944 Hidalgo

Infobox Planet | discovery=yes | physical_characteristics = yes | bgcolour=#FFFFC0
name=944 Hidalgo
discoverer=Walter Baade
discovered=October 31, 1920
alt_names=1920 HZ
mp_category=Main belt,
Jupiter-crosser asteroid,
Saturn-crosser asteroid
centaur?cite web
date=2008-05-09 last obs
title=JPL Small-Body Database Browser: 944 Hidalgo (1920 HZ)
url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=944
accessdate=2008-03-09] cite web
title=List Of Centaurs and Scattered-Disk Objects
publisher=Minor Planet Center
url=http://cfa-www.harvard.edu/iau/lists/Centaurs.html
accessdate=2008-10-04]
epoch=July 14, 2004 (JD 2453200.5)
semimajor=859.425 Gm (5.745 AU)
perihelion=291.846 Gm (1.951 AU)
aphelion=1427.003 Gm (9.539 AU)
eccentricity=0.660
period=5029.467 d (13.77 a)
inclination=42.567°
asc_node=21.549°
arg_peri=56.569°
mean_anomaly=346.285°
avg_speed=12.43 km/s
dimensions=38 km ^{[http://neo.jpl.nasa.gov/glossary/h.html H]}
mass=8.4×10¹⁵ kg ???
density=2 g/cm³ ???
surface_grav=0.0056 m/s² ???
escape_velocity=0.011 km/s ???
rotation=0.419 29 d ^{[http://www.ipa.nw.ru/PAGE/DEPFUND/LSBSS/parmaeng.htm]}
spectral_type=D-type asteroid
abs_magnitude=10.77
albedo=0.06
single_temperature=~116 K

944 Hidalgo (IPAEng|hɨˈdælɡoʊ "hi-dal'-goe") is an unusual asteroid, and has the longest orbital period (13.77 years) of any asteroid in the traditional asteroid belt.

It is a Centaur like asteroid. (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.

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. Its diameter is estimated to be 38 km.

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. [ Schmadel Lutz D. Dictionary of Minor Planet Names (fifth edition), Springer, 2003. ISBN-10: 3540002383.]

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.Fact|date=March 2008

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. [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.] 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. [http://www.antelopehillsobservatory.org/Lightcurves/944.gif]

When Pluto was discovered Hidalgo was the furthest known asteroid from the Sun.cite web
title=JPL Small-Body Database Search Engine
publisher=JPL Solar System Dynamics
url=http://ssd.jpl.nasa.gov/sbdb_query.cgi
accessdate=2008-05-27 (characteristic:a>5.7)]

References

External links

* [http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=944;orb=1 Orbital simulation] from JPL (Java) / [http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=944 Horizons Ephemeris]