(589683) 2010 RF43
Large scattered-disc object discovered in 2010, awaiting Hubble imaging.
(589683) 2010 RF43 is a sizable object located in the scattered disc, a distant region of the Solar System beyond Neptune. It was discovered on September 9, 2010, by a team of American astronomers—David Rabinowitz, Megan Schwamb, and Suzanne Tourtellotte—while observing at the La Silla Observatory in Chile, which is operated by the European Southern Observatory. No high-resolution images of this object have been taken yet, and consequently, no moons have been detected around it. However, the Hubble Space Telescope is scheduled to observe 2010 RF43 in 2026, which should reveal whether it hosts any moons of significant size.
The object follows an orbit that brings it between 37.5 and 61.9 astronomical units (AU) from the Sun, completing one revolution roughly every 350 years and four months (about 127,948 days), with a semi-major axis of 49.7 AU. Its orbital eccentricity is 0.25, and it is inclined 31 degrees relative to the ecliptic plane. The earliest known observation of 2010 RF43 is a precovery image taken at Siding Spring Observatory in August 1976. Because of its relatively high eccentricity and inclination, it is classified as a scattered-disc object rather than a member of the classical Kuiper belt. Its perihelion of 37.5 AU, however, is too close to Neptune’s orbit for it to be considered a detached object, which typically have perihelia above 40 AU.
The Minor Planet Center assigned this minor planet the number 589683 on September 20, 2021, as recorded in the Minor Planet Circular 135075. As of January 2026, it has not yet been given a formal name.
Estimates of its diameter vary: Johnston's Archive suggests a mean diameter of about 656 kilometers (408 miles), while Mike Brown calculates roughly 611 kilometers (380 miles). Brown’s estimate, however, relies on an older absolute magnitude (H) of 4.2, rather than the more recent value of 3.80. No rotational lightcurve has been obtained from photometric observations as of 2026, so its rotation period, pole orientation, and shape remain unknown. In 2013, Benecchi and colleagues placed an upper limit of 0.08 magnitudes on its lightcurve amplitude.
Color indices for 2010 RF43 are g′−r′ = 0.80 ± 0.03, g′−i′ = 1.21 ± 0.04, and r′−i′ = 0.41 ± 0.03. Its albedo has not been directly measured, but estimates place it at 0.10 and 0.124.
Quick Facts
- Minorplanet
- yes
- Discoverer
- D. L. Rabinowitz / M. Schwamb / S. Tourtellotte
- Discovery Site
- La Silla Obs.
- Discovered
- 6 September 2010
- Mpc Name
- (589683) 2010 RF · 43
- Mp Category
- TNOSDOdistant
- Epoch
- 31 May 2020 (JD 2459000.5)
- Uncertainty
- 2
- Observation Arc
- 46.17 yr (~16,860 days)
- Earliest Precovery Date
- 19 August 1976
- Aphelion
- 61.903 AU
- Perihelion
- 37.482 AU
Facts from the source article.
Lore & Background
2010 RF43 orbits the Sun at a distance of 37.5–61.9 AU once every 350 years and 4 months, with a semi-major axis of 49.7 AU. Its orbit has an eccentricity of 0.25 and an inclination of 31° with respect to the ecliptic. The observation arc begins with a precovery observation taken at Siding Spring Observatory in August 1976. Due to its relatively high eccentricity and inclination, it is classified as a scattered-disc object rather than a regular Kuiper belt object; however its perihelion of 37.5 AU is too low to make it a detached object.
As of 2026, no rotational lightcurve has been obtained, so its rotation period, pole, and shape remain unknown. In 2013, Benecchi and colleagues put an upper bound of 0.08 mag on its lightcurve amplitude. The object's albedo has not been measured directly but has been estimated at 0.10 and 0.124. Its color indices are g′−r′ 0.80 ± 0.03, g′−i′ 1.21 ± 0.04, and r′−i′ 0.41 ± 0.03.
The minor planet was numbered by the Minor Planet Center on 20 September 2021, receiving the number 589683. As of January 2026, it has not been named.
Reader's Guide
The significance of (589683) 2010 RF43 lies in its status as a large, unstudied scattered-disc object whose physical properties remain largely unknown. Its estimated diameter ranges from 611 to 656 kilometers depending on the source, with Mike Brown's estimate using an outdated absolute magnitude. The object has no known moons, and the planned Hubble Space Telescope imaging in 2026 may reveal whether it hosts significantly sized satellites. Its high orbital inclination and eccentricity place it firmly in the scattered disc, a population thought to have been dynamically scattered by Neptune. The lack of a rotational lightcurve means its spin and shape are completely unconstrained, and its albedo is only roughly estimated. The precovery observation from 1976 extends its observation arc to decades, aiding orbital refinement. As an unnumbered and unnamed object until 2021, it represents the many distant bodies awaiting detailed characterization.
Did You Know?
- 2010 RF43 was discovered on 9 September 2010 at ESO's La Silla Observatory in northern Chile.
- Its observation arc begins with a precovery image from Siding Spring Observatory in August 1976.
- The Hubble Space Telescope is planned to image 2010 RF43 in 2026 to search for moons.
- As of January 2026, this minor planet has not been named.
More in Trans-Neptunian Objects, Part 3 1-24
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