Category Archives: galaxy interactions

AAS meeting stories, american astronomical society, astronomy media, astronomy news, galaxies, galaxy interactions, Milky Way Galaxy

More from the Astronomy Fire Hose

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Some Thoughts on a Galaxy of Possibilities

I am always amazed at the depth and breadth of discoveries in astronomy that get announced at these AAS meetings. I mean, we all KNOW it’s a big universe and there are always going to be amazing discoveries – but, what we don’t always know is just WHAT those finds will be.

Earlier today we heard from scientists using data from the Sloan Digital Sky Survey to create the largest multicolor image of the night sky. It’s essentially the Palomar Sky Survey of our time, but in digital format. You can browse through their work here, and eventually you’ll see much of their work in GalaxyZoo, World Wide Telescope, and GoogleSky.

As I sat there and listened to the scientists talk about their work, it struck me just how much astronomers learn each DAY and how LITTLE we see about it in the news media.  To be sure, there’s a LOT of news every day, and science has to struggle for attention among all the other events of our time.

An SDSS stellar map of the northern sky part of the sky as seen from Earth. It shows trails and streams of stars. These are from satellite galaxies of the Milky Way Galaxy that were torn apart as they strayed too far into our galaxy’s gravitational field of influence. The insets show new dwarf companions discovered by the SDSS (credit: V. Belokurov).

Did you know that astronomers are using the Sloan Survey using a technique called “spectroscopy” to look at the light from those stars and figure out their chemical compositions, the velocity (speed) they’re moving through space, and a host of other characteristics?  It’s true.  One of the coolest outcomes of such a study is that they can now tell which stars came from our own galaxy and which ones were or are parts of galaxies that are being sucked into the Milky Way galaxy.  Stars from galaxies being gobbled up have slight differences in their metallicity (the heavier elements they contain), as well as definite variations in their velocities and direction of travel.

These factors, in turn, give astronomers some important clues to how galaxies form – essentially, the Milky Way has gotten bigger by gobbling up stars from smaller galaxies that were once neighbors moving along the cosmic highway with it. Trace the characteristics of those stars spectroscopically and you learn more about the former neighbor satellites that are now mingling their stars with the Milky Way Galaxy.

Well… THAT was just one tiny part of what Sloan Digital Sky Survey scientists discussed this morning–just a small drip from the firehose of astronomy information flowing at this meeting.  There is literally a galaxy of science to be learned here.

astrocast.tv, galaxies, galaxy interactions

The Cosmic Dance

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Galactic Minuets

Yesterday I talked about galaxy mergers and acquisitions, the subject of my latest segment on Astrocast.tv. These scenes fascinate me because galaxies are not exactly tiptoing through the tulips as they interact with each other.

Think of the sheer amount of mass involved!  For the Milky Way, you’re talking about the mass of what, somewhere between 300-400 billion stars.  If every star in the galaxy had the same mass as the Sun — which has a mass of 1.9 x 1030 kilograms — you’re talking about a LOT of mass. Of course, not every star is the mass of the Sun — some are more massive, some are less massive. And, of course, we have that pesky massive black hole at the center, and huge amounts of interstellar gas and dust also poking around the space lanes.

When two galaxies interact, however, that mass doesn’t all clash together in a huge crash.  Stars aren’t necessarily colliding with each other, although the action of the merger does compress the interstellar gas and dust, and sets off waves of star formation. But, all of that mass exerts a gravitational influence, which is the main “actor” in a galaxy collision.  That influence is what tears out streams of gas and dust from interacting galaxies, and reshapes the morphology (the shape) of all the galaxies doing the interacting.  While a galaxy interaction may look graceful in the images we see from HST and Spitzer and other observatories, it’s quite a massive and impressive undertaking.

To understand how these collisions and interactions take place, astronomers are creating impressive computer models. These get turned into animations that allow us to follow the galactic dance from start to finish, many many times faster than it happens in real life.  I used one from a scientist named John Dubinksi in my segment (see it below) to show the upcoming Milky Way/Andromeda Galaxy interaction, which will happen in our far future. Check it out!  And, head over to Astrocast.tv to see the rest of this month’s space news show!