Happy Mother's Day

I'm spending my second night in a row watching thick clouds roll by over our telescope. The night started off with another sucker hole, so we got ready to try and observe. But then the clouds started rolling in, and that pretty much ended things. Tomorrow is my last night, and it isn't looking very hopeful right now. I hope the weather is wrong -- it is not a good feeling to come away with only one night out of four.

So, I'm trying to stay up as late as I can, just in case tomorrow night is clear I'll still be on a night schedule. I've been trying to catch up on work, but I am so hopelessly behind, I'm not making much of a dent!

Anyway, happy Mother's Day to all of you mothers. I didn't get everything to my mom and grandmothers in the mail before I came up here, so some gifts will be arriving late. (Sorry, Mom!)

Cloud happens

Tonight has not been a fun night at the telescope. At sunset, it was completely cloudy, but the cloud forecasts from the Clear Sky Chart claimed it would clear by 1am, so we hunkered down. Within an hour, the skies overhead cleared, so we opened the dome and started our observations.

However, the clear spot was what is known as a "sucker hole," meaning you are a sucker to think you can get good data. After about 45 minutes, the hole closed, and the skies have been mostly cloudy ever since, always teasing to clear, but never good enough to start working.

In another half hour, I'm giving up if it is not clear. Our observations need several hours to be worthwhile, and it is four hours to dawn now. I could be trying to work, but sometimes no data is better than bad data. Hopefully tomorrow will be better!

Observing in west Texas

It's been a busy few days here. Tuesday I went to speak with students in a couple of high school astronomy classes in Kyle, Texas (a little south of Austin). It was an interesting experience. Some students were interested in what I had to say, some were interested in asking me questions but on topics other than what I was talking about, some were bored and passing notes or texting during class, and others were sleeping. That visit was a lot of fun. but it took a lot out of me. I would not be able to get in front of that group every day, though.

Wednesday I drove out to McDonald Observatory for a weekend of observing. The drive was worse than normal. I had a 30 mph headwind, with occasional gusts that nearly blew my poor little car off the road. Because of the headwind, my gas mileage wasn't very good, and I slowed down to keep better control of my car. In the end, I arrived too late for dinner (but there were leftovers).

My goal is to do some more observing of our pulsating carbon atmosphere white dwarf. In order to use these pulsations, we need to get many nights of data spread out over time. This is our first real push to get lots of data on this star since we discovered it.

So, keep your fingers crossed for good weather. We may get a lot of clouds here later tonight and the first part of tomorrow night.

When your work is almost as exciting as ketchup...

Image Source: H. J. Heinz Company We knew that our press release from last week was not the most earth-shaking astronomy news ever. We put the story out there in the hopes that someone would find it interesting, and to advertise some of the new findings that your tax dollars are helping to pay for. It being the first press release I was directly involved with, I have done some Googling of the news to see where our story ended up.

Our story was picked up by Discovery Channel News, who even linked to it from the Discovery Channel's home page for a time. That was cool. And some other space blogs picked it up, as well as several foreign news aggregators (news outlets that seem to automatically or semi-automatically pick up news stories and publish them; since the stories are all identical to our press release, I'm not sure a human actually looked at them).

I was kind of hoping that a few astronomy news sources might mention our story. I often link to and talk about stories in Space.com, Sky and Telescope magazine, and Astronomy magazine, so I kept an eye out there. Nothing. Which is their right, and, as I said, our story is an interesting sidelight of astronomy research, and probably not the most Earth-shaking discovery of the year.

However, I did notice some of the stories that got posted around the same time, and they serve to just about completely burst our bubble. Space.com ran a story on how some data from an experiment related to ketchup physics was recovered from the debris of the Space Shuttle Columbia. While I fully admit that this is an amazing data recovery and that the Columbia disaster remains far more newsworthy than anything I've done, ketchup?!!

Some other white dwarf news also beat us out. A story on a supercomputer that will study exploding white dwarfs got some press, too. The computer has only been built; it doesn't have results yet. So, the promise of what may eventually be crucial studies of white dwarf explosions beat out our real data.

Oh well. In the grand scheme of things, this doesn't matter. But maybe next time we should put a little more shine on our work. Like promising to lift the federal white dwarf tax for the summer, or pointing out how terrorists could wreak havoc with a cube of white dwarf material (never mind that they couldn't obtain it), or speculating on how a white dwarf superdelegate might vote for president (probably for the most degenerate candidate).

What if I'm wrong?

Yesterday I blogged about the new pulsating white dwarf my collaborators and I found. Or at least we think it is a pulsating white dwarf. We're pretty sure, but we aren't absolutely certain. How do we know that we may not know what we're looking at? And what else might this be? And why did we put out a press release if we might be wrong?

First, there are a couple of things we are pretty certain about. We know we are looking at a white dwarf, and we know that all we see of the white dwarf is carbon. We also know that the amount of light coming from the star is changing by a few percent every 7 minutes, and that variation is very repetitive and stable. We also know that theory predicts that this white dwarf should be varying, assuming we have its temperature and mass right. If this were all the information we had (and it is 90% of it!), there'd be no doubt in our minds that this is a pulsating white dwarf.

But there is one extra bit of information we have. As I said yesterday, the star is beating at two very precise frequencies, one octave apart. This is rare (but not unheard of) in pulsating white dwarfs, and it lets us average all of the few hundred individual pulsations we've observed into a single pulse. When you do that for other pulsating white dwarfs, you get something that looks like a shark fin:

The white dwarf rapidly gets brighter, gradually fades, and then stays faint or a bit before getting brighter again. Complicated but expected physics that I won't try to explain gets you this shape.

But for our pulsating white dwarf, the average pulse looks like this:

To my eye, this looks more like the upside-down version of the normal pulse shape. In fact, at first we checked and re-checked our data to make sure that it wasn't backwards. But this is right, and it is totally unexpected.

There are objects in the universe that vary their light with this shape, but most of them we wouldn't mistake for our white dwarf. There is one type of object that worries us, though -- it's a star called AM Canes Venatici (which we give the nickname AM CVn, and pronounce it like "AM Can Van"). AM CVn is a big white dwarf that is slowly eating its neighbor star, which used to be a little white dwarf made of helium. When AM CVn was first discovered, it was thought to be a helium-atmosphere pulsating white dwarf. It took a lot of careful observations to learn the truth. And there are some eerie similarities between the story of the discovery of AM CVn and our discovery.

But, if our star is like AM CVn, it also must be different. Instead of a big white dwarf eating a little white dwarf made of helium, our star would have to be a big white dwarf eating an almost-as-big carbon white dwarf. Now, let's imagine that our white dwarfs were fish in the sea. A big fish has no problem eating a little fish, but two big fish usually don't try and eat each other. If they did, they'd get in a fight and rip each other apart.

In this case, the fish are white dwarfs, and the eating is done with gravity instead of teeth. And if our star were really two white dwarfs trying to eat each other, computers tell us that their mutual gravity would rip each other apart in a matter of seconds, and the debris would quickly fall back together into a single big white dwarf (or perhaps even explode as a supernova). And while the computer models may well be wrong, these same models get a lot of other things right, so we tend to trust them.

So, in short, we are pretty sure we have a pulsating white dwarf. We predicted it, looked for it, and found it. Nature would have to be pretty perverse to make our star yet another type of oddball object. Nature does sometimes play tricks on us (or, more often, we are a bit too clever for our own good and fool ourselves into believing something that is not true). And the ony evidence that this is not a pulsing white dwarf is the weird shape of the pulsing. It is possible to explain the weird pulsing within current theories, it's just that we've never seen it in a pulsing white dwarf before. I would estimate that 85% of the evidence says that this is a pulsing carbon-atmosphere white dwarf, and that's pretty good.

Why did we make a press release when we could be wrong? A couple of reasons. First, we are pretty sure we are right. I wouldn't bet the farm that we have found a pulsating white dwarf, but I'd be willing to bet a fair amount of money. Second, the other option -- two big white dwarfs trying to eat each other -- would be even more exciting. None of those are known to exist, and, as I said, they could explode as a supernova. Either way, we've found a very interesting object, and we wanted to share that excitement with people outside of our professional colleagues.