8 Flora

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8 Flora 8 Flora Astronomical Symbol.svg
8Flora (Lightcurve Inversion).png
A lightcurve-based 3D-model of Flora
Discovered byJ.R. Hind
Discovery date18 October 1847
MPC designation(8) Flora
Named after
Main belt (Flora family)
Orbital characteristics[1]
Epoch November 26, 2005 (JD 2453700.5)
Aphelion380.850 Gm (2.546 AU)
Perihelion277.995 Gm (1.858 AU)
329.422 Gm (2.202 AU)
1193.549 d (3.27 a)
Proper orbital elements[2]
2.2014283 AU
110.205216 deg / yr
3.26663 yr
(1193.138 d)
Precession of perihelion
32.016655 arcsec / yr
Precession of the ascending node
−35.510731 arcsec / yr
Physical characteristics
Dimensions136 km × 136 km × 113 km[3]
145 km × 145 km × 120 km[4]
Mean diameter
128 km[3]
Mass8.47×1018 kg[3]
4.3×1018 kg[5][6]
Mean density
3.13±1.43 g/cm3[3]
~3.3 g/cm³[7]
0.533 d (12.799 h)[1]
7.9[8] to 11.6
0.21" to 0.053"

Flora (minor planet designation: 8 Flora) is a large, bright main-belt asteroid. It is the innermost large asteroid: no asteroid closer to the Sun has a diameter above 25 kilometres or two-elevenths that of Flora itself, and not until the tiny 149 Medusa was discovered was a single asteroid orbiting at a closer mean distance known,[9] it is the seventh-brightest asteroid with a mean opposition magnitude of +8.7.[10] Flora can reach a magnitude of +7.9 at a favorable opposition near perihelion, such as occurred in November 2007. Flora may be the residual core of an intensely heated, thermally evolved, and magmatically differentiated planetesimal which was subsequently disrupted.[11]

Discovery and naming[edit]

Flora was discovered by J. R. Hind on October 18, 1847. It was his second asteroid discovery after 7 Iris.

The name Flora was proposed by John Herschel, from Flora, the Latin goddess of flowers and gardens, wife of Zephyrus (the personification of the West wind), and mother of Spring; the Greek equivalent is Chloris, who has her own asteroid, 410 Chloris, but in Greek Flora is also called Chloris (8 Χλωρίς).


The orbit of 8 Flora compared with the orbits of Earth, Mars and Jupiter

Lightcurve analysis indicates that Flora's pole points towards ecliptic coordinates (β, λ) = (16°, 160°) with a 10° uncertainty;[4] this gives an axial tilt of 78°, plus or minus ten degrees.

Flora is the parent body of the Flora family of asteroids, and by far the largest member, comprising about 80% of the total mass of this family. Nevertheless, Flora was almost certainly disrupted by the impact(s) that formed the family, and is probably a gravitational aggregate of most of the pieces.[citation needed]

Flora's spectrum indicates that its surface composition is a mixture of silicate rock (including pyroxene and olivine) and nickel-iron metal. Flora, and the whole Flora family generally, are good candidates for being the parent bodies of the L chondrite meteorites;[12] this meteorite type comprises about 38% of all meteorites impacting the Earth.

Observational mishap[edit]

During an observation on March 25, 1917, 8 Flora was mistaken for the 15th-magnitude star TU Leonis, which led to that star's classification as a U Geminorum cataclysmic variable star.[13] Flora had come to opposition on 1917 February 13, 40 days earlier;[13] this mistake was uncovered only in 1995.[13][14]


On July 26, 2013, Flora at magnitude 8.8 occulted the star 2UCAC 22807162 over parts of South America, Africa, and Asia.[15]

Popular culture[edit]

In the 1968 science-fiction film The Green Slime, an orbital perturbation propels the asteroid Flora into a collision course with Earth.

Size comparison: the first 10 asteroids profiled against Earth's Moon. Flora is third from the right.


  1. ^ a b c d e "JPL Small-Body Database Browser: 8 Flora". Retrieved 2008-11-27. 2008-04-14 last obs
  2. ^ "AstDyS-2 Flora Synthetic Proper Orbital Elements". Department of Mathematics, University of Pisa, Italy. Retrieved 2011-10-01.
  3. ^ a b c d Jim Baer (2008). "Recent Asteroid Mass Determinations". Personal Website. Archived from the original on 2013-07-02. Retrieved 2008-11-27.
  4. ^ a b Torppa, Johanna; Kaasalainen, Mikko; Michalowski, Tadeusz; Kwiatkowski, Tomasz; Kryszczynska, Agnieszka; Denchev, Peter; et al. (August 2003). "Shapes and rotational properties of thirty asteroids from photometric data". Icarus. 164 (2): 346–383. Bibcode:2003Icar..164..346T. doi:10.1016/S0019-1035(03)00146-5. Retrieved 1 June 2018.
  5. ^ Michalak, G. (August 2001). "Determination of asteroid masses. II. (6) Hebe, (10) Hygiea, (15) Eunomia, (52) Europa, (88) Thisbe, (444) Gyptis, (511) Davida and (704) Interamnia" (PDF). Astronomy and Astrophysics: 703–711. Bibcode:2001A&A...374..703M. doi:10.1051/0004-6361:20010731. Retrieved 1 June 2018.
  6. ^ Michalak2001 assumed masses of perturbing asteroids used in calculations of perturbations of the test asteroids.
  7. ^ Density (D=Mass/Volume=4.376/1.317=~3.3) calculated using JPL radius of 68km and the Michalak2001 assumed mass of 4.376E+18.
  8. ^ Donald H. Menzel & Jay M. Pasachoff (1983). A Field Guide to the Stars and Planets (2nd ed.). Boston, MA: Houghton Mifflin. p. 391. ISBN 0-395-34835-8.
  9. ^ Binsel, Richard P.; Gehrels, Tom and Matthews, Mildred Shapley (editors); Asteroids II; published 1989 by University of Arizona Press; pp. 1038-1040. ISBN 0-8165-1123-3
  10. ^ The Brightest Asteroids (archived)
  11. ^ Gaffey, Michael (1984). "Rotational spectral variations of asteroid (8) Flora: Implications for the nature of the S-type asteroids and for the parent bodies of the ordinary chondrites". Icarus. 60 (1): 83–114. Bibcode:1984Icar...60...83G. doi:10.1016/0019-1035(84)90140-4.
  12. ^ Nesvorný, D.; et al. (2002). "The Flora Family: A Case of the Dynamically Dispersed Collisional Swarm?". Icarus. 157 (1): 155. Bibcode:2002Icar..157..155N. doi:10.1006/icar.2002.6830.
  13. ^ a b c Schmadel, L. D.; Schmeer, P.; Börngen, F. (August 1996). "TU Leonis = (8) Flora: the non-existence of a U Geminorum star". Astron. Astrophys. 312: 496. Bibcode:1996A&A...312..496S.
  14. ^ "IAUC 6174".[permanent dead link]
  15. ^ Asteroid Occultation Index Page[permanent dead link]

External links[edit]