And Galaxies are Happenin’ Kinds of Places!

There are SO many interesting strands of astronomy research going on these days. I’m reminded of the complexity of it all every time I go to an AAS meeting or open up a week’s worth of press releases to see the latest news.  This past week I spent a couple of days at Jet Propulsion Laboratory, working with a team that’s putting together a set of exhibits for their visitor’s center. One of our discussions was about the topics we could illustrate that show spectacular “things” happening in the universe. Of course, galaxies are a hot research topic, what with their central supermassive black holes (that seem to be playing a bigger role in galaxy evolution than we used to think).  And, we know that galaxies are sites of star formation — which is followed (some millions or billions of years later) by star death.  Star birth and star death are also hot topics in research circles.  And, so you can see that our discussion could get pretty complex — do we show starbirth? Star death? And what about planets?  Lots of those show up in galaxies, too (at least, in the Milky Way they do, and there’s no reason to think that they don’t exist in other galaxies, as well).  Well, we ended up selecting images that show all of those topics in a sort of iconic way.

During the two days I was at JPL, the Hubble Space Telescope’s latest image was released.  It’s a portion of a galaxy (called NGC 2976) that is undergoing bursts of star formation.  Now, normally, you see lots of star formation in spiral galaxies — but if you look closely at this image, you don’t see the typical spiral arms where star-forming regions. this galaxy’s a bit of a strange one because it forms stars but doesn’t really have the look and feel of a spiral where such things are common.

You can spot dusty filaments running through the disk, but those really aren’t spiral arms.  It’s amost like something disrupted what was once a spiral galaxy, roughed it up a bit, caused bursts of star formation, and then things quieted down — leaving the formerly active starbirth regions  (the blue areas) filled with hot, massive young stars.

So, what happened here?  This galaxy had the bad luck to run afoul of some neighboring massive galaxies. The gravitational effect of the interaction stripped away some gas (which is an important ingredient in star formation) and then channeled gas to the galaxy’s inner region.  That compressed gas in the inner area spurred a spate of starbirth that began about  500 million years ago.  The outer regions didn’t have enough gas to form new stars, so you don’t see any regions of starbirth out there.

Now, as it turns out, the inner disk is just almost out of gas. This is because all the star-forming activity has has “eaten” up the available star-forming stuff.  When astrononomers look at this galaxy, they now see a small region of hot new stars and starbirth crêches near the center, and nothing but stars in the rest of the galaxy.

The blue dots in the image are the young blue giant stars residing in the remaining active star-birth regions. They’ll start to die in perhaps tens of millions of years (as opposed to the Sun, which will live about 10 BILLION years), creating gorgeous supernova remnants — which will seed the galaxy with the material for the next generation of stars. For those of you who are stargazers, NGC 2976 is part of the M81 group of galaxies. They lie about 12 million light-years away in the constellation Ursa Major.