Using NASA's space-based X-ray telescope Nuclear Spectroscopic Telescope Array, astronomers have found two supermassive black holes lurking relatively close to our own galaxy.
Supermassive Black Holes Hiding In Solar System's Cosmic Neighborhood
Ady Annur, from Durham University in the United Kingdom, and colleagues discovered the bodies while focusing on a nearby galaxy called IC 3639, which lies about 170 million light-years away, and NGC 1448, which is located just about 38 million light-years away from Earth.
The two black holes are in closer proximity to our planet than the black holes that the Chandra X-ray Observatory focused on and captured for an image with the highest collection of supermassive black holes that astronomers have so far observed.
If the black holes lie relatively close to the solar system, why did it take too long for scientists to find these bodies?
Hidden By Mass Of Gas And Dust
Annu and colleagues said that the supermassive black holes hiding in our cosmic neighborhood went undetected for a long time because of the mass of gas and dust that surrounded them that prevented direct observations through telescopes. The bodies were eventually found using X-rays.
Active Galactic Nuclei
The black holes provide power at the center of what astronomers call the "active galactic nuclei," a class of extremely bright objects that include the likes of blazars and quasars.
Active galactic nuclei are extremely bright since the particles found in the regions surrounding the black hole become extremely hot and produce radiation.
Astronomers think that most active nuclei, such as the ones that the NuSTAR recently studied, are surrounded by a doughnut-shaped region consisting of a thick mass of gas and dust that hides the central regions from certain angles. Because of this, the reflected X-ray from the doughnut-shaped materials are primarily seen by telescopes instead of the bright central regions.
Spiral Galaxy NGC 1448
Spiral galaxy NGC 1448 is among the large galaxies nearest to the Milky way but the black hole at its center was only found in 2009. The X-ray emission from the galaxy as seen by NuStar and Chandra hints for the first time that there must be a thick layer of dust and gas that hides the active black hole in it. Researchers found that the galaxy has a large population of young stars, which suggests that NGC 1448 produces new stars as its black hole feeds on gas and dust.
Comparing data from NuSTAR, Chandra and the Japan-led Suzaku satellite, astronomers confirmed the active galactic nucleus nature of IC 3639. NuSTAR likewise provided a precise measurement of the amount of material that obscures the central engine of the galaxy.
"We present NuSTAR observations of two nearby Active Galactic Nuclei (AGN), NGC 1448 and IC 3639, located at distances of 12 Mpc and 54 Mpc, respectively," the researchers said. "NuSTAR high-energy X-ray (> 10 keV) observations, combined with archival lower energy X-ray observations from Chandra and Suzaku, reveal both sources to contain heavily obscured, accreting supermassive black holes."
The findings were presented at the 229th Meeting of the American Astronomical Society in Texas.