User:Ams2025/PG 1553+113

PG 1553+113 is a galaxy located in the constellation Serpens, approximately 5 billion light years from Earth. It was discovered through the Palomar-Green Bright Quasar Survey, which was conducted between 1976 and 1982.

PG 1553+113 is what astronomers call an “active” galaxy, which have dense cores that emit x-rays and gamma rays. The most widely accepted theory as to the cause of their dense cores is the presence of a supermassive black hole at the center of each active galaxy; this could account for the apparent excess of energy released from active galaxies in the form of infrared, radio, UV, and X-ray wavelengths. As matter falls towards the black hole, subatomic particles escape in two jets of radiation, each pointing away from the galaxy in opposite directions. In a blazar like PG 1553+113, an active galaxy is positioned so Earth receives one of the jets directly, making it appear especially bright. Data acquired from NASA's Fermi Gamma-ray Space Telescope has shown periodic changes in the brightness of PG 1553+113. If the pattern in the galaxy’s emissions is confirmed, PG 1553+113 will be the first galaxy detected to emit gamma radiation in a years-long cycle. Astronomers may be able to use data drawn from this cycle to learn more about the conditions surrounding a black hole.

The cause of these unique cyclic emissions and the varying brightness of the galaxy hasn’t been confirmed, but the leading theory among astronomers is the presence of a second supermassive black hole near the one in the center of the galaxy. This possible other black hole would exert a second gravitational pull on PG 1553+113 and the black hole at its center. The second black hole would pull on the central supermassive black hole’s accretion disk, the area of debris that isn’t quite past the event horizon of a black hole. This pulling from both black holes would cause the central one’s accretion disk to tilt occasionally, resulting in an oscillation of the gamma ray streams and brightness.