Gravitational-wave astronomy

Gravitational-wave astronomy is a subfield of <a href="/facts/Astronomy/0ArJVM1p">astronomy</a> concerned with the detection and study of <a href="/facts/Gravitational_wave/4XWN3NtG">gravitational waves</a> emitted by astrophysical sources.
Gravitational waves are minute distortions or ripples in <a href="/facts/Spacetime/uRIN1x4b">spacetime</a> caused by the acceleration of massive objects. They are produced by cataclysmic events such as the merger of <a href="/facts/Binary_black_hole/2BVQCy52">binary black holes</a>, the coalescence of <a href="/facts/Neutron_star/4enfoxBA">binary neutron stars</a>, <a href="/facts/Supernova/Pfo2J23l">supernova</a> explosions and processes including those of the <a href="/facts/Early_universe/ezBKAdjy">early universe</a> shortly after the <a href="/facts/Big_Bang/I5T1vTnv">Big Bang</a>. Studying them offers a new way to observe the universe, providing valuable insights into the behavior of matter under extreme conditions. Similar to electromagnetic radiation (such as light wave, radio wave, infrared radiation and X-rays) which involves transport of energy via propagation of electromagnetic field fluctuations, gravitational radiation involves fluctuations of the relatively weaker gravitational field. The existence of gravitational waves was first suggested by <a href="/facts/Oliver_Heaviside/ktYBpAt7">Oliver Heaviside</a> in 1893 and then later conjectured by <a href="/facts/Henri_Poincar%C3%A9/AazL2j4X">Henri Poincaré</a> in 1905 as the gravitational equivalent of electromagnetic waves before they were predicted by <a href="/facts/Albert_Einstein/CNTet8qu">Albert Einstein</a> in 1916 as a corollary to his theory of <a href="/facts/General_relativity/jVsoIg8X">general relativity</a>.
In 1978, <a href="/facts/Russell_Alan_Hulse/g8lTxvu9">Russell Alan Hulse</a> and <a href="/facts/Joseph_Hooton_Taylor_Jr./Dn44wNWD">Joseph Hooton Taylor Jr.</a> provided the first experimental evidence for the existence of gravitational waves by observing two neutron stars orbiting each other and won the 1993 Nobel Prize in physics for their work. In 2015, nearly a century after Einstein's forecast, the <a href="/facts/First_observation_of_gravitational_waves/7yep4aM0">first direct observation of gravitational waves</a> as a signal from the merger of two black holes confirmed the existence of these elusive phenomena and opened a new era in astronomy. Subsequent detections have included binary black hole mergers, neutron star collisions, and other violent cosmic events. Gravitational waves are now detected using <a href="/facts/Laser_interferometry/X3E1SsQT">laser interferometry</a>, which measures tiny changes in the length of two perpendicular arms caused by passing waves. Observatories like <a href="/facts/LIGO/jX6jyJzM">LIGO</a> (Laser Interferometer Gravitational-wave Observatory), <a href="/facts/Virgo_interferometer/wfaxuUqc">Virgo</a> and <a href="/facts/KAGRA/7GzCGpmS">KAGRA</a> (Kamioka Gravitational Wave Detector) use this technology to capture the faint signals from distant cosmic events. LIGO co-founders <a href="/facts/Barry_C._Barish/ISj0Aajt">Barry C. Barish</a>, <a href="/facts/Kip_S._Thorne/o6wkjTtP">Kip S. Thorne</a>, and <a href="/facts/Rainer_Weiss/LD6X2WoK">Rainer Weiss</a> were awarded the 2017 Nobel Prize in Physics for their ground-breaking contributions in gravitational wave astronomy.
When distant astronomical objects are observed using electromagnetic waves, different phenomena like scattering, absorption, reflection, refraction, etc. cause information loss. There are various regions in space only partially penetrable by photons, such as the insides of nebulae, the dense dust clouds at the galactic core, the regions near black holes, etc. Gravitational astronomy has the potential to be used in parallel with electromagnetic astronomy to study the universe at a better resolution. In an approach known as <a href="/facts/Multi-messenger_astronomy/7pvCx4PL">multi-messenger astronomy</a>, gravitational wave data is combined with data from other wavelengths to get a more complete picture of astrophysical phenomena. Gravitational wave astronomy helps understand the <a href="/facts/Early_universe/ezBKAdjy">early universe</a>, test theories of <a href="/facts/Gravity/bqAN7DdQ">gravity</a>, and reveal the distribution of <a href="/facts/Dark_matter/y5HgX55N">dark matter</a> and <a href="/facts/Dark_energy/6bWIYewA">dark energy</a>. In particular, it can help find the <a href="/facts/Hubble_constant/FJYfELCP">Hubble constant</a>, which describes the rate of accelerated expansion of the universe. All of these open doors to a <a href="/facts/Physics_beyond_the_Standard_Model/UX68py44">physics beyond the Standard Model</a> (BSM).
Challenges that remain in the field include noise interference, the lack of ultra-sensitive instruments, and the detection of low-frequency waves. Ground-based detectors face problems with seismic vibrations produced by environmental disturbances and the limitation of the arm length of detectors due to the curvature of the Earth’s surface. In the future, the field of gravitational wave astronomy will try develop upgraded detectors and next-generation observatories, along with possible space-based detectors such as LISA (<a href="/facts/Laser_Interferometer_Space_Antenna/DAISKwem">Laser Interferometer Space Antenna</a>). LISA will be able to listen to distant sources like compact supermassive black holes in the galactic core and primordial black holes, as well as low-frequency sensitive signals sources such as binary white dwarf merger and sources from the early universe.

Gravitational-wave astronomy open-in-new

Gravitational-wave astronomy