Supermassive black hole binary flares as predicted

The distant binary of two super massive black holes, dubbed QJ287, flared within four hours of its predicted time in July 2019, proving the existence of this system.

The central black hole has a mass 18 billion times that of the Sun. The smaller black hole has a mass of 150 million Suns. Its orbit is twelve years long, and when it makes its close approach the interaction between these two monsters causes high energy flares.

We know all this because astronomers have been watching OJ 287 since the 1890s, before they knew what it was. In the intervening century, the system has shot off two outbursts roughly every 12 years, almost like clockwork.

Yet this pattern took time to decipher, as the bigger black hole in OJ 287 is also a blazar. Its black hole, or the disk that feeds it, powers twin plasma jets shooting out along opposite directions, and one of these jets is pointed almost right at Earth. The volatility of this plasma-and-photon stream makes OJ 287 a highly variable visible-light source. It wasn’t until a century after its discovery that astronomers realized that there was a periodic signal hidden within the noise — and that dual dancing black holes could cause it.

Observations in 2005 confirmed those ideas, and astronomers made increasingly precise predictions for subsequent flares in 2007 and 2015. Now, Seppo Laine (Spitzer Science Center, Caltech), Lankeswar Dey (Tata Institute of Fundamental Research, India), and colleagues are publishing observations of the latest flare in the Astrophysical Journal. The authors predicted, and then watched for, a flare expected to arrive in the early hours of July 31, 2019.

QJ287 is 3.5 billion light years away, which makes this prediction and the observations even more remarkable.

Astronomers track neutrino from galaxy 3.7 billion light years away

Using multiple telescopes astronomers have successfully tracked the source of a neutrino that was detected on September 22 2017 by the IceCube neutrino telescope in Antarctica to a galaxy 3.7 billion light years away.

Because scientists on the IceCube experiment had worked out the path the particle took through their subterranean ice instrument, astronomers knew where in the sky to look for the particle’s source. A string of early observations came up blank, but days later Nasa’s Fermi Gamma-ray Space Telescope spotted the likely source: a flaring “blazar”.

Most galaxies are thought to have spinning supermassive black holes at their centres. But some of these black holes appear to pull in material at ferocious rates, a process that simultaneously sends streams of highly energetic particles out into space. Such galaxies are called blazars, although the term only applies when one of these streams is directed straight at Earth.

The blazar that appears to have sent the neutrino our way lies 3.7bn light years from Earth, just off the left shoulder of the constellation of Orion. While a single detection is not strong evidence, the IceCube scientists went back through their records and found a flurry of neutrinos coming from the same spot over 150 days in 2014 and 2015.

This I think is the first time scientists have linked a neutrino to its source, outside our solar system. Most neutrino detections come from the Sun. That they could trace this one back to a blazar so far away means their neutrino telescopes are now becoming sensitive enough to find and study the neutrinos coming from other sources.