Conventional wisdom holds that most large galaxies harbor supermassive black holes at their centers. Scientists also believe that only so-called “active” galaxies should have visible accretion disc of matter, but the Hubble Space Telescope has found one around a black hole with unusually low luminosity. This galaxy might bend the rules a bit, but it offers an opportunity to study how the theory of relativity applies in the real world.
NGC 3147 is a large spiral galaxy just a bit smaller than our own Milky Way. It sits about 120 million light-years away — you’ve probably seen pictures of it because it’s quite stunning. Active galaxies like quasars are easy to spot. The matter falling into them produces emissions across the electromagnetic spectrum, and the accretion discs are quite visible. Everyone thought NGC 3147 was far too dim to have a disc of its own, but a new analysis from an international team suggests otherwise.
Hubble collected data from the central black hole in NGC 3147, which has a mass about 250 million times greater than our sun. The object turns out to have a thin disc of material similar to what you’d find around an active galactic nucleus. Observations from Hubble show the disc spins at about 10 percent the speed of light. Researcher Stefano Bianchi from the Università degli Studi Roma Tre in Italy says this discovery indicates the current models for low luminosity galaxies have “clearly failed.”
This discovery could have far-reaching effects on the way we model galaxies and black holes, but it also could lead to a better understanding of the physics underlying supermassive objects. The fast-moving disc combined with the low apparent brightness of NGC 3147 could make it possible to test both general and special relativity.
General relativity deals with the mechanisms of gravity in the universe, and special relativity describes the relationship between space and time. Since NGC 3147 is dimmer than a typical active galaxy, we can make out the accretion disc around it much better. The disc is inside the black hole’s powerful gravity field where scientists can study the way it affects light.
Based on findings in NGC 3147, astronomers may now go on the hunt for other weakly active galaxies. Some may even be closer to Earth where we can make even more precise measurements to test Einstein’s theories.