2014 ST373

2014 ST₃₇₃ (prov. designation: 2014 ST₃₇₃) is a trans-Neptunian object and a detached object from the outermost region of the Solar System. With a perihelion of 50.2 AU, it belongs to the top 10 minor planets with the highest known perihelia of the Solar System.^[a] and is neither a scattered disc nor an extreme trans-Neptunian object. It measures approximately 370 kilometers (230 miles) in diameter and was first observed on 25 September 2014, by astronomers using the Dark Energy Camera (DECam) at Cerro Tololo Inter-American Observatory in Chile.^[1]

2014 ST₃₇₃

Discovery[1][2]
Discovered by	CTIO-DECam (first observed only)
Discovery date	25 September 2014
Designations
MPC designation	2014 ST373
Minor planet category	TNO[3][4] · detached distant[1] p-DP
Orbital characteristics[3]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 5[3] · 3[1]
Observation arc	792 d
Aphelion	158.86 AU
Perihelion	50.20 AU
Semi-major axis	104.53 AU
Eccentricity	0.52
Orbital period (sidereal)	1069 yr
Mean anomaly	353.71°
Mean motion	0° 0m 3.24s / day
Inclination	43.158°
Longitude of ascending node	130.218°
Time of perihelion	≈ 14 July 2039[5] ±4 months
Argument of perihelion	297.117°
Physical characteristics
Mean diameter	370 km (est at 0.09)[6]
Absolute magnitude (H)	5.4[1][3]

Orbit and classification

2014 ST₃₇₃ (not displayed) is located in the "gap", a poorly understood region.

2014 ST₃₇₃ (not displayed) is located in an virtually unpopulated region (q=50 AU and e=0.5.

2014 ST₃₇₃ orbits the Sun at a distance of 50.2–158.9 AU once every 1069 years; semi-major axis of 104.53 AU. Its orbit has an eccentricity of 0.52 and an inclination of 43.16° with respect to the ecliptic.^[3]

2014 ST₃₇₃ is a distant minor planet and trans-Neptunian object (TNO) beyond the orbit of Neptune and the Kuiper cliff.^[3][4] As of February 2020^[update], it has the 8th highest perihelia of all known minor planets. Based on a still sufficiently determined perihelion a of 50.2 AU, it is not a member of the scattered disc population, as these objects are thought to have been ejected from the classical Kuiper belt into their current orbits by gravitational interactions with Neptune (semi-major axis of 30.1 AU), and typically have highly eccentric orbits and perihelia of less than 38 AU. 2014 ST₃₇₃'s orbit, however, has never brought it close enough to Neptune to be gravitational disturbed.

On the other hand, this TNO is not an extreme trans-Neptunian object as these objects generally have higher perihelia and/or higher eccentricities. Instead, it is located in a virtually unpopulated region at a perihelion of 50 AU and an eccentricity of 0.5 (see adjunct images, where the grid crosses at q=50 AU and e=0.5)

The Kozai mechanism is capable of transferring orbital eccentricity to a higher inclination.^[7][8] It can be speculated that this dynamical phenomenon also affected the orbit of 2014 ST₃₇₃. If this was the case, and the object had once belonged to the extreme detached disc objects – which have eccentricities above 0.8 and semi-major axes of at least 250 AU, for a perihelion of 50 AU – the Kozai effect would have slowly decreased 2014 ST₃₇₃'s aphelion from over 450 AU to currently 159 AU while increasing its inclination. 2014 ST₃₇₃ seems to belong to the same group as 2004 XR190.^{[citation needed]}

Physical characteristics

Diameter and albedo

Based on an absolute magnitude of 5.4,^[1] and an assumed astronomical albedo of 0.9, which is a standard default value adopted for trans-Neptunian objects by Johnston's Archive,^[9] 2014 ST₃₇₃ measures approximately 370 kilometers (230 miles) in diameter.^[6] The body's color, rotation period, pole and shape remain unknown.^[3][10]

Notes

1. Data Base Query, at the JPL Small-Body Database: all objects with a perihelion (q) larger than 38 AU; sorted in descending order. In February 2020, 2014 ST₃₇₃ ranks #8 among objects with the highest perihelion. Top objects in the list: (#1) 2012 VP113, (#2) 90377 Sedna, (#3) 541132 Leleākūhonua, (#4) 2014 FZ71, (#5) 2014 FC72, (#6) 2004 XR190 and (#7) 2015 FJ345.