8 Flora

8 Flora  

Discovery
Discovered by	J.R. Hind
Discovery date	October 18, 1847
Designations
Named after	Flora
Alternate name(s)	none
Minor planet category	Main belt (Flora family)
Adjective	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)
Semi-major axis	329.422 Gm (2.202 AU)
Eccentricity	0.1561
Orbital period	1193.549 d (3.27 a)
Average orbital speed	19.95 km/s
Mean anomaly	156.401°
Inclination	5.886°
Longitude of ascending node	111.011°
Argument of perihelion	285.128°
Proper orbital elements[4]
Proper semi-major axis	2.2014283 AU
Proper eccentricity	0.1448717
Proper inclination	5.5736218°
Proper mean motion	110.205216 deg/yr
Proper orbital period	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[2] 128 km (mean) 145×145×120 km[3]
Mass	8.47×1018 kg[2] 4.3×1018 kg[5][6]
Mean density	3.13±1.43 g/cm³[2] ~3.3 g/cm³[7]
Equatorial surface gravity	~0.045 m/s²
Escape velocity	~0.081 km/s
Rotation period	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]
Apparent magnitude	7.9[8] to 11.6
Absolute magnitude (H)	6.49[1]
Angular diameter	0.21" to 0.053"

8 Flora ( /ˈflɔrə/; Latin: Flōra) 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.

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.^[3] 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.

Notable 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]

In the film The Green Slime, the asteroid Flora falls out of orbit and is on a collision course with Earth.

References

1. ^ ^{a b c d e} "JPL Small-Body Database Browser: 8 Flora". 2008-04-14 last obs. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=8. Retrieved 2008-11-27. 
2. ^ ^{a b c} Jim Baer (2008). "Recent Asteroid Mass Determinations". Personal Website. http://home.earthlink.net/~jimbaer1/astmass.txt. Retrieved 2008-11-27. 
3. ^ ^{a b} Torppa, J.; et al. (2003). "Shapes and rotational properties of thirty asteroids from photometric data" (PDF). Icarus 164 (2): 346. Bibcode 2003Icar..164..346T. doi:10.1016/S0019-1035(03)00146-5. http://www.rni.helsinki.fi/~mjk/thirty.pdf. 
4. ^ "AstDyS-2 Flora Synthetic Proper Orbital Elements". Department of Mathematics, University of Pisa, Italy. http://hamilton.dm.unipi.it/astdys/index.php?pc=1.1.6&n=8. Retrieved 2011-10-01. 
5. ^ Michalak, G. (2001). "Determination of asteroid masses". Astronomy & Astrophysics 374 (2): 703–711. Bibcode 2001A&A...374..703M. doi:10.1051/0004-6361:20010731. http://www.aanda.org/index.php?option=article&access=standard&Itemid=129&url=/articles/aa/abs/2001/29/aa10228/aa10228.html. Retrieved 2008-11-10. 
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 and Jay M. Pasachoff (1983). A Field Guide to the Stars and Planets (2nd ed.). Boston, MA: Houghton Mifflin. pp. 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
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". http://cfa-www.harvard.edu/iauc/06100/06174.html#Item1. 

External links

• shape model deduced from lightcurve
• "Announcement of discovery of Flora", MNRAS 8 (1848) 82
• Orbital simulation from JPL (Java)
• 8 Flora at opposition Nov 15th, 2007 (0.89AU from Earth)
• Yeomans, Donald K.. "Horizons system". NASA JPL. Archived from the original on 28 March 2007. http://ssd.jpl.nasa.gov/?horizons. Retrieved 2007-03-20.  — Horizons can be used to obtain a current ephemeris.