5 Astraea

Infobox Planet | discovery=yes | physical_characteristics = yes | bgcolour=#FFFFC0
name=5 Astraea
symbol=
discoverer=Karl Ludwig Hencke
discovered=December 8, 1845
alt_names=1969 SE
adjectives=Astraean
mp_category=Main belt
epoch=November 26, 2005 (JD 2453700.5)
semimajor=384.945 Gm (2.573 AU)
perihelion=310.688 Gm (2.077 AU)
aphelion=459.202 Gm (3.070 AU)
eccentricity=0.193
period=1507.676 d (4.13 a)
inclination=5.369°
asc_node=141.690°
arg_peri=357.530°
mean_anomaly=194.442°
avg_speed=18.39 km/s
dimensions=167×123×82 km [http://www.psi.edu/pds/archive/astdata04/simps04/diamalb.tab Supplemental IRAS Minor Planet Survey] ] [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005P%26SS...53.1147L&db_key=AST&data_type=HTML&format=&high=437a3039ff02368 M. J. López-Gonzáles & E. Rodríguez "Lightcurves and poles of seven asteroids"] , Planetary and Space Science, Vol. 53, p. 1147 (2005).]
mass=~2.4e|18 kg
density=~2.7 g/cm³G. A. Krasinsky et al "Hidden Mass in the Asteroid Belt", Icarus, Vol. 158, p. 98 (2002).]
surface_grav=~0.023 m/s²
escape_velocity=~0.062 km/s
rotation=0.700 03 d (16.801 h)
spectral_type=S-type asteroid
magnitude = 8.7 to 12.92
abs_magnitude=6.85
albedo=0.227 (geometric)
angular_size = 0.15" to 0.041"
single_temperature=~167 K
"max:" 263 K (-10 °C)

5 Astraea (pronEng|əˈstriːə respell|ə|STREE|ə, _gr. "Αστραία," written Astræa in the early literature) is a large main belt asteroid. Its surface is highly reflective (bright) and its composition is probably a mixture of nickel-iron with magnesium- and iron-silicates. The adjectival form of the name, although unused, would be "Astraean" (which also designates a genus of star corals).

Astraea was the fifth asteroid discovered, on December 8, 1845 by K. L. Hencke. It was his first of two asteroid discoveries. The second was 6 Hebe. An amateur astronomer and post office employee, Hencke was looking for 4 Vesta when he stumbled on Astraea. The King of Prussia awarded him with an annual pension of 300 US$ (1968 dollars) for the discovery.Fact|date=February 2007

Photometry indicates prograde rotation, that the north pole points in the direction of right ascension 9 h 52 min, declination 73° with a 5° uncertainty. This gives an axial tilt of about 33°.

Astraea is physically unremarkable but notable mainly because for 38 years (after the discovery of Vesta in [http://www.spacebanter.com/archive/index.php/t-18464.html] .

After the discovery of Astraea, thousands of other asteroids would follow. Indeed, the discovery of Astraea proved to be the starting point for the eventual demotion of the four original asteroids (which were regarded as planets at the time) to their current status, as it became apparent that these four were only the largest of a whole new type of celestial body.

There has been only one observed stellar occultation by Astraea (February 2, 1991).

References

* — Horizons can be used to obtain a current ephemeris

External links

* [http://adsabs.harvard.edu//full/seri/AN.../0023//0000211.000.html AN 23 (1846) 393] (in German)
* [http://adsabs.harvard.edu//full/seri/MNRAS/0007//0000027.000.html MNRAS 7 (1846) 27]