Photo of the Day

 What will survive this battle of the galaxies? Known as Seyfert's Sextet, this intriguing group of galaxies lies in the head portion of the split constellation of the Snake (Serpens). The sextet actually contains only four interacting galaxies, though. Near the center of this Hubble Space Telescope picture, the small face-on spiral galaxy lies in the distant background and appears only by chance aligned with the main group. Also, the prominent condensation on the upper left is likely not a separate galaxy at all, but a tidal tail of stars flung out by the galaxies' gravitational interactions. About 190 million light-years away, the interacting galaxies are tightly packed into a region around 100,000 light-years across, comparable to the size of our own Milky Way galaxy, making this one of the densest known galaxy groups. Bound by gravity, the close-knit group may coalesce into a single large galaxy over the next few billion years.

The photo to the right shows twin iridium flares streaking above the Ogooue River in Gabon as a thunderstorm approaches in the distance. I snapped this picture while preparing for last month’s total solar eclipse -- on November 3, 2013. Iridium flares can be observed whenever one of the Iridium satellites happens to be positioned to direct sunglint toward the surface. Even when night has fallen at ground level, satellites in low earth orbit can still be lit up by the Sun, briefly reflecting sunlight toward the viewer. These flares came into view within 8 seconds of each other and were approximately  0.7 degrees apart – equivalent to the diameter of about one and a half full moons. The brightness of the flares was -6.5 magnitude or more than 5 times brighter than Venus at its maximum brightness.  Lights from Gabon’s capital city of Lambarene are at right.