Chief, Astroparticle Physics Laboratory, NASA Goddard Space Flight Center
They are the biggest explosions in the universe, visible from billions of light years away. Now, thanks to new instruments like the Swift satellite, we think we know how they happen. Hear the story from Swift Principal Investigator Neil Gehrels. Bruce Betts reports in from a planetary science conference, and Emily Lakdawalla is out in the rings of Saturn for Q&A.