The strange world of embargoed science

Press releases on scientific discoveries are sometimes "embargoed," meaning that the press is given materials in advance, but only on the condition that the findings not be released before a given date (often the date of a press conference or publication of a magazine). Nature, one of the most prestigious scientific journals, is extraordinarily strict; at one point, they requested that scientists not publish their work as "pre-prints" (copies of articles distributed in advance of official publication, primarily to other scientists in the same field). That borders on being scientifically unethical, as science thrives only on the free flow of information. Thankfully Nature backed down on that request.

Anyway, I'm on a NASA email list with advanced notice of press releases. I'm not sure how I got on the list, but I get notices anyway (I may have requested membership somewhere at some point, but I don't remember). Typically the news is embargoed for a day or two.

Yesterday, I got an announcement about a press release that will be made tomorrow, and strict notice of the media embargo was given. Looking at the release, I had to laugh at how silly the embargo is. The topic is science close to what I work on, and the results have been freely available on our preprint server for six months! The results are also quite intriguing, so I've been chatting about it with colleagues, and I even spoke about it with the science teachers at the workshop I helped lead a couple of weeks ago. So the idea of an embargo is, frankly, silly.

Now, I won't spoil the fun and talk about NASA's release early (there are some cool pictures); I'll talk about it tomorrow. But I'd urge media outlets to re-think the purpose of an embargo. If you are going to make a press release, is there a good reason for embargoing the news? If you just want everyone to get the data at the same time, why not release everything at the time of the press conference (if there is one)?

Our new discovery

Image Credit: Sloan Digital Sky Survey

The faint blue dot in the center of the picture above is a white dwarf, the ashes left behind after a star used up all of its nuclear fuel and completed its life. Tens of thousands of white dwarfs are known (and tens of billions exist in our galaxy), but this particular one is unique among the known white dwarfs.

About a year ago, a collaborator of mine discovered that a small fraction of white dwarfs have carbon atmospheres. Most white dwarfs have atmospheres composed mainly of hydrogen, and almost all of the rest have atmospheres made up mostly of helium (and by mostly, we mean more than 99% of the atoms). The reason for most white dwarfs having these two atmospheres is that these are the two lightest elements in the Universe, and the gravity of white dwarfs is so high that it can separate the atoms in its atmosphere in a matter of days or weeks. So, if there is even the tiniest amount of hydrogen in an atmosphere, it will rise to the top and be the only thing we can see from Earth.

So, carbon atmosphere white dwarfs (which make up only about one in a thousand white dwarfs) tell us that these white dwarfs have somehow lost virtually all of their hydrogen and helium. This is strange and hard to explain. In fact, none of the guesses for the origins of the atmospheres of these white dwarfs are really that well-developed, and these guesses are all lacking in evidence. What we really would like is to get inside the star, and see its internal structures. That would tell us a lot about what sort of processes went on in the star before it became a white dwarf.

Amazingly, there is a way to look inside a star -- it's called asteroseismology. Some stars can ring, like a bell, as sound waves move around and through the star. And just like geologists can study the interior of the Earth by examining the "ringing" of the Earth due to events like earthquakes, we can use the waves on stars to probe their inner regions. Helioseismology, or the study of sound waves in the sun, has told us a lot about the sun and confirmed some of our most basic theories of the structure of normal stars.

So, one day I was wondering if these carbon-atmosphere stars might be susceptible to this "ringing," (in white dwarfs we call this ringing pulsating) and therefore able to be studied by asteroseismology. Luckily, one of my friends and colleagues here at the University of Texas, Mike Montgomery, is an expert in the theory of white dwarf pulsations. So, I asked him if these stars would pulsate. He went off, ran some simple models, and decided that they might pulsate under specific conditions (depending on the star's temperature).

It isn't too hard to find pulsating stars. The waves in the star act as though the atmosphere is sloshing around the surface of the star. When the gas piles up, it heats up a bit, and where it has left, the star cools down a bit. Where the gas is hotter, the star glows a little brighter, and where it is cooler, the star is a little fainter. So, as we watch the star from Earth, we'll see brighter and fainter spots moving in and out of view, and the star will appear to get a little brighter at some times, and a little fainter at other times. This brightening and fading happens on time scales around a few minutes. So, if the star is bright enough to take a picture of every 15 to 30 seconds or so, we can see the star actually changing brightness.

Mike and I then went and asked for telescope time to look at some carbon-atmosphere white dwarfs. Only one white dwarf appeared to meet the right conditions to pulsate, and the rest looked like they should be quiet. This made for a great test that scientists talk a lot about: we have a theory to test (if the stars pulsate when their temperatures are in the range that Mike calculated), a test sample that includes "control" stars (those that shouldn't be pulsating), and a experimental procedure (to look at them with a telescope). So we were given telescope time in February. Both Mike and I were busy on the days we were given (I was in England at a conference), so we got a grad student, Steven DeGennaro, to go run the telescope for us. Steven spent the first few nights looking at our control stars (we didn't tell him which one was likely to vary). That was quite boring, because they didn't do anything. Hours upon end, they looked identical from one picture to the next. This is what we expected, but we wanted to be sure.

Then, however, Steven went to the star we thought might vary. Within about 20 minutes, it became clear that the star was getting brighter and fainter every 7 minutes! Steven had discovered the first every pulsating carbon-atmosphere white dwarf. Here is a colorful plot of the brightness of the star:

You can see that the star is getting brighter and fainter in a fairly regular fashion. In fact, the star is ringing at just two pure tones one octave apart. If we could hear sound across space, the star would be singing strongly at a slightly out-of-tune E-flat 16 octaves below middle C, with a softer overtone one octave higher. Alas, in space, no one can hear you sing.

This was exciting -- Mike had made a prediction, we went and looked and confirmed the prediction! We then wrote up a short paper on our discovery, which appears in today's edition of the Astrophysical Journal Letters.

Alas, the star has a very boring name: SDSS J1426+5752 (that's its nickname; its real name has about twice as many numbers). The white dwarf is about 800 light-years away in the constellation Ursa Major (the "Big Dipper"). Unfortunately, you need a really big telescope to see our star, as it is 200,000 times fainter than the faintest star you can see with your unaided eye. (For those of you who speak "magnitudes," astronomy's measure of brightness, it is magnitude 19.2.)

The other types of white dwarfs (hydrogen-atmosphere and helium-atmosphere) have been known to pulsate for over 25 years, so this marks the first new type of pulsating white dwarf in 25 years. For that reason, we decided to put out a press release announcing our discovery. So, you may very well read about this in the newspaper. Maybe. Really, it is hard to tell in advance what people find interesting and what they don't find interesting, so maybe no newspaper will pick up this story. But we put it out there, in the hopes that someone may enjoy the tale.

Tomorrow, I'll try and talk about why we may be completely wrong. I don't think we are, but we have to admit that possibility for now.

The (miniscule) threat of a US spy satellite

Image Credit: Chris Peat, Heavens-Above GmbH

This weekend, I opened the newspaper to see a story with the title "Disabled Spy Satellite Threatens Earth." I was curious, since I didn't know that a single satellite, especially a defunct satellite, could threaten the entire planet. So, I read the article, and I still know that I was right -- Earth is not threatened by this satellite.

First, let's figure out what the story is about beyond the over-hyped headline. The if you read the story, you'll see that the facts are that a U.S. spy satellite has lost power. That also means it has lost the use of its thrusters. And that's about it for details, with some knowledgeable sources saying the satellite will re-enter Earth's atmosphere in late February or in March.

Our satellites in low-Earth orbit (those satellites orbiting less than about 1200 miles above Earth's surface) are not in a pure vacuum of space. Sure, there isn't exactly a lot of air around, but there are tiny bits of Earth's atmosphere up there. As a satellite orbits, that tiny bit of atmosphere drags on the satellite, slowing it down and causing it to slowly inch toward the Earth. As it gets closer to the Earth, the thickness of the atmosphere increases, so the drag increases, so the rate of slowing increases, so the satellite's descent speeds up, and the atmosphere continues to get thicker, and so on until the satellite falls back to Earth. It doesn't matter whether a satellite has electricity or not, or whether it is under control or not. All Earth satellites in low-Earth orbit will fall back to Earth in a timescale of months to decades, depending on how high up the satellite is.

There is one way to keep from falling back, and that is to use a rocket engine to give a satellite a little acceleration to counter-act Earth's atmospheric drag. As long as the engine still works and has fuel, the satellite can orbit as long as it wants.

The graph at the top of this post is a plot of the height of the International Space Station over time. You can see that, most of the time, the space station is slowly sinking back toward Earth, and every once in a while it very quickly moves further away again. These boosts in the station's altitude are caused by rocket engines on visiting spacecraft (Russian Progress supply rockets and the Space Shuttle). These boosts keep the station in orbit.

The Hubble Space Telescope doesn't have a rocket engine, but it is higher than the space station and so can survive longer. Every time a shuttle visits the Hubble, they use the shuttle's engines to boost Hubble back up to a safe orbit.

But satellites without rockets, or satellites that lose power and go out of control (like the US spy satellite) will eventually fall back to Earth. Most satellites disintegrate high in the atmosphere and completely burn up; larger satellites (like NASA's Skylab or Russia's Mir space station) can have pieces that survive re-entry; pieces of Skylab were found across Australia.

For that reason, countries now try and de-orbit useless satellites by using a rocket engine to cause the satellite to fall into the ocean. Astronauts on the next Hubble repair mission will attach some equipment to the Hubble that will allow a future robotic spacecraft to attach an engine to Hubble to bring it down. But, if a satellite doesn't have an engine, or if the engine isn't working, then the spacecraft could fall anywhere.

As you might imagine, some satellites have some pretty nasty stuff. Rocket fuel can be hazardous, and some satellites have radioactive power supplies (these are built to withstand re-entry intact so as not to spread radioactive particles over the Earth). If those satellites fall in a populated area, people could get sick. But most of the Earth is water, and most of the rest is unpopulated, so the chances of a noxious rogue satellite part hitting a city are very tiny.

So, the real story of the US spy satellite is, if a piece lands in your backyard, don't touch it. The chances are it wouldn't harm you, but it might make you sick. And, more to the point, there are parts of that satellite that the government doesn't want anyone to see. So picking up a piece of the satellite for decoration is probably not a good idea, unless you'd like an inside look at Guantanamo Bay.