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GRB 090902462
GRB 090902462 is the Fermi GBM trigger number for GRB 090902B, a bright, long-duration gamma-ray burst detected on 2 September 2009 that produced the highest-energy photon then measured from a burst, 33.4 GeV.
GRB 170817A
GRB 170817A is a short gamma-ray burst detected by NASA's Fermi satellite on August 17, 2017, arriving 1.7 seconds after gravitational waves from merging neutron stars in galaxy NGC 4993.
GRB 190114C
GRB 190114C was a luminous gamma-ray burst detected on 14 January 2019 in the constellation Fornax, the first burst with its afterglow detected at teraelectronvolt energies.
GRB 190425
GRB 190425 is a weak short gamma-ray burst detected by INTEGRAL on 25 April 2019, a candidate counterpart to the gravitational-wave binary neutron star merger GW190425.
GRB 200415A
GRB 200415A is a brief, extremely bright gamma-ray burst detected on 15 April 2020, generally interpreted as a magnetar giant flare in the nearby galaxy NGC 253, about 11.4 million light-years away.
GRB 211211A
GRB 211211A is a long gamma-ray burst detected on 11 December 2021 by Swift and Fermi, lasting over 50 seconds yet showing kilonova emission consistent with a compact-object merger at about 346 megaparsecs.
GRB 221009A
GRB 221009A is a long-duration gamma-ray burst detected on 9 October 2022, the brightest ever observed, nicknamed the BOAT for brightest of all time, occurring about two billion light-years from Earth.
GRB 970228
GRB 970228 was a gamma-ray burst detected on 28 February 1997 by the satellite BeppoSAX, the first burst with an X-ray afterglow and optical counterpart.
GRB 970508
GRB 970508 was a gamma-ray burst detected on 8 May 1997, the first of its class with a measured distance, at redshift 0.835, settling whether bursts are cosmological.
GRB 971214
GRB 971214, a gamma-ray burst detected in December 1997, had a host galaxy at redshift z = 3.42 and an implied energy near 3 × 10^53 erg.
GRB 980703
GRB 980703 was a long-duration gamma-ray burst detected on July 3, 1998, whose afterglow produced the third known host-galaxy redshift, z = 0.966, and an energy of about 10^53 erg.
GRB 990123
GRB 990123 was a gamma-ray burst detected on 23 January 1999, the first burst simultaneously caught in visible light, with an apparent energy exceeding a neutron star's rest-mass energy.
GRB 990510
GRB 990510 was a long-duration gamma-ray burst detected on 10 May 1999 in the constellation Chamaeleon, whose afterglow yielded the first linear polarization measurement of any burst.
GRB 991216
GRB 991216 is an extremely bright gamma-ray burst detected on 16 December 1999, notable for the first unambiguous detection of X-ray emission lines from a burst afterglow.
Grease (lubricant)
Grease is a semi-solid lubricant made by dispersing a thickener in a lubricating oil with additives, so it stays in place instead of draining away like oil.
Greasing ground glass joints
Greasing ground glass joints means applying a thin film of grease to tapered glass connections so they seal against gas and can be taken apart again.
Great Artesian Basin
The Great Artesian Basin is Australia's largest groundwater basin, a system of pressurized sandstone aquifers underlying about 1.7 million square kilometers, more than one-fifth of the Australian continent.
Great Attractor
The Great Attractor is a concentration of mass hidden behind the Milky Way in the Hydra-Centaurus region, whose gravity draws nearby galaxies, including our own Local Group.
Great Blizzard of 1888
The Great Blizzard of 1888, also called the Great White Hurricane, struck the northeastern United States from March 11 to 14, 1888, killing hundreds of people.
Great Blizzard of 1978
The Great Blizzard of 1978 was a severe winter storm that struck the Great Lakes and Ohio Valley on January 26-27, 1978, paralyzing Ohio, Indiana, and Michigan.
Great circle
A great circle, or orthodrome, is the largest circle on a sphere, formed by a plane through its center; its shorter arc is the shortest path between two points.
Great Clock of Westminster
The Great Clock of Westminster is the five-ton mechanical turret clock in Elizabeth Tower of the Palace of Westminster, striking the hour bell Big Ben since 1859.
Great comet
A great comet is a comet that becomes exceptionally bright to the naked eye, such as Hale-Bopp in 1997, usually by passing close to the Sun or Earth.
Great conjunction
A great conjunction, or Jupiter Saturn conjunction, is the apparent close meeting of Jupiter and Saturn, occurring about every 20 years; the 2020 event was the closest since 1623.
Great Dark Spot
The Great Dark Spot (GDS-89) was an Earth-sized anticyclonic storm on Neptune, discovered by Voyager 2 during its 1989 flyby and named for Jupiter's Great Red Spot; it had vanished by 1994.
Great Debate (astronomy)
The Great Debate was a 1920 discussion between astronomers Harlow Shapley and Heber Curtis at the National Academy of Sciences over whether spiral nebulae were within the Milky Way.
Great Dimming of Betelgeuse
The Great Dimming of Betelgeuse was an unprecedented fade in the star's brightness between November 2019 and March 2020, causing speculation it would explode as a supernova.
Great Filter
The Great Filter is a hypothesized obstacle so improbable it explains why a life-friendly universe shows no sign of technological civilizations, coined by economist Robin Hanson in 1998.
Great Frost of 1709
The Great Frost of 1709, known in France as Le grand hiver, was an extraordinarily cold European winter, the coldest on the continent in 500 years.
Great Green Wall
The Great Green Wall is an African Union initiative launched in 2007 to combat desertification in the Sahel, now an 8,000 km restoration mosaic across Africa.