5145 Pholus

Infobox Planet | discovery=yes | physical_characteristics = yes | bgcolour=#FFFFC0
name=5145 Pholus
discoverer=Spacewatch
(David L. Rabinowitz)
discovered=January 9, 1992
alt_names=1992 AD
mp_category=Centaur, Asteroid
orbit_ref =
epoch=November 30, 2008 (JD 2454800.5)
semimajor=3045.2 Gm
(20.356 AU)
perihelion=1305.9 Gm
(8.730 AU)
aphelion=4784.1 Gm
(31.98 AU)
eccentricity=0.5711
period=33547.41 d
(91.85 yr)
inclination=24.65°
asc_node=119.44°
arg_peri=354.92°
mean_anomaly=67.49°
avg_speed=6.01 km/s
dimensions=185±16 km [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1996ciss.conf...97D&db_key=AST&high=3d6ea7529520743]
mass=~6.6e|18 kg
density=2.0? g/cm³ (assumed)
surface_grav=~0.052 m/s²
escape_velocity=~0.098 km/s
rotation=9.98 hourscite web
date=2008-05-27 last obs
title=JPL Small-Body Database Browser: 5145 Pholus (1992 AD)
url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Pholus
accessdate=2008-09-01]
spectral_type= (red) B-V=1.19; V-R=0.78 [cite web|url=http://www.physics.nau.edu/~tegler/research/survey.htm |title=Kuiper Belt Object Magnitudes and Surface Colors |accessdate=2006-11-05 |last=Tegler |first=Stephen C. |coauthors= |date=2006-01-26]
abs_magnitude=7.0
albedo=0.046±0.02
single_temperature=~62 K

5145 Pholus (pronEng|ˈfoʊləs "foe'-ləs," from _gr. "Φόλος") is a centaur in an eccentric orbit, with a perihelion less than Saturn's and aphelion greater than Neptune's. Close approches are rare: It has not come within one astronomical unit of a planet since 764 BC, and will not again until 5290. It is believed to have originated as a Kuiper belt object.

It was discovered by David L. Rabinowitz, then of the University of Arizona's Spacewatch Project, and named after Pholus, the brother of the mythological Chiron, after which 2060 Chiron was named in order to follow the tradition of naming this class of outer planet crossing objects after Centaurs.

Pholus was the second centaur type asteroid to be discovered and was quickly found to be quite red in color, for which it has been occasionally nicknamed "Big Red". The color has been speculated to be due to organic compounds on its surface (Wilson, "et al.", 1994).

The surface composition of Pholus has been estimated from its reflectance spectrum using two spatially segregated components (Cruikshank, "et al.", 1998): dark amorphous carbon and an intimate mixture of water ice, methanol ice, olivine grains, and complex organic compounds (tholins). The carbon black component was used to match the low albedo of the object.

Unlike the first Centaur, 2060 Chiron, Pholus has shown no signs of cometary activity.

The diameter of Pholus is estimated to be 185±16 km [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1996ciss.conf...97D&db_key=AST&high=3d6ea7529520743] .

References

* PMID 11539180

*

* [http://chemistry.unina.it/~alvitagl/solex/ SOLEX ]

External links

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