(24) Themis ( Latin Themis ) is an asteroid of the main belt , which belongs to the dark spectral class B and leads the family of Themis . It was discovered on April 5, 1853 by the Italian astronomer Annibale de Gasparis at the Capodimonte Observatory , Italy , and named after Themis , the ancient Greek goddess of justice, the second wife of Zeus [8] .
| (24) Themis | |
|---|---|
| Asteroid | |
 Three-dimensional model of Themis. | |
| Opening | |
| Discoverer | Annibale de Gasparis |
| Detection point | Capodimonte |
| Date of discovery | April 5, 1853 |
| Eponym | Themis |
| Alternative designations | 1947 BA; 1955 OH |
| Category | Main ring ( Themis family ) |
| Orbital characteristics | |
| Age of March 14, 2012 JD 2456000.5 | |
| Eccentricity ( e ) | 0.1289328 |
| Semi-axis ( a ) | 469.161 million km (3,1361509 A.E.) |
| Perihelion ( q ) | 408.671 million km (2.7317982 AU) |
| Aphelion ( Q ) | 529.652 million km (3,5405036 AU) |
| Circulation Period ( P ) | 2028.588 days (5.554 g. ) |
| Average orbital speed | 16.749 km / s |
| Inclination ( i ) | 0.75754 ° |
| Longitude node (Ω) | 36.12367 ° |
| Perihelion Argument (ω) | 106.97924 ° |
| Median Anomaly ( M ) | 253.95300 ° |
| Physical Characteristics [5] [6] | |
| Diameter | 198 km |
| Weight | 1.13 ± 0.43⋅10 19 kg [1] 2,3⋅10 19 kg [2] [3] |
| Density | 1.81 ± 0.67 [4] 2.78 ± 1.35 g / cm³ |
| Acceleration of free fall on the surface | 0.15 +0.08 −0.07 m / s² |
| 2nd space speed | 0.87 +15 −20 km / s |
| Rotation period | 8.374 h |
| Spectral class | B [7] |
| Apparent magnitude | 12.63 m (current) |
| Absolute magnitude | 7.08 m |
| Albedo | 0,067 |
| Average surface temperature | 159 K (−114 ° C ) |
| Current distance from the sun | 2.746 a. e. |
| Current distance from Earth | 3,674 a. e. |
Content
Orbit and rotation
This asteroid is located closer to the outer part of the main belt, at a distance of 3.14 a. e. from the sun. It moves in an elliptical orbit with a very small slope to the ecliptic plane of 0.757 ° and a relatively low eccentricity, close to 0.129, so its distance from the Sun varies rather slightly - from about 408.671 million km perihelion to 529.652 million km aphelion . The orbital period is about 5.54 years [9] . The asteroid is part of the family of Themis, which is a fairly compact core consisting of large asteroids and surrounded by a cloud of smaller bodies [10] .
It is also interesting to note that on the basis of the perturbations of the asteroid’s orbit created by Jupiter in 1875, its mass was calculated [11] . And 100 years later, on December 24, 1975, there was a rather close approach of Themis to the asteroid (2296) Kugultinov , during which the minimum distance between the bodies was 0.016 a. e. (2,400,000 km) - the distance, at first glance, is quite significant, but quite sufficient for noticeable gravitational forces to act between the asteroids. Based on the analysis of gravitational perturbations over the period of approach, the mass of Themis was refined - 2.89 --10 −11 of the mass of the Sun [12] (9.62⋅10 −6 of the mass of the Earth).
Surface ice
The presence of ice on the surface of the asteroid was confirmed immediately by two independent groups of astronomers. On October 7, 2009, based on the results of processing the spectral data of the NASA IRTF infrared telescope in the Hawaiian Islands, astronomers from the University of Central Florida in Orlando announced that they had discovered water on the asteroid (24) Themis. Thus, they confirmed last year's discovery of their colleagues from Johns Hopkins University in Laurel, Maryland, who worked on the program for the search for extraterrestrial civilizations (SETI). In addition to water, both teams also stated that complex hydrocarbons were discovered on the surface of Themis, including molecules - the precursors of life [13] . Water ice mixed with organic compounds occupies most of the surface of the asteroid and is distributed fairly evenly on it [14] . At the same time, ice cannot be in a stable state on it for a long time, since due to the relative proximity of the asteroid to the Sun, the processes of ice evaporation should be quite intense on it, which limits its lifetime to just a few years [15] . Consequently, there must be sources on the asteroid that constantly replenish the surface ice reserves. Scientists have identified two possible mechanisms for replenishing water ice on the surface [16] .
Option one. Shallow beneath the surface of Themis are large stocks of water ice. During the impact of small space bodies, hidden water evaporates and then freezes and settles over a large area [17] .
Option two. The formation of water on the surface of an asteroid occurs as a result of chemical reactions taking place under the influence of the solar wind . High-energy solar protons interact with metal oxides from the surface of the asteroid, splitting them into ions. The resulting hydroxyl groups , as well as hydrogen and oxygen ions, when combined, are able to form water molecules that settle on the surface of the asteroid and accumulate there in the form of ice [18] .
Scientists suggest that it was precisely such asteroids that collided with the Earth during the late meteorite bombardment that could be sources of water on our planet, because in the early stages of its history, the Earth was too hot to hold enough water. Thus, almost all the water existing on Earth at this time has an external origin. And the presence of complex organic compounds once again strengthens the hypothesis of panspermia .
The Japanese infrared satellite Akari confirmed the presence of hydrated minerals on Themis [19] .
See also
- List of asteroids ( 1-100 )
- Classifications of Minor Planets
- Asteroid family
- Themis (hypothetical companion)
Notes
- ↑ Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris. Celestial Mechanics and Dynamical Astronomy (2008). Date of treatment October 13, 2008.
- ↑ Michalak, G. Determination of asteroid masses (Eng.) // Astronomy and Astrophysics . - EDP Sciences , 2001. - Vol. 374 , no. 2 . - P. 703-711 . - DOI : 10.1051 / 0004-6361: 20010731 . - .
- ↑ (Themis mass 0.12 / Ceres mass 4.75) × Ceres mass 9.43⋅10 20 = 2.38⋅10 19
- ↑ Carry, B. (December 2012), Density of asteroids , vol. 73, p. 98-118 , DOI 10.1016 / j.pss.2012.03.03.009
- ↑ Asteroid Data Sets
- ↑ Baer, James; Steven R. Chesley. Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris (English) // Celestial Mech Dyn Astr: journal. - Springer Science + Business Media BV 2007, 1999 .-- June 25 ( vol. 100 , no. 2008 ). - P. 27–42 . - DOI : 10.1007 / s10569-007-9103-8 . - .
- ↑ Asteroid Taxonomy
- ↑ Schmadel, Lutz D. Dictionary of Minor Planet Names . - Fifth Revised and Enlarged Edition. - B. , Heidelberg, N. Y .: Springer, 2003 .-- P. 17. - ISBN 3-540-00238-3 .
- ↑ The Astronomical Almanac. - United States Naval Observatory and United Kingdom Hydrographic Office, 2011 .-- P. G2. - ISBN 978-0-7077-4103-1 .
- ↑ "Dictionary of Astronomy", Oxford Dictionary of Astronomy , Oxford University Press, 2010-05-27, pp. 528
- ↑ Our Astronomical Column (Eng.) // Nature. - 1875. - 18 November ( vol. 13 , no. 316 ). - P. 48 . - DOI : 10.1038 / 013047d0 . - .
- ↑ García, A. López; Medvedev, Yu. D .; Fernández, JA Moraño (1997). " Using Close Encounters of Minor Planets for the Improvement of their Masses ." Dynamics and Astrometry of Natural and Artificial Celestial Bodies : 199–204, Poznań, Poland: Kluwer Academic Publishers.
- ↑ Scientists find traces of water and organic molecules in the asteroid belt located between Jupiter and Mars
- ↑ Water ice was found for the first time on an asteroid . Archived on August 27, 2010.
- ↑ Andrew S. Rivkin, Joshua P. Emery. Detection of ice and organics on an asteroidal surface (Eng.) // Nature: journal. - 2009. - Vol. 464 . - P. 1322-1323 . (eng.)
- ↑ Humberto Campins et al. Water ice and organics on the surface of the asteroid 24 Themis // English : journal. - 2009. - Vol. 464 . - P. 1320-1321 . (eng.)
- ↑ Campins, Humberto; Hargrove, K; Pinilla-Alonso, N; Howell, ES; Kelley, MS; Licandro, J; Mothé-Diniz, T; Fernández, Y; Ziffer, J. Water ice and organics on the surface of the asteroid 24 Themis (Eng.) // Nature : journal. - 2010. - Vol. 464 , no. 7293 . - P. 1320-1321 . - DOI : 10.1039 / nature09029 . - PMID 20428164 .
- ↑ More Water Out There, Ice Found on an Asteroid | International Space Fellowship (English) ( (translation of the article) )
- ↑ Fumihiko Usui et al. AKARI / IRC near-infrared asteroid spectroscopic survey: AcuA-spec , December 17, 2018
Literature
- Cowen, Ron . Ice confirmed on an asteroid , Science News (October 8, 2009). Archived October 12, 2009. Date of treatment October 9, 2009.
- Atkinson, Nancy More water out there, ice found on an asteroid . International Space Fellowship (October 8, 2009). Date of treatment October 11, 2009. Archived October 11, 2009.
- Rivkin, Andrew S .; Emery, Joshua P. Detection of ice and organics on an asteroidal surface (Eng.) // Nature : journal. - 2010 .-- Vol. 464 , no. 7293 . - P. 1322-1323 . - DOI : 10.1038 / nature09028 . - . - PMID 20428165 .