|Discovered by||August Kopff|
|Discovery site||Heidelberg Observatory|
|Discovery date||21 February 1906|
|Orbital characteristics |
|Epoch 4 September 2017 (JD 2458000.5)|
|Uncertainty parameter 0|
|Observation arc||111.19 yr (40,611 days)|
|5.01 yr (1,830 days)|
|0° 11m 48.48s / day|
|56.67±1.15 km (IRAS)|
|2.0 g/cm3 (assumed)|
2.5 g/cm3 (assumed)
Equatorial escape velocity
|60 m/s (calculated)|
75 m/s (calculated)
|15.8480 h (0.66033 d)|
|11.67 to 15.32|
Scheila (minor planet designation: 596 Scheila) is a main-belt asteroid and main-belt comet orbiting the Sun. It was discovered on 21 February 1906 by August Kopff from Heidelberg. Kopff named the asteroid after a female English student with whom he was acquainted.
On 11 December 2010, Steve Larson of the Catalina Sky Survey detected a comet-like appearance to asteroid Scheila: it displayed a "coma" of about magnitude 13.5. Inspection of archival Catalina Sky Survey observations showed the activity was triggered between 11 November 2010 and 3 December. Imaging with the 2-meter Faulkes Telescope North revealed a linear tail in the anti-sunward direction and an orbital tail, indicative of larger slower particles.
When first detected it was unknown what drove the ejecta plumes. Scheila's gravity is too large for electrostatics to launch dust. Cometary outgassing could not be ruled out until detailed spectroscopic observations indicated the absence of gas in Scheila's plumes. Observations by the Hubble Space Telescope and the Neil Gehrels Swift Observatory's ultraviolet-optical telescope make it most likely that Scheila was impacted at ~5 km/s by a previously unknown asteroid ~35 meters in diameter. Each asteroid the size of Scheila might be hit by an impactor 10–100 meters in diameter approximately every 1000 years, so with 200 asteroids of this size or bigger in the asteroid belt, we can observe a collision as often as every 5 years.
As a consequence of the 2010 impact, the surface spectrum of Scheila changed, from a moderately red T-type spectrum to a more reddish D-type spectrum, showing how "fresh" material weathers over time in space. This is similar to laboratory experiments done on the Tagish Lake meteorite.
Scheila last came to perihelion on 2012 May 19.