Have you ever wondered what goes on in outer space, especially around black holes? I know as a kid, viewing black holes as giant vacuum-like structures, I wondered about the kind of things that might be getting sucked into them while drifting through space. Well, a few weeks ago, I heard a talk by Dr. David Ballantyne about what is actually happening in space around supermassive black holes (SMBHs). (cue Twilight soundtrack)
Black holes are categorized based on their number of solar masses, where one solar mass is equal to 1.989×1030 kg. In order for a black hole to be considered supermassive, it must be greater than 105 solar masses. Goodness gracious! That’s the equivalent of several million or, in some cases, several BILLION suns. A BILLION suns?!? Yes, folks. A billion. And while the formation of black holes isn’t completely understood, it’s possible for black holes to add to one another and form new, supermassive black holes (known as merging).
One location of particular interest is the center of the Milky Way galaxy at Sagittarius A* (pronounced “Sagittarius A star”) where a SMBH potentially resides. Abbreviated Sgr A*, this radio source is about 2.5×104 light years away from our solar system. It can be hard to see due to the murky clouding around it, but with advancements in adaptive optics and the use of telescope arrays, astrophysicists have been able to track young stars orbiting around the area— a key indicator that a black hole is present. In the animation below, you can see various stars orbiting around Sgr A* (the stationary star shape). Star S0-2 is particularly cool to watch as it can be seen making a complete orbit:
Another interesting thing scientists have found is a dense cloud of gas which is moving directly toward this same SMBH. As the gas nears the black hole, part of its structure gets sucked inside. As you can see in the video below (at around 3:22), the cloud will have its closest encounter with the black hole in 2013. That’s next year! As the gas gets sucked into the SMBH, the black hole will gain energy and begin to glow brighter.
Black holes are typically found at the center of galaxies organized in structures referred to as active galactic nuclei (AGNs), which are comprised of the black hole and any surrounding material, in addition to any gas or radiation present. As the material near the black hole swirls around, it creates what is known as the accretion disk. Like our sun, whose corona emits x-rays, black holes can also emit various forms of radiation, including x-rays. What?! Yessir! In a process called magnetic reconnection, magnetic field lines interact and reconnect with one another, causing (x-ray radiating) plasma to be emitted. These x-rays are then dispersed into space, some of which hit the accretion disc and create a ‘reflection spectrum’ which scientists can study.
Now, while supermassive black holes weigh millions (sometimes billions) of suns and have the ability to tear apart nearby objects in space, you don’t have to worry about being sucked into one any time soon. Unless you’re this guy, in which case you may have some issues…
MUSE’s “Supermassive Black Hole”:
UCLA Galactic Center Group (http://www.astro.ucla.edu/~ghezgroup/gc/)
Special thanks to Dr. Ballantyne