Astronomers Have Never Detected Merging Supermassive Black Holes. That Might Be About to Change - by BrianKoberlein
For more than a decade, NANOGrav has observed the pulses of 45 millisecond pulsars, looking for small shifts in their timings. The idea is that as long-wavelength gravitational waves pass through space they will shift the pulsars slightly, which would shift the timing of the pulses we observe. By looking at the overall statistical shifts of lots of pulsars, we can detect the large-scale effect of the gravitational waves from merging supermassive black holes.It idea is not without its challenges.
In this study, the team looks at how gravitational wave effects can look like red noise at first glance, and how we might be able to distinguish red noise from real gravitational waves. The study doesn’t yet find any gravitational wave pulses but does put some upper constraints on gravitational wave observations. They are able to show that there has not been any billion-solar-mass black hole merger within 300 million light years.
With further observations, that constrain will tighten, which means they will be able to observe million-solar-mass black hole mergers in that range, or billion-solar-mass ones at greater distances. So it’s only a matter of time before they observe a galactic-scale merger, and expand gravitational wave astronomy out of the red noise.
France Dernières Nouvelles, France Actualités
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