(528381) 2008 ST291
Trans-Neptunian object
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(528381) 2008 ST291, provisional designation 2008 ST291, is a 1:6 resonant trans-Neptunian object located in the outermost region of the Solar System that takes almost a thousand years to complete an orbit around the Sun.[5] It was discovered on 24 September 2008 by American astronomers Megan Schwamb, Michael Brown and David Rabinowitz at the Palomar Observatory in California, with no known earlier precovery images.[1]
Orbit of (528381) 2008 ST291 | |
| Discovery[1][2] | |
|---|---|
| Discovered by | M. E. Schwamb M. E. Brown D. L. Rabinowitz |
| Discovery site | Palomar Obs. |
| Discovery date | 24 September 2008 |
| Designations | |
| (528381) 2008 ST291 | |
| 2008 ST291 | |
| TNO · SDO res 1:6[3] | |
| Orbital characteristics[4] | |
| Epoch 27 April 2019 (JD 2458600.5) | |
| Uncertainty parameter 3 | |
| Observation arc | 9.27 yr (3,385 d) |
| Aphelion | 157.437 AU (23.5522 Tm) |
| Perihelion | 42.3114440 AU (6.32970193 Tm) |
| 99.8742972 AU (14.94098220 Tm) | |
| Eccentricity | 0.5763530 |
| 998.30 yr (364,629 d) | |
| 23.349° | |
| 0° 0m 3.6s / day | |
| Inclination | 20.758° |
| 330.97° | |
| 324.65° | |
| Known satellites | 0 |
| Physical characteristics | |
| 549 km (est.)[5] 584 km (est.)[3] 612 km[6][7][a] 345–773 km[7][b] | |
| 0.09 (assumed)[3][5] | |
| 22.24[6] | |
| 4.22[1][4] 4.3[6] 4.6[5] | |
Numbering and naming
This minor planet was numbered by the Minor Planet Center on 18 May 2019 (M.P.C. 114657).[8] As of 2025, it has not been named.[1]
Orbit and classification
2008 ST291 is located at the 1:6 Neptune resonance of 99 AU meaning that it completes roughly 1 orbit for every 6 orbits Neptune makes.[3] It orbits the Sun at a distance of 42.3–157.5 AU once every 998 years and 4 months (semi-major axis of 99.89 AU). Its orbit has an eccentricity of 0.58 and an inclination of 21° with respect to the ecliptic.[4] Currently located at 60.9 AU from the Sun,[6] 2008 ST291 came to perihelion in 1954.[4]
Physical characteristics
Based on an absolute magnitude of 4.4,[1] 2008 ST291 is estimated by Johnston's Archive to be about 584 kilometres (363 mi) in diameter, assuming a typical albedo of 0.09 for trans-Neptunian objects.[3] Astronomer Mike Brown estimates a slightly smaller 549 km from the same albedo and a fainter 4.6 magnitude.[5] The Asteroid Dynamic Site records a brighter 4.3 magnitude, which calculates to 612 km using the same albedo (and same formula as Johnston's); using the average of these magnitudes and a standard assumed minor planet albedo range of 0.25 ~ 0.05, possible sizes of 345 to 773 km are produced.