AAS #16: Bits and Pieces

Contributed by
Jan 11, 2008
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Fraser, Pamela and I have been

whining remarking to each other that there is a huge amount of news coming from this meeting, and we're having a heckuva time keeping up. Some is worth a long writeup, while others can probably be handled with a short post. Below are a few of the stories that are worth noting briefly.

And as a reminder: if you like what you're seeing here, Digg the articles! Click the button at the top of the post, and it'll help spread the word. Thanks!

1) The bigger the telescope the better, right? So what if your scope is the size of the Earth?

A technique called interferometry combines the light from telescopes that are widely separated, and with it you can make a virtual telescope that's the same size as the distance between the physical telescopes. If those 'scopes are on opposite sides of the Earth, you get a telescope thousands of miles across. Using this technique, astronomers have made phenomenal measurements, including actually seeing the rotation of the galaxy M33 as well as its physical motion across the sky; something that had never been done before. They have been able to see the effects of the Sun's motion around the Milky Way's center, even though a full orbit takes 240 million years!

2) One long-standing mystery in astronomy is an apparent fountain of antimatter streaming out from the center of the Galaxy. What's causing it? Most astronomers assumed it was coming from the giant supermassive black hole there, but now observations indicate it's actually being accelerated by binary stars, where one of the two orbiting stars is a neutron star or black hole.

The cloud of antimatter is detected because it gives off gamma rays, which are a very high energy form of light. The gamma rays from the Galactic center are not centered on the center (hmmm, remember to edit that line), but extend a little bit more on the western side. This matches the distribution of the black hole or neutron star binaries. These binaries can generate antimatter when regular matter from the normal (sunlike) star swirls around the denser object.

I wrote about this in my book, so now I might have to do some editing. Nuts.

3) The most luminous objects in the Universe are, ironically and paradoxically, the faintest.

Huh? Black holes can generate fantastic amounts of light as matter falling in to the hole first forms a disk around it. The disk is hot, and magnetic forces (along with friction and gravity) can make it extremely bright, as bright as billions of stars like the Sun. Supermassive black holes in the centers of galaxies are big, and have proportionately big disks which can outshine the rest of the galaxy in which it sits. We call these active galaxies, and there are different kinds (quasars, blazars, Seyferts) depending on the various characteristics of the galaxy.

It turns out, though, that in many cases our view of these black holes is blocked by tick gas and dust in the galaxy. The folks at the Sloan Digital Sky Survey have figured out a way to detect a fingerprint of these obscured galaxies, and found 887 hidden quasars that were previously unknown, by far the largest such sample ever made. What this means is that we have to be careful in the future about what objects we can and cannot see -- astronomers may say "We expect to see XXX of these kind of galaxies and see none, which means our cosmology is wrong," we can take it with a judicious grain of salt.