On 11 December 2010, Steve Larson of theCatalina Sky Survey detected a comet-like appearance to asteroid Scheila: it displayed a "coma" of aboutmagnitude 13.5.[6] Inspection of archival Catalina Sky Survey observations showed the activity was triggered between 11 November 2010 and 3 December.[7] Imaging with the 2-meterFaulkes Telescope North revealed a linear tail in the anti-sunward direction and an orbital tail, indicative of larger slower particles.[8]
When first detected it was unknown what drove theejecta plumes. Scheila's gravity is too large forelectrostatics to launch dust.[2] Cometaryoutgassing could not be ruled out until detailedspectroscopic observations indicated the absence of gas in Scheila's plumes.[4] Observations by theHubble Space Telescope and theNeil Gehrels Swift Observatory's ultraviolet-optical telescope make it most likely that Scheila wasimpacted at ~5km/s by a previously unknown asteroid ~35 meters in diameter.[3][4] 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.[4]
As a consequence of the 2010 impact, the surface spectrum of Scheila changed, from a moderately redT-type spectrum to a more reddishD-type spectrum, showing how "fresh" material weathers over time in space. This is similar to laboratory experiments done on theTagish Lake meteorite.[9]
^Ernesto Guido & Giovanni Sostero (12 December 2010)."Comet-like appearance of (596) Scheila". Remanzacco Observatory in Italy (blog).Archived from the original on 7 January 2011. Retrieved12 December 2010.
.png)
