So far, such light counterparts to gravitational-wave signals have been seen only once, in an event called GW170817. Dozens of ground- and space-based telescopes followed up in search of light waves generated in the event, but none picked up any signals. When the LIGO and Virgo scientists spotted this merger, they immediately sent out an alert to the astronomical community.

Credit: LIGO-Virgo/ Frank Elavsky & Aaron Geller (Northwestern) GW190814 is highlighted in the middle of the graphic as the merger of a black hole and a mystery object around 2.6 times the mass of the sun. This graphic shows the masses for black holes detected through electromagnetic observations (purple), the black holes measured by gravitational-wave observations (blue), the neutron stars measured with electromagnetic observations (yellow), and the neutron stars detected through gravitational waves (orange). However, at 2.6 times the mass of our sun, it exceeds modern predictions for the maximum mass of neutron stars, and may instead be the lightest black hole ever detected.' 'The mystery object may be a neutron star merging with a black hole, an exciting possibility expected theoretically but not yet confirmed observationally. This discovery implies these events occur much more often than we predicted, making this a really intriguing low-mass object,' explains Kalogera. 'It's a challenge for current theoretical models to form merging pairs of compact objects with such a large mass ratio in which the low-mass partner resides in the mass gap. Another recently reported LIGO-Virgo event, called GW190412, occurred between two black holes with a mass ratio of about 4:1. The newly formed black hole lies about 800 million light-years away from Earth.Р”В«efore the two objects merged, their masses differed by a factor of 9, making this the most extreme mass ratio known for a gravitational-wave event. The cosmic merger described in the study, an event dubbed GW190814, resulted in a final black hole about 25 times the mass of the sun (some of the merged mass was converted to a blast of energy in the form of gravitational waves). 'The mass gap may in fact not exist at all but may have been due to limitations in observational capabilities. 'This is going to change how scientists talk about neutron stars and black holes,' says co-author Patrick Brady, a professor at the University of Wisconsin, Milwaukee, and the LIGO Scientific Collaboration spokesperson. 'We don't know if this object is the heaviest known neutron star, or the lightest known black hole, but either way it breaks a record.' 'We've been waiting decades to solve this mystery,' says co-author Vicky Kalogera, a professor at Northwestern University.

A paper about the detection has been accepted for publication in The Astrophysical Journal Letters. The object was found on August 14, 2019, as it merged with a black hole of 23 solar masses, generating a splash of gravitational waves detected back on Earth by LIGO and Virgo. Now, in a new study from the National Science Foundation's Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo detector in Europe, scientists have announced the discovery of an object of 2.6 solar masses, placing it firmly in the mass gap.

Black star pistol