17492 Hippasos (/ˈhɪpəsəs/provisional designation1991 XG₁) is aJupiter trojan and member of theEnnomos family from theTrojan camp, approximately 54 kilometers (34 miles) in diameter. It was discovered on 10 December 1991, by astronomerFreimut Börngen at theKarl Schwarzschild Observatory in Tautenburg, Germany.^[1] The Jovianasteroid belongs to the80 largest Jupiter trojans and has arotation period of 17.8 hours.^[7] It was named after the Trojan princeHippasus (Hippasos) from Greek mythology.^[1]

Hippasos is a Jovianasteroid in the so-calledTrojan camp, located in theL₅Lagrangian point, 60° behind Jupiter, orbiting in a1:1 resonance with the Gas Giant(seeTrojans in astronomy).^[4]

It orbits the Sun at a distance of 4.8–5.5 AU once every 11 years and 8 months (4,262 days;semi-major axis of 5.14 AU). Its orbit has aneccentricity of 0.07 and aninclination of 29° with respect to theecliptic.^[3] The body'sobservation arc begins with aprecovery published by theDigitized Sky Survey and taken at theSiding Spring Observatory in September 1977, more than 14 years prior to its official discovery observation at Tautenburg.^[1]

Hippasos is a member of theEnnomos family (009),^[5] one of few known Jovianasteroid families, named after4709 Ennomos(see also4709 Ennomos § Small Ennomos family).^[9] A differentHCM analysis finds this asteroid to be theparent body of its ownHippasos family,^[10] first described by Jakub Rozehnal and Miroslav Brož in 2014. According to the astronomers' model, the Hippasos family consists of 104 known members, and was formed 1 to 2 billion years ago. The extrapolated size of the original body is between 67 and 168 kilometers, which is strongly influenced by the amount of possibleinterlopers into the family.^[11]

Thisminor planet was named fromGreek mythology after the Trojan princeHippasus (Hippasos). The son of KingPriam supportedAeneas in theTrojan War.^[1] The official naming citation was published by theMinor Planet Center on 9 March 2001 (M.P.C. 42365).^[12]

Hippasos is an assumedC-type asteroid,^[7] while most larger Jupiter trojans areD-type asteroids.

In December 2013, a rotationallightcurve of Hippasos was obtained fromphotometric observations byRobert Stephens at theCenter for Solar System Studies in Landers, California. Lightcurve analysis gave a well-definedrotation period of17.75±0.01 hours with a brightness amplitude of 0.21magnitude (U=3).^[8][a]

According to the survey carried out by theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer, Hippasos measures 53.98 kilometers in diameter and its surface has analbedo 0.066,^[6] while theCollaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 55.67 kilometers based on anabsolute magnitude of 10.0.^[7]

• Asteroid Lightcurve Database (LCDB), query form (infoArchived 16 December 2017 at theWayback Machine)
• Dictionary of Minor Planet Names, Google books
• Discovery Circumstances: Numbered Minor Planets (15001)-(20000) – Minor Planet Center
• 17492 Hippasos atAstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 17492 Hippasos at theJPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters

• Minor planet object articles (numbered)
• Jupiter trojans (Trojan camp)
• Ennomos asteroids
• Discoveries by Freimut Börngen
• Named minor planets
• Astronomical objects discovered in 1991

• Use dmy dates from June 2018
• Webarchive template wayback links