From Simple English Wikipedia, the free encyclopedia
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.
[4]
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.
[2]
This gives an
axial tilt
of about 33°.
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.
There has been only one seen
stellar
occultation
by Astraea (
February 2
,
1991
).
- Yeomans, Donald K.
"Horizons system"
. NASA JPL
. Retrieved
2007-03-20
.
? Horizons can be used to obtain a current ephemeris
Small Solar System bodies
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