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

Orbital diagram of 2015 RX245 and other objects along with hypothetical Planet Nine
Discovery[1][2][3]
Discovered by	(first observed only) OSSOS
Discovery site	Mauna Kea Obs.
Discovery date	8 September 2015
Designations
MPC designation	2015 RX245
Alternative designations	o5t52[4]
Minor planet category	TNO[5] · EDDO[6] p-DP[7] · ETNO distant[1]
Orbital characteristics[5]
Epoch 27 April 2019 (JD 2458600.5)
Uncertainty parameter 5
Observation arc	1.61 yr (587 d)
Aphelion	788.22 AU
Perihelion	45.563 AU
Semi-major axis	416.89 AU
Eccentricity	0.8907
Orbital period (sidereal)	8512 yr (3,109,107 d)
Mean anomaly	358.03°
Mean motion	0° 0m 0.36s / day
Inclination	12.144°
Longitude of ascending node	8.5994°
Argument of perihelion	65.124°
Neptune MOID	17.5 AU
Physical characteristics
Mean diameter	245 km (est.)[7] 255 km (est.)[6]
Geometric albedo	0.08 (assumed)[7] 0.09 (assumed)[6]
Absolute magnitude (H)	6.2[1][5]

Orbit and classification

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.[8] 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).[6]

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.[5]

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 naming

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 characteristics

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.[6][7] 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.[7] As of 2018, no rotational lightcurve has been obtained from photometric observations. The body's rotation period, pole and shape remain unknown.[5][9]

See also

• List of unnumbered trans-Neptunian objects § 2015 RX245

References

External links

• OSSOS VI. Striking Biases in the detection of large semimajor axis Trans-Neptunian Objects 16 Jun 2017
• List Of Centaurs and Scattered-Disk Objects, Minor Planet Center
• 2015 RX245 at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 2015 RX245 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters

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