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(523731) 2014 OK₃₉₄
Discovery
Discovered by	Pan-STARRS 1
Discovery site	Haleakalā Obs.
Discovery date	8 October 2010
Designations
MPC designation	1995 SN55 ; 2014 OK394
Minor planet category	3:5 resonant · TNO · distant
Orbital characteristics
	Epoch 31 May 2020 (JD 2459000.5)
	Uncertainty parameter 2
Observation arc	25.14 yr (9,181 days)
Earliest precovery date	20 September 1995 (Spacewatch)
Aphelion	49.153 AU
Perihelion	35.351 AU
Semi-major axis	42.252 AU
Eccentricity	0.16333
Orbital period (sidereal)	274.65 yr
Mean anomaly	30.889°
Mean motion	0° 0m 12.919s / day
Inclination	4.140°
Longitude of ascending node	128.384°
Time of perihelion	≈ 4 January 1997
Argument of perihelion	247.580°
Physical characteristics
Mean diameter	160–280 km (est. 0.08–0.20)
Absolute magnitude (H)	6.2

(523731) 2014 OK₃₉₄ (provisional designation 1995 SN₅₅) is a trans-Neptunian object that orbits in the outer Solar System beyond the orbit of Neptune. First observed as 1995 SN₅₅ by Spacewatch on 20 September 1995, it was a lost minor planet with an insufficiently defined orbit with only 36 days of observations.^[9] On 8 October 2010, it was rediscovered by the Pan-STARRS 1 survey and later announced as 2014 OK₃₉₄ in July 2016.^[1] It was not until November 2020 when amateur astronomers S. Deen and K. Ly identified 2014 OK₃₉₄ and 1995 SN₅₅ as the same object.^[10] This identification was confirmed and announced by the Minor Planet Center in January 2021.^[11]

Once thought to be a centaur crossing the orbits of the gas giants,^[9] 1995 SN₅₅ is now known to be a trans-Neptunian object in a 3:5 orbital resonance with Neptune.^[4] With an estimated diameter between 160–280 kilometers (99–170 miles), it was formerly considered one of the largest centaurs.^[7]^[12]^[13]

Observations

First observation and loss

1995 SN₅₅ was near perihelion 35.4 AU from the Sun when it was first observed in 1995, by astronomers Nichole Danzl and Arianna Gleason of the Spacewatch survey at Kitt Peak Observatory in Arizona, United States.^[5] It was only observed 14 times over 36 days, from 20 September to 26 October 1995.^[9] The discovery observations of 1995 SN₅₅ were published and announced by the Minor Planet Center on 11 June 1999.^[5] By 2020 the 3-sigma uncertainty in the heliocentric distance to the original orbit solution for 1995 SN₅₅ was approximately ±20 AU (3.0 billion km).^{[citation needed]}

Recovery

On 30 November 2020, amateur astronomers S. Deen and K. Ly identified 1995 SN₅₅ as the 3:5 resonant trans-Neptunian object (523731) 2014 OK₃₉₄, which was discovered by Pan-STARRS 1 in 2010.^[10] The identification was published by the Minor Planet Center on 27 January 2021.^[11]

Classification and orbit

2014 OK₃₉₄ orbits the Sun at an average distance of 42.33 AU once every 275 years. Its orbit has an eccentricity of 0.16 and an inclination of 4° with respect to the ecliptic plane. Over the course of its orbit, its distance from the Sun ranges from 35.4 AU at perihelion to 49.3 AU at aphelion. 2014 OK₃₉₄ is in a 3:5 mean-motion orbital resonance with Neptune; for every three orbits it makes, Neptune orbits five times.^[3] Its orbit has a minimum orbit intersection distance approximately 5.6 AU (840 million km; 520 million mi) from Neptune's orbital path.^[4]

Numbering and naming

2014 OK₃₉₄ was numbered by the Minor Planet Center on 25 September 2018 and received the number 523731 in the minor planet catalog.^[14] The alternate provisional designation 1995 SN₅₅ was given by the Minor Planet Center on 27 January 2021 after the two objects were linked.^[11] As of 2021^[update], it has not been named.^[2]

References

^ ^a ^b Gibson, B.; Goggia, T.; Primak, N.; Schultz, A.; Willman, M.; Chambers, K.; Chastel, S.; Chen, Y. -T.; Denneau, L.; Flewelling, H.; Holman, M.; Huber, M.; Jedicke, R.; Lackner, M.; Lilly, E.; Lin, H. -W.; Magnier, E.; Micheli, M.; Payne, M.; Veres, P.; Wainscoat, R.; Waters, C.; Weryk, R. (17 July 2016). "MPEC 2016-O154 : 2014 OK394". Minor Planet Electronic Circular. 2016-O154. Minor Planet Center. Bibcode:2016MPEC....O..154G. Retrieved 23 February 2021.
^ ^a ^b ^c ^d "(523731) = 1995 SN55 = 2014 OK394". Minor Planet Center. International Astronomical Union. Archived from the original on 30 November 2020. Retrieved 23 February 2021.
^ ^a ^b Johnston, Wm. Robert (18 August 2020). "List of Known Trans-Neptunian Objects". Johnston's Archive. Retrieved 24 February 2021.
^ ^a ^b ^c ^d ^e "JPL Small-Body Database Browser: 523731 (2014 OK394 = 1995 SN55)" (2020-11-19 last obs.). Jet Propulsion Laboratory. Archived from the original on 30 November 2020. Retrieved 23 February 2021.
^ ^a ^b ^c Marsden, Brian G. (11 June 1999). "MPEC 1999-L25 : 1995 SN55, 1998 TF35". Minor Planet Electronic Circular. 1999-L25. Minor Planet Center. Bibcode:1999MPEC....L...25D. Retrieved 30 November 2020.
^ "JPL Horizons On-Line Ephemeris for 523731 (2014 OK394 = 1995 SN55)". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. Retrieved 10 February 2021.
Ephemeris Type: OBSERVER, Target Body: 523731 (2014 OK394), Observer Location: Sun (body center) [500@10], Table Settings: QUANTITIES=20. Observer range
(Perihelion occurs when deldot changes from negative to positive.)
^ ^a ^b Brown, Michael E. (23 February 2021). "How many dwarf planets are there in the outer solar system?". California Institute of Technology. Retrieved 24 February 2021.
^ Bruton, Dan. "Conversion of Absolute Magnitude to Diameter for Minor Planets". Department of Physics, Engineering, and Astronomy. Stephen F. Austin State University. Archived from the original on 23 July 2011. Retrieved 24 February 2021.
^ ^a ^b ^c "JPL Small-Body Database Browser: (1995 SN55)" (1995-10-26 last obs.). Jet Propulsion Laboratory. Archived from the original on 30 November 2020. Retrieved 24 February 2021.
(Archive of 36 day observation arc of 1995 SN₅₅)
^ ^a ^b Deen, Sam (30 November 2020). "1995 SN55". groups.io. Retrieved 23 February 2021.
^ ^a ^b ^c "M.P.C. 127300" (PDF). Minor Planet Circular. Minor Planet Center. 27 January 2021. Retrieved 23 February 2021.
^ "List Of Centaurs and Scattered-Disk Objects". Minor Planet Center. International Astronomical Union. Archived from the original on 18 November 2020. Retrieved 24 February 2021. (Archived list of centaurs including 1995 SN₅₅)
^ Sokol, Joshua (25 October 2017). "A 300-kilometre space rock has vanished since we saw it in 1995". New Scientist. Retrieved 24 February 2021.
^ "M.P.C. 111781" (PDF). Minor Planet Circular. Minor Planet Center. 25 September 2018. Retrieved 23 February 2021.