Astronomy Picture of the DayHow fast can a black hole spin? If any object made of regular matter spins too fast — it breaks apart. But a black hole might not be able to break apart — and its maximum spin rate is really unknown. Theorists usually model rapidly rotating black holes with the Kerr solution to Einstein’s General Theory of…Read More

Titan: Moon over SaturnLike Earth’s moon, Saturn’s largest moon Titan is locked in synchronous rotation with its planet. This mosaic of images recorded by the Cassini spacecraft in May of 2012 shows its anti-Saturn side, the side always facing away from the ringed gas giant. The only moon in the solar system with a dense atmosphere, Titan is the…Read More

Young Star Cluster NGC 346The most massive young star cluster in the Small Magellanic Cloud is NGC 346, embedded in our small satellite galaxy’s largest star forming region some 210,000 light-years distant. Of course the massive stars of NGC 346 are short lived, but very energetic. Their winds and radiation sculpt the edges of the region’s dusty…Read More

MESSENGER’s Last Day on MercuryThe first to orbit inner planet Mercury, the MESSENGER spacecraft came to rest on this region of Mercury’s surface on April 30, 2015. Constructed from MESSENGER image and laser altimeter data, the projected scene looks north over the northeastern rim of the broad, lava filled Shakespeare basin. The large, 48…Read More

A Happy Sky over Bufa Hill in MexicoSometimes, the sky itself seems to smile. A few days ago, visible over much of the world, an unusual superposition of our Moon with the planets Venus and Saturn created just such an iconic facial expression. Specifically, a crescent Moon appeared to make a happy face on the night sky when paired with seemingly…Read More