A black hole festooned with a neutron star. 10 days later it happened again.

Two years later, LIGO detected the collision of two neutron stars – the burnt remnants of stars more massive than the sun but not large enough to collapse into black holes. Such collisions create most of the gold and silver in the universe.

With the help of VIRGO, a similar but smaller European gravitational wave observatory located in Italy, astronomers were able to locate the part of the sky where the explosion occurred, and a series of telescopes were then able to detect particles. of light, from radio waves to x-rays, emanating from this fireball.

Astronomers have long expected to find a neutron star orbiting a black hole, but in nearly half a century of researching our Milky Way galaxy, they have never found one. “So indeed, we had this mysterious question,” Dr. Brady said. “Why haven’t we seen a star neutron-black hole system? “

In 2019, two gravitational wave detections seemed to have finally sacked this elusive astronomical career. But one of them, in April 2019, did not stand up to scrutiny. Maybe it was what they were hoping for – the rumbles of a black hole-neutron wave collision – or maybe it was just random, meaningless jerks in imperfect data.

“We think it’s unlikely that this is really an astrophysical signal,” Dr Brady said. “So that sort of sits there as one of those things that could be, but at the moment we don’t have enough evidence to say that.”

The second detection, on August 14, 2019, remains puzzling. The larger object in the collision was definitely a black hole. The smallest had a mass 2.6 times that of the sun. It’s bigger than any neutron star ever detected – and smaller than any black hole ever detected. Astronomers still don’t know if it was a neutron star or a black hole.

The new observations of gravitational waves finally prove, without a doubt, that these couples exist, although far from the Milky Way. The first detection of a neutron star merging with a black hole occurred on January 5, 2020. The Hanford, Washington facility was temporarily offline, so the signal was detected in Livingston, Louisiana. A similar but smaller detector in Italy called VIRGO detected a weak signal, providing corroboration.