22899 Alconrad
A Koronian binary asteroid with a moon discovered in 2003.
22899 Alconrad, originally designated 1999 TO14, is a stony asteroid belonging to the Koronis family and is part of a binary system. Located in the outer region of the main asteroid belt, it measures roughly 5 kilometers across. Croatian astronomers Korado Korlević and Mario Jurić discovered it on 11 October 1999 at the Višnjan Observatory in Croatia. In 2003, when its moon was found, Alconrad became the smallest known main-belt asteroid with a satellite.
Alconrad travels around the Sun in the outer main belt, ranging from 2.6 to 3.1 astronomical units (AU) from the Sun. Its orbit takes about 4 years and 10 months (1,752 days) to complete, with an eccentricity of 0.08 and an inclination of 3 degrees relative to the ecliptic. The first observation of this asteroid was actually a precovery image taken by the Spacewatch program at Steward Observatory in October 1994, five years before its official discovery.
In December 2009, photometric observations at the Wise Observatory in Mitzpe Ramon, Israel, produced a lightcurve showing a rotation period of 4.03 hours and a brightness variation of 0.19 magnitude. Another set of R-band observations in October 2013, made at the Palomar Transient Factory in California, gave a rotation period of 5.0206 hours with an amplitude of 0.14 magnitude.
Data from NASA’s NEOWISE mission indicates that Alconrad has a diameter of 5.7 kilometers and a surface albedo of 0.18. The Collaborative Asteroid Lightcurve Link, using a standard albedo of 0.24 for Koronis family members, calculates a diameter of 4.9 kilometers based on an absolute magnitude of 13.7.
The asteroid was named after American astronomer Albert R. Conrad (born 1953), who worked at several U.S. observatories. An expert in adaptive optics, he studied the shapes and topography of solar system moons and co-discovered many asteroid satellites. The naming citation was published by the Minor Planet Center on 20 June 2016.
In October 2003, researchers at the Southwest Research Institute, using the Hubble Space Telescope, discovered a moon orbiting Alconrad. They estimated the primary’s diameter at 4.5 kilometers, assuming an albedo of 0.21. The angular separation between the two bodies was measured at 0.14 arcseconds, corresponding to a distance of about 170 kilometers (or 182 kilometers using a radius ratio of 81).
Quick Facts
- Minorplanet
- yes
- Background
- #D6D6D6
- Discovered
- 11 October 1999
- Discoverer
- K. Korlević / M. Jurić
- Discovery Site
- Višnjan Obs.
- Mpc Name
- (22899) Alconrad
- Named After
- Albert R. Conrad / (American AO-expert)
- Mp Category
- main-beltKoronis
- Epoch
- 4 September 2017 (JD 2458000.5)
- Uncertainty
- 0
- Observation Arc
- 21.57 yr (7,877 days)
- Aphelion
- 3.0790 AU
Facts from the source article.
Lore & Background
Alconrad belongs to the Koronis family, a collisional group of stony asteroids with nearly ecliptical orbits. It orbits the Sun in the outer main-belt at a distance of 2.6–3.1 AU, completing one orbit every 1,752 days. Its orbit has an eccentricity of 0.08 and an inclination of 3° with respect to the ecliptic. The body's observation arc begins with a precovery taken by Steward Observatory's Spacewatch program in October 1994, five years before its official discovery. In December 2009, a rotational lightcurve obtained at the Wise Observatory in Israel gave a rotation period of 4.03 hours with a brightness variation of 0.19 magnitude. In October 2013, observations at the Palomar Transient Factory in California gave a period of 5.0206 hours with an amplitude of 0.14 magnitude. According to the NEOWISE survey, Alconrad measures 5.7 kilometers in diameter with an albedo of 0.18, while the Collaborative Asteroid Lightcurve Link assumes an albedo of 0.24 and calculates a diameter of 4.9 kilometers. The minor planet was named after American astronomer Albert R. Conrad, an expert in adaptive optics who co-discovered many asteroid moons. The naming citation was published on 20 June 2016.
Reader's Guide
Alconrad's significance lies in its binary nature and its historical status as the smallest known main-belt asteroid with a satellite at the time of its moon's discovery in 2003. The moon, later named Juliekaibarreto, was discovered by researchers at Southwest Research Institute using the Hubble Space Telescope. They calculated a diameter of 4.5 kilometers for the primary based on an assumed albedo of 0.21, and measured a large angular separation of 0.14 arcseconds, equivalent to a distance of 170 or 182 kilometers. Based on a magnitude difference of 2.5, the satellite is estimated to be 1 to 1.5 kilometers in diameter. The moon was named after Julie Kai Barreto, Albert Conrad's wife. Since 2003, other binaries with smaller primaries have been discovered, such as 4868 Knushevia (1.5 km) in 2015 and 8026 Johnmckay (1.7 km) in 2010, but Alconrad remains a notable early example of a small binary system in the main belt. The asteroid's rotation period remains uncertain, with two different measurements from 2009 and 2013, and its diameter varies depending on the assumed albedo.
Did You Know?
- Alconrad was the smallest known main-belt asteroid with a satellite when its moon was discovered in 2003.
- The moon, Juliekaibarreto, is named after Albert Conrad's wife, Julie Kai Barreto.
- The asteroid has two measured rotation periods: 4.03 hours (2009) and 5.0206 hours (2013).
- A precovery image of Alconrad was taken by the Spacewatch program in October 1994.
Frequently Asked Questions
What is 22899 Alconrad?
Alconrad is a stony asteroid in the Koronis family that orbits in the outer main belt, roughly 2.6 to 3.1 AU from the Sun. It spans about 5 kilometers across and was originally catalogued under the provisional name 1999 TO14.
Who discovered 22899 Alconrad and where?
Croatian astronomers Korado Korlević and Mario Jurić identified the asteroid on 11 October 1999 from the Višnjan Observatory in Croatia. The object was later assigned the permanent number 22899 and the name Alconrad.
Why is 22899 Alconrad notable among asteroids?
When its companion moon was detected in 2003, Alconrad became the smallest known main-belt asteroid confirmed to host a satellite. It also belongs to the Koronis family, making it a useful reference object for studying that collisional group.
What is 22899 Alconrad's orbital period?
Alconrad completes one full revolution around the Sun in approximately 4 years and 10 months, or about 1,752 days. Its orbit carries it between 2.6 and 3.1 astronomical units from the Sun.
How fast does 22899 Alconrad rotate?
Two lightcurve measurements give slightly different spin values: roughly 4.03 hours from a 2009 observation and about 5.02 hours from a 2013 observation. The spread is likely due to the asteroid's irregular shape affecting the photometric readings.
More in Notable Asteroids, Part 4 1-24
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