One of the recurring themes of our show and of modern astronomy is the search for merging black holes. As the story goes, massive stars make stellar-mass black holes that merge into bigger and bigger systems, and eventually, somehow, we get supermassive black holes in the centers of galaxies. Or maybe, sometimes, a massive cloud of material would just wholesale collapse to form a massive black hole all at once. We just don’t know because we are still developing the tools to see what is going on in the cores of galaxies.
And the Very Large Telescope has demonstrated that its MUSE instrument is up to the challenge. Using a combination of Hubble Space Telescope images to pinpoint the black hole locations and high-resolution spectra from MUSE, like a cop with radar, the doppler shifts of the light allowed researchers to measure the orbital velocity of stars close to each supermassive black hole.
These results appear in a paper led by K. Boggel and published in Astronomy & Astrophysics and show that, in the core of the galaxy NGC 7727, there are black holes with masses of 154 million and 6.3 million times the mass of the Sun, and they are just 1,600 light-years apart and on their way toward merger. This galaxy is just 89 million light-years away, and when they merge in however very many millions of years, the gravitational waves will distort our world in ways easily measured by gravitational wave detectors. Sadly, I don’t expect we’ll be around to observe it, but it is still a cool thing for future humanity to watch transpire.
ESO press release
“First direct dynamical detection of a dual super-massive black hole system at sub-kpc separation,” K. T. Voggel et al., to be published in Astronomy & Astrophysics