light source at center of galaxies

[dmzer5]

I'm new to APOD and have questions:

1. What is the source of the bright light seen at the centers of all (?) galaxies?
2. Can we see the "bright light" at the center of our Milky Way galaxy?
3. What percentage of the "stars" we see with the naked eye, actually are these centers of galaxies?

If someone would be kind enough to answer these queries, I would sleep better at night!

[Chris Peterson]

1. What is the source of the bright light seen at the centers of all (?) galaxies?

Stars. Lots and lots of stars.

2. Can we see the "bright light" at the center of our Milky Way galaxy?

Not very well. There is a lot of dust between us and it. But we can see it in non-visible wavelengths, like radio and IR.

3. What percentage of the "stars" we see with the naked eye, actually are these centers of galaxies?

None. All the stars we can see are just that, stars. There are a few naked eye galaxies, but all appear very diffuse and un-starlike. The only reason that the centers of galaxies look so bright in images is because the contrast is stretched to make them that way. Their visual appearance, either naked eye or telescopically, is much dimmer and lower contrast.

[rstevenson]

1. What is the source of the bright light seen at the centers of all (?) galaxies?

When we look at galaxies we do so with optical devices which can't resolve single stars in those galaxies because they are so far away. So the large number of stars closely packed near the centers of galaxies just appears as a glow to us. That glow is made up of from hundreds of millions to billions of stars.

2. Can we see the "bright light" at the center of our Milky Way galaxy?

We can see some of it but mostly it's obscured by a lot of dust and gas between us and it. Here's an APOD that shows a view towards the center of our Milky Way.

3. What percentage of the "stars" we see with the naked eye, actually are these centers of galaxies?

Most of what we can see with the naked eye are stars in the Milky Way galaxy. (Pretty much 100%, in fact.) A few specks would be distant galaxies, but they're best seen through telescopes. One of the things I've only recently learned is that the background in some telescopic images of space is almost entirely filled with galaxies. Here's an APOD showing that. There are only a few stars in that image -- the ones with the diffraction spikes glaring off them. Everything else you see is galaxies. It's awe inspiring.

Rob

[I see Chris beat me to it, but I'll leave my answer too, since I didn't make any egregious errors.]

[Chris Peterson]

When we look at galaxies we do so with optical devices which can't resolve single stars in those galaxies because they are so far away.

Actually, we are able to resolve individual stars in some galaxies. (It's still true that the glowing centers consist of billions of unresolved stars, though.)