The use of Wide Field Camera 3 images taken from the Hubble Space Telescope, has enabled a Princeton-led team of astrophysicists to look back 2.5 billion light-years in time to find a pair of enormous black holes set to collide with one another. A paper published in the July issue of the Astrophysical Journal Letters discusses the importance of the team’s discovery. Team members from the Department of Astrophysical Sciences include: Andy Goulding, associate research scholar and lead author of the paper, and the paper’s co-authors, Kris Pardo, graduate student; Jenny Greene, professor of astrophysical sciences; and Michael Strauss, department chair.
This is the first time that astronomical observations have been able to detect a pair of supermassive black holes (SMBH) at such a small separation. Uncovering this pair of black holes allowed the team to make a prediction for the rate of SMBH mergers in the nearby Universe. Mergers of SMBH are theoretically believed to create gravitational waves (GWs), in a process analogous to the emission of GWs from merging stellar-mass black holes. Detection of GWs from stellar mass black holes led to a Nobel Prize for the LIGO team in 2017, but GWs from SMBH have yet to be detected. The discovery of the SMBH pair enabled the Princeton team to make a prediction for the expected gravitational wave background (GWB) observable with pulsar timing arrays. If the predicted GWB is not detected by intently “listening” over the next few years, it may be necessary to revise theoretical ideas regarding the final stages of SMBH binary evolution and coalescence.
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