NASA’s April Update On The Size Of Comet ISON’s Nucleus, Coma And Tail Following April 10 Hubble Telescope Image.
by Anura Guruge
>> Hubble telescope imaging April 10, 2013
>>— Apr. 26, 2013.
So the estimate as to the size of the nucleus is more or less the same as that from March 29, 2013 NASA update.
The coma is just developing. 3,100 miles across is nothing for a great comet. 60,000 miles across is not unusual. 17P/Holmes, for a few memorable days in October 2007, sported a coma that was 900,000 miles across. Yes, that is bigger than the mean diameter of the Sun!
57,000 mile tail is not even worth talking about. Comets have tails that are millions of miles long. A tail 1 AU long, i.e., 92 million miles, is not considered unusual. C/1996 B2 (Hyakutake), near perihelion in May 1996, had a tail that was measured to be longer than 311 million miles.