Astronomers from York University in Canada have identified an undocumented type of quasar where gas appears to be getting sucked into a black hole. This may not sound surprising, but current theories say that isn't supposed to happen.
Quasars are hyperactive and extremely bright discs of hot gas that surround supermassive black holes. They're also known as galactic nucleuses. The Milky Way has one at its center. All the junk that's rapidly spinning down the drain hole forms a compact disc with a radius that's larger than Earth's orbit around the Sun and a temperature that's hotter than the surface of a star. They are so unbelievably bright that they can actually be seen across the observable universe, making them one of the most luminous objects known to science.
Observations show that this gas gets blown away from the black hole by the intense heat and light of the quasar — and it does so at incredible velocities, sometimes reaching upwards of 20% the speed of light. This creates cosmic winds that can affect the galaxy surrounding the quasar.
Now, gas in the disc will eventually fall into the black hole to power the quasar. But scientists have never actually seen it flowing into the black hole through the disc. It would be like watching an object take a direct route into a drain hole instead of spinning around and around until it reaches bottom.
But this is exactly what the astronomers observed.
Rather than being blown out at extreme velocities — an effect that's seen 99.99% of the time — the new data suggests that in some quasars the gas flows directly into the black hole. (Hall et al/York University)
After looking at data produced by the Sloan Digital Sky Survey (SDSS) and the SDSS-III Baryon Oscillation Spectroscopic Survey, a research team led by York University Associate Professor Patrick Hall noticed some strange behavior in 17 quasars of distant galaxies: gas that's falling into black holes at high velocity. Their observations show that it only happens in about 1 in every 10,000 quasars, so it represents a completely new type of quasar black hole.
The discovery was made by looking at the Doppler shift for light, which told the researchers which direction the gas was traveling in and at what speed.
So why is this happening? The researchers have two explanations.
First, the rather obvious one: Isn't that what's supposed to happen to gas near black holes!? Even light cannot escape black holes, so why should gas be immune to strange and unpredictable behaviors? And indeed, Hall admits that it's actually weird to not see this kind of behavior in most, if not all, quasars. Astronomers simply don't understand why it's so rare to see infalling gas.
The second theory is that the gas is not actually falling into the black hole. It's just orbiting around it just above the disc of hot gas, and gradually being pushed away from the black hole. This would explain why the Doppler readings show the gas both moving away and towards us.
Regardless, Hall's team is rewriting the book on quasars. You can read the entire study at the Royal Astronomical Society: "Broad absorption line quasars with redshifted troughs: high-velocity infall or rotationally dominated outflows?"
Top image: ESO/M. Kornmesser.