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Anne’s Picture of the Day: Messier 69
read more at Anne’s Astronomy News http://annesastronomynews.com/
October 29, 2012
Messier 69, a globular cluster in Sagittarius
Image Credit: ESA/Hubble & NASA
Messier 69 (also known as NGC 6637) is a globular cluster of roughly 85 light-years across, with an estimated mass of 300,000 solar masses and an age of 13.06 billion years. It is located some 29,700 light-years away in the constellation Sagittarius (the Archer), quite close to the galactic center (only about 6,200 light-years distant), and is moving away from Earth at approximately 39.1 kilometers per second.
Globular clusters are dense collections of old stars. Messier 69, rather similar to its neighbor Messier 70 (with only 1,800 light-years separating the two objects), is one of the smaller and fainter globular clusters in Messier’s catalog.
Despite its age, Messier 69 is one of the most metal-rich globular clusters known. In astronomy, the term “metal” refers to any element heavier than the two most common elements in our Universe, hydrogen and helium. The nuclear fusion that powers stars created all of the metallic elements in nature, from the calcium in our bones to the carbon in diamonds. Successive generations of stars have, via supernova explosions at the end of their lives, built up the metallic abundances we see today.
Because the stars in globular clusters are ancient, their metallic abundances are much lower than more recently formed stars, such as the Sun. Studying the makeup of stars in globular clusters like Messier 69 has helped astronomers trace back the evolution of the cosmos.
In this picture, foreground stars look big and golden when set against the backdrop of the thousands of white, silvery stars that make up M69.
The image is made by the NASA/ESA Hubble Space Telescope, and is a combination of exposures taken in visible and near-infrared light by Hubble’s Advanced Camera for Surveys.
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2012-10-29 08:40:10
Source: http://annesastronomynews.com/annes-picture-of-the-day-messier-69/
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