Looking UP: Ex-cetus

Nov 7, 2016

M77 waving goodbye.
Credit NASA, ESA, André van der Hoeven

This week on Looking Up Hal speculates on why a strange galaxy (M77) is in such a hurry to leave the company of the Milky Way.  

Is it something we said? Why are you leaving? You know the phrase, “keeping your distance?” Well, there is one galaxy that seems to be taking this idea to a whole new level.

The 77th object in Charles Messier’s famous catalog of interesting things in the sky, is a galaxy in the constellation Cetus, visible in southern Colorado skies right now. 

And this galaxy must have really been offended by something we said, because it is heading away from our own Milky Way galaxy at the remarkable speed of 2.4 million mph.

M 77 is a beautiful object to look at through a big telescope. It’s also a strange galaxy, with three distinct sets of spiral arms, which we don’t see too often. And it’s also screaming at us, at least in radio waves.

Put more simply, it’s a pretty strange place. And the core of the problem may be, well, the core of the galaxy. Astronomers were able to measure the speed of giant clouds of gas near the center, or core, of M 77. These vast clouds of gas are moving away from the core at several hundred miles per second. This would take tremendous amounts of energy, energy that has to come from the very center of the galaxy. Starting in the 1950s, astronomers began to measure what they now call Cetus A. This region of space, about 12 ly across, is giving off tremendous amounts of energy.

At the core of the core, so to speak, astronomers believe there is a supermassive black hole, weighing at least as much as 10 million time our own Sun’s mass. And from this core springs forth so much in the way of radio waves that they have a special name – Seyfert galaxies. And did I mention it’s a little wet there? Surrounding this black hole appears to be a giant disk of material, five light years across, with lots and lots of water. There is good evidence that lots of new stars are forming in this very strange galaxy core, perhaps more stars forming there than anywhere else within 100 million light years. So maybe it’s just as well that M 77 is heading away from us. Who wants to put up with all those cranky baby stars?

If you’d like to take a closer look at M 77, or any of the other wonderful and amazing things in the sky, please visit CSASTRO.org for a link to information on our monthly meetings and our free public star parties! 

This is Hal Bidlack for the Colorado Springs Astronomical Society, telling you to keep looking up, Southern Colorado!