Background on The Supernova's Discovery from Sky & Telescope:
The first people to recognize the supernova were a group of students — Ben Cooke, Tom Wright, Matthew Wilde and Guy Pollack, assisted by teaching fellow Stephen J. Fossey — taking a quick image at the University of London Observatory (within the London city limits!) on the evening of January 21st at 19:20 UT.
—a 10-minute telescope workshop for undergraduate students that led to a global scramble to acquire confirming images and spectra.
"The weather was closing in, with increasing cloud," Fossey says. "So instead of the planned practical astronomy class, I gave the students an introductory demonstration of how to use the CCD camera on one of the observatory’s automated 0.35-meter telescopes."
The students chose M82, a bright and photogenic galaxy, as their target, as it was in one of the shrinking patches of clear sky. While adjusting the telescope’s position, Fossey noticed a star overlaid on the galaxy which he did not recognise from previous observations.
They inspected online archive images of the galaxy, and it became apparent that there was indeed a new starlike object in M82. With clouds closing in, they switched to taking a rapid series of 1- and 2-minute exposures through different colour filters to check that the object persisted, and to be able to measure its brightness and colour.
The original press release, and a BBC story repeating it, claimed that this is the nearest supernova since Supernova 1987A in the Large Magellanic Cloud. In fact, SN 1993J in M81 was at essentially the same distance within the uncertainties, and two subsequent supernovae, SN 2004am and SN 2008iz (an obscured radio supernova), occurred within M82 itself.
However, this is said to be the nearest Type Ia supernova since 1972. That's the kind that is so valuable for measuring the size and expansion rate of the universe. Despite the dimming and reddening, astronomers hope that SN 2014J will provide new details about exactly what happens in these "standard-candle" explosions.