Open main menu

2015 RX245 is an extreme trans-Neptunian object, detached, on a highly eccentric orbit in the outermost region of the Solar System. It measures approximately 250 kilometers (160 miles) in diameter and is "possibly" a dwarf planet. It was first observed on 8 September 2015, by astronomers with Outer Solar System Origins Survey using the 3.6-meter Canada–France–Hawaii Telescope at Mauna Kea Observatories, Hawaii, in the United States.[1][2][3]

2015 RX245
Planet nine-etnos now-new2.png
Orbital diagram of 2015 RX245 and other objects along with hypothetical Planet Nine
Discovery [1][2][3]
Discovered by(first observed only)
Discovery siteMauna Kea Obs.
Discovery date8 September 2015
MPC designation2015 RX245
TNO[4] · EDDO[5]
p-DP[6] · ETNO
Orbital characteristics[4]
Epoch 27 April 2019 (JD 2458600.5)
Uncertainty parameter 5
Observation arc1.61 yr (587 d)
Aphelion788.22 AU
Perihelion45.563 AU
416.89 AU
8512 yr (3,109,107 d)
0° 0m 0.36s / day
Neptune MOID17.5 AU
Physical characteristics
Mean diameter
245 km (est.)[6]
255 km (est.)[5]
0.08 (assumed)[6]
0.09 (assumed)[5]


Orbit and classificationEdit

2015 RX245 has a similar size and orbit as 2013 SY99.

2015 RX245 belongs to a small group of detached objects with perihelion distances of 30 AU or more, and semi-major axes of 150 AU or more.[7] These extreme trans-Neptunian objects (ETNOs) can not reach such orbits without some perturbing object, which lead to the speculation of Planet Nine. It is also denoted at extended detached disc object or extreme distant detached object (EDDO).[5]

It orbits the Sun at a distance of 45.6–788 AU once every 8512 years (3,109,107 days; semi-major axis of 417 AU). Its orbit has an exceptionally high eccentricity of 0.89 and an inclination of 12° with respect to the ecliptic.[4]

The body's observation arc begins with a precovery taken at Mauna Kea on 23 June 2015, or 11 weeks prior to its official first observation.[1] It has a minimum orbital intersection distance with Neptune of 17.5 AU.[1] 2015 RX245 has a similar size and orbit as 2013 SY99, as well as close positions to each other at the moment, both about 60 AU from the Sun (see adjunct diagram, in the middle bottom).

Numbering and namingEdit

As of 2018, this minor planet has neither been numbered nor named by the Minor Planet Center. The official discoverers will be defined when the object is numbered.[1]

Physical characteristicsEdit

According to American astronomer Michael Brown and to the Johnston's archive, 2015 RX245 measures 128 and 130 kilometers in diameter based on an assumed albedo of 0.09 and 0.08, respectively.[5][6] On his website, Michael Brown lists this object as "possibly" a dwarf planet (200–400 km) which is the least certain category in his 5-class taxonomic system.[6] As of 2018, no rotational lightcurve has been obtained from photometric observations. The body's rotation period, pole and shape remain unknown.[4][8]

See alsoEdit


  1. ^ a b c d e f g "2015 RX245". Minor Planet Center. Retrieved 26 October 2018.
  2. ^ a b "MPEC 2017-M25 : 2015 RX245". Minor Planet Center. 19 June 2017. Retrieved 26 October 2018.
  3. ^ a b "List Of Centaurs and Scattered-Disk Objects". Minor Planet Center. Retrieved 25 October 2018.
  4. ^ a b c d e "JPL Small-Body Database Browser: (2015 RX245)" (2017-01-30 last obs.). Jet Propulsion Laboratory. Retrieved 26 October 2018.
  5. ^ a b c d e "List of Known Trans-Neptunian Objects". Johnston's Archive. 7 October 2018. Retrieved 25 October 2018.
  6. ^ a b c d e Brown, Michael E. "How many dwarf planets are there in the outer solar system?". California Institute of Technology. Retrieved 25 October 2018.
  7. ^ "Database Query: objects q>30, a>150". Minor Planet Center. Retrieved 25 October 2018.
  8. ^ "LCDB Data for (2015+RX245)". Asteroid Lightcurve Database (LCDB). Retrieved 26 October 2018.

External linksEdit