Wednesday, October 10, 2007

Undergrad Team Discovers 1,300 Asteroids

A team of undergrad astronomers at the University of Washington figured out how to turn an annoyance into a major discovery, uncovering 1,300 new asteroids; nearly 1 out of every 250 known objects in the Solar System. How did they pull of this feat? It was actually a side project to their actual research: searching for supernovae. The asteroids were getting in the way.

The undergrad researchers were looking through data gathered as part of the Sloan Digital Sky Survey. This is a collection of detailed images of the sky gathered by an automated 2.5-metre telescope. The researchers were looking for evidence of exploded stars, called supernovae, but asteroids kept getting in the way.

Instead of just working around the asteroids that were blocking their view, they decided to keep track of them, and see if any were unidentified. It turned out that 1,300 were brand new.

Andrew Becker, a UW research assistant professor in astronomy explains the initial frustrations, "I kept asking the students what they had found and they kept saying, 'More asteroids. No supernovae, but lots of asteroids.'"

The undergrads developed programs that let them search through the Sloan data automatically, identifying asteroids, and helping them classify them. In addition to discovering 1,300 new asteroids, they compiled additional data on 14,000 asteroids that were already known. This allows astronomers to calculate their trajectories with better accuracy, and determine if any are a threat to the Earth in the future.

Two-Toned Iapetus

Saturn's moon Iapetus is one of the most mysterious objects in the Solar System. It's shaped like a football, has a strange ridge that runs along most of its equator, and it's got vastly different hemispheres. One side is as white as driven snow, and the other side is dark as tar. Scientists think they've at least got an answer for this last mystery.

Even before humans sent spacecraft to Saturn, astronomers have known there's something bizarre about Iapetus. Its brightness changed significantly depending on its facing towards the Earth. Follow up observations with spacecraft, like Voyager and Cassini showed that this was because half the moon is covered in snowy white material, while the other half is dark as night.

During its most recent flyby, NASA's Cassini spacecraft confirmed that Iapetus is warm enough on the dark side - 127 Kelvin (-230 F) - that water vapour can slowly release from water ice. This vapour then travels around the moon, and freezes back down onto the white side. This process of vaporization and accumulation is called "thermal segregation".

So where does the dark material come from? Astronomers think that it didn't originate on Iapetus, but instead came from the surrounding outer moons. As Iapetus goes around its orbit, this darker material piles up on the leading hemisphere. The material heats up the surface of moon, allowing it to release the water vapour which then reforms on the other side.

Scientists describe this as a runaway process. Once it got going, both hemispheres went to extremes. The water completely boiled away from the dark side, and then accumulated on the bright side. You don't see shades of grey, just black and white.

New Horizons Makes Surprising Discoveries at Jupiter

Remember when New Horizons sped past Jupiter on its way to Pluto. It kept its cameras rolling during the flyby, and captured hard drives full of data. Researchers have had a chance crunch through some of this data, and announced a series of discoveries this week: polar lightning storms, clumpy rings, volcanic eruptions on Io, and more.

New Horizon's goal may be Pluto, but it's got some time to kill between now and then. Might as well gather some science along the way. The spacecraft sped past Jupiter on February 28, 2007, picking up a valuable gravity assisted speed boost. It was the 8th spacecraft to make a close encounter with Jupiter, and just those before, it revealed valuable new insights into Jupiter and its satellites.

When the spacecraft was approaching Jupiter, mission planners carefully planned out 700 observations they wanted New Horizons to make. In fact, this is twice the number planned for the brief flyby of Pluto in 2015. They focused their collection on outstanding scientific issues that needed further investigation; to try and give scientists some kind of closure to mysteries opened up by previous spacecraft flybys.

Top on the list is Jupiter's weather. New Horizons observed the planet's clouds using visible light, infrared and ultraviolet. They saw ammonia clouds welling up from deeper down and heat-induced lightning strikes in the polar regions - the first polar lightning seen apart from Earth.

The spacecraft also focused in on Jupiter's tenuous rings. The detailed observations revealed clumps of material that could indicate there was a recent impact inside the rings. Just like Saturn, Jupiter has tiny moons that serve as shepherds, keeping the ring material together.

New Horizons also focused its cameras on Jupiter's volcanic moon Io. The spacecraft observed 11 different volcanic plumes of varying size, and could see 36 hotspots on the moon in the infrared spectrum. Three of these volcanoes were seen for the very first time.

Finally, the spacecraft measured the magnetic tail that trails behind Jupiter. New Horizons saw material ejected by Io moving down the tail in large, dense, slow-moving blobs, captured in the magnetic field.

New Horizons is now halfway between the orbits of Jupiter and Saturn, and more than 1.19 billion km (743 million miles) from Earth.