20325 Julianoey
A Vestian binary asteroid with a synchronous moon.
20325 Julianoey, first designated 1998 HO27, is a small asteroid from the inner main belt, roughly 5 kilometers across. It belongs to the Vesta family and is also a synchronous binary system, meaning it has a moon that orbits in lockstep with its rotation. The asteroid was discovered on 21 April 1998 by the Spacewatch survey at Kitt Peak National Observatory in Arizona. Its moon was announced in December 2014.
Julianoey orbits the Sun between 2.2 and 2.6 AU, completing one lap every 3 years and 8 months. Its orbit is only slightly elliptical (eccentricity 0.08) and tilted about 6° relative to the ecliptic. Although it is a member of the Vesta family, it is considered a background asteroid when using proper orbital elements. The first known observation of this object was a precovery image from Palomar Observatory in May 1954, nearly 44 years before its official discovery.
The asteroid is assumed to be a stony S-type. In December 2014, a global team of photometrists led by Donald Pray measured its lightcurve, finding a well-defined rotation period of 3.24474 hours and a small brightness variation of 0.13 magnitudes.
Those same observations revealed a moon orbiting Julianoey every 23.54 hours. The satellite is about 1.42 kilometers in diameter and orbits at an estimated distance of 10 kilometers. The discovery was announced on 24 December 2014.
Data from the NEOWISE mission give Julianoey a diameter of 4.942 kilometers and a high albedo of 0.416. In contrast, the Collaborative Asteroid Lightcurve Link assumes a standard stony albedo of 0.20, which yields a larger diameter of 6.81 kilometers based on an absolute magnitude of 13.2.
The asteroid was numbered on 9 January 2001. It was named after Julian Oey (born 1964), an Australian photometrist who led the discovery of four binary asteroids and co-discovered many others. The naming was suggested by Alan Harris and Petr Pravec, and the citation was published on 5 June 2016.
Quick Facts
- Minorplanet
- yes
- Background
- #D6D6D6
- Discoverer
- Spacewatch
- Discovery Site
- Kitt Peak National Obs.
- Discovered
- 21 April 1998
- Mpc Name
- (20325) Julianoey
- Named After
- Julian Oey / (Australian photometrist)
- Mp Category
- main-beltVestian / background
- Epoch
- 4 September 2017 (JD 2458000.5)
- Uncertainty
- 0
- Observation Arc
- 63.43 yr (23,169 days)
- Aphelion
- 2.5620 AU
Facts from the source article.
Lore & Background
20325 Julianoey orbits the Sun in the inner asteroid belt at a distance of 2.2–2.6 AU, completing one orbit every 3 years and 8 months. Its orbit has an eccentricity of 0.08 and an inclination of 6° with respect to the ecliptic. The body's observation arc begins with a precovery taken at Palomar Observatory in May 1954, nearly 44 years before its official discovery. It is a member of the Vesta family (401) but is considered a non-family asteroid of the main belt's background population when applying the Hierarchical Clustering Method to its proper orbital elements. The asteroid is an assumed stony S-type. In December 2014, photometric observations by Donald Pray and several other astronomers yielded a well-defined rotation period of 3.24474 hours with a brightness amplitude of 0.13 magnitude. The same observations revealed that Julianoey is a synchronous binary asteroid, with a moon orbiting every 23.54 hours. The satellite measures approximately 1.42 kilometers in diameter, and its orbit has an estimated semi-major axis of 10 kilometers. The discovery was announced on 24 December 2014. NEOWISE measurements give a diameter of 4.942 kilometers and a high albedo of 0.416, while the Collaborative Asteroid Lightcurve Link assumes a standard albedo of 0.20 and calculates a larger diameter of 6.81 kilometers.
Reader's Guide
20325 Julianoey holds significance as a synchronous binary asteroid in the inner main belt, providing insight into the formation and dynamics of small-body satellite systems. Its discovery as a binary system in December 2014 added to the growing catalog of asteroids with moons, particularly within the Vesta family. The asteroid's naming honors Julian Oey, an Australian photometrist who led the discovery of four binary asteroids and co-discovered many others, reflecting the collaborative nature of asteroid research. The discrepancy between NEOWISE and assumed-albedo diameter estimates highlights ongoing uncertainties in asteroid physical characterization. The precovery observation from 1954 extends the observational arc by decades, aiding orbital refinement. Julianoey's study contributes to understanding the prevalence and properties of binary systems among small asteroids, and its well-defined rotation period and satellite orbit offer data for modeling tidal evolution and binary formation mechanisms.
Did You Know?
- 20325 Julianoey is a synchronous binary asteroid with a moon that orbits every 23.54 hours.
- The asteroid was named after Australian photometrist Julian Oey, who discovered four binary asteroids.
- Its rotation period is 3.24474 hours, determined from photometric observations in December 2014.
- The first precovery observation of Julianoey dates back to May 1954 at Palomar Observatory.
Frequently Asked Questions
Who is 20325 Julianoey?
Julianoey is a small inner main-belt asteroid roughly 5 kilometers across, originally catalogued under the provisional designation 1998 HO27. It belongs to the Vesta family and hosts a small moon in a synchronous orbit around it.
What makes 20325 Julianoey special?
Its standout feature is being a synchronous binary system, meaning its moon orbits in perfect lockstep with the asteroid's roughly 3.24-hour rotation. That makes it a neat natural example of how small companion bodies can become tidally locked to their parent.
How was 20325 Julianoey discovered?
The Spacewatch survey at Kitt Peak National Observatory in Arizona first detected the asteroid on 21 April 1998. Its satellite was not announced until December 2014, more than sixteen years after the primary was first spotted.
What is 20325 Julianoey's orbit like?
Julianoey circles the Sun between roughly 2.2 and 2.6 AU, completing one revolution in about 3 years and 8 months. Its path is only mildly elliptical with an eccentricity near 0.08 and a tilt of about 6 degrees from the ecliptic plane.
Why is 20325 Julianoey important?
As a Vesta-family member with a confirmed synchronous satellite, it serves as a useful case study for understanding how small binary systems form and evolve in the inner asteroid belt. Its modest size and spin period make it a representative example of that population.
More in Notable Asteroids, Part 4 1-24
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