Ring Around The Sun

Dawn craft to circle giant asteroid in 1st stop

LOS ANGELES (AP) — After four years sailing through space, the Dawn spacecraft was expected to slip into orbit late Friday around a giant asteroid to begin a yearlong investigation into the origins of the solar system.

It is the first of two scheduled tour stops for the NASA probe that almost never made it to the launch pad.

Dawn will spend the next several weeks spiraling ever closer to the surface of Vesta, a dry and rocky asteroid about the length of Arizona that's thought to be the source of numerous meteorites found on Earth.

Scientists are eagerly awaiting the first close-up shots of Vesta, expected next month. Until now, it has only been photographed from afar.

Residing in a vast field of rubble between Mars and Jupiter, asteroids are like the Peter Pans of the solar system that never quite grew into full-fledged planets. That they remain frozen in time is a boon for researchers attempting to reconstruct how Earth and the other planets formed.

Because of its stunted growth, Vesta holds "a record of the earliest history of the solar system," said the mission's lead scientist Christopher Russell of the University of California, Los Angeles.

After spending a year at Vesta, Dawn will cruise on to an even bigger asteroid, Ceres.

Vesta and Ceres are not your garden-variety asteroids; if the asteroid belt were a boxing ring, they would be the heavyweights in a sea of lightweights.

Past spacecraft have zipped by, circled around and even landed on much smaller asteroids. Dawn will be the first to orbit two asteroids on the same mission, a feat that is possible because of Dawn's futuristic ion propulsion engines, which allow for gentle yet constant acceleration. Once the stuff of science fiction, ion propulsion, which has been tested in space over the years, is far more efficient than conventional rocket fuel used by the majority of spacecraft.

Circling an extraterrestrial body is usually a risky, nail-biting business. A speeding spacecraft often has to fire its engines to slow down and be captured into orbit. One wrong move and it can overshoot its target.

In Dawn's case, it journeyed slowly on purpose so that it could line up with Vesta's path around the sun. Dawn was approaching the asteroid at 60 mph, slower than the speed limit on most U.S. highways, and engineers expected it to enter orbit around 10 p.m. PDT Friday.

Because Dawn's antenna was pointed away from Earth, actual confirmation of the capture would not be possible until after the weekend when it's programmed to re-establish contact.

RING AROUND THE SUN: Changing Weather Ahead « Lee Rentz ...

Eyes and cameras raised, squinting at the glaring sun, we were amazed as an unexpected phenomenon took place in the sky. There was a perfect halo circling the sun, showing the faint colors of a rainbow. Nature once again put on a great show, this one visible from the park where I was showing my photography in suburban Portland, Oregon.

Sky phenomena are the result of physics, so bear with my numbers and technical information. My photographs show several aspects of the phenomenon, which is known as the “22° Halo.” It was quite wide in the sky, and I barely captured the whole circle with a wide 24mm lens. The rainbow prism is almost precisely at 22° out from the center of the sun. There is a second ring visible in the corners of the photo; this is a 46° Halo, which is supposed to be rarer than the 22° Halo. The sky color inside the 22° Halo is darker than the sky color outside the ring.

A faint second halo appears at 46°