Why in News
Gravitational-wave catalogues now support studies of black-hole populations and tests of general relativity. The clear GW250114 signal came from a merger 1.3 billion light-years away.
Prelims Pointers
Gravitational waves are ripples in spacetime, predicted by Einstein’s general theory of relativity.
They travel at the speed of light.
Orbiting and merging black holes and neutron stars can generate detectable gravitational waves.
Laser interferometers detect tiny changes in their arms’ relative lengths by comparing laser light.
Gravitational-wave detectors operate at widely separated locations.
The Laser Interferometer Gravitational-Wave Observatory (LIGO) has detectors at Hanford and Livingston in the United States.
Virgo in Italy and KAGRA in Japan belong to the ground-based detector network.
LIGO-India, under development in Hingoli, Maharashtra, will improve source localisation.
The planned Laser Interferometer Space Antenna (LISA) will use three Sun-orbiting spacecraft to detect lower-frequency waves than LIGO.
A merger signal changes as the objects spiral together and the final black hole settles down.
A chirp is the rise in wave frequency as the objects spiral closer together.
Ringdown is the signal emitted as the newly formed black hole settles down after the merger.
Prelims Traps
“Black-hole merger observations detected Higgs bosons.” This is incorrect. They detected gravitational waves. (UPSC Prelims 2019)
“eLISA detects neutrinos.” This is incorrect. The evolved Laser Interferometer Space Antenna proposal targeted gravitational waves. (UPSC Prelims 2017)
“LISA and LIGO target the same frequencies.” This is incorrect. LISA targets lower frequencies.