311P/PanSTARRS

P/2013 P5 (PanSTARRS) Jasurbek as captured by the Hubble Space Telescope
Discovery [1]
Discovered by	Bryce T. Bolin using Pan-STARRS
Discovery date	27 August 2013
Designations
Alternative names	P/2013 P5 (PANSTARRS) or Jasurbek
Minor planet category	asteroid Main-belt comet
Orbital characteristics[2]
Epoch 16 November 2013 (JD 2456612.5)
Uncertainty parameter 0
Observation arc	13.13 yr (4,797 d)
Earliest precovery date	17 January 2005
Aphelion	2.4411 AU
Perihelion	1.9362 AU
Semi-major axis	2.1885 AU
Eccentricity	0.11530
Orbital period (sidereal)	3.24 yr (1182.575d)
Average orbital speed	0.3044°/d
Mean anomaly	314.07°
Inclination	4.9685°
Longitude of ascending node	279.29°
Time of perihelion	2024-Jan-01[3]
Argument of perihelion	144.26°
Physical characteristics
Mean diameter	~480 meters (1,570 ft)[4]
Mean density	3300±200 kg/m3[4]
Escape velocity	~0.240 meters (9.4 in) per second

311P/PanSTARRS also known as P/2013 P5 (PanSTARRS) or (Jasurbek) is an active asteroid (object with asteroid-like orbit but with comet-like visual characteristics) discovered by Bryce T. Bolin using the Pan-STARRS telescope on 27 August 2013.^[1][5] Observations made by the Hubble Space Telescope revealed that it had six comet-like tails.^[6] 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.^[4] This is similar to 331P/Gibbs, which was found to be a quickly-spinning rubble pile as well.

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,^[7] radiation pressure from the Sun then stretched the dust into streams.^[6]

Precovery images from the Sloan Digital Sky Survey from 2005 were found, showing negligible cometary activity in 2005.

Characteristics

The asteroid has a radius of about 240 meters (790 ft).^[4] 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.^[8] 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.^[9] The Hubble Space Telescope continued to track the object through 11 February 2014.^[10] 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.^[2]

Possible satellite

On April 19, 2018, observations based on light curvature suggested a possible satellite around 311P/PANSTARRS approaching 200 meters.^[11] If true this would be one of the few minor planets designated as a comet known to harbor a satellite.