2015 TB145

2015 TB145 is a sub-kilometer asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 650 meters (2,000 feet) in diameter.[3] It safely passed 1.27 lunar distances from Earth on 31 October 2015 at 17:01 UTC,[7] and passed by Earth again in November 2018.

2015 TB145
Radar image of 2015 TB145 taken by the Arecibo Observatory on 30 October 2015
Discovery[1]
Discovered byPan-STARRS
Discovery date10 October 2015
Designations
2015 TB145
Orbital characteristics[2]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 0
Observation arc3.11 yr (1,137 d)
Aphelion3.9073 AU
Perihelion0.2941 AU
2.1007 AU
Eccentricity0.86002
3.04 yr (1,112.1 d)
121.744°
0° 19m 25.364s / day
Inclination39.6899°
37.698°
121.744°
Earth MOID0.00295731 AU (442,407 km)
Jupiter MOID2.41052 AU
TJupiter2.97
Physical characteristics
Dimensions
0.06[5]
20.0[2][6]

    Discovery
    Discovery image of 2015 TB145 from the Pan-STARRS1 telescope, operated by the Institute for Astronomy at the University of Hawaii

    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][6][lower-alpha 1] The asteroid was not discovered sooner because it spends most of its time beyond the orbit of Mars, has a large orbital inclination, and is usually well below the plane of the ecliptic.[9] 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.[7]

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

    2015 flyby
    2015 TB145 passed 1.27 LD from the earth, and 0.75 LD from the moon.

    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.[7]

    The last approach this close by an object with absolute magnitude brighter than 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]

    History of close approaches of large near-Earth objects since 1908 (A)
    PHA Date Approach distance in lunar distances Abs. mag
    (H)    		 Diameter (C)
    (m)    		 Ref (D)
    Nominal(B) Minimum Maximum
    (152680) 1998 KJ91914-12-310.6060.6040.60819.4279–900data
    (458732) 2011 MD51918-09-170.9110.9090.91317.9556–1795data
    (163132) 2002 CU111925-08-300.9030.9010.90518.5443–477data
    69230 Hermes1937-10-301.9261.9261.92717.5700-900[19]data
    69230 Hermes1942-04-261.6511.6511.65117.5700-900[19]data
    (27002) 1998 DV91975-01-311.7621.7611.76218.1507–1637data
    2002 NY402002-08-181.3711.3711.37119.0335–1082data
    2004 XP142006-07-031.1251.1251.12519.3292–942data
    2015 TB1452015-10-311.2661.2661.26620.0620-690data
    (137108) 1999 AN102027-08-071.0141.0101.01917.9556–1793data
    (153814) 2001 WN52028-06-260.6470.6470.64718.2921–943data
    99942 Apophis2029-04-130.09810.09630.100019.7310–340data
    2017 MB12072-07-261.2161.2152.75918.8367–1186data
    2011 SM682072-10-171.8751.8651.88619.6254–820data
    (163132) 2002 CU112080-08-311.6551.6541.65618.5443–477data
    (416801) 1998 MZ2116-11-261.0681.0681.06919.2305–986data
    (153201) 2000 WO1072140-12-010.6340.6310.63719.3427–593data
    (276033) 2002 AJ1292172-02-081.7831.7751.79218.7385–1242data
    (290772) 2005 VC2198-05-051.9511.7912.13417.6638–2061data
    (A) This list includes near-Earth approaches of less than 2 lunar distances (LD) of objects with H brighter than 20.
    (B) Nominal geocentric distance from the center of Earth to the center of the object (Earth has a radius of approximately 6,400 km).
    (C) Diameter: estimated, theoretical mean-diameter based on H and albedo range between X and Y.
    (D) Reference: data source from the JPL SBDB, with AU converted into LD (1 AU≈390 LD)
    (E) Color codes:   unobserved at close approach   observed during close approach   upcoming approaches

    2018 flyby
    Orbit of 2015 TB145

    After it had been unobservable for almost three years, 2015 TB145 was recovered on 7 October 2018 by L. Buzzi at Schiaparelli Observatory (observatory code 204), at apparent magnitude 21.[20]

    The 11 November 2018 flyby was about 0.267 AU (39,900,000 km; 24,800,000 mi) from Earth.[7][21]

    Observations

    Radar imagery

    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.[22] Arecibo images had a resolution of 7.5 meters (25 ft) per pixel.[5]

    30 October 31 October
    12:55–13:08 UTC    		 1 November

    Possible cometary origin

    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.[5][23] Orbital calculations by Petrus Jenniskens and Jérémie Vaubaillon showed that it was not expected to produce associated meteors in 2015.[24] Any meteoroids were expected to pass more than 0.0007 AU (100,000 km; 65,000 mi) from Earth's orbit.[24] If meteoroids related to this asteroid were to cross Earth's path, the radiant is expected to be near Northern Eridanus.[24] Cameras for Allsky Meteor Surveillance (CAMS) did not detect any activity in the presumed area of the sky during 2013 and 2014.[24] 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.[5]

    Notes
    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 0.4 AU from Earth.[8]

    References
    1. "MPEC 2015-T86 : 2015 TB145". IAU Minor Planet Center. 13 October 2015. Retrieved 14 October 2015. (K15TE5B)
    2. "JPL Small-Body Database Browser: (2015 TB145)" (2018-11-20 last obs.). Jet Propulsion Laboratory. Retrieved 1 March 2020.
    3. Müller, T. G.; Marciniak, A.; Butkiewicz-Bąk, M.; Duffard, R.; Oszkiewicz, D.; Käufl, H. U.; Szakáts, R.; Santana-Ros, T.; Kiss, C.; Santos-Sanz, P. (February 2017). "Large Halloween asteroid at lunar distance" (PDF). Astronomy & Astrophysics. 598: A63. arXiv:1610.08267. doi:10.1051/0004-6361/201629584. Retrieved 13 October 2018.
    4. "Asteroid Size Estimator". CNEOS NASA/JPL. Retrieved 16 February 2018.
    5. Halloween Skies to Include Dead Comet Flyby. NASA-JPL press release. 30 October 2015
    6. "2015 TB145 Orbit". IAU Minor Planet Center. Retrieved 24 January 2016.
    7. "JPL Close-Approach Data: (2015 TB145)" (last observation: 2015-10-27; arc: 17 days). Retrieved 22 October 2015.
    8. "2015TB145 Ephemerides for October 2012". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 24 October 2015.
    9. Kelly Beatty (22 October 2015). "Close-in Asteroid Offers Halloween Treat". Sky & Telescope. Retrieved 26 October 2015.
    10. Sarah Begley (30 October 2015). "NASA Says 'Great Pumpkin' Asteroid Will Fly by on Halloween". TIME Magazine.
    11. Nick Divito (31 October 2015). "Spooky 'skull asteroid' whizzes past Earth on Halloween". New York Post.
    12. Andrew Fazekas (23 October 2015). "Asteroid Called 'Spooky' Will Buzz Earth on Halloween". National Geographic Society.
    13. RT (31 October 2015). "'Spooky' asteroid to fly by Earth on Halloween". RT (Russia Today).
    14. Koren, Marina (31 October 2015). "A Halloween Comet". The Atlantic. Retrieved 1 January 2019.
    15. ESA (28 October 2015). "Halloween Asteroid Gives us a Miss, Confirms ESA". European Space Agency.
    16. Dr. Lance A. M. Benner (24 October 2015). "Goldstone Radar Observations Planning: 2009 FD and 2015 TB145". NASA/JPL Asteroid Radar Research. Retrieved 24 October 2015.
    17. "WISE Revises Numbers of Asteroids Near Earth". NASA/JPL. 29 September 2011. Retrieved 29 October 2015. (NASA Space Telescope Finds Fewer Asteroids Near Earth)
    18. "2015TB145 Ephemerides for 15 October 2015 through 31 October 2015". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 14 October 2015.
    19. Marchis, F.; et al. "Multiple asteroid systems: Dimensions and thermal properties from Spitzer Space Telescope and ground-based observations". Icarus. 221 (2): 1130–1161. Bibcode:2012Icar..221.1130M. doi:10.1016/j.icarus.2012.09.013. Retrieved 24 August 2018.
    20. "MPEC 2018-T130: 2015 TB145". Minor Planet Center. 10 October 2018. Retrieved 13 October 2018.
    21. Williams, Matt (1 October 2018). "The "Death Comet" Will Pass By Earth Just After Halloween". Universe Today. Retrieved 13 October 2018.
    22. "PIA20043: Halloween Asteroid Rotation". NASA/JPL-Caltech/GSSR/NRAO/GB. 3 November 2015. Retrieved 4 November 2015.
    23. Agle, D. C. (21 October 2015). "NASA Spots the 'Great Pumpkin': Halloween Asteroid a Treat for Radar Astronomers". NASA News. Retrieved 26 October 2015.
    24. "Possible October 31 Meteors From Minor Planet 2015 TB_145". SETI Institute. 26 October 2015. Archived from the original on 28 October 2015. Retrieved 26 October 2015. (CBET 4154)
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