On April 25-26, 2019, the Gravity Wave Observatory with Laser Interferometer (LIGO) from the NSF and the European-based Virgin detector recorded two new gravitational waves, the space-time ripples predicted by Albert Einstein. The first was from a neutron star colliding with another neutron star 500 million light-years away, and the second was from a neutron star devoured by a black hole 1.2 billion light-years away. If confirmed, the second event will be the first of its kind to be detected.
The discoveries come weeks after the LIGO and Virgo observatories have returned.
Twin LIGO detectors – one in Washington and one in Louisiana – along with Virgo, located at the European Gravitational Observatory in Italy, resumed operations on April 1, 2019 after undergoing a series of updates to increase their sensitivities to gravitational waves .
Each detector now examines larger volumes of the Universe than before, looking for extreme events like puzzles between black holes and neutron stars.
"The latest LIGO-Virgo observation race is proving to be the most exciting so far," said Professor David Reitze, executive director of LIGO at Caltech.
"We're already seeing tips from the first observation of a black hole swallowing a neutron star. If it lasts, that would be a trifecta for LIGO and Virgo – in three years we will have observed all kinds of black hole and neutron star collisions. "
The explosion of the neutron star on April 25, called S190425z, is believed to have occurred about 500 million light-years from Earth.
Only one of LIGO's twin installations captured its signal along with Virgo. As only two of the three detectors recorded the signal, estimates of the location in the sky from which it originated were not accurate, leaving astronomers searching nearly a quarter of the sky for the source.
The possible collision of a neutron star black hole on April 26, called S190426c, is believed to have occurred about 1.2 billion light-years away.
It was seen by all three LIGO-Virgo facilities, which helped narrow its location better in regions that cover about 1,100 square-feet, or about 3% of the sky's total.
"The Universe is keeping us attentive," said Patrick Brady, a professor at the University of Wisconsin-Milwaukee, a spokesman for LIGO Scientific Collaboration.
"We are especially curious about the 26 April candidate. Unfortunately, the signal is quite weak. It's like listening to someone whisper a word in a busy cafe; it can be difficult to distinguish the word or even make sure the person whispered. It will take some time to come to a conclusion about this candidate. "