NASA's Cassini spacecraft took this picture of Mimas, Saturn's "Death Star" moon on February 18, 2005 at a distance of 938,000 km (583,000 miles). The image was taken using Cassini's ultraviolet filter, which helps to reveal better contrast of the moon's craters than would be possible in visible light. Mimas' large crater Herschel dominates the upper right of the picture.

Have you ever replaced the light bulb inside your fridge? Take a look next time. It draws about 25 watts of power. Now imagine this bulb on a spacecraft somewhere around Neptune and it's flashing madly away, trying to send a signal back to Earth. Somehow we need to see these flashes. Sound impossible? Well almost, but Douglas Mudgway in his book Big Dish describes the system, in particular the antenna sites, that was put into place to capture just this type of signal.

Launched from "Cape Kennedy" just 13 months of one another in 1972/73, Pioneer 10 and 11 are still up there though no longer kicking. But well before last phone home (in 2003 and 1995 respectively), the notes each pair played had changed pitch unexpectedly - they were slowly losing speed. Could the Pioneering Pair have been feeling a bit in the "dark" (as in "dark matter" or "dark energy")? Were they having a "Solar Quadrupole" moment? Could n-dimensional "branes" be behind it? Or has "back-gravity" from behind the Sun played a role? Before things get too exotic, maybe there's a simpler explanation.

A powerful Proton K rocket blasted off from the Baikonur Cosmodrome in Kazakhstan Tuesday night, carrying a Russian Express-AM2 communications satellite. It lifted off at 2231 GMT (5:31 pm EST), and placed its payload into a geosynchronous transfer orbit a few hours later. The Express-AM2 satellite will provide broadcast television and other communication services for Russia and Southeast Asia.

It's for people. That's why we explore space, push ourselves to the next level, and continually strive forward. Machines may be the advance guard but they can never capture our hearts and souls. Perhaps people may forget this adage, but, under Ron Howard's direction, the cast and members of "Apollo 13" put on a memorable drama and remind us that people are number one.

After a long life, most sun-like stars grow into red giants once they've depleted most of their hydrogen fuel. The relatively small region around the star which is just at the right temperature to support liquid water will extend as the red giant expands. This means that previously frozen planets (like Mars) could thaw out and life might have a second chance to happen in a solar system. There are currently 150 red giant stars within 100 light-years of the Earth, and many of these could be a place to search for life in addition to main-sequence stars similar to our own Sun.

Galaxies are built up over time through a series of collisions with other galaxies. Each time this happens, clouds of gas and dust collapse and become regions of furious star formation. The European Space Agency's ISO infrared space telescope has shown the early stage of a collision between two galaxies (NGC 4038/4039) 60 million light-years away. The overlapping region between the galaxies is very rich in molecular hydrogen in an excited state. The shock waves are just starting to collapse the gas, and should lead to starbirth in the next few million years.

The European Space Agency's Mars Express spacecraft took this image of the Medusa Fossae Region on the Red Planet. This is an unusual region of Mars that was probably built up by a series of volcanic flows or rains of ash, and then partially eroded by water. Finally, a large asteroid, several kilometres across, struck the region and "splashed" ejecta onto the plateau.

Some current models of galaxy formation predict that large spirals such as the Milky Way and Andromeda Galaxy should have more satellite galaxies than are currently known to astronomers. Many of these galaxies should be much smaller than those already discovered. Astronomers reviewing data from the automated Sloan Digital Sky Survey (SDSS) have now added a tenth satellite to the Milky Way's dwarf spheroidal galaxy contingent and this one is a real lightweight.

Greetings, fellow SkyWatchers! This week will bring some excitement as asteroid Pallas flies through the galaxy fields of Virgo and the Moon occults Antares for Hawaii. We'll focus on exploring some strange and unusual nebulae, and learn why it's "aurora season". The week will end with the several meteor streams and the opposition of Jupiter. So grab those binoculars, set up the telescope and hope for clear skies, because...

Here's what's up!

The astronauts on board the International Space Station spent a few hours walking around in space today. They installed new antennas to help guide the new European "Jules Verne" cargo ship when it launches next year. They also released a tiny Russian satellite by hand - flight engineer Salizhan Sharipov "threw" it off the station at a velocity of about 1 metre/second. The whole spacewalk finished ahead of schedule, and the two men returned inside after spending about 4.5 hours in space.

A team of European astronomers has found some unusual objects in the central part of our galaxy which are emitting very high-energy gamma rays. What's strange, though, is these objects are invisible in the optical and X-ray spectra. So what they are is a complete mystery. Not only that, but these objects are also quite large; possibly on the order of several light years across. The observations were done using the High Energy Stereoscopic System (H.E.S.S.) telescopes in Namibia.

This is a satellite photograph of two huge sandy regions in the Fezzan region of Southwest Libya, near the border of Algeria. A persistent high-pressure system keeps this region of Libya completely dry for years at a time. The photograph was taken by the European Space Agency's Envisat satellite using its Medium Resolution Imaging Spectrometer (MERIS).

When a 10-km (6-mile), dinosaur-killing asteroid struck the Earth 65 million years ago, it released so much energy that it vaporized rock, which then fell like rain around the world. Scientists now think that these droplets of rock, called spherules, condensed out of a cloud of water vapour that surrounded the Earth shortly after the impact. They were able to trace the composition of the spherules back to the original Chicxulub impact crater, demonstrating that the material came from the Earth, and not the asteroid itself.

NASA announced on Wednesday their first Centennial Prizes, which will reward the development of new technologies for space exploration. The first is the Tether Challenge, where various teams will compete to see who can built the strongest cable material. In the Beam Challenge, teams will build power transmitters that send energy wirelessly to a robot climber - the winner's robot will lift the most weight to the top of a 50-metre cable. The winner of each prize will be awarded $50,000. Follow on challenges are planned for next year, and will award even higher prizes.

Officials announced on Tuesday that Greece has formally become the 16th country to join the European Space Agency. The country's Hellenic National Space Committee had been participating with the ESA since the 1990s, exchanging information, fellowship awards and access to databases and laboratories, but it only applied for official inclusion in 2003.

A new astronomical survey is in the works to help uncover the source of the mysterious dark energy which is accelerating the expansion of the Universe. Set to begin in 2009, the Dark Energy Survey will collect data on approximately 300 million galaxies, reaching back two-thirds of the history of the Universe. A 520-megapixel camera will be installed onto the 4-metre Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile, allowing astronomers to survey the sky 10 times faster than they could before.

NASA's Spitzer telescope has detected the light from distant planets for the first time. Until now, extrasolar planets have only been discovered indirectly, by the effect of their gravity on their parent star. Astronomers first detected two planets using indirect methods, and then used Spitzer to perform followup observation with its infrared instruments. They detected the difference in star brightness when the planet was in front and behind the star, and were able to calculate how much of this light was supplied by the planet.

The Milky Way has several star clusters; collections of stars pulling each other into a tight group. But now astronomers have located a super star cluster, containing hundreds of thousands of stars in a region only 6 light-years across. It's called Westerlund 1, and nobody discovered it before now because it's hidden behind thick clouds of dust. Astronomers used several of European Southern Observatory's infrared telescopes to peer through the dust and see the super cluster's true size.

Greetings, fellow SkyWatchers! With a full Moon this week, it will be hard to find things to do under the stars - or will it? We begin the week with morning observations of Comet LINEAR and move on towards meteor showers, variable and double stars and a Jupiter/Moon conjunction with an occultation for southern Australia. We'll explore lunar features and rudimentary astrophotography as well as just have some fun. So take out those telescopes and binoculars, because...

Here's what's up!