SJAA Ephemeris August 2011 | SJAA Home | Contents | Previous | Next

The Last Month in Astronomy


JUL-16-2011 • Dawn in orbit • The spacecraft called Dawn has gone into orbit around the asteroid Vesta. Vesta was the fourth asteroid to be discovered. Dawn was launched in September of 2007. It will orbit Vesta for one year. After that, it will leave Vesta and go into orbit around the asteroid (oops, dwarf planet) Ceres.

JUL-13-2011 • Neptune News • You are probably aware that Neptune has finally completed its first orbit around the sun since is was discovered in 1846. But this new item is about rotation not revolution. Erich Karkoschka from the University of Arizona has used atmospheric features on the mysterious planet to compute a Neptunian day of 15 hours, 57 minutes and 59 seconds. The images used to make this calculation came from Hubble (see image below). The length of a Jovian day is easy because of the radio signals that Jupiter emits but those signals from the other gas giants are swamped by the solar wind.

JUN-29-2011 • ULAS J1120+0641 • The clumsily named quasar is the most distant quasar found to date. The light from this quasar took 12.9 billion years to reach us. That means we are seeing it just 770 million years after the Big Bang. It was found by the European Southern Observatory’s Very Large Telescope (editor: so why is the telescope given a simple, even prosaic, name but the quasar is named like the merger of two phone numbers). According to Stephen Warren of the Imperial College London “This quasar is a vital early probe of the early universe ... It is a very rare object that will help us to understand how supermassive black holes grew a few hundred million years after the Big Bang.”

JUN-22-2011 • Enceladus Salty • The Cassini spacecraft has discovered new evidence that there is a large salt water reservoir (read, ocean) beneath the surface of Enceladus. Ice grains found closer to the surface are richer in sodium and potassium than the more distant ice grains that were studied earlier. The data suggests a layer of water that might be 50 miles deep. As the outermost surface cracks open up, the decrease in pressure ejects a plume. Why is this important? “This finding is a crucial new piece of evidence showing that environmental conditions favorable to the emergence of life can be sustained on icy bodies orbiting gas giant planets” according to Nicolas Altobelli a Cassini scientist with the ESA.


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