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2015 TB145
2015 TB145 discovery.gif
Discovery image of 2015 TB145 from the Pan-STARRS1 telescope, operated by the Institute for Astronomy at the University of Hawaii
Discovery[1]
Discovered by Pan-STARRS (F51)
Discovery date 10 October 2015
Designations
MPC designation 2015 TB145
Apollo Apollo
NEO, PHA,
Mercury-crosser asteroid,
Venus-crosser asteroid,
Mars-crosser asteroid[2]
Orbital characteristics[2]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 2
Observation arc 22 days
Aphelion 3.9076 AU (584.57 Gm) (Q)
Perihelion 0.29345 AU (43.899 Gm) (q)
2.1005 AU (314.23 Gm) (a)
Eccentricity 0.86030 (e)
3.04 yr (1112.0 d)
10.4818° (M)
0° 19m 25.5s / day (n)
Inclination 39.6863° (i)
37.7318° (Ω)
121.731° (ω)
Earth MOID 0.00155156 AU (232,110 km)
Jupiter MOID 2.41379 AU (361.098 Gm)
Jupiter Tisserand parameter 2.964
Physical characteristics
Dimensions 600 m (2,000 ft)[3][4]
5 hours,[4] 2.938 h (0.1224 d)[2]
0.06[4]
20.0[2][5]

2015 TB145 (also written 2015 TB145) is an Apollo near-Earth asteroid roughly 600 meters (2,000 feet) in diameter. It safely passed 1.27 lunar distances from Earth on 31 October 2015 at 17:01 UTC.[6]

The asteroid was first observed on 10 October 2015 by Pan-STARRS at an apparent magnitude of 20 using a 1.8-meter (71 in) Ritchey–Chrétien telescope.[1][5][a] The asteroid was not discovered sooner because it spends most of its time beyond the orbit of Mars, has a large orbital inclination, and spends most of its time well below the plane of the ecliptic.[8] The asteroid last passed within 0.064 AU (9,600,000 km; 5,900,000 mi) of Earth on 29 October 1923 and will not pass that close again until 1 November 2088.[6] The 2015 flyby was its closest approach to Earth in at least the next 500 years.

The media has nicknamed the asteroid the "Great Pumpkin"[9] after the animated Halloween television special It's the Great Pumpkin, Charlie Brown,[10] "Spooky",[11][12] the “Halloween Asteroid”,[13][14][15] and the “Skull Asteroid”[10] due to its human skull-like appearance following radio frequency images taken at Arecibo Observatory.[10]

Contents

2015 flybyEdit

On 31 October 2015 the asteroid passed 0.00191 AU (286,000 km; 178,000 mi) from the Moon and then passed 0.00325 AU (486,000 km; 302,000 mi) from Earth.[6]

The last approach this close by an object (with absolute magnitude < 20) was 2004 XP14 on 3 July 2006 at 1.1 lunar distances. The next object this large known to pass this close to Earth is (137108) 1999 AN10 that will pass about 1 lunar distance from Earth on 7 August 2027.[16] It is estimated that there are about 2400 near-Earth asteroids 300–500 meters in diameter, of which about 1100 have been discovered.[17]

During closest approach to Earth the asteroid reached about apparent magnitude 10,[18] which is much too faint to be seen by the naked eye. Even at peak brightness, the asteroid was a challenging target for amateur astronomers with small telescopes, best seen in the Northern hemisphere. The glare from an 80% waning gibbous Moon also hindered observations.

At 11:00 UT the asteroid was in the constellation of Taurus about 9 degrees from the Moon and moving at a rate of 3.4 degrees per hour.[18] At the time of closest approach of 17:00 UT the asteroid was in the constellation of Ursa Major about 56 degrees from the Moon and moving at a rate of 14.7 degrees per hour.[18] After closest approach it quickly became too faint and too close to the Sun in the sky to be seen.[16]

Radar imageryEdit

The close approach was studied with radar using Goldstone, the Green Bank Telescope,[16] and the Arecibo Observatory. It was one of the best radar targets of the year with a resolution as high as 2 meters (7 ft) per pixel.[16] Bistatic radar images created with the Green Bank Telescope had a resolution of 4 meters (13 ft) per pixel.[19] Arecibo images had a resolution of 7.5 meters (25 ft) per pixel.[4]

October 30 October 31
12:55 - 13:08 UTC
November 1 Goldstone radar image of 2015 TB145
   

Possible cometary originEdit

The high orbital inclination and eccentricity suggest 2015 TB145 may be an extinct comet that has shed its volatiles after numerous passes around the Sun.[4][20] Orbital calculations by Petrus Jenniskens and Jérémie Vaubaillon show that it is not expected to produce associated meteors in 2015.[21] Meteoroids should pass more than 0.0007 AU (100,000 km; 65,000 mi) from Earth's orbit.[21] If meteoroids do cross Earth's path, the radiant should be Northern Eridanus.[21] Cameras for Allsky Meteor Surveillance (CAMS) did not detect any activity in the presumed area of the sky during 2013 and 2014.[21] The object has a low albedo of 0.06, which is only slightly more than a typical comet that has an albedo of 0.03-0.05.[4]

NotesEdit

  1. ^ For comparison, around 6 October 2012 the asteroid peaked at about apparent magnitude 20.9, but had a solar elongation of only about 75 degrees while 0.4AU from Earth.[7]

ReferencesEdit

  1. ^ a b "MPEC 2015-T86 : 2015 TB145". IAU Minor Planet Center. 2015-10-13. Retrieved 2015-10-14.  (K15TE5B)
  2. ^ a b c d "JPL Small-Body Database Browser: (2015 TB145)" (last observation: 2015-10-27; arc: 17 days). Jet Propulsion Laboratory. Retrieved 4 April 2016. 
  3. ^ "Absolute Magnitude (H)". NASA/JPL. Retrieved 2015-10-14. 
  4. ^ a b c d e f Halloween Skies to Include Dead Comet Flyby. NASA-JPL press release. October 30, 2015
  5. ^ a b "2015 TB145 Orbit". IAU Minor Planet Center. Retrieved 2016-01-24. 
  6. ^ a b c "JPL Close-Approach Data: (2015 TB145)" (last observation: 2015-10-27; arc: 17 days). Retrieved 2015-10-22. 
  7. ^ "2015TB145 Ephemerides for October 2012". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 2015-10-24. 
  8. ^ Kelly Beatty (2015-10-22). "Close-in Asteroid Offers Halloween Treat". Sky & Telescope. Retrieved 2015-10-26. 
  9. ^ Sarah Begley (30 October 2015). "NASA Says 'Great Pumpkin' Asteroid Will Fly by on Halloween". TIME Magazine. 
  10. ^ a b c Nick Divito (31 October 2015). "Spooky 'skull asteroid' whizzes past Earth on Halloween". New York Post. 
  11. ^ Andrew Fazekas (23 October 2015). "Asteroid Called 'Spooky' Will Buzz Earth on Halloween". National Geographic Society. 
  12. ^ RT (31 October 2015). "'Spooky' asteroid to fly by Earth on Halloween". RT (Russia Today). 
  13. ^ Charles Poladian (20 October 2015). "Halloween Asteroid 2015 TB145 Hurtling Toward Earth At 80,000 MPH: Doomsday Threat?". International Business Times. 
  14. ^ Morina Koren (31 October 2015). "A Halloween Comet". The Atlantic. 
  15. ^ ESA (28 October 2015). "Halloween Asteroid Gives us a Miss, Confirms ESA". European Space Agency. 
  16. ^ a b c d Dr. Lance A. M. Benner (24 October 2015). "Goldstone Radar Observations Planning: 2009 FD and 2015 TB145". NASA/JPL Asteroid Radar Research. Retrieved 2015-10-24. 
  17. ^ "WISE Revises Numbers of Asteroids Near Earth". NASA/JPL. 2011-09-29. Retrieved 2015-10-29.  (NASA Space Telescope Finds Fewer Asteroids Near Earth)
  18. ^ a b c "2015TB145 Ephemerides for 15 October 2015 through 31 October 2015". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 2015-10-14. 
  19. ^ "PIA20043: Halloween Asteroid Rotation". NASA/JPL-Caltech/GSSR/NRAO/GB. 2015-11-03. Retrieved 2015-11-04. 
  20. ^ Agle, D. C. (21 October 2015). "NASA Spots the 'Great Pumpkin': Halloween Asteroid a Treat for Radar Astronomers". NASA News. Retrieved 2015-10-26. 
  21. ^ a b c d "Possible October 31 Meteors From Minor Planet 2015 TB_145". SETI Institute. 2015-10-26. Retrieved 2015-10-26.  (CBET 4154)

External linksEdit