Today’s American Astronomical Society press conference is a wee bit different: it’s about more speculative stuff. We’ll be talking to astronomers about putting telescopes on the Moon, looking for dark matter in the Sun, and upping the odds on looking for (and talking to) aliens.

It all starts at 9:30 a.m. Central time (15:30 UT). I’ve embedded the video below. If you want to participate in the chat room, go to the UStream channel. You an change your nickname (and please do!) by typing "/nick Al E. Inn".

The thing about black holes is, they’re black. That makes them hard to find, of course, but once you find one it’s also hard to get any information about it. The only way we can figure out anything about them is by looking at how they affect things around them: how stars orbit them, how material falls in and gives off light, and so on.

After observing many galaxies over many decades, it was found that every large galaxy has a supermassive black hole at its core, where supermassive means thousands, millions, or even billions of times the mass of the Sun. The way to weigh a black hole is to carefully measure the velocity of stars in orbit around them; the faster they move, the more massive the black hole. Thanks to Kepler, we can use those measurements to get a decent estimate of the central black hole mass.

But this can be hard to do, especially for distant galaxies. It takes long exposure times, intensive analysis, and generally quite a bit of work. But now astronomers have announced a very interesting discovery: spiral galaxies with more massive central black holes tend to have their arms more tightly wrapped. Galaxies with lower mass black holes seem to have more loosely wound spiral arms.

Why this would be is something of a mystery, and to be honest the discovery is not on absolutely firm ground. What they have uncovered is a correlation, not a rock solid cause-and-effect, but their data so far look pretty good. This idea pans out, that means that getting the mass of the central black hole in a spiral galaxy may be as easy as simply taking the galaxy’s snapshot and looking at the spiral arms. Incredibly, this means the central black hole’s mass can be determined for galaxies that are eight billion light years away!

The Andromeda (left) and Triangulum (right) galaxies. Andromeda has tight arms and a massive black hole, while Triangulum has loose arms and a lightweight black hole. Images courtesy T. Rector and B. Wolpa, NOAO/AURA/NSF, and T. Rector and M. Hanna/NRAO/AUI/NSF/NOAO/AURA, repsectively.

So, for example, the Andromeda galaxy, which has a very massive black hole in its heart — nearly 200 million times the mass of the Sun, or about 50 times the mass of the black hole in the center of our Milky Way — has its arms relatively tightly wound up. But the Triangulum galaxy, which has loose arms, has a low-mass black hole in its core, just a few thousand times the Sun’s mass.

The mass of the central black hole turns out to be pretty important in the life of the galaxy… though probably not why you’d think. Even the most massive black hole is only a tiny fraction of the total mass of the parent galaxy — far less than even 1%! But it turns out that the mass of the black hole seems to play an important role in how the galaxy itself forms. The black hole forms at roughly the same time as the galaxy itself. As the black hole gobbles down matter, it can get what is basically indigestion, eating material too quickly. This sets up a wind of matter that blows out from the black hole, and that in turn disturbs the gas in the galaxy. That gas is what forms stars, so the star formation history of the galaxy can be affected by its central black hole. This in turn can affect how mass gets distributed in the disk of the galaxy, and that’s — maybe — why the arm structure is affected by the black hole.

However, galaxy history is fraught with danger. Galaxies collide, or slide past each other and mess each other up. This also affects how the disk and arms behave, so obviously this situation gets complicated quickly. Worse, dark matter may play a role as well, but it’s not clear how that might work either. But if the result that black hole mass somehow correlates with the spiral arm shape is correct, that will give astronomers yet another handle on how galaxies interact with the monsters at their hearts.

So you know how it is. You and your other gorgeous, tan, and fit 20-something friends go out to a secluded site to have a star party and maybe make out a little.

But then of course — of course — wouldn’t you know it? Little blue shiny balls of weird stuff come down and abduct people and change the very laws of the universe itself!

Man, if I had a nickel for every time that happened at a star party.

But it happens at Star Party, or more accurately, the movie of that title. I watched the trailer online, and well, it doesn’t look that great. It has that whole I’m-a-horror-movie-where-stupid-people-open-doors-they-shouldn’t-and-scream-a-lot-and run-around-and-make-bad-decisions-until-you-want-to-scream-and-get-your-money-back feel to it.

But maybe that’s just me.

This is in fact a real movie (it has an IMDB page). It’s an indy film, though a lot of it looks pretty slick.

Still, I have to laugh whenever movie people try to portray scientists, or science enthusiasts. This picture is not a J Crew ad:

Yes, all us astronomers look like this, why do you ask?

The plot of the movie looks pretty silly, too, but it’s hard to tell from the trailer. I can find no copies of this movie online (including the torrents, not that I would ever use those). It came out in 2005, and obviously didn’t make much of a splash. I’m not even sure the production company, Dark Matter Productions, even exists anymore. The number listed on a website for them comes up with an answering machine that sounded very much like a totally different company.

So it sounds like this is one for the history books. Has anyone seen it?

Tip o’ the dew shield to BABloggee Heather Steingruebl, who grossly overestimates the import of these links.

I just got word from Steve Ritz, the Project Scientist for GLAST (the Gamma-Ray Large Area Space Telescope), that it’s ready for launch! Woohoo!

GLAST will study extremely high energy light emitted by some of the most violent events in the Universe: exploding stars, gamma-ray bursts, black holes gobbling down matter, and even from solar flares and maybe, just maybe, from dark matter, too (one form that DM may take will emit gamma rays when two particles of it collide).

The earliest GLAST can go is June 3. Here’s a shot from the NASA GLAST page (where you can get more info) showing GLAST being mated with the rocket that will take it into space.

This is terribly exciting. I worked on the education and public outreach for GLAST for six years — it was what funded my move out to California, back in December 2000. I wrote a vast amount of words for that project, and along with my teammates gave dozens of workshops to hundreds of teachers across the country.

I never touched the hardware; I never even saw it. But still, a piece of me will go up on that rocket in June. Pieces of lots of other people too. I’ve been able to watch twice as projects with which I’ve been involved have rocketed into space (STIS on board Hubble, and then Swift), and GLAST will make three. This will be amazing.

After the successful landing and testing of Phoenix, GLAST promises to make this a great time for robotic exploration.

Later on, nearer to launch, I’ll write more about this project; but check out the links above or my earlier posts about it to satiate yourself for now. GLAST will revolutionize gamma-ray astronomy.

Update (5/7/08): The image I had posted originally was distorted due to the wrong picture being made available to the press (like me!). I got a nice email from Joerg Dietrich, one of the astronomers who took the data, with a link to the correct image. I have updated both the image and the link. Sorry, and enjoy!

We’ve known for a long time that most of the Universe is invisible. 72.1% of it is dark energy, about which we know very little. 23.3% of it is dark matter, which was only recently tagged for real and for sure; we still don’t know what particles make it up, but we’re on the verge of finding out.

Normal matter — us — makes up just 4.6% of the Universe’s energy and mass budget. But here we are! At least, here we mostly are: actually, we only see roughly half of the normal matter in the Universe. Stars, galaxies, and warm-to-middling gas aren’t too hard to spot in general, but they only make up about half of what we expect to see of normal matter.

Where’s the other half?

Let’s turn the wayback machine to about 13.6 billion years or so ago. The Big Bang is old news at this point, but the first stars have yet to be born. Matter and energy are mixed everywhere, but some of it is different. What we now call dark matter is starting to clump together through gravity, forming long sheets and filaments far bigger than any galaxy we see today. This forms a grid, a framework, upon which normal matter starts to fall. Eventually, galaxies and clusters of galaxies and clusters of clusters of galaxies will form along these cosmic skeletons.

Fast forward to today. Bang! We see galaxies everywhere… well, not exactly everywhere. We see them lying in those long sheets and filaments, showing us where the dark matter structures are, like dew drops on a spider’s web.

But that’s just the stars and galaxies, remember? It’s only half. Where’s the other normal matter?

The hypothesis is was that it would be in the form of very hot gas strung out along those filaments as well. Hunting for it would be hard: it would be very diffuse, making it dim, and very hot, meaning it would only emit at short wavelengths, like extreme ultraviolet or X-rays.

Hey, we have telescopes that can see those!

And now we have (and more pictures can be found here). Astronomers upped the odds of finding the gas by looking around galaxy clusters, where it would be denser, and also doing something clever: looking near clusters that are near each other in the sky due to perspective. One would actually be farther away than the other, but peering very nearly along the angle separating them they would look like they’re right next to each other. Since we’d be looking along a long thin cylinder of gas, that would make it appear brighter than if we saw it through its side.

The picture above shows the galaxy clusters Abell 222 and 223, both about 2.5 billion light years away. The visible light image just shows them as clumps of points, but remember: each dot is a massive galaxy like our own! The technicolor bit is from the XMM-Newton orbiting X-ray observatory, and shows the hot gas. Since these are separate clusters, they should be detached from each other. But instead, they’re connected by a gas bridge of ten-million-degree plasma. That’s the missing stuff! That’s made up of baryons; particles like protons and neutrons, atomic nuclei and the like. Look around you: everything you see is made of baryons (and leptons, which include electrons), so this gas is your kin.

It’s a bit more rarified, though: there are only about 30 baryons per cubic meter in this bridge. Good thing it’s big (about 4 million light years wide) and we’re looking down its length! But then, that’s why so much of this stuff is missing. It’s really hard to detect.

According to the models, there is enough stuff in this bridge to extrapolate the existence of the rest of the missing normal matter. Of course, we only have a data set of one, which is a bit rocky, but I suspect more of these will be found now that we know they’re out there.

And may I add, phew! It’s always nice when half the stuff you can’t find finally turns up.

Why have I never heard of Jonny Berliner before?

I somehow found him through Null Hypothesis. His music’s not for everyone… but how can you resist a song about dark matter?

Here are the lyrics if you want to keep up at home, too.

The Milky Way Galaxy is relatively typical of galaxies today, if a bit on the beefy side. It has about 200 billion stars, and is 100,000 light years across.

Now imagine a galaxy with that same mass, but only 5000 light years across. That would be an incredibly densely packed galaxy, and in all honesty, pretty freaky.

But that’s exactly what astronomers using Hubble and Keck have found! Probing the early Universe, 11 billion light years away, they found nine galaxies that are as massive as galaxies today, but far more compact. The galaxies are very young, only a half to one billion years old, judging from the types of stars they contain. Not only that, they appear to be quiet: unlike our galaxy today, these distant compact galaxies are not actively forming stars. It’s as if they formed all their stars all at once right from the start, and then that was that.

This plot shows that these galaxies really are small and massive. Size is shown on the vertical scale (bigger galaxies are near the top) and mass along the horizontal (more massive galaxies to the right). A big massive galaxy would be to the upper right, and a low mass, dinky galaxy to the lower left. These oddballs are marked, and are clearly separate from other galaxies: they are massive, yet small.

That’s really weird! What could cause such galaxies to form so tightly jammed with stars? One idea is that in the early Universe there were pockets of dark matter, places where it was somewhat denser than on average. Hydrogen would have collected there, attracted by the fierce gravity, and formed the galaxies. Constrained by the dark matter pockets, the galaxies would have been very dense and formed stars furiously for a short period until all the hydrogen was used up. That would explain their small stature, dense stellar population, and lack of ongoing star formation. But it’s just a hypothesis for now.

What’s also odd is that we do not see any galaxies like these today; any galaxy of comparable mass that we see in the current Universe today is far larger, like our Milky Way. So these galaxies existed in the past — possibly in large numbers — but we don’t see them now. Where did they go?

They may get bigger with time. It’s not clear how they would do that, but perhaps the more massive stars fall to the center, flinging lighter stars outward, puffing up the galaxies over time (I describe this process a bit in a post yesterday about globular clusters). Maybe they collide and puff up — though that means they would get even more massive than we see them, and they’re already as hefty as galaxies today. Maybe they grow dark over time, and we just don’t see them any more.

Actually, I don’t like any of these answers very much. We obviously need a lot more observations of these tiny dense suckers. However, we’re pretty much at the limit now; it took Hubble’s and Keck’s incredible resolution to be able to see these things at all. We’ll have to wait for the Hubble servicing mission in September to get even deeper images, when the new Wide Field Camera goes online. I suspect that STIS, the spectrograph that I used to work on, may be able to help as well, if the astronauts can fix it too.

Either way, it’s cool to know the Universe can still throw us the odd curveball or two. The more we look, the more weirdness we find.