|Discovered by||Karl Ludwig Hencke|
|Discovery date||December 8, 1845|
|Alternative names||1969 SE|
|Minor planet category||Main belt|
|Epoch November 26, 2005 (JD 2453700.5)|
|Aphelion||459.202 Gm (3.070 AU)|
|Perihelion||310.688 Gm (2.077 AU)|
|Semi-major axis||384.945 Gm (2.573 AU)|
|Orbital period||1507.676 d (4.13 a)|
|Average orbital speed||18.39 km/s|
|Longitude of ascending node||141.690°|
|Argument of perihelion||357.530°|
|Mean density||~2.7 g/cm³|
|Equatorial surface gravity||~0.023 m/s²|
|Escape velocity||~0.062 km/s|
|Rotation period||0.700 03 d (16.801 h)|
max: 263 K (-10 °C)
|Spectral type||S-type asteroid|
|Apparent magnitude||8.7 to 12.92|
|Absolute magnitude (H)||6.85|
|Angular diameter||0.15" to 0.041"|
5 Astraea (written Astræa in the early literature) is a big main belt asteroid. Its surface is very reflective (bright) and what it's made of 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 found, 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.
Astrea is physically unremarkable but notable mainly because for 38 years (after the discovery of Vesta in 1807) it had been thought that there were only four asteroids. In terms of maximum brightness, it is indeed only the seventeenth brightest main belt asteroid, being fainter than 192 Nausikaa and even, at rare near-perihelion oppositions, the highly eccentric carbonaceous 324 Bamberga.
After the discovery of Astraea, thousands of other asteroids would follow. Indeed, the discovery of Astrea 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 biggest of a whole new type of celestial body.
References[change | edit source]
- 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
- Supplemental IRAS Minor Planet Survey
- M. J. López-Gonzáles & E. Rodríguez Lightcurves and poles of seven asteroids, Planetary and Space Science, Vol. 53, p. 1147 (2005).
- G. A. Krasinsky et al. Hidden Mass in the Asteroid Belt, Icarus, Vol. 158, p. 98 (2002).
- "DAWN: A Journey to the Beginning of the Solar System". NASA: Jet Propulsion Laboratory; California Institute of Technology. http://dawn.jpl.nasa.gov/DawnCommunity/flashbacks/fb_09.asp. Retrieved 20 July 2013.
Other websites[change | edit source]