(5407) 1992 AX
A stony binary Mars-crosser with a 780-meter moon.
(5407) 1992 AX is a stony, S-type asteroid that crosses the orbit of Mars and also hosts a small moon, making it a binary system. Measuring roughly 3.6 kilometers across, it was first spotted on January 4, 1992, by Seiji Ueda and Hiroshi Kaneda at Japan’s Kushiro Observatory on Hokkaidō. The asteroid’s satellite, about 780 meters in diameter, was detected in 1997. As of 2018, the pair had not received a formal name.
The object orbits the Sun at a distance ranging from 1.3 to 2.3 AU, completing one circuit every 910 days. Its orbit has an eccentricity of 0.28 and an inclination of 11 degrees relative to the ecliptic. A Mars-crosser, it occasionally swings close to the Red Planet; its next such approach is predicted for January 22, 2027, when it will pass 11,260,000 kilometers from Mars. Pre-discovery images from Palomar Observatory date back to November 1951, over four decades before its official discovery.
The minor planet was assigned its number by the Minor Planet Center on December 9, 1992. It has been classified as an Sk-subtype in the SMASS taxonomy, bridging S and K-type asteroids. Its color indices are 0.690 (B–V), 0.500 (V–R), and 0.840 (V–I). Lightcurve studies, primarily by Petr Pravec and colleagues since 1997, show a rotation period of 2.5488 hours with a brightness variation of 0.10 to 0.12 magnitude. This supersedes an earlier, tentative period of 3.6 hours.
The satellite orbits the primary in 13.52 hours on a very circular path, with a semi-major axis of about 5.8 kilometers. Observations in 2012 confirmed both the binary nature and the stability of the rotational and orbital periods. Size estimates from various surveys—Akari, Spitzer, and NEOWISE—range from 2.78 to 4.18 kilometers in diameter, with albedos between 0.199 and 0.40. A 2017 WISE study focused on Mars-crossers gave a diameter of 3.60 kilometers and an albedo of 0.376. The Collaborative Asteroid Lightcurve Link, assuming an albedo of 0.20, derives a diameter of 3.79 kilometers from an absolute magnitude of 14.47. Johnston’s archive lists an effective combined diameter of 3.98 kilometers, with the primary at 3.9 kilometers and the secondary at 0.78 kilometers.
Quick Facts
- Minorplanet
- yes
- Background
- #FA8072
- Discoverer
- S. Ueda / H. Kaneda
- Discovery Site
- Kushiro Obs.
- Discovered
- 4 January 1992
- Mpc Name
- (5407) 1992 AX
- Mp Category
- Mars crosser / binary
- Epoch
- 27 April 2019 (JD 2458600.5)
- Uncertainty
- 0
- Observation Arc
- 66.90 yr (24,434 d)
- Aphelion
- 2.3486 AU
- Perihelion
- 1.3279 AU
Facts from the source article.
Lore & Background
1992 AX orbits the Sun at a distance of 1.3–2.3 AU once every 2 years and 6 months, with an eccentricity of 0.28 and an inclination of 11°. It is a member of the Mars-crossing asteroids, crossing the orbit of Mars at 1.66 AU. The body's observation arc begins with a precovery taken at Palomar Observatory in November 1951, over 40 years before its official discovery.
Physically, it is an S-type asteroid, further classified as an Sk-subtype in the SMASS taxonomy. Its color indices are B–V 0.690, V–R 0.500, and V–I 0.840. Rotational lightcurves obtained since 1997 by Petr Pravec and collaborators give a best-rated rotation period of 2.5488 hours with a brightness amplitude of 0.10–0.12 magnitude. The satellite, discovered in January 1997, measures about 780 meters in diameter and orbits the primary in a very circular orbit with a semi-major axis of 5.8 km and a period of 13.52 hours.
Diameter estimates vary: surveys by Akari, Spitzer, and NEOWISE give values between 2.78 and 4.18 km, with albedos from 0.199 to 0.40. A 2017 WISE study dedicated to Mars-crossers determined a diameter of 3.60 km and an albedo of 0.376. The asteroid has not been named as of 2018.
Reader's Guide
The significance of (5407) 1992 AX lies in its binary nature and its classification as a Mars-crossing asteroid. Its satellite, discovered in 1997, makes it one of the relatively rare known binary systems among Mars-crossers, providing insights into the formation and evolution of such pairs. The asteroid's short rotation period of 2.5 hours and synchronous orbit of its moon offer data for studying tidal interactions and binary asteroid dynamics. The multiple diameter estimates from different surveys (Akari, Spitzer, NEOWISE) highlight the challenges in characterizing small bodies, with values ranging from 2.78 to 4.18 km. Its precovery from 1951 extends its observational history by decades, aiding orbital refinement. As of 2018, it remains unnamed, a common status for many minor planets. Its next close approach to Mars on 22 January 2027 at 11,260,000 km will provide further opportunities for study. The asteroid's Sk-subtype classification bridges the S and K types, adding to the taxonomic diversity of Mars-crossers.
Did You Know?
- Its satellite was discovered in January 1997 and measures about 780 meters in diameter.
- The asteroid has a rotation period of 2.5488 hours, determined from lightcurve analysis.
- It was discovered on 4 January 1992 by Japanese astronomers Seiji Ueda and Hiroshi Kaneda.
- A precovery from November 1951 at Palomar Observatory exists, over 40 years before its official discovery.
Frequently Asked Questions
Who discovered (5407) 1992 AX?
Seiji Ueda and Hiroshi Kaneda first spotted the asteroid on January 4, 1992, using equipment at Kushiro Observatory on Hokkaidō, Japan.
What type of asteroid is (5407) 1992 AX?
It is a stony, S-type Mars-crosser, meaning its path carries it through the region where Mars orbits the Sun. Because it also carries a small companion, it is classified as a binary asteroid system.
Does (5407) 1992 AX have a moon?
Yes—a roughly 780-meter-wide satellite was identified in 1997 orbiting the 3.6-kilometer primary. As of 2018, neither body had been given a formal proper name.
How big is (5407) 1992 AX and how fast does it spin?
The primary asteroid spans about 3.6 kilometers in diameter and completes one full rotation roughly every 2.55 hours.
What does (5407) 1992 AX's orbit look like?
It circles the Sun between 1.3 and 2.3 AU, taking about 910 days per revolution. Its orbit is moderately stretched (eccentricity 0.28) and tilted 11 degrees relative to the ecliptic plane.
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