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Late yesterday, NASA turned the 230-foot (70-meter) Deep Space Network antenna at Goldstone, California towards Asteroid 1998 QE2 as it was heading towards its closest approach to Earth, and they got a big surprise: the asteroid is a binary system. 1998 QE2 itself is 1.7 miles (2.7 kilometers) in diameter, and the newly found orbiting moon is about 600 meters in diameter. The radar images were taken were taken on May 29, 2013, when the asteroid was about 3.75 million miles (6 million kilometers) from Earth. “Radar really helps to pin down the orbit of an asteroid as well as...

The Geminid meteor shower, which peaks each year in December... are *not* caused by debris left behind from an active comet... Until recently, the favored view of Phaethon was that it's a dead comet -- the rocky core of a "dirty snowball" that lost its ices after too many close encounters with the sun. ... In June 2009 astronomers using the STEREO sun-watching probe suddenly saw the rocky body flare to life as it neared the sun, brightening by a factor of two... So, not so dead after all. But that brings us back to figuring out what exactly Phaethon...

Ten years ago, NASA researchers discovered that the Pioneer 10 and 11 spacecraft had fallen slightly behind course during their 35-year journeys to the outer reaches of the solar system. In what has become known as the Pioneer anomaly, which was the subject of one of the talks this weekend at the American Physical Society here in St. Louis, nobody knows for sure why it happened. It probably stemmed from leaking gas or heat. But there's also the possibility, however remote, that gravity doesn't behave the way we expect. Until recently, researchers haven't had the data to distinguish the different...

"It turns out that there are a significant number of asteroids that aren't just a single object, but two and even on occasion three in orbit around one another," Pollock said. He and his colleagues record information related to changes in amount of light reflected from asteroids. Sometimes this indicates the existence of a pair of asteroids that are revolving around each other... "When a single, irregularly shaped asteroid spins, the amount of reflective area changes and it appears to change brightness," Pollock said. "When you have two rotating asteroids revolving around one another, the brightness changes are much more...

Neptune's largest moon, Triton, was originally a member of a duo orbiting the Sun but was kidnapped during a close encounter with Neptune, a new model suggests. Triton is unique among large moons in that it orbits Neptune in a direction opposite to the planet's rotation, which long ago led scientists to speculate that the moon originally orbited the Sun. But until now, no convincing theory for how Triton paired with Neptune existed. Gravity might have pulled Triton away from its companion to make it an orbiting satellite of Neptune, researchers report in a new study published in the May...