4 Vesta

Vesta, formal designation 4 Vesta, is an asteroid with a mean diameter of about 530 km.[1] Comprising an estimated 9% of the mass of the entire asteroid belt,[10] it is the second most massive object in the belt (the largest being the dwarf planet Ceres). It was discovered by the German astronomer Heinrich Wilhelm Olbers on March 29, 1807[1] and named after the Roman virgin goddess of home and hearth, Vesta.

Vesta is the brightest asteroid. Its greatest distance from the Sun is slightly more than the minimum distance of Ceres from the Sun,[11] and its orbit is entirely within the orbit of Ceres.[12] Vesta lost some 1% of its mass in a collision less than one billion years ago. Many fragments of this event have fallen to Earth as Howardite-Eucrite-Diogenite (HED) meteorites, a rich source of evidence about the asteroid.[13]


Discovery
Size comparison: the first 10 asteroids profiled against Earth's Moon. Vesta is fourth from the left. (The leftmost object, 1 Ceres, is now classified as a dwarf planet)

The discovery of Ceres in 1801 and Pallas in 1802 led German astronomer Heinrich Wilhelm Olbers to propose that the two objects were the remnants of a destroyed planet. In 1802 he sent a letter with his proposal to the English astronomer William Herschel, suggesting that a search near the locations where the orbits of Ceres and Pallas intersected might reveal more fragments. These orbital intersections were located in the constellations of Cetus and Virgo.[14]

Olbers commenced his search in 1802, and on March 29, 1807 he coincidentally discovered Vesta in the constellation Virgo. As the asteroid Juno had been discovered in 1804, this made Vesta the fourth object to be identified in the region that is now known as the main asteroid belt. This discovery was announced in a letter addressed to German astronomer Johann H. Schröter dated March 31.[15] Olbers allowed the prominent mathematician Carl Friedrich Gauss to name the asteroid after the Roman virgin goddess of home and hearth, Vesta.[16] The mathematician manually computed the first orbit for Vesta in the remarkably short time of 10 hours.[17][18]

After the discovery of Vesta, no further objects were discovered for 38 years.[19] During this time Ceres, Pallas, Juno and Vesta were classified as planets and each had its own planetary symbol. Vesta was normally represented by a stylized hearth (Vesta symbol.svg, ⚶). Other symbols are Old symbol of Vesta and Old planetary symbol of Vesta. All are simplifications of the original 4 Vesta Unsimplified Symbol.svg.[20]

Photometric observations of the asteroid Vesta were made at the Harvard College Observatory between 1880–82 and at the Observatoire de Toulouse in 1909. These and other observations allowed the rotation rate of the asteroid to be determined by the 1950s. However, the early estimates of the rotation rate came into question because the light curve included variations in both shape and albedo.[21]

Early estimates of the diameter of Vesta ranged from 383 (in 1825) to 444 km. William H. Pickering produced a estimated diameter of 513 ± 17 km in 1879, which is close to the modern value for the mean diameter, but the subsequent estimates ranged from a low of 390 km up to a high of 602 km during the next century. The measured estimates were first based on photometry, then later on micrometers and a device called a diskmeter. In 1989, speckle interferometery was used to measure a dimension that varied between 498 and 548 km during the rotational period.[22] In 1991, an occultation of the star SAO 93228 by Vesta was observed from multiple locations in the eastern US and Canada. Based on observations from 14 different sites, the best fit to the data is an elliptical profile with dimensions of about 550 km × 462 km.[23]

Vesta became the first asteroid to have its mass determined. Every 18 years, the asteroid 197 Arete approaches within 0.04 AU of Vesta. In 1966, based upon observations of Vesta's gravitational perturbations of Arete, Hans G. Hertz estimated the mass of Vesta as (1.20 ± 0.08) × 10-10 solar masses.[24] More refined estimates followed, and in 2001 the perturbations of 17 Thetis were used to estimate the mass of Vesta as (1.31 ± 0.02) × 10-10 solar masses.[25]

Physical characteristics
The IAU 2006 draft proposal on the definition of a planet listed Vesta as a candidate.[26]

Vesta is the second-most massive body in the asteroid belt,[4] though only 28% as massive as Ceres.[10] It lies in the Inner Main Belt interior to the Kirkwood gap at 2.50 AU. It has a differentiated interior,[27] and is similar to 2 Pallas in volume (to within uncertainty) but about 25% more massive.[4]

Vesta's shape is relatively close to a gravitationally relaxed oblate spheroid,[28] but the large concavity and protrusion at the pole (see 'Surface features' below) combined with a mass less than 5 × 1020 kg precluded Vesta from automatically being considered a dwarf planet under International Astronomical Union (IAU) Resolution XXVI 5.[29] Vesta may be listed as a dwarf planet in the future, if it is convincingly determined that its shape, other than the large impact basin at the southern pole, is due to hydrostatic equilibrium, as currently believed.[27]

Its rotation is relatively fast for an asteroid (5.342 h) and prograde, with the north pole pointing in the direction of right ascension 20 h 32 min, declination +48° (in the constellation Cygnus) with an uncertainty of about 10°. This gives an axial tilt of 29°.[28]

Temperatures on the surface have been estimated to lie between about −20 °C with the Sun overhead, dropping to about −190 °C at the winter pole. Typical day-time and night-time temperatures are −60 °C and −130 °C, respectively. This estimate is for May 6, 1996, very close to perihelion, while details vary somewhat with the seasons.[7]

Geology

There is a large collection of potential samples from Vesta accessible to scientists, in the form of over 200 HED meteorites, giving insight into Vesta's geologic history and structure.

Vesta is thought to consist of a metallic iron–nickel core, an overlying rocky olivine mantle, with a surface crust. From the first appearance of Ca-Al-rich inclusions (the first solid matter in the Solar System, forming about 4,567 million years ago), a likely time line is as follows:[30][31][32][33][34]

Timeline of the evolution of Vesta 2–3 million years Accretion completed
4–5 million years Complete or almost complete melting due to radioactive decay of 26Al, leading to separation of the metal core
6–7 million years Progressive crystallization of a convecting molten mantle. Convection stopped when about 80% of the material had crystallized
Extrusion of the remaining molten material to form the crust, either as basaltic lavas in progressive eruptions, or possibly forming a short-lived magma ocean.
The deeper layers of the crust crystallize to form plutonic rocks, while older basalts are metamorphosed due to the pressure of newer surface layers.
Slow cooling of the interior

Elevation diagram of 4 Vesta (as determined from Hubble Space Telescope images of May 1996) viewed from the south-east, showing the south pole crater.

Vesta is the only known intact asteroid that has been resurfaced in this manner. However, the presence of iron meteorites and achondritic meteorite classes without identified parent bodies indicates that there once were other differentiated planetesimals with igneous histories, which have since been shattered by impacts.

Composition of the Vestan crust (in order of increasing depth)[35] A lithified regolith, the source of howardites and brecciated eucrites.
Basaltic lava flows, a source of non-cumulate eucrites.
Plutonic rocks consisting of pyroxene, pigeonite and plagioclase, the source of cumulate eucrites.
Plutonic rocks rich in orthopyroxene with large grain sizes, the source of diogenites.

On the basis of the sizes of V-type asteroids (thought to be pieces of Vesta's crust ejected during large impacts), and the depth of the south polar crater (see below), the crust is thought to be roughly 10 kilometres (6 mi) thick.[36]

Surface features
Elevation map of 4 Vesta, as determined from Hubble Space Telescope images of May 1996

Some Vestian surface features have been resolved using the Hubble Space Telescope and ground based telescopes, e.g. the Keck Telescope.[37]

The most prominent surface feature is an enormous crater 460 kilometres (290 mi) in diameter centered near the south pole.[28] Its width is 80% of the entire diameter of Vesta. The floor of this crater is about 13 kilometres (8.1 mi) below, and its rim rises 4–12 km above the surrounding terrain, with total surface relief of about 25 km. A central peak rises 18 kilometres (11 mi) above the crater floor. It is estimated that the impact responsible excavated about 1% of the entire volume of Vesta, and it is likely that the Vesta family and V-type asteroids are the products of this collision. If this is the case, then the fact that 10 km fragments of the Vesta family and V-type asteroids have survived bombardment until the present indicates that the crater is only about 1 billion years old or younger.[38] It would also be the original site of origin of the HED meteorites. In fact, all the known V-type asteroids taken together account for only about 6% of the ejected volume, with the rest presumably either in small fragments, ejected by approaching the 3:1 Kirkwood gap, or perturbed away by the Yarkovsky effect or radiation pressure. Spectroscopic analyses of the Hubble images have shown that this crater has penetrated deep through several distinct layers of the crust, and possibly into the mantle, as indicated by spectral signatures of olivine.[28]
Spectral and albedo maps of 4 Vesta, as determined from Hubble Space Telescope images from November 1994

Several other large craters about 150 kilometres (93 mi) wide and 7 kilometres (4.3 mi) deep are also present. A dark albedo feature about 200 kilometres (120 mi) across has been named Olbers in honour of Vesta's discoverer, but it does not appear in elevation maps as a fresh crater would. Its nature is presently unknown; it may be an old basaltic surface.[39] It serves as a reference point with the 0° longitude prime meridian defined to pass through its center.

The eastern and western hemispheres show markedly different terrains. From preliminary spectral analyses of the Hubble Space Telescope images,[38] the eastern hemisphere appears to be some kind of high albedo, heavily cratered "highland" terrain with aged regolith, and craters probing into deeper plutonic layers of the crust. On the other hand, large regions of the western hemisphere are taken up by dark geologic units thought to be surface basalts, perhaps analogous to the lunar maria.[38]

Fragments
4 Vesta, 1 Ceres and Earth's Moon shown to scale

Some small solar system objects are believed to be fragments of Vesta caused by collisions. The Vestoid asteroids and HED meteorites are examples. The V-type asteroid 1929 Kollaa has been determined to have a composition akin to cumulate eucrite meteorites, indicating its origin deep within Vesta's crust.[13]

Because a number of meteorites are believed to be Vestian fragments, Vesta is currently one of only five identified Solar system bodies for which we have physical samples, the others being Mars, the Moon, comet Wild 2, and Earth itself.

Exploration

In 1981, a proposal for an asteroid mission was submitted to the ESA. Named the Asteroidal Gravity Optical and Radar Analysis (AGORA), this spacecraft was to launch some time in 1990–1994 and perform two flybys of large asteroids. The preferred target for this mission was Vesta. AGORA would reach the asteroid belt either by a gravitational slingshot trajectory past Mars or by means of a small ion engine. However, the proposal was refused by the ESA. A joint NASA-ESA asteroid missions was then drawn up for a Multiple Asteroid Orbiter with Solar Electric Propulsion (MAOSEP), with one of the mission profiles including an orbit of Vesta. NASA indicated they were not interested in an asteroid mission. Instead, the ESA set up a technological study of a spacecraft with an ion drive. Other missions to the asteroid belt were proposed in the 1980s by France, Germany, Italy, Russia and the United States, but none were approved.[40]

In the early 1990s, NASA initiated the Discovery Program, which was intended to be a series of low cost scientific missions. In 1996, the program's study team recommended as a high priority a mission to explore the asteroid belt using a spacecraft with an ion engine. Funding for this program remained problematic for several years, but by 2004 the Dawn vehicle had passed its critical design review.[41]

NASA's Dawn probe—launched on September 27, 2007—is the first space mission to Vesta. It will orbit the asteroid for nine months from August 2011 until May 2012.[42] Dawn will then proceed to its other target, Ceres, and will possibly continue to explore the asteroid belt on an extended mission using any remaining fuel. The spacecraft is the first that can enter and leave orbit around more than one body as a result of its weight-efficient ion driven engines.[42] Once Dawn arrives at Vesta, scientists will be able to calculate Vesta's precise mass based on gravitational interactions. This will allow scientists to refine the mass estimates of the asteroids that are in turn perturbed by Vesta.[42]

Visibility
Vesta is seen from San Francisco on June 14, 2007

Its size and unusually bright surface make Vesta the brightest asteroid, and it is occasionally visible to the naked eye from dark (non-light polluted) skies. In May and June 2007, Vesta reached a peak magnitude of +5.4, the brightest since 1989.[43] At that time, opposition and perihelion were only a few weeks apart. It was visible in the constellations Ophiuchus and Scorpius.[44]

Less favorable oppositions during late autumn in the Northern Hemisphere still have Vesta at a magnitude of around +7.0. Even when in conjunction with the Sun, Vesta will have a magnitude around +8.5; thus from a pollution-free sky it can be observed with binoculars even at elongations much smaller than near opposition.[45]

2010-2011

In 2010, Vesta reached opposition in the constellation of Leo on the night of February 17–18, when it was about magnitude 6.1,[46] a brightness that makes it visible in binocular range but probably not for the naked eye. However, under perfect dark sky conditions where all light pollution is absent it might be visible to an experienced observer without the use of a telescope or binoculars. Vesta will next come to opposition on August 5, 2011, in the constellation of Capricornus at about magnitude 5.6.[46]

See also

* 3103 Eger
* 4055 Magellan
* 3908 Nyx
* 3551 Verenia
* V-type asteroid
* HED meteorites
* Diogenite
* Eucrite
* Howardite
* Asteroids in fiction
* List of Solar System bodies formerly considered planets


Notes and references

Footnotes

1. ^ a b c d e f "JPL Small-Body Database Browser: 4 Vesta". http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=4. Retrieved 2008-06-01.
2. ^ "The MeanPlane (Invariable plane) of the Solar System passing through the barycenter". 2009-04-03. http://home.comcast.net/~kpheider/MeanPlane.gif. Retrieved 2009-04-10. (produced with Solex 10 written by Aldo Vitagliano; see also Invariable plane)
3. ^ Thomas, P. C.; et al. (1997). "Impact excavation on asteroid 4 Vesta: Hubble Space Telescope results". Science 277: 1492. doi:10.1126/science.277.5331.1492.
4. ^ a b c d Baer, James; Chesley, Steven R. (2008). "Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris" (PDF). Celestial Mechanics and Dynamical Astronomy (Springer Science+Business Media B.V. 2007) 100 (2008): 27–42. doi:10.1007/s10569-007-9103-8. http://www.springerlink.com/content/h747307j43863228/fulltext.pdf. Retrieved 2008-11-11.
5. ^ Harris, A. W.; Warner, B. D.; Pravec, P.; (Eds.) (2006). "Asteroid Lightcurve Derived Data. EAR-A-5-DDR-DERIVED-LIGHTCURVE-V8.0.". NASA Planetary Data System. http://www.psi.edu/pds/resource/lc.html. Retrieved 2007-03-15.
6. ^ a b Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (2004). "Infra-Red Astronomy Satellite (IRAS) Minor Planet Survey. IRAS-A-FPA-3-RDR-IMPS-V6.0.". NASA Planetary Data System. http://www.psi.edu/pds/resource/imps.html. Retrieved 2007-03-15.
7. ^ a b Mueller, T. G.; Metcalfe, L. (2001). "ISO and Asteroids". European Space Agency (ESA) bulletin 108: 38. http://www.esa.int/esapub/bulletin/bullet108/chapter4_bul108.pdf.
8. ^ Neese, C.; Ed. (2005). "Asteroid Taxonomy EAR-A-5-DDR-TAXONOMY-V5.0". NASA Planetary Data System. http://www.psi.edu/pds/resource/taxonomy.html. Retrieved 2007-03-15.
9. ^ Menzel, Donald H.; and Pasachoff, Jay M. (1983). A Field Guide to the Stars and Planets (2nd ed.). Boston, MA: Houghton Mifflin. pp. 391. ISBN 0395348358.
10. ^ a b Pitjeva, E. V. (2005). "High-Precision Ephemerides of Planets—EPM and Determination of Some Astronomical Constants" (PDF). Solar System Research 39 (3): 176. doi:10.1007/s11208-005-0033-2. http://iau-comm4.jpl.nasa.gov/EPM2004.pdf.
11. ^ On February 10, 2009, during Ceres perihelion, Ceres was closer to the Sun than Vesta since Vesta has an aphelion distance greater than Ceres' perihelion distance. (2009-02-10: Vesta 2.56AU; Ceres 2.54AU)
12. ^ "Ceres, Pallas Vesta and Hygiea". Gravity Simulator. http://www.orbitsimulator.com/gravity/articles/ceres.html. Retrieved 2008-05-31.
13. ^ a b Kelley, M. S.; et al. (2003). "Quantified mineralogical evidence for a common origin of 1929 Kollaa with 4 Vesta and the HED meteorites". Icarus 165: 215. doi:10.1016/S0019-1035(03)00149-0.
14. ^ Littmann, Mark (2004). Planets Beyond: Discovering the Outer Solar System. Courier Dover Publications. p. 21. ISBN 0486436020.
15. ^ Lynn, W. T. (February 1907). "The discovery of Vesta". The Observatory 30: 103–105. http://articles.adsabs.harvard.edu/abs/1907Obs....30..103L/0000105.000.html. Retrieved 2009-05-20.
16. ^ Schmadel, Lutz D. (2003). Dictionary of Minor Planet Names: Prepared on Behalf of Commission 20 Under the Auspices of the International Astronomical Union. Springer. pp. 15. ISBN 3540002383.
17. ^ Dunnington, Guy Waldo; Gray, Jeremy; Dohse, Fritz-Egbert (2004). Carl Friedrich Gauss: Titan of Science. The Mathematical Association of America. p. 76. ISBN 088385547X.
18. ^ Rao, K. S.; Berghe, G. V. (2003). "Gauss, Ramanujan and Hypergeometric Series Revisited". Historia Scientiarum 13 (2): 123–133.
19. ^ Wells, David A.; Bliss, George, Jr.; (Eds.) (1851). "The Planet Hygiea". Annual of Scientific Discovery for the year 1850, quoted by spaceweather.com archives, 2006-09-13. http://spaceweather.com/archive.php?view=1&day=13&month=09&year=2006. Retrieved 2008-06-01.
20. ^ Older form and discussion of its complexity from Gould, 1852 (Gould, B. A. (1852), On the Symbolic Notation of the Asteroids, Astronomical Journal, 2, as cited and discussed at http://aa.usno.navy.mil/faq/docs/minorplanets.php.
21. ^ McFadden, L. A.; Emerson, G.; Warner, E. M.; Onukwubiti, U.; Li, J.-Y. (March 10–14, 2008). "Photometry of 4 Vesta from its 2007 Apparition". Proceedings, 39th Lunar and Planetary Science Conference. League City, Texas. Bibcode: 2008LPI....39.2546M. http://adsabs.harvard.edu//abs/2008LPI....39.2546M. Retrieved 2009-05-20.
22. ^ Hughes, D. W. (September 1994). "The Historical Unravelling of the Diameters of the First Four Asteroids". The Royal Astronomical Journal Quarterly Journal 35 (3). Bibcode: 1994QJRAS..35..331H. http://adsabs.harvard.edu/abs/1994QJRAS..35..331H. Retrieved 2009-05-20.
23. ^ Povenmire, H. (September 2001). "The January 4, 1991 Occultation of SAO 93228 by Asteroid (4) Vesta". Meteoritics & Planetary Science 36 (Supplement): A165. Bibcode: 2001M&PSA..36Q.165P.
24. ^ Hertz, Hans G. (April 19, 1968). "Mass of Vesta". Science 160 (3825): 299–300. doi:10.1126/science.160.3825.299. PMID 17788233.
25. ^ Kovačević, A. (January 2005). "Determination of the mass of (4) Vesta based on new close approaches". Astronomy and Astrophysics 430: 319–325. doi:10.1051/0004-6361:20035872. Bibcode: 2005A&A...430..319K.
26. ^ O. Gingerich (2006). "The Path to Defining Planets" (PDF). Harvard-Smithsonian Center for Astrophysics and IAU EC Planet Definition Committee chair. http://astro.cas.cz/nuncius/nsiii_03.pdf. Retrieved 2007-03-13.
27. ^ a b Savage, Don; Jones, Tammy; and Villard, Ray (1995). "Asteroid or Mini-Planet? Hubble Maps the Ancient Surface of Vesta". Hubble Site News Release STScI-1995-20. http://hubblesite.org/newscenter/archive/releases/1995/20/image/c. Retrieved 2006-10-17.
28. ^ a b c d Thomas, P. C.; et al. (1997). "Vesta: Spin Pole, Size, and Shape from HST Images". Icarus 128: 88. doi:10.1006/icar.1997.5736.
29. ^ "The IAU draft definition of "planet" and "plutons"". IAU. August 2006. http://www.iau.org/public_press/news/detail/iau0601. Retrieved 2009-12-16. (XXVI)
30. ^ Ghosh, A.; McSween, H. Y. (1998). "A Thermal Model for the Differentiation of Asteroid 4 Vesta, Based on Radiogenic Heating". Icarus 134: 187. doi:10.1006/icar.1998.5956.
31. ^ Righter, K.; Drake, M. J. (1997). "A magma ocean on Vesta: Core formation and petrogenesis of eucrites and diogenites". Meteoritics & Planetary Science 32: 929–944. doi:10.1111/j.1945-5100.1997.tb01582.x. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997M%26PS...32..929R&db_key=AST&data_type=HTML&format=&high=4374b9c9ce01530.
32. ^ Drake, M. J. (2001). "The eucrite/Vesta story". Meteoritics & Planetary Science 36: 501–513. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001M%26PS...36..501D&db_key=AST&data_type=HTML&format=&high=4374b9c9ce04149.
33. ^ Sahijpal, S.; Soni, P.;Gagan, G. (2007). "Numerical simulations of the differentiation of accreting planetesimals with 26Al and 60Fe as the heat sources". Meteoritics & Planetary Science 42: 1529–1548. doi:10.1111/j.1945-5100.2007.tb00589.x.
34. ^ Gupta, G.; Sahijpal, S. (2010). "Differentiation of Vesta and the parent bodies of other achondrites". J. Geophys. Res. (Planets). doi:10.1029/2009JE003525.
35. ^ Takeda, H. (1997). "Mineralogical records of early planetary processes on the HED parent body with reference to Vesta". Meteoritics & Planetary Science 32: 841–853. doi:10.1111/j.1945-5100.1997.tb01574.x. http://adsabs.harvard.edu/abs/1997M%26PS...32..841T.
36. ^ Yamaguchi, A.; Taylor, G. J.; Keil, K. (1995). "Metamorphic History of the Eucritic Crust of 4 Vesta". Meteoritical Society 30: 603. http://adsabs.harvard.edu/abs/1995Metic..30..603Y. Retrieved 2008-11-06.
37. ^ Zellner, N. E. B.; Gibbard, S.; de Pater, I.; et al. (2005). "Near-IR imaging of Asteroid 4 Vesta" (pdf). Icarus 177: 190–195. doi:10.1016/j.icarus.2005.03.024. 38. ^ a b c Binzel, R. P.; et al. (1997). "Geologic Mapping of Vesta from 1994 Hubble Space Telescope Images". Icarus 128: 95. doi:10.1006/icar.1997.5734.
39. ^ Zellner, B. J.; et al. (1997). "Hubble Space Telescope Images of Asteroid Vesta in 1994". Icarus 128: 83. doi:10.1006/icar.1997.5735.
40. ^ Ulivi, Paolo; Harland, David (2008). Robotic Exploration of the Solar System: Hiatus and Renewal, 1983-1996. Springer Praxis Books in Space Exploration. Springer. pp. 117–125. ISBN 0387789049.
41. ^ Russell, C. T.; et al. (October 2007). "Dawn Mission to Vesta and Ceres". Earth, Moon, and Planets 101 (1–2): 65–91. doi:10.1007/s11038-007-9151-9. Bibcode: 2007EM&P..101...65R. http://spc.igpp.ucla.edu/personnel/russell/papers/dawn_mission_vesta_ceres.pdf. Retrieved 2010-04-02.
42. ^ a b c Russell, C. T.; Capaccioni, F.; Coradini, A.; et al. (2007). "Dawn Mission to Vesta and Ceres". Earth Moon Planet 1001: 65–91. doi:10.1007/s11038-007-9151-9. http://adsabs.harvard.edu/abs/2007EM%26P..101...65R.
43. ^ Bryant, Greg (2007). "Sky & Telescope: See Vesta at Its Brightest!". http://www.skyandtelescope.com/observing/home/7297386.html. Retrieved 2007-05-07.
44. ^ "Vesta Finder". Sky & Telescope. http://media.skytonight.com/images/Vesta07_Finder_color.jpg. Retrieved 2007-05-07.
45. ^ James, Andrew (2008). "Vesta". Southern Astronomical Delights. http://homepage.mac.com/andjames/PageVesta000.htm. Retrieved 2008-11-06.
46. ^ a b Donald K. Yeomans and Alan B. Chamberlin. "Horizons Ephemeris". JPL Solar System Dynamics. http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=4. Retrieved 2010-01-09.


General references

* Yeomans, Donald K.. "Horizons system". NASA JPL. http://ssd.jpl.nasa.gov/?horizons. Retrieved 2007-03-20. – Horizons can be used to obtain a current ephemeris
* Keil, K.; Geological History of Asteroid 4 Vesta: The Smallest Terrestrial Planet in Asteroids III, William Bottke, Alberto Cellino, Paolo Paolicchi, and Richard P. Binzel, (Editors), University of Arizona Press (2002), ISBN 0-8165-2281-2


External links

* NASA's Dawn Spacecraft will reach orbit around Vesta in July 2011.
* NASA video clips of Vesta rotating in color
* Views of the Solar System: Vesta
* HubbleSite: Hubble Maps the Asteroid Vesta
* Encyclopaedia Britannica, Vesta – full article
* HubbleSite: Hubble Reveals Huge Crater on the Surface of the Asteroid Vesta
* HubbleSite: short movie composed from Hubble Space Telescope images from November 1994.
* Adaptive optics views of Vesta from Keck Observatory
* Differentiated interior of Vesta
* Orbital simulation from JPL (Java) / Horizons Ephemeris
* 4 Vesta images at ESA/Hubble
* Hubble views of Vesta on the Planetary Society Weblog (includes animation)
* Farinella, Paolo (2005). "Houston: Focus on Vesta and the HEDs". Arkansas Center for Space & Planetary Sciences. http://meteoritemag.uark.edu/612.htm. Retrieved 2007-10-25.

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