Gamma ray bursts (GRBs), the brief flashes of light signalling distant, extremely energetic events, have been elusive targets for astronomical observation. (It's something like the fairground game of Whack-a-Mole:by the time you're aware of the GRB, it's vanished, and you have no way of knowing where the next one will appear.) An orbiting observatory that quickly alerts ground-based astronomers about GRBs has allowed a very quick response and an unprecedented look at the GRBs' aftermath.

GRBs are the most energetic and among the most enigmatic events that we see happening in the universe. These outbursts of high-energy radiation appear unpredictably and then vanish quickly, leaving a faint and fast-fading afterglow at visible wavelengths. They're believed to occur in some circumstances when a black hole forms, through some dramatic and distant event like the explosion of a massive star or the collision of neutron stars, but until recently it's been hard to learn more about them because they occur so unpredictably and are over so quickly.

People where I live still talk about the New Madrid earthquakes that occurred in southern Missouri in 1811 and 1812. I've heard that church bells rang hundreds of miles away in New England, disturbed by the seismic waves, and supposedly the surface of the earth subsided as a result of the quakes to such a degree that it created a new lake (Reelfoot Lake in Tennessee). The aftershocks go on to this day.

I spent part of my childhood in southern California and grew up with the instructions about standing in a door jamb during a quake and all that, so I was used to the idea of California as earthquake-prone, and I understand the reasons for California quakes. It was something of a surprise to me when I learned in my teens about this massive quake in the middle of the continent, far away from any major active tectonic plate boundary, and I gather that it's been something of a mystery what was behind the seismic activity. It turns out that maybe there's a connection between the west coast and the New Madrid area.

The Hubble Space Telescope (HST) has produced some of the most famous still images in astronomy (e.g., the pillars of creation in the Eagle Nebula). The latest images from HST are movies of Saturn and its moons. Astronomers wrote software that multiplies the relatively small number of images taken by Hubble for each event into the much larger number needed to make a movie. The original images covered several hours of observing time, and the videos range in length from 15 to 30 seconds, so time is compressed in the videos and the motions of Saturn and its moons are speeded up.

Two of the videos show Saturn with the rings edge-on either to Earth or to the sun. In this video, you can see Saturn's largest moon Titan and a smaller moon Tethys as they orbit the planet.





Actually you see Titan's shadow falling on the planet first, before the moon itself appears and crosses the face of the planet. Tethys emerges from behind Saturn on the left and quickly whizzes across the ring plane and vanishes off to the left.