When they were first discovered, quasars were an enigma: they were first found as radio sources in the cosmos so intense, researchers were convinced the radio sources were extraterrestrial in origin. When they were finally spotted in the night sky, the objects seemed to be as bright as stars, yet with qualities to their light that indicated they were very, very far away, some near the edge of the visible universe.
After decades of research, a prevailing theory came forward: quasars are the supermassive black holes at the center of very young galaxies, slurping up the hot gasses of young stars. This galactic feast creates the strong radio signals heard by radio astronomers. But now astronomers have caught a quasar in the act of transition: it's going from a hot, active quasar into an area of relative normalcy, settling into its quieter years as an average galactic center, and they've released this video to show what's going on.
"The hydrogen-alpha emission dropped by a factor of 50 in less than 12 years, and the quasar now looks like a normal galaxy," University of Washington grad student and coauthor on the paper John Ruan said in a press release.
So what happened to make these changes? It may be a little hard to sort out from the video, but it seems that the supermassive black hole at the center of quasar SDSS J1011+5442 cleared the neighborhood of anything it could possibly eat. Without anything to snack on, the voracious eater dropped in brightness across spectra, whether visible or radio light. In other words, this is a demonstration of the transformation of a quasar into a more typical galactic center.
There's always a possibility the quasar could reignite if another star or stars crosses its path, but for now, it seems that it's likely to stay a normal galactic center, becoming the first detected "changing-look quasar," a new class of quasars in transitional states.
The object was found through the Sloan Digital Sky Survey, a massive cataloging of stellar objects that also yielded a similarly starved black hole, one that had a large chunk of its surrounding stars taken in a galactic merger, causing it to shrink in size. That scenario is unlikely to have happened to the SDSS J1011+5442 quasar, however.
The results were published last year in the Astrophysical Journal and presented this week at the American Astronomical Society meeting in Florida.