90 Antiope
Discovery [1] | |
---|---|
Synodic rotation period | 0.687 d (16.50 h)[6] (synchronous) |
0.060[7] | |
C[8] | |
8.27 (together)[2] 9.02 (each component) | |
Synodic rotation period | 0.687 d (16.50 h)[6] (synchronous) | |
9.02 | ||
Antiope (
Naming
The asteroid's proper name comes from
Since the discovery of Antiope's binary nature, the name "Antiope" technically refers to the slightly larger of the two components, with the smaller component bearing the
Properties
The most remarkable feature of Antiope is that it consists of two components of almost equal size (the difference in mass is less than 2.5%
Orbital
Antiope orbits in the outer third of the core region of the asteroid belt, and is a member of the Themis family.[13]
Since each component is about 86±1 km across, with their centers separated by only about 171 kilometers,[4] the gap separating the two halves is about the same as the diameter of each component. As a result, the two bodies orbit around the common center of mass which lies in the space between them. The orbital period is approximately 16.50 hours, and the eccentricity below 0.006.[4] Every several years, a period of mutual occultations occurs when the asteroid is viewed from Earth.[6] Using Kepler's third law, the mass and density of the components can be derived from the orbital period and component sizes.
The axis of the mutual orbit of the two components points towards ecliptic coordinates (β, λ) = (200°, 38°)[5] with 2 degrees uncertainty.[5] This is tilted about 63° to the circumsolar orbit of the system.
Physical
Antiope itself has an average diameter of about 88 km, while its twin, S/2000 (90) 1, has an average diameter of 84 km. Like most bodies in this region, the components of the Antiope system are of the dark C spectral type, indicating a carbonaceous composition. The low density (1.3±0.2 g/cm3) of its components (see below) suggests a significant porosity (>30%), indicating rubble-pile asteroids composed of debris that accumulated in the aftermath of a previous asteroid collision, possibly the one that formed the Themis family.[citation needed]
Complementary observations using
Observations from the
The two parts of the Antiope have very similar spectra. This implies they may have a common origin, such as being formed from the breakup of a larger rubble-pile asteroid, but other formation scenarios cannot be ruled out.[16]
Occultations
There have been 9 occultations observed since 1988,[17] many of which are multichord occultations.
The best is the July 19, 2011 event observed from 57 stations spread out along the western USA coast where 46 stations recorded positive occultations and 11 stations observed misses. However many of the misses were important to clearly separate the two components of 90 Antiope. Many planned stations were unfortunately clouded. Many stations were so-called Mighty-Mini or Mighty-Maxi, consisting of a binocular objective (homemade using binoculars + hacksaw + plumbing fittings) with a video camera and Video Time Inserter (VTI), and were pre-pointed and left to run unattended, thereby allowing one observer to deploy many stations.
The crater mentioned above was confirmed by this occultation.[18][19]
References
- ^ Noah Webster (1884) A Practical Dictionary of the English Language
- ^ a b c d e "JPL Small-Body Database Browser: 90 Antiope" (2010-06-13 last obs). Archived from the original on 21 December 2015. Retrieved 8 July 2010.
- ^ a b c d Wm. Robert Johnston (23 November 2008). "(90) Antiope and S/2000 (90) 1". Johnston's Archive. Retrieved 23 January 2008.
- ^ a b c d 90 Antiope A & B Archived 2008-08-28 at the Wayback Machine, online data sheet, F. Marchis
- ^ a b c d Descamps et al., 2007, Icarus article published in April 2007
- ^ .
- ^ Supplemental IRAS Minor Planet Survey Archived 2009-08-17 at the Wayback Machine
- ^ PDS spectral class data Archived 2009-08-05 at the Wayback Machine
- ^ a b IAUC 7503
- ^ "90 Antiope: Raw Keck Image". SWrI Press Release. August 2000. Retrieved 20 October 2009.
- ISBN 9781139495226.
- Bibcode:2004DPS....36.4602M.
- .
- Bibcode:2009DPS....41.5610M.
- S2CID 119300811.
- S2CID 119279769.
- ^ "Asteroid Data Sets". sbn.psi.edu. Retrieved 28 April 2018.
- ^ Antiope Occultation Yields Double Bonanza Archived 12 November 2013 at the Wayback Machine. Sky & Telescope
- ^ Franck Marchis (21 July 2011). "An Occultation by the double asteroid (90) Antiope seen in California". NASA blog (Cosmic Diary). Retrieved 28 January 2012.
External links
- Discovery of Companions to Asteroids 762 Pulcova and 90 Antiope SWrI Press Release.
- (90) Antiope, datasheet, johnstonsarchive.net
- Asteroids with Satellites, Robert Johnston, johnstonsarchive.net
- online data on the Antiope system maintained by F. Marchis; includes images and simulated occultation movies.
- ESO Press-Release published on May 29, 2007 The Impossible Siblings
- UC-Berkeley Press-Release published on May 29, 2007 Binary asteroid revealed as twin rubble piles
- Antiope, a true binary asteroid, The Planetary Societyweblog, E. Lakdawalla, 11 April 2007.
- An Occultation by the double asteroid (90) Antiope seen in California (Franck Marchis)
- Beatty, Kelly (9 September 2011). "Antiope Occultation Yields Double Bonanza". Sky and Telescope. Archived from the original on 12 November 2013. Retrieved 13 September 2011.
- 90 Antiope at AstDyS-2, Asteroids—Dynamic Site
- 90 Antiope at the JPL Small-Body Database