It’s the end of the line for a distant quasar. Or, it’s at least the end of feeding time, for now.
Last week, astronomers reported their findings concerning J1011+5442, a quasar that was the subject of the Sloan Digital Sky Survey (SDSS), at the 227th meeting of the American Astronomical Society.
The black hole at the center of J1011+5442, which is around 50 million times more massive than the sun, has swallowed all its surrounding gas, according to the researchers. As it ate up the gas, it emitted large amounts of light and radio wave, resulting in the quasar.
But a spectrum observation in 2015 revealed a significant decrease in the rate of falling gas.
“The difference was stunning and unprecedented,” said Univ. of Washington graduate student John Ruan, who was a member of the research team. “The hydrogen-alpha emission dropped by a factor of 50 in less than 12 years, and the quasar now looks like a normal galaxy.”
J1011+5442 first came to the attention of SDSS astronomers in 2003. They successfully determined the properties of the gas being swallowed by the black hole. Additionally, via the “hydrogen-alpha” line, the astronomers determined how much gas was falling into the black hole.
The 2015 drop led members of the SDSS collaboration and the astronomy community to call the quasar a “changing-look quasar.” With the gas used up, astronomers were unable to find the quasar’s spectroscopic signature.
“If we saw this quasar swallowing gas in 2003 and don’t see it any more, that can mean one of three things,” said Ruan.
First, it could mean a thick layer of dust could’ve passed through the quasar’s host galaxy, blocking the view of the black hole. However, the researchers determined that no dust cloud is capable of moving fast enough to cause a 50-fold drop in brightness in a couple of years.
Second, the original 2003 observation may have been a fluke, perhaps a temporary flare caused by a nearby star being ripped apart by the black hole. However, such a conclusion can’t explain why J1011+5442 had been shining for many years prior to turning off.
The third explanation, the one the astronomers agree with, is that the black hole has run out of gaseous food.
“We are used to thinking of the sky as unchanging,” said Scott Anderson, the principal investigator behind the SDSS’s Time-Domain Spectroscopic Survey. “The SDSS gives us a great opportunity to see that change as it happens. In fact, we found this quasar because we went back to study thousands of quasars seen before. This discovery was only possible because the SDSS is so deep and has continued so long.”
The “changing-look quasar” is the first major discovery to come out of the Time-Domain Spectroscopic Survey.