(20000) Varuna

Asteroid (20000) Varuna
Image taken by the Hubble Space Telescope
Properties of the orbit ( animation ) Epoch:  April 27, 2019 ( JD 2,458,600.5)
Orbit type	CKBO  ( «Hot» )  or DO (E SDO ), «Distant Object»
Major semi-axis	42.781  AU
eccentricity	0.054
Perihelion - aphelion	40.466 AU - 45.097 AU
Inclination of the orbit plane	17.2 °
Length of the ascending node	97.4 °
Argument of the periapsis	262.9 °
Time of passage of the perihelion	March 14, 1928
Sidereal period	279 a 10.0 M
Mean orbital velocity	4.516 km / s
Physical Properties
Medium diameter	${\displaystyle 668_{-86}^{+154}\mathrm {km} }$
Dimensions	≈ 3.7  ·  10 20 kg
Albedo	${\displaystyle 0{,}127_{-0,042}^{+0,040}\mathrm {} }$
Medium density	${\displaystyle 0{,}992_{-0,015}^{+0,086}\mathrm {} }$ g / cm³
Rotation period	6.3418 ± 0.0005 h (0.264 d )
Absolute brightness	3.760 ± 0.035 mag
Spectral class	C B-V = 0.880 ± 0.020 VR = 0.620 ± 0.010 VI = 1.240 ± 0.010 BR = 1.530 ± 0.036
history
Explorer	Robert S. McMillan
Date of discovery	November 28, 2000
Another name	2000 WR 106
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . The affiliation to an asteroid family is automatically determined from the AstDyS-2 database . Please also note the note on asteroid items.

(20000) Varuna (formerly known as 2000 WR ₁₀₆ ) is a large trans-Neptunian object in the Kuiper belt , which is classified as a Cubewano (CKBO) or an extended Scattered Disk Object (DO) in terms of railway dynamics . Because of its size, the asteroid is a dwarf planet candidate .

Discovery and naming

Varuna was on 28 November 2000 by Robert McMillan , an employee of the SPACEWatch teams, the 0.9-m telescope at the Kitt Peak Observatory at Steward Observatory ( Arizona discovered). The discovery was announced on December 1, 2000; the planetoid was given the provisional designation 2000 WR ₁₀₆ and in January 2001, due to its size, which was then estimated to be higher, the IAU received the special minor planet number 20000 . - He was finally given the name Varuna (वरुण, Sanskrit ) after the Hindu deity of the cosmic and moral order. Varuna was one of the most important gods of the early Vedic Indians who watched over the waters of the sky and the ocean. Due to his association with water, he is often equated with the Greek Poseidon and the Roman Neptune .

After its discovery, Varuna could be identified in photos up to November 24, 1954, which were taken as part of the Digitized Sky Survey program (DSS) at the Palomar Observatory ( California ) and thus extended its observation period by 46 years. so that its orbit could be calculated more precisely. Since then, the asteroid has been observed through various telescopes such as the Herschel and Spitzer space telescopes, as well as through earth-based telescopes. In April 2017, a total of 439 observations over a period of 63 years were available. The last observation so far was made in January 2019 at the Slooh.com – Canary Islands Observatory. (As of March 9, 2019)

properties

Orbit comparison of Varuna (white) versus Pluto (purple) and the planets.

Orbit

Varuna orbits the sun in 279.83 years in an almost circular orbit between 40.47  AU and 45.10 AU from its center. The orbital eccentricity is 0.054, the web is 17.22 ° to the ecliptic inclined . The planetoid is currently 39.05 AU from the Sun. He passed through perihelion for the last time in 1928, so the next perihelion should take place in 2208.

The orbital elements of Varuna are similar to Quaoar ; Varuna has a similar orbital period and eccentricity to Quaoar, but a slightly more inclined orbit. The orbits of Varuna and Pluto have a similar orbital inclination (both about 17 °) and are oriented similarly, so that the nodes of both asteroids are comparatively close. In contrast to Pluto, which is subject to a 2: 3 resonance with the planet Neptune and therefore belongs to the Plutinos , the orbit of Varuna does not experience any significant orbital disturbances from Neptune. The minimum possible distance to Neptune (MOID) is 12.28 AU.

Marc Buie ( DES ) classifies the planetoid as an extended SDO (ESDO or DO ), while the Minor Planet Center him as Cubewano classifies, and he to the ground dynamically "hot" classical KBO heard; the latter also lists it as a non-SDO and generally as a “distant object” .

Size and shape

After its discovery, the diameter of Varuna, like that of Ceres, was initially estimated to be around 1000 km, from which the round numbering resulted. In 2013, the diameter of Varuna was determined to be 668 km, which was determined by studying the data from the Herschel Space Telescope. The shape of a three-axis ellipsoid (Jacobi type) could already be deduced from the light curve , which was confirmed on the occasion of an occultation in February 2010 near Varuna's maximum apparent brightness : The background star was eclipsed for 52.5 s from São Luís , which projected corresponds to a chord section of 1003 km. At the same time, Quixadá, only 255 km away, did not cover the background star, which is a strong indication of an elongated form of the asteroid. A possible dual system character seems rather unlikely due to the light curve. The investigations resulted in an axis ratio of either 1: 0.63: 0.45 or 1: 0.80: 0.52, which based on an assumed maximum diameter of 668 km corresponds to the dimensions 668 × 421 × 301 and 668 × 534 × 347, respectively km would correspond.

Based on a diameter of 668 km, the total surface area is around 1,402,000 km². The apparent brightness of Varuna is 20.21 ^m , the mean surface temperature is estimated based on the distance from  the sun to 41 to 43  K (−230 to −232 ° C).

It is assumed that Varuna is in hydrostatic equilibrium due to its mass, despite its shape, which presumably deviates significantly from the spherical shape , and thus meets the criteria for classification as a dwarf planet . Mike Brown assumes that it is most likely a dwarf planet; Gonzalo Tancredi also accepted Varuna as a dwarf planet in 2010, but did not propose to the IAU that it be officially recognized as such.

Size comparison of some large TNOs .

Provisions of the diameter for Varuna

year	Dimensions km	source
2001	900.0 + 0129.0- 0145.0	Jewitt et al. a.
2002	1060.0 + 0180.0- 0220.0	Lellouch u. a.
2005	936.0 + 0238.0- 0324.0	Grundy et al. a.
2005	> 621.0 ± 150.0	Stansberry et al. a.
2006	586.0 + 0190.0- 0129.0	Cruikshank et al. a.
2007	502.0 ± 100	Stansberry et al. a.
2008	528.0	Tancredi
2008	714.0 + 0178.0- 0128.0	Brucker et al. a.
2010	1003.0 ± 9.0	Sicardy et al. a.
2010	500.0	Tancredi
2013	816.0	Mommert et al. a.
2013	668.0 + 0154.0- 086.0	Lellouch u. a.
2014	678.0	Braga-Ribas et al. a.
2015	600.0	LightCurve DataBase
2018	698.0	Brown
The most precise determination is marked in bold .

rotation

Using light curve observations , Varuna rotates once around its axis in 6 hours and 20.5 minutes. From this it follows that in a Varuna year he performs 386792.5 self- rotations (“days”). For a comparatively large object like Varuna, such a rapid rotation period is quite unusual; In 2006, Haumea, an even larger celestial body that rotates even faster at 3.9 hours, was found, which also has an elongated shape due to its rapid rotation.

surface

Fantasy representation of a possible view of the surface.

The surface of the planetoid is reddish in color and shows an absorption line at 2.0 µm , which indicates the presence of small amounts of water ice on the surface. Volatile substances such as methane or nitrogen could not be detected. Examining the spectra of different phases of rotation showed no evidence of differences in brightness on the surface; so this seems to be quite homogeneous. A mixture of complex organic compounds (35%), amorphous silicates (25%), water ice (25%) and amorphous carbon (15%) is assumed to be the most likely constituent . Another possible composition is also being discussed, which could contain up to 10% methane. For an object with the properties of Varuna, volatile substances such as methane cannot be primordial, so an event such as a high-energy impact would be necessary to explain their presence on the surface.

See also

• List of trans-Neptunian objects
• List of dwarf planets of the solar system
• List of asteroids
• List of moons from asteroids

Web links

Commons : (20000) Varuna  - collection of images, videos and audio files

• How many dwarf planets are there in the outer solar system? Current list of the largest TNOs from Mike Brown
• Free the dwarf planets! Mike Brown's column on the IAU and the dwarf planets regarding their classifications (23 August 2011)

Individual evidence

1. ↑ ^{a b} MPC : MPEC 2010-S44: Distant Minor Planets (2010 OCT.11.0 TT) . IAU . September 25, 2010. Retrieved March 9, 2019.
2. ↑ ^{a b c d e f g} E. Lellouch u. a .: “TNOs are Cool”: A survey of the trans-Neptunian region. IX. Thermal properties of Kuiper belt objects and Centaurs from combined Herschel and Spitzer observations (PDF) . In: Astronomy and Astrophysics . 557, No. A60, June 10, 2013, p. 19. bibcode : 2013A & A ... 557A..60L . doi : 10.1051 / 0004-6361 / 201322047 .
3. ^ ^{A b} Wm. R. Johnston: List of Known Trans-Neptunian Objects . Johnston's Archives. October 7, 2018. Retrieved March 12, 2019.
4. ^ ^{A b} Marc W. Buie : Orbit Fit and Astrometric record for 20000 . SwRI (Space Science Department). Retrieved March 9, 2019.
5. ↑ ^{a b c d} (20000) Varuna at the IAU Minor Planet Center (English). Accessed March 9, 2019.
6. ↑ v ≈ π * a / period (1 + sqrt (1-e²))
7. ↑ ^{a b c} P. Lacerda, D. Jewitt: Densities Of Solar System Objects From Their Rotational Lightcurve . In: The Astronomical Journal . 133, No. 4, February 26, 2007, pp. 1393-1408. arxiv : astro-ph / 0612237 . bibcode : 2007AJ .... 133.1393L . doi : 10.1086 / 511772 .
8. ↑ Calculated using the data from Lacerda and Jewitt (2007) diameter 900 km, density 0.992 g / cm³. The current value is probably much smaller.
9. ^ ^{A b} D. Jewitt , S. Sheppard : Physical Properties Of Trans-Neptunian Object (20000) Varuna (PDF) . In: Astronomical Journal . 123, No. 4, April 2002, pp. 2110-2120. arxiv : astro-ph / 0201082 . bibcode : 2002AJ .... 123.2110J . doi : 10.1086 / 339557 .
10. ↑ A. Thirouin et al. a .: Short-term variability of a sample of 29 trans-Neptunian objects and Centaurs . In: Astronomy and Astrophysics . 522, No. A93, April 27, 2010, p. 43. arxiv : 1004.4841 . bibcode : 2010A & A ... 522A..93T . doi : 10.1051 / 0004-6361 / 200912340 .
11. ↑ ^{a b} LCDB Data for (20000) Varuna . MinorPlanetInfo. 2015. Accessed March 9, 2019.
12. ↑ ^{a b c} I. Belskaya et al. a .: Updated taxonomy of trans-neptunian objects and centaurs: Influence of albedo . In: Icarus . 250, April 2015, pp. 482-491. bibcode : 2015Icar..250..482B . doi : 10.1016 / j.icarus.2014.12.004 .
13. ↑ N. Peixinho et al. a .: The bimodal colors of Centaurs and small Kuiper belt objects (PDF) . In: Astronomy and Astrophysics . 546, No. A86, June 14, 2012, p. 12. arxiv : 1206.3153 . bibcode : 2012A & A ... 546A..86P . doi : 10.1051 / 0004-6361 / 201219057 .
14. ↑ MPC : MPEC 2000-X02: 2000 WR106 . IAU . December 1, 2000. Retrieved March 9, 2019.
15. ↑ MPC : MPC / MPO / MPS Archive . IAU . Retrieved March 9, 2019.
16. ↑ MPC 41805. (PDF) The Minor Planet Circulars / Minor Planets and Comets, January 9, 2001, accessed March 9, 2019 .  
17. ↑ (20000) Varuna in the Small-Body Database of the Jet Propulsion Laboratory (English). Retrieved March 9, 2019.
18. ↑ MPC : MPEC List Of Centaurs and Scattered-Disk Objects . IAU . Retrieved March 9, 2019.
19. ↑ ^{a b} B. Sicardy et al. a .: The 2010, February 19 stellar occultation by Varuna . In: American Astronomical Society, DPS meeting . 42, October 2010, p. 993. bibcode : 2010DPS .... 42.2311S .
20. ↑ (20000) Varuna in the database of the "Asteroids - Dynamic Site" (AstDyS-2, English).
21. ↑ ^{a b} Mike Brown : How many dwarf planets are there in the outer solar system? . CalTech . November 12, 2018. Retrieved March 12, 2019.
22. ^ ^{A b} G. Tancredi: Physical and dynamical characteristics of icy “dwarf planets” (plutoids) (PDF) . In: International Astronomical Union (Ed.): Icy Bodies of the Solar System: Proceedings IAU Symposium No. 263, 2009 . 2010. doi : 10.1017 / S1743921310001717 . Retrieved March 9, 2019.
23. ^ D. Jewitt : The size and albedo of the Kuiper-belt object (20000) Varuna. In: Nature , January 24, 2001, PMID 11373669
24. ↑ E. Lellouch et al. a .: Coordinated thermal and optical observations of Trans-Neptunian object (20000) Varuna from Sierra Nevada (PDF) . In: Icarus . June 27, 2002, p. 26. arxiv : astro-ph / 0206486 . doi : 10.1051 / 0004-6361: 20020903 .
25. ↑ W. Grundy et al. a .: Various Albedos of Small Trans-Neptunian Objects . In: Icarus . 176, No. 1, February 10, 2005, pp. 184-191. arxiv : astro-ph / 0502229 . bibcode : 2005Icar..176..184G . doi : 10.1016 / j.icarus.2005.01.007 .
26. ↑ J. Stansberry et al. a .: Albedos, Diameters (and a Density) of Kuiper Belt and Centaur Objects . In: American Astronomical Society, DPS meeting . 37, August 2005, p. 737. bibcode : 2005DPS .... 37.5205S .
27. ↑ D. Cruikshank et al. a .: Physical Properties of Transneptunian Objects (PDF) . In: University of Arizona Press: Protostars and Planets . 951, 2006, pp. 879-893. bibcode : 2007prpl.conf..879C .
28. ↑ J. Stansberry et al. a .: Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope (PDF) . In: University of Arizona Press . 592, No. 161-179, February 20, 2007. arxiv : astro-ph / 0702538 . bibcode : 2008ssbn.book..161S .
29. ^ G. Tancredi, S. Favre: DPPH List . In: Dwarf Planets and Plutoid Headquarters, from Which are the dwarfs in the solar system? (PDF) . August. Retrieved March 9, 2019.
30. ↑ M. Brucker et al. a .: High Albedos of Low Inclination Classical Kuiper Belt Objects (PDF) . In: Icarus . January 1, 2009, p. 26. arxiv : 0812.4290 . bibcode : 2012A & A ... 546A..86P . doi : 10.1016 / j.icarus.2008.12.040 .
31. ↑ M. Mommert et al. a .: Remnant planetesimals and their collisional fragments: Physical characterization from thermal-infrared observations . September 23, 2013. Accessed March 9, 2019.
32. ↑ Braga-Ribas et al. a .: Stellar Occultations by Transneptunian and Centaurs Objects: results from more than 10 observed events (PDF) . In: XIV Latin American Regional IAU Meeting . 44, October 2014, pp. 3-3. bibcode : 2014RMxAC..44 .... 3B .
33. ↑ D. Rabinowitz et al. a .: Photometric Observations Constraining the Size, Shape, and Albedo of 2003 EL ₆₁ , a Rapidly Rotating, Pluto-Sized Object in the Kuiper Belt (PDF) . In: The Astronomical Journal . 639, No. 2, March 2006, pp. 1238-1251. arxiv : astro-ph / 0509401 . bibcode : 2006ApJ ... 639.1238R . doi : 10.1086 / 499575 .
34. ↑ J. Licandro et al. a .: NICS-TNG infrared spectroscopy of trans-neptunian objects 2000 EB ₁₇₃ and 2000 WR ₁₀₆ . In: Astronomy and Astrophysics . 373, May 24, 2001, pp. L29-L32. arxiv : astro-ph / 0105434 . bibcode : 2001A & A ... 373L..29L . doi : 10.1051 / 0004-6361: 20010758 .
35. ^ V. Lorenzi et al. a .: Rotationally resolved spectroscopy of (20000) Varuna in the near-infrared . In: Astronomy and Astrophysics . 562, no.A85 , February 11, 2014, p. 6. arxiv : 1401.5962 . bibcode : 2014A & A ... 562A..85L . doi : 10.1051 / 0004-6361 / 201322251 .