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(55636) 2002 TX₃₀₀
	Hubble Space Telescope image of 2002 TX300 taken in 2005
Discovery
Discovered by	NEAT (644)
Discovery site	Palomar Mountain
Discovery date	15 October 2002
Designations
MPC designation	(55636) 2002 TX300
Minor planet category	TNO; Cubewano; Extended (DES);
Orbital characteristics
	Epoch 13 January 2016 (JD 2457400.5)
	Uncertainty parameter 2
Observation arc	22380 days (61.27 yr)
Aphelion	48.365 AU (7.2353 Tm)
Perihelion	37.8672 AU (5.66485 Tm)
Semi-major axis	43.116 AU (6.4501 Tm)
Eccentricity	0.12174
Orbital period (sidereal)	283.12 yr (103408 d)
Mean anomaly	73.7618°
Mean motion	0° 0m 12.533s / day
Inclination	25.87838°
Longitude of ascending node	324.6984°
Argument of perihelion	338.958°
Physical characteristics
Mean radius	143±5 km (occultation); <320.6+125.2; −103.4 km (Spitzer two-band thermal model);
Mass	~1.2×1019 kg (assumed)
Synodic rotation period	8.12 h (0.338 d)
Sidereal rotation period	0.504 d (12.101 h)
Geometric albedo	0.88+0.15; −0.06; > 0.173+0.203; −0.083 (Spitzer);
Temperature	< 41 K
Spectral type	(Neutral); B–V = 0.66; V–R = 0.36; B0–V0 = 0.869;
Apparent magnitude	19.4
Absolute magnitude (H)	3.4

(55636) 2002 TX₃₀₀ is a bright Kuiper belt object in the outer Solar System estimated to be about 286 kilometres (178 mi) in diameter.^[4] It is a large member of the Haumea family that was discovered on 15 October 2002 by the Near-Earth Asteroid Tracking (NEAT) program.^[1]

2002 TX₃₀₀ is a classical Kuiper belt object with an absolute magnitude between that of 50000 Quaoar and 20000 Varuna. 2002 TX₃₀₀ has the most eccentric and inclined orbit of the three.

A variability of the visual brightness was also detected which could fit to 7.9 h or 15.8 h rotational period (the distinction between single or double-peaked curved could not be made with confidence). The changes in brightness are quite close to the error margin and could also be due to an irregular shape.^[10]

Orbit

The adjacent diagrams show polar and ecliptic views of the orbits of the two cubewanos. The perihelia (q) and the aphelia (Q) are marked with the dates of passage. The present positions (as of April 2006) are marked with the spheres, illustrating relative sizes and differences in albedo (both objects appear neutral in the visible spectrum).

2002 TX₃₀₀ is classified as a classical Kuiper belt object and follows an orbit very similar to that of Haumea: highly inclined (26°) and moderately eccentric (e ~0.12), far from Neptune's perturbations (perihelion at ~37 AU). Other mid-sized cubewanos follow similar orbits as well, notably 2002 UX₂₅ and 2002 AW₁₉₇.

It has been observed 303 times, with precovery images back to 1954.^[1]

Size

2002 TX₃₀₀ (apparent magnitude 19.4) as viewed with a 24" telescope

In 2004, the non-detection of IR thermal emissions put an upper limit of 709 kilometres (441 mi) on its diameter and a lower limit on the albedo of 0.19.^[11] In a 2006 International Astronomical Union press release discussing the IAU 2006 draft proposal, a diagram suggested that 2002 TX₃₀₀ could be as large as 50000 Quaoar.^[12] The artist's diagram was largely based on the concept that 2002 TX₃₀₀, with an absolute magnitude (H) of 3.4,^[1] may have an albedo around 0.08,^[10] which resulted in an overly optimistic diameter estimate of around 1,000 kilometres (620 mi).^[13]

In 2007, measurements by the Spitzer Space Telescope showed that it may be less than 641 kilometres (398 mi) in diameter.^[5] In 2008, it was considered to be a dwarf planet based on its lightcurve amplitude and the assumption that it was larger than 450 kilometres (280 mi) in diameter.^[14] Because 2002 TX₃₀₀ is a member of the Haumea family, it is assumed to have an albedo of around 0.7, which would result in a diameter of about 360 kilometres (220 mi).^[15]

2002 TX₃₀₀ occulted a relatively bright apparent magnitude 13.1 star in the constellation of Andromeda on 9 October 2009.^[16] This event was visible from Australia, possibly New Zealand, and the southern United States and Mexico.^[16] The RA and declination for this event was about 00 37 13.64 +28 22 23.2.: detailed information for observers was made available.^[17] The occultation produced a diameter of 286 kilometres (178 mi), suggesting an albedo of about 0.88.^[4] Mike Brown lists it as a possible dwarf planet.^[18]

Surface

The spectrum in the visible and near-infrared rages is very similar to that of Charon, characterized by neutral to blue slope (1%/1000 Å) with deep (60%) water absorption bands at 1.5 and 2.0 μm.^[19] Mineralogical analysis indicates a substantial fraction of large ice (H₂O) particles.^[20] The signal-to-noise ratio of the observations was insufficient to differentiate between amorphous or crystalline ice (crystalline ice was reported on Charon, Quaoar and Haumea). The proportion of highly processed organic materials (tholins), typically present on numerous trans-Neptunian objects, is very low. As suggested by Licandro et al. 2006, this lack of irradiated mantle suggest either a recent collision or comet activity.

Origin

Common physical characteristics with the dwarf planet Haumea together with similar orbit elements^[21] led to suggestion that 2002 TX₃₀₀ was a member of the Haumean collisional family. The object, together with other members of the family ((19308) 1996 TO66, (24835) 1995 SM55, (120178) 2003 OP32 and (145453) 2005 RR43), would be created from ice mantle ejected from the proto-Haumea as result of a collision with another large (around 1,660 kilometres (1,030 mi)) body.^[22]

References

^ ^a ^b ^c ^d ^e ^f ^g "JPL Small-Body Database Browser: 55636 (2002 TX300)" (last observation: 2015-12-05). Retrieved 6 April 2016.
^ "MPEC 2009-R09 :Distant Minor Planets (2009 SEPT. 16.0 TT)". IAU Minor Planet Center. 4 September 2009. Retrieved 4 October 2009.
^ Marc W. Buie. "Orbit Fit and Astrometric record for 55636" (2013-12-04 using 341 observations over 59 years). SwRI (Space Science Department). Retrieved 14 October 2014.
^ ^a ^b ^c ^d Elliot, J. L.; Person, M. J.; et al. (2010). "Size and albedo of Kuiper belt object 55636 from a stellar occultation" (PDF). Nature. 465 (7300): 897–900. Bibcode:2010Natur.465..897E. doi:10.1038/nature09109. PMID 20559381. S2CID 4431420. Archived from the original (PDF) on 22 February 2014.
^ ^a ^b ^c John Stansberry; Will Grundy; Mike Brown; Dale Cruikshank; John Spencer; David Trilling; Jean-Luc Margot (2007). "Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope". arXiv:astro-ph/0702538.
^ Using a spherical radius of 143 km; volume of a sphere * an assumed density of 1.0 g/cm³ yields a mass ({{{1}}}) of 1.224×10¹⁹ kg
^ Snodgrass, Carry; Dumas, Hainaut (16 December 2009). "Characterisation of candidate members of (136108) Haumea's family". Astronomy and Astrophysics. 511: A72. arXiv:0912.3171. Bibcode:2010A&A...511A..72S. doi:10.1051/0004-6361/200913031. S2CID 62880843.
^ David L. Rabinowitz; Bradley E. Schaefer; Martha W. Schaefer; Suzanne W. Tourtellotte (2008). "The Youthful Appearance of the 2003 EL61 Collisional Family". The Astronomical Journal. 136 (4): 1502. arXiv:0804.2864. Bibcode:2008AJ....136.1502R. doi:10.1088/0004-6256/136/4/1502. S2CID 117167835.
^ "(55636) 2002TX300 Ephemerides". AstDys. Department of Mathematics, University of Pisa, Italy. Archived from the original on 26 May 2011. Retrieved 16 March 2009.
^ ^a ^b Ortiz, J. L.; Sota, A.; Moreno, R.; Lellouch, E.; Biver, N.; Doressoundiram, A.; Rousselot, P.; Gutiérrez, P. J.; Márquez, I.; González Delgado, R. M.; Casanova, V. (2004). "A study of Trans-Neptunian object (55636) 2002 TX₃₀₀". Astronomy & Astrophysics. 420 (1): 383–388. doi:10.1051/0004-6361:20034507.
^ Grundy, W. M; Noll, K; Stephens, D (2005). "Diverse albedos of small trans-neptunian objects". Icarus. 176 (1): 184–191. arXiv:astro-ph/0502229. Bibcode:2005Icar..176..184G. doi:10.1016/j.icarus.2005.01.007. S2CID 118866288. (Preprint on arXiv)
^ Gingerich, Owen (16 August 2006). "The Path to Defining Planets" (PDF). Harvard-Smithsonian Center for Astrophysics and IAU EC Planet Definition Committee chair. p. 4. Retrieved 13 March 2007.
^ Dan Bruton. "Conversion of Absolute Magnitude to Diameter for Minor Planets". Department of Physics & Astronomy (Stephen F. Austin State University). Archived from the original on 23 March 2010. Retrieved 27 December 2009.
^ Gonzalo Tancredi & Sofía Favre (13 October 2008). "Dwarf Planet & Plutoid Headquarters". Portal Uruguayo de Astronomía. Retrieved 22 September 2010. (Which are the dwarfs in the Solar System?)
^ Mike Brown (29 December 2009). "A ghost of Christmas past". Mike Brown's Planets (blog). Archived from the original on 2 January 2010. Retrieved 29 December 2009.
^ ^a ^b Steve Preston. "(55636) 2002 TX300 / UCAC2 41650964 event on 2009 Oct 09, 10:28 UT". Archived from the original on 8 October 2009. Retrieved 5 October 2009.
^ Michael J. Person (8 October 2009). "55636.20091009 Occultation October 09, 2009". Planetary Astronomy Lab. MIT. Retrieved 9 October 2009.
^ Michael E. Brown (23 September 2011). "How many dwarf planets are there in the outer solar system? (updates daily)". California Institute of Technology. Retrieved 31 August 2016.
^ Licandro, J.; di Fabrizio, L.; Pinilla-Alonso, N.; de León, J.; Oliva, E. (2006). "Trans-Neptunian object (55636) 2002 TX₃₀₀, a fresh icy surface in the outer Solar System". Astronomy and Astrophysics. 457 (1): 329–333. Bibcode:2006A&A...457..329L. doi:10.1051/0004-6361:20064906.
^ Pinilla-Alonso, N.; Licandro, J.; Campins, H. (2004). "Mineralogical analysis of two different kinds of icy surfaces in the trans-neptunian belt, TNOs (50000) Quaoar and 2002 TX₃₀₀". American Astronomical Society, DPS Meeting #36, #11.07; Bulletin of the American Astronomical Society. 36: 1088. Bibcode:2004DPS....36.1107P.
^ Pinilla-Alonso, N.; Licandro, J.; Gil-Hutton, R.; Brunetto, R. (June 2007). "The water ice rich surface of (145453) 2005 RR43: a case for a carbon-depleted population of TNOs?". Astronomy and Astrophysics. 468 (1): L25–L28. arXiv:astro-ph/0703098. Bibcode:2007A&A...468L..25P. doi:10.1051/0004-6361:20077294. S2CID 18546361.
^ Michael E. Brown; Kristina M. Barkume; Darin Ragozzine; Emily L. Schaller (March 2007). "A collisional family of icy objects in the Kuiper belt". Nature. 446 (7133): 294–296. Bibcode:2007Natur.446..294B. doi:10.1038/nature05619. PMID 17361177. S2CID 4430027.