Presented here is a new color image of the southwest region of the Andromeda Galaxy taken with Subaru's prime focus camera "Suprime-Cam". We see the stars of the Andromeda Galaxy as a great many small white dots. Many of the stars, star clusters, and nebulae in the image are seen clearly resolved for the first time. It is expected that new knowledge about the formation and evolution of stars within a galaxy will result from detailed studies of these observations.

The Andromeda Galaxy. Photo: Subaru Telescope, National Astronomical Observatory of Japan

This spectacular image was constructed from a total of 15 exposures lasting 2 minutes each, made through filters passing blue ("B"), green ("V") and red ("H-alpha") light. The red filter is specially designed to accentuate the light emitted by glowing hydrogen gas. The area shown covers a field spanning 18 arc-minutes by 25 arc-minutes on the sky. Analysis of the data is being carried out by Drs. Satoshi Miyazaki (NAOJ), Keiichi Kodaira (Graduate University for Advanced Studies, Japan) and Vladas Vansevicius (Vilnius Observatory).

The Andromeda Galaxy lies 2.3 million light-years away, making it the nearest large galaxy to our own. In many respects, the Andromeda Galaxy (also known as M31 or NGC224) is quite similar to our Milky Way Galaxy. Our "bird's-eye" view of the Andromeda Galaxy makes it relatively easy to obtain an answer to the question of how star-formation varies as a function of distance from the center of a galaxy. A remarkable color gradient is seen running diagonally across the image (yellow towards the upper left, blue towards the lower right). This gradient is caused by the history of star-formation and evolution within the galaxy. It is believed that, as we look in the direction of the galaxy's center (towards the upper left in this image), we are seeing light produced predominantly by stars created many billions of years ago when the galaxy was just forming; the combined yellowish glow of these stars gives way to a bluish light produced by much younger stars found further out from the galaxy's center (towards the lower right).

Subaru Telescope can produce significantly sharper wide-field images and has a four-time increase in light-gathering power over the previous generation of large telescopes used to produce the currently best available catalogs and maps for the Andromeda Galaxy. Using Subaru in combination with Suprime-Cam, new maps with much finer detail and catalogs containing far more objects is now possible. The Andromeda Galaxy has long been recognized as an important stepping stone to test our understanding of how galaxies came to be and how they evolve. Subaru Telescope is taking a leading role in bringing this approach to greater fruition.

A "light-year" is the distance light travels in one year. In more familiar units, a light-year equals about 6 trillion miles (9.46 trillion km), or over 12 million round-trips to the Moon.