1995 SN55

1995 SN55
Discovery [1][2]
Discovered by Spacewatch
A. Gleason [1]
Discovery site Kitt Peak Obs.
Discovery date 20 September 1995
(discovery: first observed only)
Designations
MPC designation 1995 SN55
centaur [2][3]
Orbital characteristics [3]
Epoch 6 October 1995 (JD 2449996.5)
Uncertainty parameter 9
Observation arc 36 days
Aphelion 39.190 AU
Perihelion 7.9399 AU
23.565 AU
Eccentricity 0.6631
114.39 yr (41,782 days)
180.35°
0° 0m 30.96s / day
Inclination 4.9725°
144.61°
49.332°
Physical characteristics
Dimensions 290 km[4]
295 km (est. at 0.08)
0.08 (assumed)[4][5][6]
6.0[3]6.2[4]

    1995 SN55, is a minor planet and likely centaur that orbits in the outer Solar System beyond the orbit of Jupiter. With an estimated diameter of approximately 290 kilometer, it would be one of the largest centaurs. First observed by Spacewatch in 1995, it became a lost minor planet with an insufficiently defined orbit after only 7 weeks of observations and has not been observed ever since.[2]

    First observation and loss

    1995 SN55 was about 39 AU from the Sun when it was first observed in 1995, by astronomer Arianna Gleason of the Spacewatch survey at Kitt Peak Observatory in Arizona, United States.[1][2] It was only observed 14 times over 36 days from 20 September 1995, until 26 October 26 the same year.[3][7]

    Classification and orbit

    Centaurs have a perihelion greater than Jupiter and a semi-major axis less than that of Neptune. 1995 SN55 orbits the Sun at a distance of 7.9–39.2 AU once every 114 years and 5 months (41,782 days). Its orbit has an eccentricity of 0.66 and an inclination of 5° with respect to the ecliptic.[3] Due to this short observation arc , the object has a very poorly known orbit with the highest possible uncertainty parameter value of 9 and is considered a lost minor planet.

    JPL's small body data base shows this object having an aphelion distance of 39.2 AU,[3] whereas the Deep Ecliptic Survey (DES) finds an aphelion distance of 91 AU,[7] which would make it a trans-Neptunian object by JPL's orbital classification (hence the uncertainty whether 1995 SN55 is a centaur at all).

    Physical characteristics

    Diameter and albedo

    If confirmed to be a centaur, 1995 SN55 would be one of the largest centaurs known. Centaurs typically have an albedo of about 0.08.[5][6] With an absolute magnitude (H) of 6.0,[3] and using an average centaur albedo of 0.08,[5][6] 1995 SN55 could be 295 km in diameter. The two largest known centaurs are 10199 Chariklo (250 km, H=7.40, albedo = 0.035) and 2060 Chiron (220 km, H=6.2, albedo = 0.07).

    Lightcurves

    As of 2017, the body's rotation period, shape and spin axis remain unknown.[8]

    Numbering and naming

    Due to its uncertain orbit, this minor planet has not been numbered. A numbering and subsequent naming will only be considered upon its possible "rediscovery".

    References

    1. 1 2 3 "List Of Centaurs and Scattered-Disk Objects". Minor Planet Center. Retrieved 2008-10-21.
    2. 1 2 3 4 "1995 SN55". Minor Planet Center. Retrieved 30 July 2017.
    3. 1 2 3 4 5 6 7 "JPL Small-Body Database Browser: (1995 SN55)" (1995-10-26 last obs.). Jet Propulsion Laboratory. Retrieved 30 July 2017.
    4. 1 2 3 Michael E. Brown. "How many dwarf planets are there in the outer solar system? (updates daily)". California Institute of Technology. Retrieved 30 July 2017.
    5. 1 2 3 Wm. Robert Johnston (2008-09-17). "TNO/Centaur diameters and albedos". Johnston's Archive. Archived from the original on 22 October 2008. Retrieved 2008-10-21.
    6. 1 2 3 Bauer, James M.; Grav, Tommy; Blauvelt, Erin; Mainzer, Amy (2013). "Centaurs and Scattered Disk Objects in the Thermal Infrared: Analysis of WISE/NEOWISE Observations". The Astronomical Journal. 773 (1). Bibcode:2013DPS....4550806B. arXiv:1306.1862 Freely accessible. doi:10.1088/0004-637X/773/1/22.
    7. 1 2 Marc W. Buie (1995-10-26). "Orbit Fit and Astrometric record for 95SN55". SwRI (Space Science Department). Retrieved 2008-10-21.
    8. ↑ "LCDB Data for (1995)". Asteroid Lightcurve Database (LCDB). Retrieved 30 July 2017.
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