NASA's Spitzer observatory has logged more than 1,000 previously unknown dwarf galaxies hiding out in a giant cluster of galaxies. Using data from the infrared observatory, a team led by Leigh Jenkins and Ann Hornschemeier, both at NASA Space Flight Centre, was able to resolve many galaxies that are too faint for other …
I think you might find that the Coma cluster is approximately 20 million light years across, rather than a mere 20 ly.
See http://www.solstation.com/x-objects/coma-sc.htm, for example.
I think you'll find that the article states that the Coma cluster is 20 million light years across :)
Light years of typos
To stop this turning into an all-out boffin bun fight: yes, I have edited the copy to include the missing millions. 20 light years would be a pitifully small galactic cluster, after all. Pitifuly small galaxy, come to that.
Thanks for flagging the typo.