Comet Grigg–Skjellerup (formally designated 26P/Grigg–Skjellerup) is a periodic

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ...

. It was visited by the

Giotto Giotto di Bondone (; – January 8, 1337), known mononymously as Giotto ( , ) and Latinised as Giottus, was an Italian painter and architect from Florence during the Late Middle Ages. He worked during the Gothic/ Proto-Renaissance period. G ...

probe in July 1992. The spacecraft came as close as 200 km, but could not take pictures because some instruments were damaged from its encounter with

Halley's Comet Halley's Comet or Comet Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 75–79 years. Halley is the only known short-period comet that is regularly visible to the naked eye from Earth, and thus the on ...

. The comet was discovered in 1902 by

John Grigg John Edward Poynder Grigg (15 April 1924 – 31 December 2001) was a British writer, historian and politician. He was the 2nd Baron Altrincham from 1955 until he disclaimed that title under the Peerage Act on the day it received Royal Assen ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...

, and rediscovered in its next appearance in 1922 by John Francis Skjellerup, an

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

n then living and working for about two decades in

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...

where he was a founder member of the

Astronomical Society of Southern Africa The Astronomical Society of Southern Africa (ASSA), formed in 1922, is a widespread body consisting of both amateur and professional astronomers. There are eight autonomous centres throughout Southern Africa. History The Cape Astronomical Associ ...

. In 1987, it was belatedly discovered by

Ľubor Kresák Ľubor Kresák (23 August 1927 in Topoľčany – 20 January 1994 in Bratislava) was a Slovakia, Slovak astronomer. He discovered two comets: the periodic comet 41P/Tuttle-Giacobini-Kresak and the non-periodic C/1954 M2 (Kresak-Peltier). He a ...

that the comet had been observed in 1808 as well, by

Jean-Louis Pons Jean-Louis Pons (24 December 176114 October 1831) was a French astronomer. Despite humble beginnings and being self-taught, he went on to become the greatest visual comet discoverer of all time: between 1801 and 1827 Pons discovered thirty-seven ...

. The comet has often suffered the gravitational influence of

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousand ...

, which has altered its orbit considerably. For instance, its

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...

distance has changed from 0.77 AU in 1725 to 0.89 AU in 1922 to 0.99 AU in 1977 and to 1.12 AU in 1999. In 1972 the comet was discovered to produce a

meteor shower A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extr ...

, the

Pi Puppids The pi Puppids are a meteor shower associated with the comet 26P/Grigg-Skjellerup. The meteor stream was viewable around April 23 but only in years around the parent comet's perihelion date, the last being in 2003. However, as the planet Jupite ...

, and its current orbit makes them peak around April 23, for observers in the southern hemisphere, best seen when the comet is near perihelion. During the comet's 1982 it was detected using radar by the

Arecibo Observatory The Arecibo Observatory, also known as the National Astronomy and Ionosphere Center (NAIC) and formerly known as the Arecibo Ionosphere Observatory, is an observatory in Barrio Esperanza, Arecibo, Puerto Rico owned by the US National Science ...

. Having its recent perihelion so close to

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

's orbit made it an easy target to reach for the

Giotto mission ''Giotto'' was a European robotic spacecraft mission from the European Space Agency. The spacecraft flew by and studied Halley's Comet and in doing so became the first spacecraft to make close up observations of a comet. On 13 March 1986, the s ...

(spacecraft) in 1992, whose primary mission was to

Comet Halley Halley's Comet or Comet Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 75–79 years. Halley is the only known short-period comet that is regularly visible to the naked eye from Earth, and thus the on ...

. Giotto had a closest approach to Grigg–Skjellerup of 200 km, much closer than its approach to Comet Halley, but was unable to obtain images as its camera was destroyed during the Halley rendezvous in 1986. The 2002 return (expected perihelion around October 8, 2002) was very unfavorable and no observations were reported. The

comet nucleus The nucleus is the solid, central part of a comet, once termed a ''dirty snowball'' or an ''icy dirtball''. A cometary nucleus is composed of rock, dust, and frozen gases. When heated by the Sun, the gases sublime and produce an atmosphere ...

is estimated to be 2.6 kilometers in diameter. The comet is a type locality for the mineral

brownleeite Brownleeite is a silicide mineral with chemical formula MnSi. It was discovered by researchers of the Johnson Space Center in Houston while analyzing the Pi Puppid particle shower of the comet 26P/Grigg-Skjellerup. The only other known natural m ...

Popular culture

* In

Neal Stephenson Neal Town Stephenson (born October 31, 1959) is an American writer known for his works of speculative fiction. His novels have been categorized as science fiction, historical fiction, cyberpunk, postcyberpunk, and baroque. Stephenson's work e ...

science fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel uni ...

novel '' Seveneves'', 26P/Grigg–Skjellerup serves as a potential source of water and rocket propellant for the "Cloud Ark" survivors, and is frequently referred to by the nickname "Greg's Skeleton" by way of homophonic transformation.

References

26P/Grigg–Skjellerup Cometography

External links

Orbital simulation
from JPL (Java)
Horizons Ephemeris

– Seiichi Yoshida @ aerith.net
ESA website about 26P/Grigg–Skjellerup

(Remanzacco Observatory : December 26, 2012) Periodic comets 0026 026P Comets visited by spacecraft Meteor shower progenitors Geological type localities Comets in 2013 Comets in 2018 19020723 {{comet-stub