15977 Pyraechmes (provisional designation1998 MA₁₁) is aJupiter trojan from theTrojan camp, approximately 45 kilometers (28 miles) in diameter. It was discovered on 19 June 1998, by astronomers with theLincoln Near-Earth Asteroid Research at theLincoln Lab's ETS near Socorro, New Mexico, in the United States.^[1] The suspectedtumbler is also aslow rotator with a period of 250 hours.^[8]

Pyraechmes is aJupiter trojan in a 1:1orbital resonance withJupiter. It is located in the traileringTrojan camp at the Gas Giant'sL₅Lagrangian point, 60° behind its orbit(seeTrojans in astronomy).^[3]

It orbits the Sun at a distance of 4.9–5.4 AU once every 11 years and 10 months (4,309 days;semi-major axis of 5.18 AU). Its orbit has aneccentricity of 0.05 and aninclination of 17° with respect to theecliptic.^[2] The body'sobservation arc begins with aprecovery published by theDigitized Sky Survey and taken atPalomar Observatory in December 1953, more than 44 years prior to its official discovery observation at Socorro.^[1]

Thisminor planet wasnumbered by theMinor Planet Center on 26 July 2000 (M.P.C. 40994).^[10] It wasnamed in April 2025 afterPyraechmes, a leader of thePaeonians who was killed byPatroclus.^[11]

Pyraechmes is an assumedC-type asteroid.^[8] It has a typicalV–I color index of 0.906(see table below).^[9]

In August 2013,Robert Stephens at the Center for Solar System Studies observed Pyraechmes over three nights. However no meaningful rotationallightcurve could be determined, as thelightcurve's amplitude never varied more than 0.02 magnitude. A period of 11.17 hours was only derived for demonstration purpose (U=2-).^[12] In December 2015, Stephens obtained an improved lightcurve with arotation period of250±5 hours and a brightness variation of 0.30magnitude (U=2-). This time the asteroid was observed on 16 nights over a period of one month. Thephotometric observations also revealed that this object possibly has a non-principal axis rotation, which is commonly known astumbling.^[7][8][a]

According to the survey carried out by theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer and the JapaneseAkari satellite, Pyraechmes measures 43.53 and 51.53 kilometers in diameter and its surface has analbedo of 0.071 and 0.046, respectively.^[5][6] TheCollaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 46.30 kilometers based on anabsolute magnitude of 10.4.^[8]

• Asteroid Lightcurve Database (LCDB), query form (infoArchived 16 December 2017 at theWayback Machine)
• Discovery Circumstances: Numbered Minor Planets (15001)-(20000) – Minor Planet Center
• Asteroid (15977) 1998 MA11 at the Small Bodies Data Ferret
• 15977 Pyraechmes atAstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 15977 Pyraechmes at theJPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters

• Minor planet object articles (numbered)
• Jupiter trojans (Trojan camp)
• Discoveries by LINEAR
• Slow rotating minor planets
• Astronomical objects discovered in 1998
• Named minor planets

• Articles with short description
• Short description is different from Wikidata
• Use dmy dates from July 2018
• Webarchive template wayback links
• JPL Small-Body Database ID different from Wikidata