This image of supernova remnant G347.3-0.5 combines data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton. The XMM-Newton satellite obtained data from a wider field of view, while Chandra focused on areas of interest to researchers (in outlines).

Chinese astronomers may have witnessed the supernova that caused G347.3-0.5, in 393 A.D. According to Chinese records, a bright star in the location of G347.3-0.5 remained visible for months, and rivaled Jupiter in brilliance. However, several supernova remnants lie within this region, making it difficult to identify the remnant of SN 393 AD with certainty.

X-rays from G347.3-0.5 are dominated by radiation from extremely high-energy electrons in a magnetized shell rather than radiation from a hot gas. The remnant also produces very high-energy gamma rays. The bright point-like source on the lower section of the image (which only shows the upper portion of the entire remnant) is similar to other known neutron stars, and indicates that G347.3-0.5 is the result of a core-collapse of a massive star. In both the Chandra and XMM-Newton images, brightness of the color represents the intensity of X-rays.

source:Nasa

2007 marks the 20th anniversary of the discovery of presolar grains. These tiny particles of stardust form when a star ejects elemental atoms from its core into interstellar space by stellar winds. As the interior of a star is too hot for molecular chemistry to take place, it is only outside the stellar core where elements can begin to combine. Stardust coalesces in the circumsolar shell, some of it eventually becoming preserved in asteroids.

The stardust is referred to as "presolar grains," since it must have been present in the molecular cloud which formed the sun, earth, and the rest of the solar system, including asteroids.

Some asteroids fall to earth as meteorites. Through analysis of these, researchers are able to isolate the presolar grains. The first such discovery was of presolar diamonds in a meteorite in 1987. More recently, the hunt was extended into space when a silicate grain from a foreign star inside a comet in our solar system was returned by the STARDUST space mission in 2006.

A nebula such as RCW49, pictured here, is a nursery for newborn stars and exists in circumstellar space, where chemistry first takes place

The mobile service tower, or gantry, prepares to move from away from the Delta II 7925 rocket carrying the Phoenix spacecraft, on Launch Pad 17A at Cape Canaveral Air Force Station.

The Delta II rocket is equipped with three stages and nine strap-on solid rocket motors, the propellant needed to send the Phoenix spacecraft on its way toward Mars.

Launch took place successfully early on the morning of Saturday, August 4 at 5:26 a.m. EDT.

Phoenix will land in icy soils near the permanent, north polar ice cap of Mars, and explore the history of water in these soils and any associated rocks, while monitoring polar climate.

The landing on Mars is estimated for May 25, 2008, in a location on arctic ground where the Mars Odyssey spacecraft, currently in orbit, has detected high concentrations of ice just beneath the top layer of soil