The night sky: Nasa quest puts age on universe

The northern sky at 7pm tonight

Astronomers are buoyed by new results from Nasa's WMAP satellite.

WMAP has spent the past three years making highly accurate measurements of the background temperature of the universe and from this data, key cosmological parameters have been derived.

They have now determined the age of the universe to be 13.7 billion years with an error of just 2 per cent.

Most significantly, the results of this survey have resoundingly endorsed the theory of cosmic inflation that most astronomers believe created the large-scale structure of the universe in the first trillionth of a trillionth of a second following the Big Bang.

This structure is reflected today in the distribution of the galaxies throughout space.

The WMAP results have provided more accurate values for the total energy content of the universe. Dark energy, a mysterious force that is driving the universe to expand ever faster, makes up 74 per cent. Dark matter, which holds together galaxies and groups of galaxies, contributes 22 per cent. Ordinary matter, like the atoms from which our world is made, contributes a mere 4 per cent of the universe's energy content.

Although very little is known about the nature of dark energy, the new results support the idea that it is a property of space itself and not just some exotic kind of particle or field. This is an important result given that dark energy was discovered only in 1998.

Meanwhile, in our tiny corner of the universe, Mars can still be spotted low in the northwest soon after sunset. Early in the evening Saturn is almost due north, lying close to the Gemini twins, Pollux and Castor. Jupiter, currently in the constellation Libra, rises in the east at 7pm and is well placed for viewing by 10.30pm. Jupiter reaches opposition on May 5, at which time it will be opposite the sun in the sky, rising exactly as the sun is setting. Saturn and Jupiter are both popular objects with visitors to the Stardome.

Early risers will be treated to a dazzling view of Venus in the eastern dawn sky, by which time Jupiter has moved over to the west. The striking winter constellations of Scorpio and Sagittarius are stretched out between these two bright planets. The elusive planet Mercury is the bright object below Venus in the east.

* Grant Christie is an astronomy researcher and columnist for the Herald.