Astronomy News and Mission Updates

Hubble Spies Kuiper Objects

A team of astronomers led by Anita Cochran report that the Hubble Telescope may have detected extremely faint objects beyond Neptune in what is called the Kuiper Belt. The objects are roughly magnitude 28, which would make them only 20 km or so across. The astronomers painstakingly combined 34 HST images, then looked for things moving the way you'd expect for objects in distant, low-inclination orbits. This process turned up 59 candidate objects in a field only 4 arcminutes on a side. If these really are members of the Kuiper Belt, there must be about 60,000 such objects per square degree of sky. That would translate to a total of some 100 million comets traveling in low-inclination orbits and shining brighter than the HST's magnitude-28 limit.

Clementine: Back From the Dead!

There's good news coming out of the Bat Cave, which is what everyone calls the center used to control the Clementine mission. According to Trevor Sorenson, ground controllers regained full control of the spacecraft on April 10th. All the systems and sensors seem functional despite having a dead battery and being in deep freeze for 8 months. On the 15th the solar panels were pointed toward the Sun and some test images taken. "So far," Sorenson says, "we have not found anything broken." The mission team estimates that the spacecraft has enough thruster gas on board to change velocity by about 200 meters per second, and various options for an extended mission are being explored.

New Weather On Neptune

The weather forecast on Neptune calls for changeable skies, according to astronomer Heidi Hammel. She has been using the Hubble Space Telescope to monitor the distant planet, and its appearance has changed radically since Voyager 2 flew by in 1989. The Great Dark Spot in Neptune's southern hemisphere is no longer, but a new dark spot has appeared in the north. And huge, bright clouds appear, evolve, and disappear from week to week. Sunlight is about 900 times weaker on Neptune than here on Earth, so it probably has little effect on the planet's weather. Instead, the cloud systems may be spawned by heat rising from the planet's interior, which radiates twice as much energy to space as Neptune receives from the Sun.