Podcaster: Richard Drumm
Title: Space Scoop:X-Rays Uncover a Black Hole Dancing With Normal Stars
Organization: Astrosphere New Media
Description: Space scoop, news for children.
Bio: Richard Drumm is President of the Charlottesville Astronomical Society and President of 3D – Drumm Digital Design, a video production company with clients such as Kodak, Xerox and GlaxoSmithKline Pharmaceuticals. He was an observer with the UVa Parallax Program at McCormick Observatory in 1981 & 1982. He has found that his greatest passion in life is public outreach astronomy and he pursues it at every opportunity.
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This is 365 Days of Astronomy. Today we bring you a new episode in our Space Scoop series. This show is produced in collaboration with Universe Awareness, a program that strives to inspire every child with our wonderful cosmos.
X-Rays Uncover a Black Hole Dancing With Normal Stars
Most of the stars in the Milky Way galaxy are not like our Sun, which is floating through space alone. A whopping 8-out-of-10 of the most massive stars have one or more companion stars. A pair or stars orbiting each other is called a “binary system”.
The photograph in this episode’s album art shows the flamboyant spiral galaxy called the Whirlpool Galaxy, Messier 51 or M51 for short. Each point of vivid purple light we are seeing in this picture represents a special type of binary system. We call them ‘X-ray binaries’ (or XRBs) because they are pairs of stars shining in X-ray light.
The purple in the image comes from about 10 years of data collection using the Chandra X-Ray orbiting telescope and the rest comes from Hubble.
Each X-ray binary is made up of a normal star and a star which has passed beyond the end of its life. These companions are exotic things, most commonly a neutron star but sometimes, a black hole. Not even Dr. Who has a companion that exotic!
If the stars are close enough together, the strong gravity of the exotic companion can drag gas off the normal star into a ring around itself, a ring called an accretion disk, before gobbling it up. (fem) Like the honey badger, these companions don’t care! It gets close enough they eat it! (/fem) Ahem.
When this happens the material is heated to over a million degrees and begins shining in the high energy light we call X-rays. Yeah, that’s the same thing we use to take pictures of broken bones. The energy is so high it zaps right through your skin & muscles! The bones stop it, though… Hmmm… Come to think of it AM & FM radio waves go through your skin too… Oh well. It’s just an analogy.
And the stronger the gravity, the brighter the X-rays. This picture of M51 has revealed that at least ten of the X-ray binaries in the galaxy are bright enough that they probably contain black holes.
In eight of these pairs the black holes are pulling material away from gigantic companion stars – stars that are much more massive than the Sun! There are about 400 XRBs in total in M51. The diffuse purple color you see though is from gas (hydrogen mostly) that has been superheated by supernova explosions!
Cool Facts: After studying many stars within the Milky Way, astronomers have found evidence that the more massive a star is, the more likely it is to have a companion.
The Whirlpool Galaxy is in the process of merging with it’s own companion, which you can see in the album art. The XRBs are likely the result of this ongoing galactic merger.
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365 Days of Astronomy
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