P/2016 BA14

P/2016 BA14 (Pan-STARRS) is a near-Earth object and periodic comet of the Jupiter family, that was radar imaged at distance of 2.2 million miles (3.5 million km, or 9 lunar distances) during a flyby of Earth in 2016.[1] This enabled the size of the nucleus to be calculated to be about 3000 feet to 3300 ft (1 km) in diameter.[1][2] Four noted aspects to BA14 are that it was discovered as an asteroid first, it was much bigger than expected going from perhaps 125 meters to 1000 meters, it was the closest approach by a comet since 1770, and finally, it has a very similar orbit as numbered comet 252P/LINEAR, and may be related to it (e.g. split off of).

P/2016 BA14
Radar images of P/2016 BA14 from its 2016 Earth flyby[1]
Discovery
Discovered byPan-STARRS
Discovery dateJanuary 2016
Orbital characteristics A
Epoch2015-Aug-01 (JD 2457235.5)
Observation arc16 years
Aphelion5.034488 AU
Perihelion1.008664 AU
Semi-major axis3.0215768 AU
Eccentricity0.666179
Orbital period5.33 years (1947 days)
Inclination18.918089°
Earth MOID0.0176579 AU (2,641,580 km)
Jupiter MOID0.0941585 AU (14,085,910 km)
Dimensions1000 meters

BA 14 had a unique history in that when it was discovered in January 2016 by a Pan-STARRS telescope, it was thought to be an asteroid and went by a provisional minor planet designation 2016 BA14.[3] An astronomer then realized the body's orbit was very similar to 252P/LINEAR, which led to a follow up observation by the Lowell Discovery Telescope.[3] The body showed a tail, identifying it as a probable comet and then named P/2016 BA14.[3]

P/2016 BA14 and 252P/LINEAR were found to have very similar orbits, and studied; it is thought that P/2016 BA14 may have split off from 252P/LINEAR.[4]

P/2016 BA14 was bigger than predicted when observed by astronomical radar; it was estimated to be perhaps 125 meters but was about 1 km in diameter.[2][1] One reason it was hard to predict its size, is because it reflects about 3% of the light, a very low albedo.[1]

P/2016 BA14 was said to be the closest approach of Earth by a comet since 1770 when Lexell's Comet is calculated to have passed within 1.4 million miles (2.2 million kilometers) of Earth according to Sky & Telescope magazine.[3] The P/2016 BA14 flyby of Earth in 2016 was noted as the third closest approach of a comet to Earth.[5][6] Another close approach by a comet in modern times was Comet IRAS–Araki–Alcock (aka C/1983 H1) in 1983.[7]

After BA14's flyby in 2016, it is calculated that is the closest it will be to Earth for at least the next 150 years.[8] P/2016 BA14 was noted as an opportunity to study comets more closely.[8]

Summary

Example facts:[3]

  • Discovered in January 2016, Earth flyby of 9 lunar distances in March 2016
  • Discovered as an asteroid but cometary activity detected
  • Expected to be 125 meters but turned out to be 1 km in size
  • Closest comet flyby since 1770 and 3rd closest recorded comet to Earth[9]
  • Orbit similar to 252P/LINEAR
  • Very, very dark reflecting about 2-3 percent of visible light according to infrared observations[1]
  • Rotates every 35–40 hours along its axis of rotation[10]
  • Is the cometary representation of a charcoal briquette

Observations

BA14 was detected by the PS-1 telescope of Pan-STARRS in Hawaii, and it was also observed by the 4.3 meter aperture Discovery Channel Telescope in Arizona.[3] NASA's Infrared Telescope Facility (IRTF) also made observations of P/2016 BA14.[2] NASA's infrared telescope (IRTF) observations revealed that BA14 was reflecting only 2-3 percent of visible light.[10]

The observations of P/2016 BA14 with the NASA IRTF gave a diameter estimate of 600 – 1200 meters (0.4 mile and 0.75 mile).[11] The radar observations reported about a kilometer in diameter.[12]

BA14 was observed with a radar telescope in California over three days, which revealed various properties including a rotation rate of 35–40 hours along one axis.[10]

Telescopes of Slooh also offered views of P/2016 BA14 and 252P/LINEAR.[13]

In context

Near-Earth comets are much less common than asteroids. As of September 22, 2018, according to statistics maintained by CNEOS, 18,837 NEOs were discovered: 107 near-Earth comets and 18,730 near-Earth asteroids. There are 1,929 NEOs that are classified as potentially hazardous asteroids (PHAs).[14] Comets' typical properties are cause for various issues, including that they typically are very dark (in astronomical speak, they have a low albedo) which can hamper taking accurate measurements; P/2016 BA14 reflected approximately 3% of visible light which is darker than fresh asphalt.[1]

Typical comets have much bigger orbits and have a lot of ice and dust that make their big tails.[15]

There is a known bias towards detecting asteroids that reflect more visible light, and one way around this is try find them with infrared telescopes (i.e. detecting the objects' heat) although this comes with other challenges. There is a bias towards finding asteroids that are easier to detect.[16] To better understand P/2016 BA14 it was observed with a combination of visible-light, infrared, and radar telescopes each with certain observation benefits.[17] Infrared observations of the comet allowed for a determination that BA14 was reflecting only 2-3 percent of visible light.[10]

The radar observations during the Earth flyby detected surface features as small as 8 meters, and determined a rotation rate of BA14 between 35–40 hours.[10]

Comet 252P/LINEAR had its close approach on March 21, 2016, and coming within 3.3 million miles (5.2 million kilometers) made it the 5th closest approach by a comet according to CNN.[18][6]

NASA is confident that it has discovered and cataloged all near-Earth asteroids large enough to cause significant global damage and determined that they are not on collision courses with Earth, but there is still some chance that large comets from the outer solar system could appear and impact the Earth with warning times as short as a few months

— National Near-Earth Object Preparedness Strategy and Action Plan (2018)[19]

Timeline
  • January 21, 2016, what is called 2016 BA14 is discovered[20]
  • February 2016, cometary activity detected using the 4.3 meter Discovery Channel Telescope[21]
  • March 22, 2016, Comet P/2016 BA14 Earth flyby closest approach 9.2 LD[22]

Names

This Solar System body has been known as:[3]

  • 2016 BA14
  • P/2016 BA14
  • Comet Pan-STARRS 2016
  • Orbit with 30 day motion
  • March 2016 flyby with 30 day motion
  • View of path from Earth with 1 day motion

See also

References
  1. "Flyby Comet Was WAY Bigger Than Thought". Space.com. Retrieved 2018-11-07.
  2. "Comet Scanned by NASA Radar". www.jpl.nasa.gov. Retrieved 2018-11-10.
  3. "Comet PanSTARRS 2016's Historic Flyby of Earth - Sky & Telescope". Sky & Telescope. 2016-03-16. Retrieved 2018-11-07.
  4. Li, Jian-Yang; Kelley, Michael S. P.; Samarasinha, Nalin H.; Farnocchia, Davide; Mutchler, Max J.; Ren, Yanqiong; Lu, Xiaoping; Tholen, David J.; Lister, Tim (2017-09-07). "The Unusual Apparition of Comet 252P/2000 G1 (LINEAR) and Comparison with Comet P/2016 BA14 (PanSTARRS)". The Astronomical Journal. 154 (4): 136. arXiv:1708.05190. Bibcode:2017AJ....154..136L. doi:10.3847/1538-3881/aa86ae. ISSN 1538-3881.
  5. McKirdy, Euan. "Close call? Third-closest comet fly-by". CNN. Retrieved 2018-11-20.
  7. "A 'Tail' of Two Comets". NASA/JPL. Retrieved 2018-11-20.
  8. McKirdy, Euan. "Close call? Third-closest comet fly-by". CNN. Retrieved 2018-11-17.
  9. "Comet flying by Earth observed with radar and infrared". Retrieved 2018-11-20.
  12. "Two Comets Just Made Historic Near-Earth Flybys: See Images and Video". Space.com. Retrieved 2018-11-10.
  13. "Discovery Statistics – Cumulative Totals". NASA/JPL CNEOS. May 14, 2018. Retrieved May 10, 2018.
  14. "The cautionary tail of Comet Swift–Tuttle". Retrieved 2018-11-12.
  15. "Discovering Asteroids and NEOs by Telescopes". www.permanent.com. Retrieved 2018-11-16.
  17. McKirdy, Euan. "Close call? Third-closest comet fly-by". CNN. Retrieved 2018-11-17.
  18. National Near-Earth Object Preparedness Strategy and Action Plan (June 2018) (Page 4)
  19. "Comet P/2016 BA14 (Pan-STARRS) and asteroid 2016 BC14". echo.jpl.nasa.gov. Retrieved 2018-11-12.
  20. Kelley, Michael S. P. "Discovery of Activity at Asteroid 2016 BA14". www.astro.umd.edu. Retrieved 2018-11-12.
  21. "Comet P/2016 BA14 (Pan-STARRS) and asteroid 2016 BC14". echo.jpl.nasa.gov. Retrieved 2018-11-12.
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