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.

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] the "Halloween Asteroid",^[13][14] and the "Skull Asteroid"^[11] due to its skull-like appearance following radio frequency images taken at Arecibo Observatory and closest approach coincidentally occurring on Halloween day.^[11]

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.^[15] It is estimated that there are about 2400 near-Earth asteroids 300–500 meters in diameter, of which about 1100 have been discovered.^[16]

During closest approach to Earth the asteroid reached about apparent magnitude 10,^[17] 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.^{[citation needed]}

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.^[17] 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.^[17] After closest approach it quickly became too faint and too close to the Sun in the sky to be seen.^[15]

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.^[19]

The 11 November 2018 flyby was about 0.267 AU (39,900,000 km; 24,800,000 mi) from Earth.^[7][20]

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][22] Orbital calculations by Petrus Jenniskens and Jérémie Vaubaillon showed that it was not expected to produce associated meteors in 2015.^[23] Any meteoroids were expected to pass more than 0.0007 AU (100,000 km; 65,000 mi) from Earth's orbit.^[23]

If meteoroids related to this asteroid were to cross Earth's path, the radiant is expected to be near Northern Eridanus.^[23] Cameras for Allsky Meteor Surveillance (CAMS) did not detect any activity in the presumed area of the sky during 2013 and 2014.^[23] 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]