Discovery [1] | |
---|---|
Discovered by | K. L. Hencke |
Discovery site | Driesen Obs. |
Discovery date | 8 December 1845 |
Designations | |
(5) Astraea | |
Pronunciation | /æˈstriːə/ [2] |
Named after | Astraea (Greek goddess) [3] |
1969 SE | |
main-belt
[1]
[4] · (
middle) Astraea [5] | |
Adjectives | Astraean |
Symbol | (historical astronomical), (modern astrological) |
Orbital characteristics [4] | |
Epoch 23 March 2018 ( JD 2458200.5) | |
Uncertainty parameter 0 | |
Observation arc | 171.93 yr (62,799 d) |
Aphelion | 3.0659 AU |
Perihelion | 2.0810 AU |
2.5735 AU | |
Eccentricity | 0.1914 |
4.13 yr (1,508 d) | |
186.83 ° | |
0° 14m 19.32s / day | |
Inclination | 5.3677° |
141.58° | |
358.75° | |
Proper orbital elements [6] | |
Proper
semi-major axis | 2.5761849 AU |
Proper
eccentricity | 0.1980486 |
Proper
inclination | 4.5118628° |
Proper
mean motion | 87.046396 deg / yr |
Proper
orbital period | 4.13573
yr (1510.574 d) |
Precession of
perihelion | 52.210903 arcsec / yr |
Precession of the
ascending node | −57.357951 arcsec / yr |
Physical characteristics | |
Dimensions | 169 km × 125 km × 83 km [7] |
Mean diameter | 125 km [7] |
48 900 km2 [a] | |
Volume | 920 000 km3 [a] |
Mass | (2.716 ± 0.326/0.45)×1018 kg [8] |
Mean
density | 3.501 ± 0.420/0.581 g/cm3 [8] [b] |
0.700 04 d (16.801 h) [7] | |
Equatorial rotation velocity | 6.49 m/s [a] |
North pole
right ascension | 115°/310° ± 5° |
North pole
declination | 55° ± 5° |
0.227 [9] | |
S | |
8.74 to 12.89 | |
6.85 | |
0.15" to 0.041" | |
Astraea ( /æˈstriːə/) ( minor planet designation: 5 Astraea) is an asteroid in the asteroid belt. Its surface is highly reflective and its composition is probably a mixture of nickel– iron with silicates of magnesium and iron. It is an S-type asteroid in the Tholen classification system. [4]
Astraea was the fifth asteroid discovered, on 8 December 1845, by Karl Ludwig Hencke and named for Astraea, a Greek goddess of justice named after the stars. It was his first of two asteroid discoveries. The second was 6 Hebe. A German amateur astronomer and post office headmaster, Hencke was looking for 4 Vesta when he stumbled on Astraea. The King of Prussia awarded him an annual pension of 1200 marks for the discovery. [10]
Hencke's symbol for Astraea is an inverted anchor, in the pipeline for Unicode 17.0 as U+1F778 ( ), [11] [12] though given Astraea's role with justice and precision, it is perhaps a stylized set of scales, or a typographic substitute for one. [13] [14] This symbol is no longer used. The astrological symbol is a percent sign, encoded specifically at U+2BD9 ⯙. [15] The modern astronomical symbol is a simple encircled 5 (⑤).
For 38 years after the discovery of the fourth known asteroid, Vesta, in 1807, no further asteroids were discovered. [16] After the discovery of Astraea, 8 more were discovered in the following 5 years, and 24 were found in the 5 years after that. 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) [16] to their current status, as it became apparent that these four were only the largest of a new type of celestial body with thousands of members.
Photometry indicates prograde rotation, that the north pole points in the direction of right ascension 115° or 310° and declination 55°, with a 5° uncertainty. [7] This gives an axial tilt of about 33°.[ citation needed] With an apparent magnitude of 8.7 (on a favorable opposition on 15 February 2016), it is only the seventeenth-brightest main-belt asteroid, and fainter than, for example, 192 Nausikaa or even 324 Bamberga (at rare near-perihelion oppositions).
An stellar occultation on 6 June 2008 allowed Astraea's diameter to be estimated; it was found to be 115 ± 6 km. [17]
Der Planet hat mit Einwilligung des Entdeckers den Namen Astraea erhalten, und sein Zeichen wird nach dem Wunsche des Hr. Hencke ein umgekehrter Anker sein.
Discovery [1] | |
---|---|
Discovered by | K. L. Hencke |
Discovery site | Driesen Obs. |
Discovery date | 8 December 1845 |
Designations | |
(5) Astraea | |
Pronunciation | /æˈstriːə/ [2] |
Named after | Astraea (Greek goddess) [3] |
1969 SE | |
main-belt
[1]
[4] · (
middle) Astraea [5] | |
Adjectives | Astraean |
Symbol | (historical astronomical), (modern astrological) |
Orbital characteristics [4] | |
Epoch 23 March 2018 ( JD 2458200.5) | |
Uncertainty parameter 0 | |
Observation arc | 171.93 yr (62,799 d) |
Aphelion | 3.0659 AU |
Perihelion | 2.0810 AU |
2.5735 AU | |
Eccentricity | 0.1914 |
4.13 yr (1,508 d) | |
186.83 ° | |
0° 14m 19.32s / day | |
Inclination | 5.3677° |
141.58° | |
358.75° | |
Proper orbital elements [6] | |
Proper
semi-major axis | 2.5761849 AU |
Proper
eccentricity | 0.1980486 |
Proper
inclination | 4.5118628° |
Proper
mean motion | 87.046396 deg / yr |
Proper
orbital period | 4.13573
yr (1510.574 d) |
Precession of
perihelion | 52.210903 arcsec / yr |
Precession of the
ascending node | −57.357951 arcsec / yr |
Physical characteristics | |
Dimensions | 169 km × 125 km × 83 km [7] |
Mean diameter | 125 km [7] |
48 900 km2 [a] | |
Volume | 920 000 km3 [a] |
Mass | (2.716 ± 0.326/0.45)×1018 kg [8] |
Mean
density | 3.501 ± 0.420/0.581 g/cm3 [8] [b] |
0.700 04 d (16.801 h) [7] | |
Equatorial rotation velocity | 6.49 m/s [a] |
North pole
right ascension | 115°/310° ± 5° |
North pole
declination | 55° ± 5° |
0.227 [9] | |
S | |
8.74 to 12.89 | |
6.85 | |
0.15" to 0.041" | |
Astraea ( /æˈstriːə/) ( minor planet designation: 5 Astraea) is an asteroid in the asteroid belt. Its surface is highly reflective and its composition is probably a mixture of nickel– iron with silicates of magnesium and iron. It is an S-type asteroid in the Tholen classification system. [4]
Astraea was the fifth asteroid discovered, on 8 December 1845, by Karl Ludwig Hencke and named for Astraea, a Greek goddess of justice named after the stars. It was his first of two asteroid discoveries. The second was 6 Hebe. A German amateur astronomer and post office headmaster, Hencke was looking for 4 Vesta when he stumbled on Astraea. The King of Prussia awarded him an annual pension of 1200 marks for the discovery. [10]
Hencke's symbol for Astraea is an inverted anchor, in the pipeline for Unicode 17.0 as U+1F778 ( ), [11] [12] though given Astraea's role with justice and precision, it is perhaps a stylized set of scales, or a typographic substitute for one. [13] [14] This symbol is no longer used. The astrological symbol is a percent sign, encoded specifically at U+2BD9 ⯙. [15] The modern astronomical symbol is a simple encircled 5 (⑤).
For 38 years after the discovery of the fourth known asteroid, Vesta, in 1807, no further asteroids were discovered. [16] After the discovery of Astraea, 8 more were discovered in the following 5 years, and 24 were found in the 5 years after that. 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) [16] to their current status, as it became apparent that these four were only the largest of a new type of celestial body with thousands of members.
Photometry indicates prograde rotation, that the north pole points in the direction of right ascension 115° or 310° and declination 55°, with a 5° uncertainty. [7] This gives an axial tilt of about 33°.[ citation needed] With an apparent magnitude of 8.7 (on a favorable opposition on 15 February 2016), it is only the seventeenth-brightest main-belt asteroid, and fainter than, for example, 192 Nausikaa or even 324 Bamberga (at rare near-perihelion oppositions).
An stellar occultation on 6 June 2008 allowed Astraea's diameter to be estimated; it was found to be 115 ± 6 km. [17]
Der Planet hat mit Einwilligung des Entdeckers den Namen Astraea erhalten, und sein Zeichen wird nach dem Wunsche des Hr. Hencke ein umgekehrter Anker sein.