(3122) Florence

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Asteroid
(3122) Florence
3122 Florence with moons.jpg
Properties of the orbit ( animation )
Epoch:  4th September 2017 ( JD 2,458,000.5)
Orbit type Cupid type
Major semi-axis 1.7691  AU
eccentricity 0.4233
Perihelion - aphelion 1.0203 AU - 2.5180 AU
Inclination of the orbit plane 22.1508 °
Length of the ascending node 336.0951 °
Argument of the periapsis 27.8470 °
Sidereal period 2,352 a
Mean orbital velocity 22.40 km / s
Physical Properties
Medium diameter 4.5 km
Dimensions ? Template: Infobox asteroid / maintenance / masskg
Albedo 0.20
Medium density ? g / cm³
Rotation period 2.3581 h
Absolute brightness 14.1 mag
Spectral class S.
history
Explorer SJ bus
Date of discovery March 2, 1981
Another name 1981 ET 3 , 1983 CN 1
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . The affiliation to an asteroid family is automatically determined from the AstDyS-2 database . Please also note the note on asteroid items.

(3122) Florence is a near-Earth asteroid from the Amor type that on 2 March 1981 by scolding John Bus at Siding Spring Observatory ( IAU code 413) in Australia was discovered.

The asteroid is named after the English social reformer Florence Nightingale (1820–1910).

Among the asteroids classified as potentially dangerous by NASA, Florence is the fourth largest with a diameter of 4.5 km, according to (53319) 1999 JM 8 (~ 7 km), (4183) Cuno (5.6 km) and (3200) Phaethon (5.1 km).

The earth comes close to the asteroid's orbit, which is stable for the foreseeable future, at the end of August / beginning of September, except for just under 0.047  AU (18 times the lunar distance). There were or will be fly-bys at almost this distance in 1930, 2017 and 2057, with the apparent brightness reaching 8.5 m . In the 87 and 40 earth years in between, the asteroid makes 37 and 17 orbits around the sun. The ratio of the orbital times is also very accurate at 73:31.

Until the flyby in 2017, the rotation period of 2.358 days was known, from fluctuations in brightness with an amplitude of 0.18 magnitude classes, and an estimate for the diameter of 4.35 km from the comparison of backscattered sunlight and thermal emission. The spectral class was uncertain, S or SQ.

Delay Doppler image of (3122) Florence and its two moons. The resolution is about 15 m in the delay (increasing from top to bottom) and 5 Hz in the Doppler frequency (increasing from right to left). For the rigid, rotating asteroid, the Doppler frequency actually corresponds to a spatial coordinate (transverse to the viewing direction and transverse to the axis of rotation), but the moons orbiting with larger periods appear too close to the axis of rotation.

During the flyby, Florence was observed intensively with the radars of the Arecibo Observatory and the Goldstone Deep Space Communications Complex . The duration and spectral bandwidth of the radar echo consistently indicate a diameter of 4.5 km, marginally larger than previously estimated. This means that material at the equator almost floats due to the rotation. The joint evaluation of transit times and Doppler shifts provides images (left as animation) that reveal an equatorial bulge and some crater-like depressions. It was also found that Florence has two moons, an outer one a good 300 m in diameter and an inner one about 200 m. Their orbits and periods of rotation (about 22 or almost 8 hours) provide the mass of the asteroid and thus the density. It is 1.4 g / cm 3 , which indicates considerable porosity. The spectrum of the asteroid in the visible and near IR range is very similar to that of the material found by the Chelyabinsk meteor , spectral class S, typical of common chondrites .

See also

Individual evidence

  1. ↑ Goldstone and Arecibo radar, August / September 2017.
  2. ↑ JPL Small-Body Database Browser: Close-Approach Data .
  3. ↑ WZWisniewski et al .: Photometric Observations of Asteroids 125 . Icarus 126, 1997, doi: 10.1006 / icar.1996.5665 .
  4. ↑ Asteroid Lightcurve Database (LCDB): (3122) Florence (based on WISE data from 2010/2011).
  5. ^ Lance Benner, Paul Chodas and Patrick Taylor: Telescopes Worldwide Collaborate to Observe Asteroid Florence During its Recent Close Approach to Earth . CNEOS ( JPL ), September 11, 2017.

Web links

Commons : (3122) Florence  - Collection of images, videos and audio files