60558 Echeclus is a

centaur A centaur ( ; grc, κένταυρος, kéntauros; ), or occasionally hippocentaur, is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse. Centaurs are thought of in many Greek myths as being ...

, approximately in diameter, located in the

outer Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

. It was discovered by

Spacewatch The Spacewatch Project is an astronomical survey that specializes in the study of minor planets, including various types of asteroids and comets at University of Arizona telescopes on Kitt Peak near Tucson, Arizona, in the United States. The Spa ...

in 2000 and initially classified as a

minor planet According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''minor ...

with

provisional designation Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been cal ...

(also written 2000 EC98). Research in 2001 by Rousselot and Petit at the Besançon observatory in France indicated that it was not a comet, but in December 2005 a cometary

coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...

was detected. In early 2006 the Committee on Small Bodies Nomenclature (CSBN) gave it the

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 ar ...

ary designation 174P/Echeclus. It last came to

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 ellip ...

in April 2015, and was expected to reach about

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

16.7 near

opposition Opposition may refer to: Arts and media * ''Opposition'' (Altars EP), 2011 EP by Christian metalcore band Altars * The Opposition (band), a London post-punk band * '' The Opposition with Jordan Klepper'', a late-night television series on Com ...

in September 2015.

Name

''Echeclus'' is a

in Greek mythology. 60558 Echeclus is only the second comet (after

Chiron In Greek mythology, Chiron ( ; also Cheiron or Kheiron; ) was held to be the superlative centaur amongst his brethren since he was called the "wisest and justest of all the centaurs". Biography Chiron was notable throughout Greek mythology ...

) that was named as a minor planet, rather than after the name of its discoverer. Chiron is also a centaur; other centaurs are being observed for signs of a cometary coma. Besides Echeclus, eight other objects are cross-listed as both comets and numbered minor planets: 2060 Chiron (95P/Chiron), 4015 Wilson–Harrington (107P/Wilson–Harrington),

7968 Elst–Pizarro Comet Elst–Pizarro is a body that displays characteristics of both asteroids and comets, and is the prototype of active asteroids. Its orbit keeps it within the asteroid belt, yet it displayed a dust tail like a comet while near perihelion in 19 ...

(133P/Elst–Pizarro),

118401 LINEAR 118401 LINEAR, provisional designation , is an asteroid and main-belt comet (176P/LINEAR)(older 2010 site)

(176P/LINEAR), (282P/2003 BM₈₀), (288P/2006 VW₁₃₉), (362P/2008 GO₉₈),Dual-Status Objects
/ref> and (433P/2005 QN₁₇₃).

Chunk

On 30 December 2005, when 13.1 AU from the Sun, a large chunk of Echeclus was observed to break off, causing a great cloud of dust. Astronomers have speculated this could have been caused by an impact or by an explosive release of volatile substances.

Outbursts

Echeclus appears to have outburst again around June 2011 when it was 8.5 AU from the Sun. On 24 June 2011, follow up imaging with the 2 meter Haleakala-Faulkes Telescope South showed the coma of Echeclus to be very close to the sky background limit. Echeclus outburst again around 7 December 2017 when it was 7.3 AU from the Sun, and was 4 magnitudes brighter than expected.33519 174P/Echeclus outburst (Brian Skiff)
/ref>

Presence of gas

In 2016,

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

was detected in Echeclus in very small amounts, and the derived CO production rate was calculated to be sufficient to account for the observed coma. The calculated CO production rate from Echeclus is substantially lower than what is typically observed for 29P/Schwassmann–Wachmann, another distantly active comet often classified as a centaur.

Orbit

Echeclus came to

in April 2015. Centaurs have short dynamical lives due to strong interactions with the giant planets. Echeclus is estimated to have an orbital half-life of about 610,000 years.

References

External links

Elements and Ephemeris for 174P/Echeclus
(IAU Minor Planet Center)

(2011 June 8)
Comet 174P Echeclus chased by Asteroid 2716 Tuulikki
(Animation by Joseph Brimacombe on 30 May 2011)
Comet 174P/ Echeclus during its 2016 outburst
(Virtual Telescope Project) * * {{DEFAULTSORT:Echeclus Centaurs (small Solar System bodies) 060558 0174 060558 Minor planets named from Greek mythology Named minor planets 20000303