132 Aethra

Mars-crossing asteroid June 2017 yes 132 Aethra #FA8072 132Aethra (Lightcurve Inversion).png Lightcurve-based 3D-model of Aethra James C. Watson 13 June 1873 Angell Hall Observatory (132) Aethra A873 LAA922 XB1949 MD1953 LFThe MPC notates Aethra's retroactive new-style designations as 1873 LA and 1922 XB. ' iː θ r əNoah Webster (1884) A Practical Dictionary of the English Language Aethra Mars crosser 21 November 2025 (JD 2461000.5) 0 2.6121 AU Gm on 1.6012 AU Gm on 3.6230 AU Gm on on 0.3870 4.2217 yr (1541.9 d) 24.9835° 258.0509° 255.6188° 113.0611° 17.72 km/s 0.2334 ms / day 152.30 yr (55628 d) 0.7822 AU 2.2051 AU 3.176 42.87 1.6 km44.47 0.74 km (1.59 ± 0.89/0.42)17 kg 3.447 ± 1.935/0.923 g/cm3 5.1684 h d on on M-type (Tholen)Xe-type (Bus)142 8.96 0.1990 0.015 132 Aethra is a metallic asteroid and Mars-crosser on an eccentric orbit from the asteroid belt. It was discovered by James Craig Watson on 13 June 1873 at Angell Hall Observatory in Ann Arbor, Michigan. It is the first Mars-crossing asteroid to be identified. It subsequently became a lost asteroid, and was only rediscovered in December 1922. It is named after Aethra, the mother of Theseus in Greek mythology. Aethra measures approximately 43–44 kilometers in diameter and has a rotation period slightly longer than five hours. It is the largest and brightest of the Mars-crossers and is classified as an M-type asteroid under the Tholen classification scheme. Its surface is relatively reflective and is likely composed of various silicate, hydroxide, and iron-bearing minerals. History and naming Aethra was discovered by astronomer James Craig Watson on 13 June 1873 at Angell Hall Observatory in Ann Arbor, Michigan. Its discovery, alongside that of 133 Cyrene, was announced in the journal Astronomische Nachrichten on 30 August. By 1874, the asteroid was named Aethra after the Greek mythological figure Aethra, mother of Theseus.25 Watson only obtained an observation arc of 22 days, insufficient to constrain its orbit very well. The usual method for calculating the orbits of asteroids discovered by Watson were inadequate due to Aethra's large orbital eccentricity, and the asteroid subsequently became lost. On 12 December 1922, Aethra was rediscovered as 1922 NA by astronomer Benjamin Jekhowsky at Algiers Observatory. It was independently observed by G. Beljavsky on 19 December at Simeiz Observatory. Calculations of its orbit strongly indicated that it was the lost asteroid, and Aethra's recovery was announced in the journal Nature on 3 February 1923. In 1925, the system of provisional designation was changed to its current system. The Minor Planet Center (MPC) retroactively applied the new-style designations to those made before 1925, thus replacing 1922 NA with A922 XB. Orbit thumb|left|An orbital diagram of Aethra, with the orbits of the inner planets and the ecliptic grid shown. Aethra orbits the Sun at an average distance—its semi-major axis—of 2.61 astronomical units (AU), taking 4.22 years to complete one orbit. Due to its eccentricity of 0.39, its distance from the Sun varies from 1.60 AU at perihelion to 3.62 AU at aphelion, crossing the orbit of Mars. It is the first Mars-crossing asteroid discovered.4 Its orbital inclination is high, with a value of 24.98° with respect to the ecliptic plane. Despite crossing Mars's orbit, Aethra appears to be dynamically stable. A 2023 study by Julio Fernández and Michel Helal found that in simulations, its orbit remains stable for 2 billion years (Gyr). Aethra is protected from destabilizing close encounters with Mars by a Kozai resonance. This resonance couples variations in its perihelion distance with the precession of its argument of perihelion such that whenever its perihelion is at a minimum, it is located away from the ecliptic plane, distancing Aethra from Mars.5 Occasionally, its perihelion is raised enough that its orbit no longer crosses Mars's. Physical characteristics Aethra has an estimated diameter of 42.87 ± 1.6 km mi or 44.47 ± 0.74 km mi. Along with its absolute magnitude of 8.96, it is the largest and brightest Mars-crossing asteroid.4 Observations of Aethra's lightcurve, or variations in its apparent brightness as it rotates, suggests a rotation period of about 5.17 hours. Under the Tholen classification scheme, Aethra is classified as an M-type asteroid. The Bus classification scheme meanwhile classifies it as an Xe-type asteroid.142 Aethra's geometric albedo is about 0.2,4 and its spectrum is significantly red. Absorption features in its spectrum indicates the presence of phyllosilicate and hydroxide minerals and water ice, and the iron-rich chamosite may be the primary surface mineral on some regions on the asteroid.1923, 1935 These features are broadly consistent with the compositions of CI and CM chondrites, but albedo and spectral slope dissimilarities rule out Aethra as a parent body of these meteorites.1931 Variations in Aethra's spectrum seen between May and August 2008 may be caused by variable abundances of phyllosilicates or opaque surface minerals with rotation or an undiscovered moon with a distinct composition.1923 Notes References (132) Aethra = 1873 LA = 1922 XB = 1949 MD = 1953 LF https://www.minorplanetcenter.net/db_search/show_object?utf8=%E2%9C%93&object_id=132 Minor Planet Center 5 November 2025 2000-06-10 last obs JPL Small-Body Database Browser: 132 Aethra https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=132 12 May 2016 Provisional Designations Minor Planets Center https://www.minorplanetcenter.net/mpcops/documentation/provisional-designation-definition/#oldstyle_provid 5 November 2025 Watson James Craig Correspondence - Discovery of Two New Planets 30 August 1873 Astronomical Register 11 284 1873AReg...11..284W Watson James Craig New Elements and an Ephemeris of Aethra (132) August 1874 Astronomische Nachrichten 84 187 1874AN.....84..187W Herget Paul The orbit and perturbations of (132) Aethra Astronomical Journal 47 1081 17–23 1938 10.1086/105455 1938AJ.....47...17H Lost Planet Recovered 3 February 1923 Nature 111 2779 159 10.1038/111159a0 Report Lost Planet of 1873 Found Again; Algerian and Simeis Astronomers Locate Aethra, First Sighted by Prof. Watson of Ann Arbor 3 February 1923 New York Times https://www.nytimes.com/1923/02/03/archives/report-lost-planet-of-1873-found-again-algerian-and-simeis.html 5 November 2025 Fienga A. Avdellidou C. Hanuš J. February 2020 Asteroid masses obtained with INPOP planetary ephemerides https://academic.oup.com/mnras/article/492/1/589/5658701 Monthly Notices of the Royal Astronomical Society 492 1 589–602 10.1093/mnras/stz3407 free subscription Values found in table A1. Fernández Julio A. Helal Michel On the observed excess of large Mars-crossers in high-inclination orbits April 2023 Icarus 394 115398 10.1016/j.icarus.2022.115398 2023Icar..39415398F Hardersen Paul S. Cloutis Edward A. Reddy Vishnu Mothé-Diniz Thais Emery Joshua P. The M-⁄ X-asteroid menagerie: Results of an NIR spectral survey of 45 main-belt asteroids 14 November 2011 Meteoritics and Planetary Science 46 12 1910–1938 10.1111/j.1945-5100.2011.01304.x free Hardersen Paul S. Gaffey Michael J. Abell Paul A. Near-IR spectral evidence for the presence of iron-poor orthopyroxenes on the surfaces of six M-type asteroids May 2005 Icarus 175 1 141–158 10.1016/j.icarus.2004.10.017 2005Icar..175..141H JeongAhn Youngmin Malhotra Renu The current impact flux on Mars and its seasonal variation December 2015 Icarus 262 140–153 10.1016/j.icarus.2015.08.032 1503.03885 2015Icar..262..140J . Dictionary of minor planet names 1 Lutz Schmadel 2003 68 9783540002383 Springer https://books.google.com/books?id=VoJ5nUyIzCsC&pg=PA68 External links 132 131 Vala 132 133 Cyrene Category:Mars-crossing asteroids Aethra Aethra Category:M-type asteroids (Tholen) Category:Xe-type asteroids (SMASS) 18730613 Category:Recovered astronomical objects