Astronomy:8 Flora

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Short description: Large main-belt asteroid
8 Flora Flora symbol (bold).svg (historical)
8 Flora VLT (2021), deconvolved.pdf
Discovery
Discovered byJ.R. Hind
Discovery date18 October 1847
Designations
(8) Flora
Pronunciation/ˈflɔːrə/
Named afterFlōra
Minor planet categoryMain belt (Flora family)
AdjectivesFlorian /ˈflɔːriən/
Orbital characteristics[1]
Epoch 13 September 2023
(JD 2453300.5)
|{{{apsis}}}|helion}}2.55 astronomical unit|AU (381 million km)
|{{{apsis}}}|helion}}1.86 AU (278 million km)
2.20 AU (329 million km)
Eccentricity0.15650
Orbital period3.27 yr (1192.84 d)
Mean anomaly317.3°
Inclination5.889°
Longitude of ascending node110.87°
|{{{apsis}}}|helion}}1 February 2024
285.6°
Earth MOID0.87 AU (130 million km)
Proper orbital elements[2]
Proper semi-major axis2.2014 AU
Proper eccentricity0.1449
Proper inclination5.574°
Proper mean motion110.2 deg / yr
3.26679 yr
(1193.194 d)
Precession of perihelion32.017 arcsec / yr
Precession of the ascending node−35.51 arcsec / yr
Physical characteristics
Dimensionsc/a = 0.82±0.05[3]
136 km × 136 km × 113 km[4]
145 km × 145 km × 120 km[5]
Mean diameter146±2 km[3]
128 km[4]
Mass(4±1.6)×1018 kg[3]
(6.62±0.84)×1018 kg[lower-alpha 1][6]
Mean density2.4±1.0 g/cm3[3]
3.04±1.39 g/cm3[6]
Rotation period0.533 d (12.799 h)[1]
Geometric albedo0.224 (calculated)[3]
0.243[1]
S[1]
Apparent magnitude7.9[7] to 11.6
Absolute magnitude (H)6.49[1]
Angular diameter0.21" 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 (20% that of Flora), and not until 20-km 149 Medusa was discovered was an asteroid known to orbit at a closer mean distance.[8] It is the seventh-brightest asteroid with a mean opposition magnitude of +8.7.[9] Flora can reach a magnitude of +8.1 at a favorable opposition near perihelion, such as occurred in November 2020 when it was 0.88 astronomical unit|AU (132 million km; 340 LD) from Earth.[10]

Discovery and naming

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

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 8 Flora is also called 8 Chloris (8 Χλωρίς).[citation needed] The old iconic symbol for 8 Flora has been variously rendered as Flora symbol (fixed width).svg, 24px, etc. It is in the pipeline for Unicode 17.0 as U+1CEC2 𜻂 (Flora symbol (fixed width).svg).[11][12]

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.[5] 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.[13] This meteorite type comprises 35% of meteorites impacting the Earth.[14]

Observational mishap

During an observation on 25 March 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.[15] Flora had come to opposition on 1917 February 13, 40 days earlier.[15] This mistake was uncovered only in 1995.[15][16]

Occultation

On 26 July 2013, Flora at magnitude 8.8 occulted the star 2UCAC 22807162 over parts of South America, Africa, and Asia.[17]

Popular culture

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.

Notes

  1. ↑ 3.33 ± 0.42) × 10−12 M☉

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 "JPL Small-Body Database Browser: 8 Flora". http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=8. "2023-08-08 last obs" 
  2. ↑ "AstDyS-2 Flora Synthetic Proper Orbital Elements". Department of Mathematics, University of Pisa, Italy. https://newton.spacedys.com/astdys/index.php?pc=1.1.6&n=8. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56
  4. ↑ 4.0 4.1 Jim Baer (2008). "Recent Asteroid Mass Determinations". Personal Website. http://home.earthlink.net/~jimbaer1/astmass.txt. 
  5. ↑ 5.0 5.1 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. doi:10.1016/S0019-1035(03)00146-5. Bibcode: 2003Icar..164..346T. 
  6. ↑ 6.0 6.1 James Baer, Steven Chesley & Robert Matson (2011) "Astrometric masses of 26 asteroids and observations on asteroid porosity." The Astronomical Journal, Volume 141, Number 5
  7. ↑ Donald H. Menzel; 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. https://archive.org/details/fieldguidetostar00menz_0/page/391. 
  8. ↑ 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
  9. ↑ The Brightest Asteroids (archived)
  10. ↑ "Horizons Batch for November 2020". JPL Horizons. https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Flora%27&START_TIME=%272020-10-31%27&STOP_TIME=%272020-11-02%27&STEP_SIZE=%271%20day%27&QUANTITIES=%279,19,20,23,29,39%27. Retrieved 2022-11-17. 
  11. ↑ Bala, Gavin Jared; Miller, Kirk (18 September 2023). "Unicode request for historical asteroid symbols". Unicode. https://www.unicode.org/L2/L2023/23207-historical-asteroids.pdf. 
  12. ↑ Unicode. "Proposed New Characters: The Pipeline". The Unicode Consortium. https://unicode.org/alloc/Pipeline.html. 
  13. ↑ Nesvorný, D. (2002). "The Flora Family: A Case of the Dynamically Dispersed Collisional Swarm?". Icarus 157 (1): 155–172. doi:10.1006/icar.2002.6830. Bibcode: 2002Icar..157..155N. 
  14. ↑ Grady, Monica (2022). "Meteorites". The Catalogue of Meteorites. Natural History Museum. doi:10.5519/tqfuwle7. https://www.nhm.ac.uk/our-science/data/metcat/search/metsPerGroup.dsml. Retrieved 28 May 2020. 
  15. ↑ 15.0 15.1 15.2 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. 
  16. ↑ "IAUC 6174". http://cfa-www.harvard.edu/iauc/06100/06174.html#Item1. [yes|permanent dead link|dead link}}]
  17. ↑ Asteroid Occultation Index Page

External links



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