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(55636) 2002 TX300
Haumea family Kuiper belt object From Wikipedia, the free encyclopedia
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(55636) 2002 TX300 (provisional designation 2002 TX300) is an icy trans-Neptunian object orbiting the Sun in the Kuiper belt. It has a diameter of about 300 km (190 mi) and it has a highly reflective surface made of fresh water ice.[10] It is the brightest and possibly the largest known member of the Haumea family (besides Haumea itself),[15]: 559 a population of Kuiper belt objects that broke off from the dwarf planet Haumea 4.4 billion years ago.[16]
2002 TX300 was discovered on 15 October 2002 by the NASA-directed Near-Earth Asteroid Tracking (NEAT) survey at Palomar Observatory. When it was discovered, astronomers initially inferred from its high brightness that it could be a large dwarf planet almost 1,000 km (620 mi) in diameter. This was later disproven in October 2009, when astronomers measured the diameter of 2002 TX300 for the first time by observing the object occulting or blocking out the light of a background star. 2002 TX300 is now known to be too small to qualify as a dwarf planet, and its brightness mainly comes from its reflective surface. 2002 TX300 was the first Kuiper belt object (besides Pluto and its moon Charon) that was observed via stellar occultation.[14]: 2 [8]: 1, 5
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History
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Discovery
2002 TX300 was discovered on 15 October 2002 by the Near-Earth Asteroid Tracking (NEAT) survey,[17] which was a NASA-directed project for finding near-Earth asteroids in the sky using telescopes at various observatories across the United States.[18] The telescope that discovered 2002 TX300 was the 1.22-meter (48 in) Samuel Oschin telescope at Palomar Observatory in San Diego County, California.[17] The people involved in making the discovery observations at Palomar included Eleanor Helin, Steven Pravdo, Kenneth Lawrence, Michael D. Hicks, and R. Thicksten.[17][18] Additional confirming observations were provided by Powell Observatory, Table Mountain Observatory, and Stephen P. Laurie at Church Stretton (obs. code 966) during the three days following the discovery of 2002 TX300.[17]
The Minor Planet Center (MPC) announced the discovery of 2002 TX300 on 22 Oct 2002.[17] Within a day after the announcement, astronomer Reiner Stoss found pre-discovery observations of 2002 TX300 in NEAT images from 2001 to 2002 and Digitized Sky Survey images from 1954 to 1995.[19] The earliest known pre-discovery observation of 2002 TX300 came from Siding Spring Observatory images taken on 27 August 1954.[19][1]
Discovery images of 2002 TX300 from 15 October 2002
Number and name
The object has the minor planet provisional designation 2002 TX300, which was given by the MPC in the discovery announcement.[17] The provisional designation indicates the year and half-month of the object's discovery date.[20] 2002 TX300 received its permanent minor planet catalog number of 55636 from the MPC on 16 February 2003.[21] The Kuiper belt objects (55637) 2002 UX25 and (55638) 2002 VE95 directly come after (55636) 2002 TX300's number in the minor planet catalog.[21]
2002 TX300 does not have a proper name and the discoverers' privilege for naming this object has expired ten years after it was numbered.[1][22]: 6 According to naming guidelines by the International Astronomical Union's Working Group for Small Bodies Nomenclature, 2002 TX300 is open for name suggestions that relate to creation myths, as required for Kuiper belt objects in general.[22]: 8
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Orbit and classification
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2002 TX300 is a trans-Neptunian object (TNO) orbiting the Sun at a semi-major axis or average distance of 43.3 astronomical units (AU).[5][b] It follows an elliptical orbit that has an eccentricity of 0.12 and a high inclination[11]: 2537 of 25.9° with respect to the ecliptic.[5] In its 284-year-long orbit, 2002 TX30 comes as close as 37.9 AU from the Sun at perihelion and as far as 48.6 AU from the Sun at aphelion.[5] 2002 TX300 last passed perihelion on 4 February 1952 and will make its next perihelion passage in 24 June 2242.[24][7]
2002 TX300 is located in the classical region of the Kuiper belt 39–48 AU from the Sun,[2]: 53 and is thus classified as a classical Kuiper belt object or cubewano.[2]: 55 The high orbital inclination of 2002 TX300 qualifies it as a dynamically "hot" member of the classical Kuiper belt, which implies that it was gravitationally scattered out to its present location by Neptune's outward planetary migration in the Solar System's early history.[25]: 230 Because of this, 2002 TX300 is sometimes classified as a "scattered" object.[4][26]: 165
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Physical characteristics
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Surface composition and spectrum
2002 TX300 has a highly reflective surface with a geometric albedo of 0.65±0.15.[8]: 7 The object's spectrum in the visible and near-infrared ranges 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.[27] Mineralogical analysis indicates a substantial fraction of large ice (H2O) particles.[28] 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.
Size
2002 TX300 has a diameter of 320 ± 50 km (199 ± 31 mi), according to measurements from stellar occultation observations.[8]: 7 At this size, 2002 TX300 is too small to gravitationally collapse itself into a sphere (be in hydrostatic equilibrium),[9]: 9 so it does not qualify as a dwarf planet.[30]: 243 For comparison, the diameter of Saturn's smallest round moon Mimas is 396 km (246 mi).[31] Although the mass and density of 2002 TX300 have not been measured, its overall composition has been inferred to be mostly water ice like its surface, which would suggest that 2002 TX300's bulk density should be likely around 1 g/cm3, similar to that of water ice.[10]: 899 [9]: 9 This density would correspond to a mass on the order of 1019 kg (about 1.6×10−4 times the mass of Earth's Moon) for 2002 TX300.[10]: 899
History of size estimates
When 2002 TX300 was discovered, astronomers initially thought it could be a large dwarf planet up to 1,000 km (620 mi) in diameter,[34]: 1321 [35]: 178 because it was one of the brightest KBOs known at the time.[36] 2002 TX300 was even included in the International Astronomical Union's (IAU) roster of dwarf planet candidates in their first draft of the 2006 IAU definition of "planet", where they cited an upper limit diameter of 700 km (430 mi) for 2002 TX300.[29]: 17 [37]: 50 This overestimation of 2002 TX300's diameter came from astronomers incorrectly assuming that it has a dark, low-albedo surface like the bright KBOs 50000 Quaoar, 55565 Aya, and 20000 Varuna.[36]: 387–388 Astronomers began suspecting that 2002 TX300 must be smaller than initially thought when far-infrared and radio telescopes showed no significant thermal emission coming from the object.[32]: 187 [26]: 173 [9]: 9
Astronomers were able to measure the diameter and albedo of 2002 TX300 for the first time on 9 October 2009, when the object occulted or blocked out the light of a background star.[10] 2002 TX300 was the first Kuiper belt object (besides Pluto and its moon Charon) that was observed via stellar occultation.[14]: 2 [8]: 1, 5 The stellar occultation was predicted and observed by a network of astronomers stationed at 18 different locations across Hawaii.[38][10]: 897 Only two of these locations successfully observed the occultation; an initial analysis of their detections indicated that 2002 TX300 should have a diameter of 286 km (178 mi) if it was spherical.[10]: 898 However, this diameter estimate was affected by a timing error between the two occultation detections; reanalysis of the 2009 occultation data in 2018 and 2019 suggested that 2002 TX300 should have a slightly larger diameter of about 320 km (200 mi).[9]: 9 [8]: 17
Shape and rotation
Although the exact shape of 2002 TX300 is unknown, it is expected to be similar to an oblate spheroid, with irregularities.[8]: 17 [9]: 9 Observations of 2002 TX300's brightness over time indicate it has a rotation period of either 8.04 or 16.08 hours, depending on whether the object's brightness variability is caused by surface albedo variations or an elongated shape.[a][11]: 2537, 2542 Studies from 2003 to 2018 have consistently shown that 2002 TX300 exhibits very little brightness variation with a light curve amplitude less than 0.1 magnitudes,[11]: 2539 which makes it difficult to determine its rotation period.[39]: 3161 [40]: 13 The axial tilt of 2002 TX300 is unknown.[36]: 386
No atmosphere
Observations of the 9 October 2009 stellar occultation by 2002 TX300 showed that the object lacks an atmosphere with a surface number density greater than 2×1015 particles per cubic centimetre.[10]: 899 2002 TX300 is expected to not have an atmosphere because its mass is too small for its gravity to hold onto light gases.[10]: 899
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Origin
Common physical characteristics with the dwarf planet Haumea together with similar orbit elements[41] led to suggestion that 2002 TX300 was a member of the Haumean collisional family. The object, together with other members of the family (1996 TO66, 1995 SM55, 2003 OP32 and 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.[42]
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See also
(19308) 1996 TO66 – the first Haumea family member discovered
Notes
- The rotation period of 2002 TX300 was measured by observing how its brightness changes over time, which is plotted as a light curve. if 2002 TX300 has a spheroidal shape, then its light curve should resemble a "single-peaked" sine wave, whereas if 2002 TX300 is elongated, then its light curve should resemble a "double-peaked" sine wave.[11]: 2539
- These orbital elements are expressed in terms of the Solar System Barycenter (SSB) as the frame of reference.[5] Due to planetary perturbations, the Sun revolves around the SSB at non-negligible distances, so heliocentric-frame orbital elements and distances can vary in short timescales as shown in JPL-Horizons.[23]
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References
External links
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