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99942 Apophis
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99942 Apophis
Discovery
Discovered by
Roy A. Tucker
David J. Tholen
Fabrizio Bernardi
Discovery site
Kitt Peak
Discovery date
19 June 2004
Designations
Apep
2004 MN4
Aten
NEO, PHA
Orbital characteristics
Epoch 7 December 2007 (JD 2454441.5)
Uncertainty parameter 0
Observation arc
3635 days (9.95 yr)
Aphelion
1.09851 AU (164.335 Gm)
Perihelion
0.74605 AU (111.607 Gm)
0.92228 AU (137.971 Gm)
Eccentricity
0.19108
0.89 yr (323.5 d)
30.728 km/s
215.53998°
1.11278°/day
Inclination
3.33129°
204.45719°
126.39364°
Earth MOID
0.000659446 AU (98,651.7 km)
Jupiter MOID
4.12656 AU (617.325 Gm)
Jupiter Tisserand parameter
6.467
Physical characteristics
Dimensions
325±15 m
0.1625 ± 0.0075 km
Mass
4×1010 kg (assumed)
~3.2 g/cm3
6996270000000000000?0.00027 m/s2 (average)
~0.52 km/h
30.4 h (1.27 d)
tumbling:
precession period:
27.38±0.07 h
rotation period:
263±6 h
period of harmonic with strongest lightcurve amplitude:
30.56±0.01 h
0.23
Temperature
270 K
Sq
19.7 ± 0.4
99942 Apophis (/?'p?f?s/, previously known by its provisional designation 2004 MN4) is a near-Earth asteroid that caused a brief period of concern in December 2004 because initial observations indicated a probability of up to 2.7% that it would hit Earth on April 13, 2029. Additional observations provided improved predictions that eliminated the possibility of an impact on Earth or the Moon in 2029. However, a possibility remained that during the 2029 close encounter with Earth, Apophis would pass through a gravitational keyhole, a small region no more than about 800 m (~0.5 mi) wide, that would set up a future impact exactly seven years later, on April 13, 2036. This possibility kept it at Level 1 on the Torino impact hazard scale until August 2006, when the probability that Apophis would pass through the keyhole was determined to be very small. During the short time when it had been of greatest concern, Apophis set the record for highest rating on the Torino scale, reaching level 4.The diameter of Apophis is, as of the most recent 2013 observations, approximately 325 metres (1,066 ft). Preliminary observations by Goldstone radar in January 2013 effectively ruled out the possibility of an Earth impact by Apophis in 2036. By May 6, 2013 (April 15, 2013 observation arc), the probability of an impact on April 13, 2036 had been eliminated. As of October 8, 2014, using observations through February 26, 2014, the odds of an impact on April 12, 2068, as calculated by the JPL Sentry risk table is (1 in 149,000). Of objects not recently observed, there are about ten asteroids with a more notable Palermo Technical Impact Hazard Scale than Apophis. On average, an asteroid the size of Apophis (325 meters) can be expected to impact Earth about every 80,000 years.
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^ Binzel, Richard P. (2007). "Can NEAs be Grouped by Their Common Physical Characteristics?" (PDF). Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology. aero.org. Archived from the original (PDF) on 2012-04-12.
^ assuming radius of 0.135 km and mass of 2.1e10 kg yields an escape velocity of 0.14 m/s or 0.52 km/h.
^ a b c Cite error: The named reference phys was invoked but never defined (see the help page).
^ a b c d Cite error: The named reference tumblingspinstate was invoked but never defined (see the help page).
^ Cite error: The named reference keyhole was invoked but never defined (see the help page).
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^ Cite error: The named reference risk-table was invoked but never defined (see the help page).
^ Cite error: The named reference Earth-impact was invoked but never defined (see the help page).
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Created By:
System
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