| 词条 | 20000 Varuna | ||||||||||||||||||||||||||||||||
| 释义 |
|minorplanet = yes |background = #C2E0FF |name = 20000 Varuna |symbol = |image = Varuna artistic.png |image_size = 250 |caption = Artist's impression of Varuna |discovery_ref = [1] |discoverer = Spacewatch {{small|(R. McMillan)}} |discovered = 28 November 2000 |earliest_precovery_date = 24 November 1954 |mpc_name = (20000) Varuna |pronounced = {{IPAc-en|ˈ|v|ær|ən|ə}} {{respell|VARR|ə-nə}}[2] |alt_names = {{mp|2000 WR|106}} |adjectives = Varunian |named_after = Varuna |mp_category = TNO{{·}}cubewano [3] Scat-Ext[4] |orbit_ref = [1] |epoch = 2017-Sep-04 (JD 2458000.5) |uncertainty = 2 |observation_arc = 22351 days (61.19 yr) |jupiter_moid = {{Convert|35.99|AU|Tm|abbr=on}} |neptune_moid = {{Convert|12.77|AU|Tm|abbr=on}}[6] |tisserand = 5.603 |aphelion = {{Convert|45.157|AU|Tm|abbr=on|lk=on}} |perihelion = {{Convert|40.742|AU|Tm|abbr=on}} |semimajor = {{Convert|42.950|AU|Tm|abbr=on}} |semiminor = |orbital_circ = |eccentricity = 0.05139 |period = 281.49 yr (102812 d) |avg_speed = 4.53 km/s |max_speed = |min_speed = |inclination = 17.197° |asc_node = 97.334° |arg_peri = 266.36° |mean_anomaly = 111.77° |dimensions = {{val|668|+154|-86}} km[7] |mass = ≈ {{val|3.7|e=20|u=kg}}[8][1] |density = {{val|0.992|u=g/cm3}}[8] |surface_grav = {{Gr|0.37|334|2}} m/s2 |escape_velocity = {{V2|0.37|334|2}} km/s |sidereal_day = 6.3418 h[7] |rot_velocity = |albedo = {{val|0.127|0.040|0.042}} [7] |single_temperature = ≈ 43–41 K |spectral_type = (moderately red) B−V=0.93 V−R=0.64[13] |magnitude = 19.9 (opposition)[14] |abs_magnitude = {{val|3.760|0.035}},[7] 3.7[1] |mean_motion = {{Deg2DMS|0.0034805|sup=ms}} / day |rotation = {{Convert|6.3436|h|d|abbr=on|lk=on}} |mean_radius = 450 ± 70 km }} 20000 Varuna ({{IPAc-en|ˈ|v|ær|ən|ə}} {{respell|VARR|ə-nə}}), provisional designation {{mp|2000 WR|106}}, is a large classical Kuiper belt object. It is probably a dwarf planet and has an elongated shape due to its rapid rotation. Discovered by Spacewatch in 2000, the trans-Neptunian object was named after the Hindu deity Varuna. HistoryDiscoveryVaruna was discovered on 28 November 2000, by the Spacewatch survey, which was led by American astronomer Robert McMillan and conducted at Kitt Peak National Observatory near Tucson, Arizona. It was given the provisional designation {{mp|2000 WR|106}} and has been precovered in plates dating back to 1954.[1] NameVaruna is named after a Hindu deity. Varuna was one of the most important deities of the ancient Indians, and he presided over the waters of the heaven and of the ocean and was the guardian of immortality.[2] Due to his association with the waters and the ocean, he is often identified with Greek Poseidon and Roman Neptune. Varuna received the minor planet number 20000 because it was the largest cubewano found so far and was believed to be as large as Ceres. Size
The size of the large Kuiper belt objects can be determined by simultaneous observations of thermal emission and reflected sunlight. Unfortunately, thermal measures, intrinsically weak for distant objects, are further hampered by the absorption of Earth's atmosphere, because only the weak 'tail' of the emissions is accessible to Earth-based observations. In addition, the estimates are model-dependent with the unknown parameters (e.g. pole orientation and thermal inertia) to be assumed. Consequently, the estimates of the albedo vary, resulting in sometimes substantial differences in the inferred size. Estimates for the diameter of Varuna have varied from 500 to 1,060 km.[28] Multi-band thermal measurements from the Herschel Space Observatory in 2013 yielded a diameter of {{val|668|+154|-86|u=km}}. OccultationA 28-second occultation of an 11.1 magnitude star by Varuna was observed from Camalaú, Paraíba, Brazil, on the night of 19 February 2010.[3] Results of the 2010 occultation as seen from São Luís with a duration of 52.5 seconds corresponds with a chord of {{val|1003|u=km}}.[4] But Quixadá 255 km away had a negative result suggesting a significantly elongated shape is required for Varuna.[4] Because the occultation occurred near Varuna's maximum brightness, the occultation was observing the maximum apparent surface area for an ellipsoidal shape.[4] OrbitVaruna is classified as a classical trans-Neptunian object and follows a near-circular orbit with a semi-major axis of ≈43 AU, similar to that of {{dp|Quaoar}} but more inclined. Its orbital period is similar to Quaoar at 283 years. The image shows the polar view (top; Varuna's orbit in blue, {{dp|Pluto}}'s in red, Neptune in grey). The spheres illustrate the current (April 2006) positions, relative sizes and colours. The perihelia (q), aphelia (Q) and the dates of passage are also marked. The orbits of Varuna and Pluto have similar inclination and are similarly oriented (the nodes of both orbits are quite close). At 43 AU and on a near-circular orbit, unlike Pluto, which is in 2:3 orbital resonance with Neptune, Varuna is free from any significant perturbation from Neptune. The ecliptic view illustrates the comparison of Varuna's near-circular orbit with that of Pluto (highly eccentric, e = 0.25), both similarly inclined. Currently, the closest approach possible to Neptune (MOID) is {{Convert|12.77|AU|e9km|sigfig=3|abbr=unit|lk=on}}.[6] Physical characteristicsVaruna has a rotational period of approximately 6.34 hours.[1] It has a double-peaked light curve. Given the rapid rotation, rare for objects so large, Varuna is thought to be an elongated spheroid (ratio of axis 2:3), with a mean density around 1 g/cm3 (roughly the density of water).[35] Examination of Varuna's light curve has found that the best-fit model for Varuna is a triaxial ellipsoid with the axes a,b,c in ratios in the range of b/a = 0.63–0.80, and c/a = 0.45–0.52 and a bulk density of {{val|0.992|0.086|0.015}} g/cm3.[8] Since the discovery of Varuna, {{dp|Haumea}}, another, even larger, rapidly rotating (3.9 h) object, has been discovered and is also thought to have an elongated shape.[37] The surface of Varuna is moderately red (similar to {{dp|Quaoar}}) and small amounts of water ice have been detected on its surface.[38] A recent study of the surface composition of (20000) Varuna.[39] After studying the spectra corresponding to different rotational phases, they do not find any indication of surface variability. They also find that the most probable composition for the surface of Varuna is a mixture of amorphous silicates (25%), complex organics (35%), amorphous carbon (15%) and water ice (25%). However, they also discuss another possible surface composition containing up to a 10% of methane ice. For an object with the characteristics of Varuna, this volatile could not be primordial, so an event, such as an energetic impact, would be needed to explain its presence on the surface. Dwarf planetThe International Astronomical Union has not classified it as a dwarf planet. However, Brown places it on the high end of "highly likely",[40] and Tancredi (2010) classifies it as "accepted" due to a density equal or higher than water,[41] but has not made a direct recommendation for its inclusion.[5] References1. ^Calculated using Lacerda and Jewitt (2007) diameter of 900 km and density of 0.992 g/cm3. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]2. ^MW Sanskrit–English dictionary 3. ^{{cite web |title = RELATÓRIO FINAL OCULTAÇÃO DA ESTRELA UCAC2 41014042 PELO ASTEROIDE VARUNA |url = http://xa.yimg.com/kq/groups/14199805/1726016548/name/Rara+Oculta%C3%A7%C3%A3o+por+Varuna+-+AAP-SAR+em+19-02-2010.pdf |accessdate = 18 September 2010 |language = pt |deadurl = yes |archiveurl = https://www.webcitation.org/65Rdw3PYi?url=http://xa.yimg.com/kq/groups/14199805/1726016548/name/Rara+Oculta%C3%A7%C3%A3o+por+Varuna+-+AAP-SAR+em+19-02-2010.pdf |archivedate = 14 February 2012 |df = dmy-all}} 4. ^1 2 3 {{cite web |title=The 2010, February 19 stellar occultation by Varuna |author=Bruno Sicardy |url=http://www.abstractsonline.com/Plan/ViewAbstract.aspx?mID=2704&sKey=91ea750d-febb-4140-90a7-18400852e1d2&cKey=74324b85-5c97-4767-a0a4-eee3306e8b98 |publisher=42nd DPS Meeting |accessdate=12 November 2010}} 5. ^{{cite journal|date=2010|title=Physical and dynamical characteristics of icy "dwarf planets" (plutoids)|journal=Icy Bodies of the Solar System: Proceedings IAU Symposium No. 263, 2009|author=Tancredi, G.|url=http://journals.cambridge.org/article_S1743921310001717|accessdate=17 January 2012}} 6. ^1 {{Cite web |title=MPEC 2009-P26 :Distant Minor Planets (2009 AUG. 17.0 TT) |publisher=IAU Minor Planet Center |date=7 August 2009 |url=http://www.minorplanetcenter.org/mpec/K09/K09P26.html |accessdate=16 September 2009}} 7. ^1 {{Cite web |author=M. W. Buie |date=12 January 2007 |title=Orbit Fit and Astrometric record for 20000 |publisher=SwRI (Space Science Department) |url=http://www.boulder.swri.edu/~buie/kbo/astrom/20000.html |accessdate=19 September 2008}} 8. ^1 2 3 4 5 {{cite web |quote=Last observation as of 2017-02-18 (soln: 2017-Apr-05) |title=JPL Small-Body Database Browser: 20000 Varuna (2000 WR106) |url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=20000 |accessdate=6 February 2018}} 9. ^1 Merriam Webster's Collegiate Dictionary. From the Sanskrit वरुण {{IPA-sa|ʋɐˈɽʊɳɐ|}} 10. ^1 2 {{cite arXiv |author=J. Stansberry |date=2007 |title=Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope |eprint=astro-ph/0702538}} 11. ^1 {{cite web |author=W. R. Johnston |date=2008 |title=TNO/Centaur diameters and albedos |url=http://www.johnstonsarchive.net/astro/tnodiam.html |accessdate=8 November 2006}} 12. ^1 2 3 {{cite journal |author=P. Lacerda |author2=D. Jewitt |date=2006 |title=Densities Of Solar System Objects From Their Rotational Lightcurve |arxiv=astro-ph/0612237 |doi=10.1086/511772 |volume=133 |journal=The Astronomical Journal |pages=1393–1408 |bibcode=2007AJ....133.1393L}} 13. ^1 {{cite web | url=http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=20000 | title=HORIZONS Web-Interface | publisher=JPL Solar System Dynamics | accessdate=2 July 2008}} 14. ^1 {{cite web |title=TNO and Centaur Colors |url=http://sbn.psi.edu/pds/asteroid/EAR_A_COMPIL_3_TNO_CEN_COLOR_V3_0/data/tnocencol.tab |accessdate=16 September 2016}} 15. ^1 {{cite book |author=J. Stansberry |date=2008 |chapter=Physical Properties of Kuiper Belt and Centaur Objects: Constraints from the Spitzer Space Telescope |title=The Solar System Beyond Neptune |isbn=978-0-8165-2755-7 |display-authors=etal}} 16. ^1 {{cite journal |author=E. Lellouch |date=2002 |title=Coordinated thermal and optical observations of Trans-Neptunian object (20000) Varuna from Sierra Nevada |journal=Astronomy & Astrophysics |volume=391 |issue=3 |pages=1133–1139 |doi=10.1051/0004-6361:20020903 |arxiv=astro-ph/0206486 |bibcode=2002A&A...391.1133L |display-authors=etal}} 17. ^1 {{cite journal |author=W. M. Grundy |author2=K. S. Noll |author3=D. C. Stephens |date=2005 |title=Diverse albedos of small trans-neptunian objects |journal=Icarus |volume=176 |issue=1 |pages=184–191 |doi=10.1016/j.icarus.2005.01.007 |bibcode=2005Icar..176..184G |arxiv=astro-ph/0502229}} 18. ^1 {{Cite journal |author=D. Jewitt |author2=H. Aussel |author3=A. Evans |date=2001 |title=The size and albedo of the Kuiper-belt object (20000) Varuna |url=http://www.ifa.hawaii.edu/~jewitt/papers/VARUNA/JAE2001.pdf |journal=Nature |volume=411 |issue=6836 |pages=446–7 |doi=10.1038/35078008 |pmid=11373669 |accessdate=23 April 2006 |archiveurl=https://web.archive.org/web/20060429172225/http://ifa.hawaii.edu/~jewitt/papers/VARUNA/JAE2001.pdf |archivedate=29 April 2006 |deadurl=yes}} 19. ^1 2 3 4 5 {{cite journal |last=Lellouch |first=E. |last2=Santos-Sanz |first2=P. |last3=Lacerda |first3=P. |last4=Mommert |first4=M. |last5=Duffard |first5=R. |last6=Ortiz |first6=J. L. |last7=Müller |first7=T. G. |last8=Fornasier |first8=S. |last9=Stansberry |first9=J. |last10=Kiss |first10=Cs. |last11=Vilenius |first11=E. |last12=Mueller |first12=M. |last13=Peixinho |first13=N. |last14=Moreno |first14=R. |last15=Groussin |first15=O. |last16=Delsanti |first16=A. |last17=Harris |first17=A. W. |date=September 2013 |title="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 |url=http://www.aanda.org/articles/aa/pdf/2013/09/aa22047-13.pdf |journal=Astronomy & Astrophysics |volume=557 |pages=A60 |doi=10.1051/0004-6361/201322047 |accessdate=7 November 2014|bibcode = 2013A&A...557A..60L |arxiv=1202.3657 }} 20. ^1 {{cite journal |author=D. Jewitt |author2=S. Sheppard |date=2002 |title=Physical Properties Of Trans-Neptunian Object (20000) Varuna |journal=Astronomical Journal |volume=123 |issue=4 |pages=2110–2120 |doi=10.1086/339557 |arxiv=astro-ph/0201082 |bibcode=2002AJ....123.2110J}} 21. ^1 {{cite journal |author=D. L. Rabinowitz |date=2006 |title=Photometric Observations Constraining the Size, Shape, and Albedo of 2003 EL61, a Rapidly Rotating, Pluto-Sized Object in the Kuiper Belt |journal=Astrophysical Journal |volume=639 |issue=2 |pages=1238–1251 |doi=10.1086/499575 |bibcode=2006ApJ...639.1238R |arxiv=astro-ph/0509401 |display-authors=etal}} 22. ^1 {{cite journal |author=J. Licandro |author2=E. Oliva |author3=M. di Martino |date=2001 |title=NICS-TNG infrared spectroscopy of trans-neptunian objects 2000 EB173 and 2000 WR106 |journal=Astronomy & Astrophysics |volume=373 |issue=3 |pages=29–32L |doi=10.1051/0004-6361:20010758 |bibcode=2001A&A...373L..29L |arxiv = astro-ph/0105434}} 23. ^1 {{cite journal |author=V. Lorenzi |author2=N. Pinilla-Alonso |author3=J, Licandro |author4=C. Dalle-Ore |author5=J. P. Emery |date=2014 |title=Rotationally- resolved spectroscopy of (20000) Varuna in the near-Infrared |journal=Astronomy & Astrophysics |volume=562 |pages=A85 |doi=10.1051/0004-6361/201322251 |bibcode=2014A&A...562A..85L |arxiv = 1401.5962}} 24. ^1 {{cite web |date=23 September 2011 |title=How many dwarf planets are there in the outer solar system? (updates daily) |publisher=California Institute of Technology |author=Michael E. Brown |url=http://web.gps.caltech.edu/~mbrown/dps.html |accessdate=16 September 2016}} 25. ^1 {{cite web |date=2008 |title=Which are the dwarfs in the solar system? |publisher=Asteroids, Comets, Meteors |author=Tancredi, G. |author2=Favre, S. |url=http://www.lpi.usra.edu/meetings/acm2008/pdf/8261.pdf |accessdate=23 September 2011}} 26. ^1 2 {{cite web |title=(20000) Varuna = 2000 WR106 Orbit |publisher=IAU Minor Planet Center |url=http://www.minorplanetcenter.net/db_search/show_object?object_id=Varuna |accessdate=2018-02-10}} }} External links
| title=Size and Albedo of Kuiper Belt Object (20000) Varuna | url=http://www2.ess.ucla.edu/~jewitt/varuna.html | work=David Jewitt's Home Page | accessdate= 23 January 2010 }}
6 : Classical Kuiper belt objects|Discoveries by the Spacewatch project|Minor planets named from Hindu mythology|Named minor planets|Possible dwarf planets|Astronomical objects discovered in 2000 |
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