Journey to the galactic core

Galactic centre: Sgr A* at the heart of the new map

By BBC News Online science editor Dr David Whitehouse

Astronomers have unveiled the biggest, most detailed and most sensitive map ever made of the centre of the Milky Way.

We experienced the driest, clearest weather that I have seen in more than 10 years of observing at the telescopes in Hawaii

Dr John Richer, Cambridge University

It shows giant streamers and huge clouds of interstellar gas where stars are being born. Astronomers say it sheds new light on the exotic structures found at our galaxy's core, 26,000 light-years from Earth.

It was compiled by astronomers from Cambridge University and the Joint Astronomy Centre (JAC) in Hawaii.

Douglas Pierce-Price, of Cambridge University, said: "This breathtaking survey is bigger and more sensitive than any previously made. It is the first detailed map to show essentially all the interstellar gas in the galactic centre."

Big black hole

The map shows not only dense clouds of gas, but also a wide network of wispy filaments. The region is also full of gas bubbles and shells; structures believed to be shaped by intense winds from stars, twisted magnetic field lines and stellar explosions.

The James Clerk Maxwell Telescope is on Hawaii

Dr John Richer of Cambridge University added: "These observations were the result of many months of careful planning. But luck also played its part. During the observations, we experienced the driest, clearest weather that I have seen in more than 10 years of observing at the telescopes in Hawaii."

The conditions in the central region of our galaxy are dramatically different from anywhere else in the Milky Way. At the very core of the galaxy lies an object astronomers call Sagittarius A*. It is believed to be a supermassive black hole of about 2.6 million times the mass of our Sun.

The researchers used a state-of-the-art camera called the Submillimetre Common-User Bolometer Array (Scuba), together with the 15-metre (50 ft) James Clerk Maxwell Telescope (JCMT) in Hawaii.

Close up: There is a giant black hole at Sgr A* (Green square)

Wayne Holland, who led the group in Hawaii, said: "Scuba is a wonderful instrument, and the most sensitive camera of its type. Its unmatched mapping speed has revolutionised this field of astronomy.

"Over a two year period we spent 15 nights at the telescope making these observations. Scuba's successor, Scuba-2, could do the same job in less than half an hour, so mapping the entire galactic plane becomes a real possibility."

Because the hearts of other galaxies are much further away, they cannot yet be mapped with as much detail as this survey has done with our own galactic core.

However, astronomers are hopeful that the planned Atacama Large Millimetre Array (Alma) telescope, which will consist of 64, 12-metre (40-ft) radio telescopes, to be built in the Atacama Desert, Chile, will enable astronomers to extend their survey to other galaxies. Alma will start construction in 2002.