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<!-- Additional parameters for this template are available at [[Template:Infobox Planet]]. -->
{{Infobox Planet | discovery=yes | physical_characteristics = yes | bgcolour=#FFFFC0 |
name=5 Astraea
| symbol=[[File:5 Astraea Symbol.svg|25px|Astronomical symbol for 5 Astraea]]
| discoverer=[[Karl Ludwig Hencke]]
| discovered=[[December 8]], [[1845]]
| alt_names=1969 SE
| mp_category=[[Main belt]]
| epoch=[[November 26]], [[2005]] ([[Julian day|JD]] 2453700.5)
| semimajor=384.945 [[Giga|G]][[metre|m]] (2.573 [[Astronomical unit|AU]])
| perihelion=310.688 Gm (2.077 AU)
| aphelion=459.202 Gm (3.070 AU)
| eccentricity=0.193
| period=1507.676 [[day|d]] (4.13 [[Julian year (astronomy)|a]])
| inclination=5.369[[degree (angle)|°]]
| asc_node=141.690°
| arg_peri=357.530°
| mean_anomaly=194.442°
| avg_speed=18.39 km/[[second|s]]
| dimensions=167×123×82 km<ref name=IRAS>[http://www.psi.edu/pds/archive/astdata04/simps04/diamalb.tab Supplemental IRAS Minor Planet Survey]</ref><ref name=Lopez-Gonzales>[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).</ref>
| mass=~2.4{{e|18}} [[kilogram|kg]]
| density=~2.7 g/[[cubic centimetre|cm³]]<ref name=Krasinsky>[[G. A. Krasinsky]] ''et al.'' ''Hidden Mass in the Asteroid Belt'', Icarus, Vol. 158, p. 98 (2002).</ref>
| surface_grav=~0.023 m/s²
| escape_velocity=~0.062 km/s
| rotation=0.700 03 d (16.801 h)<ref name=Lopez-Gonzales />
| spectral_type=[[S-type asteroid]]
| magnitude = 8.7 <!-- Horizons 2016-02-15 --> to 12.92
| abs_magnitude=6.85
| albedo=0.227 ([[geometric albedo|geometric]])<ref name=IRAS />
| angular_size = 0.15" <!-- Horizons 2016-Feb-15 --> to 0.041"
| single_temperature=~167 [[kelvin|K]] <br /> ''max:'' 263 K (-10 [[Celsius|°C]])}}
'''5 Astraea''' (written '''Astræa''' in the early literature) is a big [[Asteroid belt|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]]-[[silicate]]s. The adjectival form of the name, although unused, would be ''Astraean'' (which also designates a [[genus]] of [[star coral]]s).
[[File:Moon and Asteroids 1 to 10.svg|thumb|left|Size comparison: the first 10 asteroids profiled against Earth's [[Moon]]. Astrea is the fifth from the left.]]
Astraea was the fifth [[asteroid]] found, on [[December 8]], [[1845]] by [[Karl Ludwig Hencke|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.<ref>{{cite web|title=DAWN: A Journey to the Beginning of the Solar System|url=http://dawn.jpl.nasa.gov/DawnCommunity/flashbacks/fb_09.asp|publisher=NASA: Jet Propulsion Laboratory; California Institute of Technology|accessdate=20 July 2013}}</ref>
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.<ref name=Lopez-Gonzales /> This gives an [[axial tilt]] of about 33°.
Astrea is physically unremarkable but notable mainly because for 38 years (after the discovery of [[4 Vesta|Vesta]] in [[1807]]) it had been thought that there were only four asteroids. In terms of [[apparent magnitude|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 [[star|stellar]] [[occultation]] by Astraea ([[February 2]], [[1991]]).
== References ==
* {{cite web | last = Yeomans | first = Donald K. | url = http://ssd.jpl.nasa.gov/?horizons | title = Horizons system | publisher = NASA JPL | accessdate = 2007-03-20 }} — Horizons can be used to obtain a current ephemeris
{{reflist}}
== Other websites ==
* [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]
{{MinorPlanets Navigator|4 Vesta|6 Hebe}}
{{Small Solar System bodies}}
{{DEFAULTSORT:Astraea}}
[[Category:Asteroids]]
{{Infobox Planet | discovery=yes | physical_characteristics = yes | bgcolour=#FFFFC0 |
name=5 Astraea
| symbol=[[File:5 Astraea Symbol.svg|25px|Astronomical symbol for 5 Astraea]]
| discoverer=[[Karl Ludwig Hencke]]
| discovered=[[December 8]], [[1845]]
| alt_names=1969 SE
| mp_category=[[Main belt]]
| epoch=[[November 26]], [[2005]] ([[Julian day|JD]] 2453700.5)
| semimajor=384.945 [[Giga|G]][[metre|m]] (2.573 [[Astronomical unit|AU]])
| perihelion=310.688 Gm (2.077 AU)
| aphelion=459.202 Gm (3.070 AU)
| eccentricity=0.193
| period=1507.676 [[day|d]] (4.13 [[Julian year (astronomy)|a]])
| inclination=5.369[[degree (angle)|°]]
| asc_node=141.690°
| arg_peri=357.530°
| mean_anomaly=194.442°
| avg_speed=18.39 km/[[second|s]]
| dimensions=167×123×82 km<ref name=IRAS>[http://www.psi.edu/pds/archive/astdata04/simps04/diamalb.tab Supplemental IRAS Minor Planet Survey]</ref><ref name=Lopez-Gonzales>[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).</ref>
| mass=~2.4{{e|18}} [[kilogram|kg]]
| density=~2.7 g/[[cubic centimetre|cm³]]<ref name=Krasinsky>[[G. A. Krasinsky]] ''et al.'' ''Hidden Mass in the Asteroid Belt'', Icarus, Vol. 158, p. 98 (2002).</ref>
| surface_grav=~0.023 m/s²
| escape_velocity=~0.062 km/s
| rotation=0.700 03 d (16.801 h)<ref name=Lopez-Gonzales />
| spectral_type=[[S-type asteroid]]
| magnitude = 8.7 <!-- Horizons 2016-02-15 --> to 12.92
| abs_magnitude=6.85
| albedo=0.227 ([[geometric albedo|geometric]])<ref name=IRAS />
| angular_size = 0.15" <!-- Horizons 2016-Feb-15 --> to 0.041"
| single_temperature=~167 [[kelvin|K]] <br /> ''max:'' 263 K (-10 [[Celsius|°C]])}}
'''5 Astraea''' (written '''Astræa''' in the early literature) is a big [[Asteroid belt|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]]-[[silicate]]s. The adjectival form of the name, although unused, would be ''Astraean'' (which also designates a [[genus]] of [[star coral]]s).
[[File:Moon and Asteroids 1 to 10.svg|thumb|left|Size comparison: the first 10 asteroids profiled against Earth's [[Moon]]. Astrea is the fifth from the left.]]
Astraea was the fifth [[asteroid]] found, on [[December 8]], [[1845]] by [[Karl Ludwig Hencke|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.<ref>{{cite web|title=DAWN: A Journey to the Beginning of the Solar System|url=http://dawn.jpl.nasa.gov/DawnCommunity/flashbacks/fb_09.asp|publisher=NASA: Jet Propulsion Laboratory; California Institute of Technology|accessdate=20 July 2013}}</ref>
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.<ref name=Lopez-Gonzales /> This gives an [[axial tilt]] of about 33°.
Astrea is physically unremarkable but notable mainly because for 38 years (after the discovery of [[4 Vesta|Vesta]] in [[1807]]) it had been thought that there were only four asteroids. In terms of [[apparent magnitude|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 [[star|stellar]] [[occultation]] by Astraea ([[February 2]], [[1991]]).
== References ==
* {{cite web | last = Yeomans | first = Donald K. | url = http://ssd.jpl.nasa.gov/?horizons | title = Horizons system | publisher = NASA JPL | accessdate = 2007-03-20 }} — Horizons can be used to obtain a current ephemeris
{{reflist}}
== Other websites ==
* [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]
{{MinorPlanets Navigator|4 Vesta|6 Hebe}}
{{Small Solar System bodies}}
{{DEFAULTSORT:Astraea}}
[[Category:Asteroids]]