Andromeda’s once and future stars

ESA (infrared, X-ray) / R. Gendler (optical)

These images show how optical, infrared and X-ray imagery can be combined to produce a more complete picture of stellar activity in the Andromeda Galaxy. The optical image shows adult stars, the infrared image shows reservoirs of gas and dust in which stars are being formed, and the X-ray image shows the violent end points of stellar evolution.

A pair of space telescopes is giving astronomers an unprecedented view of stellar birth and death in the Andromeda Galaxy, located about 2.5 million light-years away.

The combined image was made using data from the European Space Agency’s Herschel and XMM-Newton observatories, which targeted the galaxy during Christmas 2010.

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The space telescopes view the universe in wavelengths of light that are absorbed by Earth’s atmosphere and thus unavailable to ground-based telescopes.

Herschel, which is sensitive to far infrared light, picks up the rings of star formation seen here as reddish circles filled with clouds of cool dust and gas. It is the most detailed image ever acquired of the galaxy in this wavelength, showing five concentric rings of star-forming dust, ESA reports in today’s image advisory.

Inside the dusty clouds, stars are pulling themselves together in a gravitational process that can last hundreds of millions of years. Once a star reaches enough density, it will shine in light visible to ordinary telescopes.

Superimposed on the infrared image is an X-ray view made with the XMM-Newton observatory. X-rays show stars in their violent death throes. This image highlights hundreds of X-ray sources clustered around the center of Andromeda. Some of the X-rays are from debris rolling through space from exploded stars; others are pairs of stars locked in a gravitational fight to the death, according to ESA.

In these fights, already-dead stars pull in gas from their still-living companions. As the gas falls through space, it heats up and emits X-rays. The living star will eventually become depleted as the stellar corpse wraps itself in the stolen gas. This corpse could then explode.

The Andromeda Galaxy is similar to our own Milky Way, though about twice as big. Over the years, it has consumed dwarf galaxies that wander too close to it, and astronomers believe it is headed our way for a merger in about 3 billion to 5 billion years.

For more on the Andromeda Galaxy, check out these stories below.

* The galaxy next door * Andromeda is a cannibal and heading our way * NASA captures amazing view of Andromeda * Andromeda involved in galactic collision

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John Roach is a contributing writer for Connect with the Cosmic Log community by hitting the “like” button on the Cosmic Log Facebook page or following’s science editor, Alan Boyle, on Twitter (@b0yle).


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