17 Thetis
Main-belt asteroid
title: "17 Thetis" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["background-asteroids", "discoveries-by-robert-luther", "named-minor-planets", "s-type-asteroids-(tholen)", "sl-type-asteroids-(smass)", "astronomical-objects-discovered-in-1852"] description: "Main-belt asteroid" topic_path: "general/background-asteroids" source: "https://en.wikipedia.org/wiki/17_Thetis" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0
::summary Main-belt asteroid ::
::data[format=table title="Infobox planet"]
| Field | Value |
|---|---|
| minorplanet | yes |
| name | 17 Thetis |
| background | #D6D6D6 |
| symbol | [[File:Thetis symbol (bold).svg |
| image | 17Thetis-LB1.jpg |
| caption | Star field showing asteroid Thetis in the center |
| discovery_ref | |
| discovered | 17 April 1852 |
| discoverer | R. Luther |
| discovery_site | Düsseldorf-Bilk Obs. |
| mpc_name | (17) Thetis |
| alt_names |
| | pronounced | | | adjectives | Thetidian | | named_after | Thetis (Greek mythology) | | mp_category | main-belt(inner) | | orbit_ref | | | epoch | 16 February 2017 (JD 2457800.5) | | uncertainty | 0 | | observation_arc | 164.55 yr (60,102 days) | | aphelion | 2.7987 AU | | perihelion | 2.1436 AU | | semimajor | 2.4712 AU | | eccentricity | 0.1325 | | period | 3.88 yr (1,419 days) | | mean_anomaly | 100.44° | | mean_motion | / day | | inclination | 5.5902° | | asc_node | 125.56° | | arg_peri | 136.10° | | avg_speed | 18.87 km/s | | dimensions | km (IRAS) | | mass | 1.23 kg | | density | g/cm3 | | rotation | | | albedo | | | spectral_type | B–V = 0.829 U–B = 0.438 S (Tholen) Sl (SMASS)S | | abs_magnitude | 7.767.85 | ::
| minorplanet = yes | name = 17 Thetis | background = #D6D6D6 | symbol = [[File:Thetis symbol (bold).svg|24px|class=skin-invert]] (historical) | image = 17Thetis-LB1.jpg | image_scale = | caption = Star field showing asteroid Thetis in the center | discovery_ref = | discovered = 17 April 1852 | discoverer = R. Luther | discovery_site = Düsseldorf-Bilk Obs. | mpc_name = (17) Thetis | alt_names =
| pronounced = | adjectives = Thetidian | named_after = Thetis (Greek mythology) | mp_category = main-belt(inner) | orbit_ref = | epoch = 16 February 2017 (JD 2457800.5) | uncertainty = 0 | observation_arc = 164.55 yr (60,102 days) | aphelion = 2.7987 AU | perihelion = 2.1436 AU | semimajor = 2.4712 AU | eccentricity = 0.1325 | period = 3.88 yr (1,419 days) | mean_anomaly = 100.44° | mean_motion = / day | inclination = 5.5902° | asc_node = 125.56° | arg_peri = 136.10° | avg_speed = 18.87 km/s | dimensions = km (IRAS)
| mass = 1.23 kg | density = g/cm3 | rotation = | albedo = | spectral_type = B–V = 0.829 U–B = 0.438 S (Tholen) Sl (SMASS)S | abs_magnitude = 7.767.85 ::figure[src="https://upload.wikimedia.org/wikipedia/commons/6/68/17_Thetis.png" caption="[[Lightcurve]]-base 3D-model of 17 Thetis." alt="Lightcurve-base 3D-model of 17 Thetis."] ::
17 Thetis is a stony asteroid from the inner regions of the asteroid belt, approximately 90 kilometers in diameter. It was discovered on 17 April 1852, by German astronomer Robert Luther at Bilk Observatory in Düsseldorf, Germany who deferred to Friedrich Wilhelm August Argelander the naming his first asteroid discovery after Thetis from Greek mythology. Its historical symbol was a dolphin and a star; it was encoded in Unicode 17.0 as U+1CECA ([[File:Thetis symbol (fixed width).svg|12px|class=skin-invert]]).{{cite web | title = Miscellaneous Symbols Supplement | date = 2025 | website = unicode.org | publisher = The Unicode Consortium | url = https://www.unicode.org/charts/PDF/U1CEC0.pdf | access-date = September 9, 2025 | url-status = live
Description
The asteroid orbits the Sun at a distance of 2.1–2.8 AU once every 3 years and 11 months (1,419 days). Its orbit has an eccentricity of 0.13 and an inclination of 6° with respect to the ecliptic.
The spectrum of this object indicates that it is an S-type asteroid with both low and high calcium forms of pyroxene on the surface, along with less than 20% olivine. The high-calcium form of pyroxene forms 40% or more of the total pyroxene present, indicating a history of igneous rock deposits. This suggests that the asteroid underwent differentiation by melting, creating a surface of basalt rock.
The mass of Thetis has been calculated from perturbations by 4 Vesta and 11 Parthenope. In 2007, Baer and Chesley calculated Thetis to have a mass of 1.23 kg with a density of 3.21 g/cm3. One Thetidian stellar occultation was observed from Oregon in 1999. However, the event was not timed.
This minor planet was named after Thetis, the mother of Achilles in Greek mythology.
Notes
References
|type = 2016-11-11 last obs. |title = JPL Small-Body Database Browser: 17 Thetis |url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2000017 |publisher = Jet Propulsion Laboratory |accessdate = 24 March 2017}}
|title = Dictionary of Minor Planet Names – (17) Thetis |last = Schmadel | first = Lutz D. |publisher = Springer Berlin Heidelberg |page = 17 |date = 2007 |isbn = 978-3-540-00238-3 |doi = 10.1007/978-3-540-29925-7_18 }}
|title = 17 Thetis |work = Minor Planet Center |url = https://www.minorplanetcenter.net/db_search/show_object?object_id=17 |accessdate = 24 March 2017}}
|first1 = Jessica M. |last1 = Sunshine |first2 = Schelte J. |last2 = Bus |first3 = Timothy J. |last3 = McCoy |first4 = Thomas H. |last4 = Burbine |first5 = Catherine M. |last5 = Corrigan |first6 = Richard P. |last6 = Binzel |date = August 2004 |title = High-calcium pyroxene as an indicator of igneous differentiation in asteroids and meteorites |journal = Meteoritics and Planetary Science |volume = 39 |issue = 8 |pages = 1343–1357 |bibcode = 2004M&PS...39.1343S |doi = 10.1111/j.1945-5100.2004.tb00950.x|doi-access=
|first1 = James |last1 = Baer |first2 = Steven R. |last2 = Chesley |date = January 2008 |title = Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris |journal = Celestial Mechanics and Dynamical Astronomy |volume = 100 |issue = 1 |pages = 27–42 |bibcode = 2008CeMDA.100...27B |doi = 10.1007/s10569-007-9103-8|doi-access= free
|display-authors = 6 |first1 = Joseph R. |last1 = Masiero |first2 = T. |last2 = Grav |first3 = A. K. |last3 = Mainzer |first4 = C. R. |last4 = Nugent |first5 = J. M. |last5 = Bauer |first6 = R. |last6 = Stevenson |first7 = S. |last7 = Sonnett |date = August 2014 |title = Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos |journal = The Astrophysical Journal |volume = 791 |issue = 2 |page = 11 |bibcode = 2014ApJ...791..121M |doi = 10.1088/0004-637X/791/2/121 |arxiv = 1406.6645}}
|title = LCDB Data for (17) Thetis |publisher = Asteroid Lightcurve Database (LCDB) |url = http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=17%7CThetis |accessdate = 24 March 2017}}
|display-authors = 6 |first1 = A. |last1 = Mainzer |first2 = T. |last2 = Grav |first3 = J. |last3 = Masiero |first4 = E. |last4 = Hand |first5 = J. |last5 = Bauer |first6 = D. |last6 = Tholen |first7 = R. S. |last7 = McMillan |first8 = T. |last8 = Spahr |first9 = R. M. |last9 = Cutri |first10 = E. |last10 = Wright |first11 = J. |last11 = Watkins |first12 = W. |last12 = Mo |first13 = C. |last13 = Maleszewski |date = November 2011 |title = NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results |journal = The Astrophysical Journal |volume = 741 |issue = 2 |page = 25 |bibcode = 2011ApJ...741...90M |doi = 10.1088/0004-637X/741/2/90 |arxiv = 1109.6407}}
|first1 = E. F. |last1 = Tedesco |first2 = P. V. |last2 = Noah |first3 = M. |last3 = Noah |first4 = S. D. |last4 = Price |date = October 2004 |title = IRAS Minor Planet Survey V6.0 |url = https://sbnarchive.psi.edu/pds3/iras/IRAS_A_FPA_3_RDR_IMPS_V6_0/data/diamalb.tab |journal = NASA Planetary Data System |volume = 12 |pages = IRAS-A-FPA-3-RDR-IMPS-V6.0 |bibcode = 2004PDSS...12.....T |accessdate = 30 October 2019}}
|display-authors = 6 |first1 = T. |last1 = Michalowski |first2 = F. P. |last2 = Velichko |first3 = M. |last3 = Di Martino |first4 = Yu. N. |last4 = Krugly |first5 = V. G. |last5 = Kalashnikov |first6 = V. G. |last6 = Shevchenko |first7 = P. V. |last7 = Birch |first8 = W. D. |last8 = Sears |first9 = P. |last9 = Denchev |first10 = T. |last10 = Kwiatkowski |date = December 1995 |title = Models of four asteroids: 17 Thetis, 52 Europa, 532 Herculina, and 704 Interamnia. |journal = Icarus |volume = 118 |issue = 2 |pages = 292–301 |bibcode = 1995Icar..118..292M |doi = 10.1006/icar.1995.1192}}
References
- Noah Webster (1884) ''A Practical Dictionary of the English Language''
- Herbert (1828) ''Nimrod: a discourse on certain passages of history and fable'', vol. 2
- (18 September 2023). "Unicode request for historical asteroid symbols". Unicode.
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