astro.wikisort.org - Comet

P/2016 BA₁₄ (PanSTARRS) 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 at about 1 km (0.62 mi) in diameter.[1][2] Four noted aspects to P/2016 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 by	Pan-STARRS
Discovery date	22 January 2016
Orbital characteristics A
Epoch	12 April 2016 (JD 2457490.5)
Observation arc	0.86 yr (313 days)
Aphelion	5.036 AU
Perihelion	1.000 AU
Semi-major axis	3.022 AU
Eccentricity	0.6663
Orbital period	5.25 years (1,919 days)
Inclination	18.919°
TJupiter	2.797
Dimensions	1 km[2]
Rotation period	36.6 h
Comet total magnitude (M1)	21.3±0.5
Comet nuclear magnitude (M2)	23.1±0.6
Last perihelion	15 March 2016
Next perihelion	June 2021

This article needs editing for compliance with Wikipedia's Manual of Style. (April 2022)

The object 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] Astronomer Denis Denisenko noted 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]

The similarity of the orbits of P/2016 BA₁₄ and 252P/LINEAR suggested 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 P/2016 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

P/2016 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 P/2016 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]

P/2016 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^[update], 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 P/2016 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 P/2016 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.[9][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)[18]

Gallery

• 
  Orbit with 30 day motion
• 
  March 2016 flyby with 30 day motion
• 
  View of path from Earth with 1 day motion

See also

• List of asteroid close approaches to Earth
• List of asteroid close approaches to Earth in 2016
• Near-Earth object
• C/2013 A1 (comet that passed close to planet Mars in 2014)
• Near-Earth object#Near-Earth comets
• 55P/Tempel–Tuttle (Earth close approach in 1366 (calculated))

References

External links

• NASA - BA14 scanned by radar
• Discovery of Activity at Asteroid 2016 BA14 (Blog)
• Historic (Pre 1900) close approaches of Earth by comets
• P/2016 BA14 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters
• A 'Tail' of Two Comets (NASA March 18, 2016)

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