The Outer Limits

At the very edge of the solar system, Voyager 2 has sailed through the termination shock, where the solar wind abruptly slows as it presses outward against the ions in interstellar space. All of the spacecraft’s fields and particles instruments returned data as it crossed the oscillating shock three times in a six-hour period on the night of August 31–September 1, 2007. (At least two other inferred crossings happened during telemetry gaps before and afterward.) A set of papers in the July 3 issue of Nature describes the conditions at the encounter, which were quite different from those observed by Voyager 1 in its single crossing four years earlier. The biggest surprise is that the shock is asymmetric—Voyager 1, traveling northward out of the plane of the solar system, crossed it at 14.1 billion kilometers, while southbound Voyager 2 hit it at a distance of a mere 12.6 billion kilometers.

Meanwhile, closer to home, the International Astronomical Union (IAU) has voted to accept Makemake (pronounced mah-kay mah-kay) as the official name for the dwarf planet previously known as Easterbunny. 2005FY9, as it is also known, was discovered by Rosenberg Professor of Planetary Astronomy Michael Brown’s team on March, 31, 2005, four days after Easter. IAU rules say that trans-Neptune objects must be named for figures in creation myths; Makemake is the creator of mankind and the god of fertility among the Rapa Nui people of—you guessed it—Easter Island. —DS