311P/PANSTARRS also known as P/2013 P5 (PANSTARRS) is an asteroid (or main-belt comet) discovered by Bryce T. Bolin using the Pan-STARRS telescope on 27 August 2013. Observations made by the Hubble Space Telescope revealed that it had six comet-like tails. The tails are suspected to be streams of material ejected by the asteroid as a result of a rubble pile asteroid spinning fast enough to remove material from it. This is similar to 331P/Gibbs, which was found to be a quickly-spinning rubble pile as well.
|Discovered by||Bryce T. Bolin using Pan-STARRS|
|Discovery date||27 August 2013|
|P/2013 P5 (PANSTARRS)|
|Epoch 16 November 2013 (JD 2456612.5)|
|Uncertainty parameter 0|
|Observation arc||13.13 yr (4,797 d)|
|3.24 yr (1182.575d)|
Average orbital speed
|~480 meters (1,570 ft)|
|~0.240 meters (9.4 in) per second|
Three-dimensional models constructed by Jessica Agarwal of the Max Planck Institute for Solar System Research in Lindau, Germany, showed that the tails could have formed by a series of periodic impulsive dust-ejection events, radiation pressure from the sun then stretched the dust into streams.
The asteroid has a radius of about 240 meters (790 ft). The first images taken by Pan-STARRS revealed that the object had an unusual appearance: asteroids generally appear as small points of light, but P/2013 P5 was identified as a fuzzy-looking object by astronomers. The multiple tails were observed by the Hubble Space Telescope on 10 September 2013, Hubble later returned to the asteroid on 23 September, its appearance had totally changed. It looked as if the entire structure had swung around. The Hubble Space Telescope continued to track the object through 11 February 2014. The comet-like appearance has resulted in the asteroid being named as a comet. The object has a low orbital inclination and always stays outside the orbit of Mars.
On April 19th, 2018 observations based on light curvature suggested a possible satellite around 311P/PANSTARRS approaching 200 meters.  If true this would be one of the few minor planets designated as a comet known to harbor a satellite.
- Bolin, B.; et al. (27 August 2013). "CBET #3639 : P/2013 P5 (PANSTARRS)". Central Bureau Electronic Telegrams. Central Bureau for Astronomical Telegrams. Archived from the original on 21 September 2020. Retrieved 27 August 2013.
- JPL Horizons Observer Location: @sun (Perihelion occurs when deldot changes from negative to positive.)
- "JPL Small-Body Database Browser: P/2013 P5 (PANSTARRS)" (2013-11-07 last obs). Retrieved 9 November 2013.
- Jewitt, D.; Agarwal, J.; Weaver, H.; Mutchler, M.; Larson, S. (2013). "The Extraordinary Multi-Tailed Main-Belt Comet P/2013 P5". The Astronomical Journal. 778 (1): L21. arXiv:1311.1483. Bibcode:2013ApJ...778L..21J. doi:10.1088/2041-8205/778/1/L21.
- "When is a comet not a comet?". Spacetelescope. 7 November 2013.
- "NASA's Hubble Sees Asteroid Spouting Six Comet-Like Tails". Hubblesite. 7 November 2013.
- "She calculated that dust-ejection events occurred on April 15, July 18, July 24, Aug. 8, Aug. 26 and Sept. 4"
- "When is a comet not a comet?". ESA. 7 November 2013.
- "Hubble astronomers observe bizarre six-tailed asteroid". Spacetelescope. 7 November 2013.
- "311P/PANSTARRS Orbit". Minor Planet Center. Retrieved 13 September 2014.