Explained: Two black holes merged billions of years ago. Why is this puzzling scientists?

News: Billions of years ago, collision between two black holes sent gravitational waves rippling through the universe.In 2019,signals from these waves were detected at the gravitational wave observatory LIGO (United States) and the detector Virgo(Italy).


  • GW190521: It is a gravitational wave signal resulting from the merger of two black holes near a third supermassive black hole.The event was observed by the LIGO and Virgo detectors on 21st May,2019.
  • Researchers say that the single entity produced from the colliding of two black holes has a mass 142 times that of our Sun.

Additional Facts:

  • Gravitational waves: These are ‘ripples’ in space-time caused by some of the most violent and energetic processes in the Universe.They are formed when a star explodes in a supernova; when two big stars orbit each other; and when two black holes merge.
    • Albert Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity.In 2015, the first gravitational wave was detected — by LIGO.
  • Black Hole: It is a region of space where matter has collapsed in on itself.The gravitational pull is so strong that nothing not even light can escape
    • Black holes emerge from the explosive demise of certain large stars.But some are truly gargantuan and are billions of times the mass of our Sun.They are detected from the way they influence their surroundings.They produce observable gravitational waves as they spiral into each other.
  • Laser Interferometer Gravitational-Wave Observatory(LIGO): It is a large-scale physics experiment and observatory to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool.
    • Locations: Hanford Site, Washington(US) and Livingston, Louisiana(US).
  • Virgo interferometer: It is a large interferometer designed to detect gravitational waves.It is a part of a scientific collaboration of laboratories from six countries: Italy and France, the Netherlands, Poland, Hungary and Spain.
    • Location:Santo Stefano a Macerata, near the city of Pisa, Italy.