Article Posted on : - Jan 06, 2011

M31 Andromeda galaxy is the nearest large galactic neighbour of Milky Way. Photo: ESA

PARIS (BNS): Two ESA observatories have brought their combined forces, to showcase the most detailed image of the Andromeda Galaxy ever taken at infrared wavelength.

Herschel sees rings of star formation, and XMM-Newton shows dying stars shining X-rays into space.

ESA’s Herschel and XMM-Newton space observatories targeted the nearest large spiral galaxy M31 in December.

M31 galaxy similar to our own Milky Way – both contain several hundred billion stars. This is the most detailed far-infrared image of the Andromeda Galaxy ever taken and shows clearly that more stars are on their way.

According to ESA, sensitive to far-infrared light, Herschel sees clouds of cool dust and gas where stars can form. Inside these clouds are many dusty cocoons containing forming stars, each star pulling itself together in a slow gravitational process that can last for hundreds of millions of years.

Once a star reaches a high enough density, it will begin to shine at optical wavelengths. It will emerge from its birth cloud and become visible to ordinary telescopes.

Many galaxies are spiral in shape but Andromeda is interesting because it shows a large ring of dust about 75 000 light-years across encircling the centre of the galaxy.

This new Herschel image reveals yet more intricate details, with at least five concentric rings of star-forming dust visible.

Superimposed on the infrared image is an X-ray view taken almost simultaneously by ESA’s XMM-Newton observatory. Whereas the infrared shows the beginnings of star formation, X-rays usually show the endpoints of stellar evolution.

XMM-Newton highlights hundreds of X-ray sources within Andromeda, many of them clustered around the centre, where the stars are naturally found to be more crowded together.

Some of these are shockwaves and debris rolling through space from exploded stars, others are pairs of stars locked in a gravitational fight to the death.