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8 Flora

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8 Flora

8 Flora
A three-dimensional model of 8 Flora based on its light curve.
Discovery
Discovered by J.R. Hind
Discovery date October 18, 1847
Designations
Pronunciation
Named after
Flōra
none
Main belt (Flora family)
Adjectives Florian
Orbital characteristics[1]
Epoch November 26, 2005 (JD 2453700.5)
Aphelion 380.850 Gm (2.546 AU)
Perihelion 277.995 Gm (1.858 AU)
329.422 Gm (2.202 AU)
Eccentricity 0.1561
1193.549 d (3.27 a)
Average orbital speed
19.95 km/s
156.401°
Inclination 5.886°
111.011°
285.128°
Proper orbital elements[2]
2.2014283 AU
Proper eccentricity
0.1448717
Proper inclination
5.5736218°
Proper mean motion
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
Dimensions 136×136×113 km[3]
128 km (mean)
145×145×120 km[4]
Mass 8.47×1018 kg[3]
4.3×1018 kg[5][6]
Mean density
3.13±1.43 g/cm³[3]
~3.3 g/cm³[7]
~0.045 m/s²
~0.081 km/s
0.533 d (12.799 h)[1]
Albedo 0.243 (geometric)[1]
Temperature ~180 K
max: 276 K (+3 °C)
Spectral type
S-type asteroid[1]
7.9[8] to 11.6
6.49[1]
0.21" to 0.053"

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]

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

Contents

  • Discovery and naming 1
  • Characteristics 2
  • Facts 3
  • Occultation 4
  • Popular Culture 5
  • References 6
  • External links 7

Discovery and naming

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).

Characteristics

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.

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.

Facts

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]

Occultation

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

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

References

  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 Jim Baer (2008). "Recent Asteroid Mass Determinations". Personal Website. Retrieved 2008-11-27. 
  4. ^ a b Torppa, J.; et al. (2003). "Shapes and rotational properties of thirty asteroids from photometric data" (PDF). Icarus 164 (2): 346.  
  5. ^ Michalak, G. (2001). "Determination of asteroid masses". Astronomy & Astrophysics 374 (2): 703–711.  
  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.  
  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.  
  12. ^ Nesvorný, D.; et al. (2002). "The Flora Family: A Case of the Dynamically Dispersed Collisional Swarm?". Icarus 157 (1): 155.  
  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.  
  14. ^ "IAUC 6174". 
  15. ^ Asteroid Occultation Index Page

External links

  • shape model deduced from lightcurve
  • (1848) 828"Announcement of discovery of Flora", MNRAS
  • JPL Ephemeris
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