944 Hidalgo
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Discovery
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| Discovered by | Walter Baade |
| Discovery date | October 31, 1920 |
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Designations
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| Alternate name | 1920 HZ |
| Minor planet category |
Main belt, Jupiter-crosser asteroid, Saturn-crosser asteroid centaur?[1][2] |
| Epoch July 14, 2004 (JD 2453200.5) | |
| Aphelion | 1427.003 Gm (9.539 AU) |
| Perihelion | 291.846 Gm (1.951 AU) |
| Semi-major axis | 859.425 Gm (5.745 AU) |
| Eccentricity | 0.660 |
| Orbital period | 5029.467 d (13.77 a) |
| Average orbital speed | 12.43 km/s |
| Mean anomaly | 346.285° |
| Inclination | 42.567° |
| Longitude of ascending node | 21.549° |
| Argument of perihelion | 56.569° |
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Physical characteristics
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| Dimensions | 38 km[1]H |
| Mass | 8.4×1015 kg ??? |
| Mean density | 2 g/cm³ ??? |
| Equatorial surface gravity | 0.0056 m/s² ??? |
| Escape velocity | 0.011 km/s ??? |
| Rotation period | 0.419 29 d[1] |
| Albedo | 0.06[1] |
| Temperature | ~116 K |
| Spectral type | D-type asteroid |
| Absolute magnitude (H) | 10.77[1] |
944 Hidalgo (pronounced /hɨˈdælɡoʊ/ hi-DAL-goh) is an unusual asteroid, and has the longest orbital period (13.77 years) of any asteroid in the traditional asteroid belt.
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[edit] Description and classification
944 Hidalgo is a Centaur-like asteroid.[1] (This designation is given to those objects that have orbits between Jupiter and Neptune.) Though Hidalgo has a semi-major axis beyond Jupiter, the Minor Planet Center (MPC) does not list it as a Centaur.[2]
With a high eccentricity of 0.66, its perihelion of 1.95 AU takes it to the inner edge of the asteroid belt, while its aphelion of 9.54 AU takes it right out to Saturn's orbit, a characteristic normally associated with Saturn's family of comets. Some astronomers therefore suspect that it was once a comet. Strictly speaking, Hidalgo is a Saturn-grazer rather than a Saturn-crosser as its aphelion does not clear Saturn's. Hidalgo's severe orbital inclination of 43° is suspected to be the result of a close encounter with Jupiter. Even as recently as 1922, Hidalgo passed within 0.89AU of the powerful influence of Jupiter.[3] Its diameter is estimated to be 38 km.[1]
[edit] Discovery and subsequent studies
944 Hidalgo was discovered by Walter Baade on October 31, 1920 at Bergedorf Observatory near Hamburg, Germany. It is named for Miguel Hidalgo y Costilla, who was responsible for declaring Mexico's independence in 1810. German astronomers who were in Mexico to observe a total eclipse on September 10, 1923, had an audience with President Álvaro Obregón. During this meeting, they asked his permission to name the asteroid after Hidalgo y Costilla.[4]
It was one of five minor planets included in the 1993 study, Transition Comets -- UV Search for OH Emissions in Asteroids, which was research involving amateur astronomers who were permitted to make use of the Hubble Space Telescope.[citation needed]
In the late 1990s, a network of astronomers worldwide gathered lightcurve data that was ultimately used to derive the spin states and shape models of 10 new asteroids, including (944) Hidalgo. [5][6] Lightcurve data has also been recorded by observers at the Antelope Hills Observatory, which has been designated as an official observatory by the Minor Planet Center.[7]
When Pluto was discovered Hidalgo was the furthest known asteroid from the Sun.[8]
[edit] References
- ^ a b c d e f "JPL Small-Body Database Browser: 944 Hidalgo (1920 HZ)". 2008-05-09 last obs. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=944. Retrieved on 2008-03-09.
- ^ a b "List Of Centaurs and Scattered-Disk Objects". Minor Planet Center. http://cfa-www.harvard.edu/iau/lists/Centaurs.html. Retrieved on 2008-10-04.
- ^ "JPL Close-Approach Data: 944 Hidalgo (1920 HZ)". 2008-06-10 last obs. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=944;orb=0;cov=0;log=0;cad=1#cad. Retrieved on 2009-05-05.
- ^ Schmadel Lutz D. Dictionary of Minor Planet Names (fifth edition), Springer, 2003. ISBN 3540002383.
- ^ Durech., J.; Kaasalainen, M., Marciniak, A.; et al., “Physical models of ten asteroids from an observers' collaboration network,” Astronomy and Astrophysics , Volume 465, Issue 1, April I 2007, pp. 331-337
- ^ Durech, J.; Kaasalainen, M.; Marciniak, A.; Allen, W. H. et al. “Asteroid brightness and geometry,” Astronomy and Astrophysics, Volume 465, Issue 1, April I 2007, pp. 331-337.
- ^ http://www.antelopehillsobservatory.org/Lightcurves/944.gif
- ^ "JPL Small-Body Database Search Engine". JPL Solar System Dynamics. http://ssd.jpl.nasa.gov/sbdb_query.cgi. Retrieved on 2008-05-27. (characteristic:a>5.7)
[edit] External links
- Orbital simulation from JPL (Java) / Horizons Ephemeris
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