disheartening for those of us who do make good faith efforts to discuss issues to be unfairly attacked.

This sort of uncivil discourse seems to be pervasive in society, and always has been. It doesn't matter whether the topic is science or religion or politics or sports. But that doesn't make it acceptable, and it certainly does not help to win people over to a cause or an opinion.

Monday, August 04, 2008

It's not rocket science

SpaceX Falcon 1 Rocket
Image Credit: SpaceX

On Saturday night I was mindlessly surfing the web, waiting for some clothes to dry before I went to bed. I visited Phil Plait's Bad Astronomy blog, and he had a post with a link to watch a live webcast of SpaceX's first commercial launch of its Falcon 1 rocket.

First, a little background. Until recently, all large rocket launches in the U.S. have been run by NASA. NASA contracts private companies, such as Lockheed and Boeing, to build the Atlas and Delta rockets used for most launches, but NASA runs the show.

Recently, there has been a push by industry and the public to encourage private (by which I mean non-governmental) corporations to build and launch rockets capable of carrying satellites and people into space. The thought is that a private company can build a reliable, functional rocket with costs far lower than NASA's going rate. Competitions such as the Ansari X Prize are spurring development.

One of the first companies to try and go commercial is Space Exploration Technologies, or SpaceX. They have developed the Falcon rocket family that is supposedly capable of launching both small and large satellites into Earth orbit. They've attempted three launches so far. The first demonstration flight failed shortly after launch because of a bad bolt on the engine. The second demonstration flight almost worked, but failed to achieve orbit when fuel sloshing in the tanks caused the engine to shut down early. But they solved those problems, and pressed ahead.

Saturday's launch was their first commercial launch, and carried a handful of small satellites. Unfortunately, the launch failed when the first stage failed to separate from the second stage. In spite of the failure, SpaceX has vowed to carry on.

I don't know much about the SpaceX company, nor any of the other companies working on private space vehicles (like Virgin Galactic). And I know nothing about their rocket designs, and next-to-nothing about overall rocketry. I'm an astronomer, not an aerospace engineer. So, I don't have a good opinion on why the failure may have happened, whether SpaceX has a good or poor rocket design, and other such topics. But I do know that getting into space is very hard. Earth's gravity is pretty strong, our atmosphere exerts significant pressure and turbulence on rockets, and any rocket has so much fuel, it is essentially a flying bomb. Rocketry is a tricky business; there's a reason our language uses "rocket science" as a metaphor for ridiculously complex endeavors.

As new companies start and try to get into space, there will be failures, and likely multiple failures by any given company. Money will be lost to seemingly minor problems (like a rusty bolt); worse will be when lives are lost in flight (and that will happen). I don't know if private space flight will be economically feasible in the near term (I'm not an economist, either). I do find it exciting that there are people willing to try, willing to risk money and lives on ventures that may or may not succeed in the short term. In the long term, I think the outlook is good, as people learn from their experience and as technology continues to improve. But whether private space flight becomes common in ten years or fifty years, I don't know.

Friday, August 01, 2008

Today's Total Eclipse Video

For those of you who weren't in Siberia today, here is a video of the entire totality, when the sun was completely covered by the moon. The video was taken by Ivan Komarov of Manjerok, Siberia, and sent to cnn.com.

The video starts in the final seconds before totality, when the last bits of the sun are disappearing behind the moon. This is often called the "diamond ring" effect, as one brilliant sliver of the sun shines through a lunar valley.

In the instant the sun is completely covered, the sun's outer atmosphere, or corona, comes into view. What you are seeing is a very tenuous, very hot (millions of degrees!) gas. The light we see is not from the gas itself, but light from the sun's surface (called the photosphere) being reflected toward us. The sun's corona is always there, but is completely obscured unless something (like a 2000-mile diameter rock) blocks the sun's photosphere.

After about 2 minutes, you can see the diamond ring happen in reverse. Notice how fast the sun gets bright again! Its photosphere is so brilliant, that even the tiniest sliver overwhelms cameras (and can damage your eyes). During the totality, it is completely safe to look at the sun without protective equipment, even through telescopes and binoculars. But the instant the photosphere re-emerges, you must use solar filters again, or you will permanently damage your eyes.

Unlike lunar eclipses, total solar eclipses have scientific value, though not as much as they used to. Solar astronomers flock to total eclipses with all sorts of expensive equipment for two minutes of intense data collection. With the sun's photosphere out of view, astronomers can study the very outermost layers of the sun's atmosphere from the ground. Before satellite telescopes, total eclipses were the only time this could be done! But, these days, satellites can use fancy optics to create their own eclipses whenever they want, so the science value of a given eclipse has gone down somewhat. But, it is far, far cheaper to run new experiments on the ground during a total eclipse than to launch a satellite, so there is still valuable and groundbreaking science that is done during total solar eclipses.

Total solar eclipses were also the first independent test of Einstein's General Theory of Relativity. Einstein predicted that the sun's gravity should bend the light from stars ever so slightly; careful measurements of stars (which become visible during totality!) taken during eclipses found that Einstein's predictions were spot on. Here is an article discussing some of those first historic measurements. It is important to remember that this was a pure prediction -- nobody had the slightest idea that gravity could bend light, so no other theory predicted any bending, and Einstein's theory got not just the bending right, but the the amount of bending right. It was an amazing prediction, and an even more amazing confirmation of Einstein's theory.

As I said, satellites can now make artificial total eclipses whenever they want; this has led to a revolution in understanding how are sun works, and how it interacts with the Earth. The SOHO spacecraft releases images and movies of the sun and its corona daily; go here and click on the image to look at, or the link to movies (at the bottom of the page). The "false eclipses" are the pictures from the "LASCO C2" and "LASCO C3" instruments, where the white circle indicates the size of the sun. The central dark area (much bigger than the sun) is a disk used to block the sun's light. Right now, you can see the planet Mercury passing the sun. And this page has movies from throughout the SOHO mission's storied life.