written by Passant Rabie, August 2019
This 20-year-old debate has finally been settled.
A cloud of dust blocks the bright light coming from the center of this black hole in the middle of a Seyfert galaxy. (Image: © A cloud of dust blocks the bright light coming from the center of this black hole in the middle of a Seyfert galaxy. )
Ever since their discovery in the late 1950s, bright beams of galactic light known as quasars — distant objects emitting bright light to the cosmos — have puzzled astronomers. However, a new study has shed more light on the mysterious cosmic objects and settles a 20-year-old astronomical debate.
Quasars are galactic nuclei located at the center of their host galaxies. Their bright light is powered by supermassive black holes, and they achieve a brightness that’s equivalent to 600 trillion suns.
For decades, scientists have debated whether a Seyfert galaxy — a class of galaxy that is known to have a quasar-like nucleus — is of one or two types. By using the Hubble Space Telescope to observe a Seyfert galaxy that met the qualifications for both types, a team of researchers found that such a galaxy is in fact one class of object, according to a statement by the University of California, Santa Barbara.
The main distinction between the alleged two types of galaxies was that type 1 Seyfert galaxies produced additional broad peaks of light, while type 2 Seyfert galaxies were missing those peaks, the statement continued.
However, the team of researchers behind the new study suggested that they are in fact the same objects, but they are seen from different perspectives, with a ring of dust obscuring the inner part of what was thought of as type 2 galaxies. By peering into the center of the nucleus of a type 2 Seyfert galaxy, called NGC 3147, the scientists were able to find the missing broad peaks of light.
The scientists had initially looked at the center of the galaxy using X-ray surveys and found neither a dust ring nor the emission lines. However, in the recent observations, they zoomed in on the center using the Hubble Space Telescope and found the region of the broad emission lines, but it had been overwhelmed by the surrounding starlight.
“What’s most important to astronomers is pruning this dead branch,” Robert Antonucci, a physics professor at UC Santa Barbara, and co-author of the study, said in the statement.
The researchers plan to continue observing NGC 3147 in order to take a closer look at its center and confirm their previous observations.
The study was published July 11 in the Monthly Notices of the Royal Astronomical Society.