(6265) 1985 TW3
Binary L-type asteroid with a 1.16 km moon.
(6265) 1985 TW3 is a binary system and background asteroid located in the inner main belt. Discovered on 11 October 1985 by T. F. Fric and Richard Gilbrech at Palomar Observatory in California, it remains the only minor planet credited to either astronomer. This stony, L-type asteroid is roughly 5 kilometers across and spins once every 2.7 hours. Its moon, about 1.2 kilometers in diameter, was detected in July 2007 and announced the following month.
Orbitally, 1985 TW3 is a non-family background asteroid when classified by proper orbital elements using the hierarchical clustering method. However, its osculating Keplerian elements place it within the Flora family, the largest stony asteroid family in the main belt. It orbits the Sun at distances of 1.7 to 2.6 AU, completing one revolution every 3 years and 2 months (1,164 days) on a semi-major axis of 2.17 AU. Its orbit has an eccentricity of 0.19 and an inclination of 4° to the ecliptic. The object was first observed as 1953 RK1 at the former Alma-Ata Observatory in September 1953, though its observation arc begins with a 1979 detection as 1979 YG9 at Crimea–Nauchnij, nearly six years before its official discovery at Palomar.
The Minor Planet Center permanently numbered this minor planet (6265) on 17 March 1995. As of 2018, it has not received a name.
In SDSS taxonomy, 1985 TW3 is classified as an unusual L-type asteroid. A rotational lightcurve obtained in June 2010 by David Higgins and Julian Oey at Hunters Hill and Leura Observatories gave a well-defined rotation period of 2.70932 ± 0.00008 hours with a brightness variation of 0.35 magnitude. Several other measurements between 2007 and 2013 yielded periods from 2.7091 to 2.710 hours and amplitudes of 0.26 to 0.36 magnitude.
The binary nature of 1985 TW3 was revealed during a photometric observation by David Higgins on 15 July 2007, announced on 2 August 2007. The satellite is about 1.16 kilometers across, orbits its primary at a separation of 8 kilometers, and completes one orbit every 15 hours and 52 minutes (15.859 hours).
NEOWISE data from the Wide-field Infrared Survey Explorer gives the asteroid a diameter between 4.95 and 5.20 kilometers and a surface albedo of 0.285 to 0.287.
Quick Facts
- Minorplanet
- yes
- Background
- #D6D6D6
- Discoverer
- T. F. Fric / R. J. Gilbrech
- Discovery Site
- Palomar Obs.
- Discovered
- 11 October 1985
- Mpc Name
- (6265) 1985 TW · 3
- Mp Category
- main-belt(inner) / background
- Epoch
- 27 April 2019 (JD 2458600.5)
- Uncertainty
- 0
- Observation Arc
- 48.42 yr (17,685 d)
- Aphelion
- 2.5839 AU
- Perihelion
- 1.7476 AU
Facts from the source article.
Lore & Background
1985 TW3 is a non-family asteroid from the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. Based on osculating Keplerian orbital elements, it has also been classified as a member of the Flora family, a giant asteroid family of stony asteroids. It orbits the Sun in the inner asteroid belt at a distance of 1.7–2.6 AU once every 3 years and 2 months, with an eccentricity of 0.19 and an inclination of 4°.
In the SDSS-based taxonomy, 1985 TW3 is an unusual L-type asteroid. A rotational lightcurve obtained in June 2010 by David Higgins and Julian Oey gave a well-defined rotation period of 2.70932 hours with a brightness variation of 0.35 magnitude. During a photometric observation by David Higgins on 15 July 2007, it was revealed to be a binary asteroid with a minor-planet moon; the discovery was announced on 2 August 2007. The satellite measures approximately 1.16 kilometers and orbits the primary at a separation of 8 km every 15 hours and 52 minutes.
According to the NEOWISE survey, 1985 TW3 measures between 4.95 and 5.20 kilometers in diameter with an albedo between 0.285 and 0.287. The Johnston's archive derives a diameter of 4.81 km for the primary and 1.16 km for the secondary. Later observations by Higgins and Pravec determined a secondary-to-primary diameter ratio of 0.30 to 0.32, which would increase the satellite's size by a quarter to a third. The Collaborative Asteroid Lightcurve Link assumes a standard albedo of 0.24 and calculates a diameter of 5.17 kilometers.
Reader's Guide
The significance of (6265) 1985 TW3 lies in its binary nature and its status as the only minor-planet discovery by astronomers T. F. Fric and Richard Gilbrech. Discovered in 1985 at Palomar Observatory, it was later found to host a 1.16-kilometer moon in July 2007, making it part of a small but growing population of known binary asteroids in the inner main belt. Its classification as an L-type asteroid in the SDSS taxonomy is unusual, and its membership in the Flora family (based on osculating elements) adds context to its stony composition. The asteroid's rotation period of 2.7 hours and the moon's orbital period of 15.859 hours have been well-characterized through photometric observations by David Higgins and Julian Oey. The NEOWISE survey provided diameter and albedo measurements, though some uncertainty remains in the satellite's size due to varying diameter-ratio estimates. As of 2018, the asteroid has not been named, and its permanent number (6265) was assigned on 17 March 1995.
Did You Know?
- It is the only minor-planet discovery for astronomers T. F. Fric and Richard Gilbrech.
- Its moon was discovered on 15 July 2007 and announced on 2 August 2007.
- The asteroid has a rotation period of 2.70932 hours, determined from photometric observations in June 2010.
- As of 2018, it has not been named.
More in Notable Asteroids, Part 3 1-24
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