Cosmic cartographers are starting work on the biggest 3D map of the universe so far. It should reveal an undulating landscape sculpted by the big bang, and might give us a clue to the underlying shape of space and the nature of the “dark energy” that is blowing the universe apart.

The Sloan III project is the latest in a sequence of sky-surveys using a special wide-angle telescope sited in Sunspot, New Mexico. Since the completion of the Sloan I and II surveys, the telescope’s camera and optics have been updated, making it a more sensitive instrument. There has also been a shift in strategy, says Daniel Eisenstein, director of the new project at the University of Arizona in Tucson.

While much of the effort in the earlier surveys was devoted to relatively nearby galaxies, the biggest objective of Sloan III will be to chart the positions of more luminous galaxies out to a distance of about 8 billion light years.

With the locations of millions of these galaxies pinpointed on such a large-scale map, the team expects to see a subtle pattern emerging. They are looking for the relic of a much more ancient pattern, seen in the cosmic microwave background radiation that was emitted 380,000 years after the big bang. That in turn was created by loud sound waves travelling through the dense, hot early universe. In this cosmic cacophony, one particular note was louder than the rest, and it survives to this day as a characteristic wavelength in the clustering of galaxies. “Galaxies are slightly more likely to be separated by 500 million light years than by 400 or 600 million light years,” Eisenstein told New Scientist. By plotting the positions of millions of galaxies, the Sloan team expects to see this pattern over a wide swath of the universe.

They also hope to see it in the clustering of intergalactic gas, whose presence is revealed by their absorption of light from distant quasars. “It’s the first time anybody has tried to do this,” says Eisenstein. The standard length-scale can then be used to measure out the universe. Its apparent size tells astronomers exactly how far away they are looking, and that distance can then be plotted against redshift – the reddening of light caused by the expansion of the universe – to provide the history of cosmic expansion. That’s a step towards knowing what forces are at play in the universe. Seeing how the acceleration changes will reveal whether dark energy is getting stronger or weaker, or just staying the same. Combined with observations of supernovae and other astronomical data, the Sloan III survey should provide the best examination yet of this cosmic puzzle. This cosmic “ruler” could also show us the shape of spacetime. If spacetime is curved on large scales, it would magnify or shrink the apparent size of very distant objects – such as the length of the ruler itself.

Such length changes could be distinguished from any caused by dark energy because the curvature of space would produce much stronger effects at high redshift than dark energy, astronomers say. Magnification would suggest that space is curved like the surface of a sphere – and it would mean we live in a finite universe. The Sloan III survey will also look closer to home, mapping the Milky Way galaxy and monitoring 10,000 stars for evidence that they host giant planets. [NewScientist]

Skywatchers around the globe can see a total eclipse of the Sun on Friday, August 1st 2008.

A dark shadow will sweep across the surface of the planet in a broad arc as the Moon passes directly between the Earth and our star.

The eclipse begins in Canada’s high Arctic and ends in northern China’s Silk Road region.

Parts of northern Russia will go dark for two minutes, 27 seconds from 1021 GMT - but Britain will only experience a partial eclipse around 1016 BST.

That partial eclipse will be seen across most of Europe, Asia and north-eastern North America.

As is always the case with eclipses, tourists and amateur and professional astronomers have been flooding towns in the best viewing locations - along the path of totality. In Novosibirsk, Siberia’s cultural and scientific capital, more than 5,000 foreign tourists were expected to show up in the city. “The viewing points will be set up in the very beautiful historical and cultural places of Novosibirsk, there will be a number of telescopes there. Thirty-eight telescopes will be set up in the park on the River Ob embankment,” said local official Alexei Borisek.

Total solar eclipses usually take place about once every 18 months, and always at new Moon - when the lunar body sits directly between the Sun and the Earth. However, they do not happen every new Moon. The lunar orbit is slightly tilted to that of our planet and therefore the Moon’s shadow often misses the Earth. The Moon’s shadow has two parts: an umbra and a penumbra. The umbra is the “inner” part of the Moon’s shadow, and people inside this zone will witness the full glory of the eclipse. The penumbra is the Moon’s faint “outer” shadow. It will only give surface viewers a partial eclipse. [BBC NEWS]

Nasa’s Phoenix lander spacecraft has for the first time identified water in a sample of soil collected from the planet’s surface.

Scientists will now be able to begin studying the sample to see whether the planet was ever, or is, habitable.

The craft previously had problems transferring samples from its robotic arm to the onboard lab for analysis.

The success and the good condition of the craft mean the mission will be extended until the end of September.

Since it touched down on 25 June, the Phoenix lander has been studying the surface of Mars to investigate whether it has ever been capable of supporting life.

It has been studying soil with a chemistry laboratory, an oven called TEGA (Thermal and Evolved-Gas Analyzer instrument), a microscope, a probe and cameras.

Scientists told a press conference at the University of Arizona in Tucson that the planet had so far “proved itself to be interesting”. [BBC NEWS via AFP]