November 7, 2013
Messier 10, a bright globular cluster in Ophiuchus
Image Credit: ESA/NASA
Messier 10 (also known as NGC 6254) is a bright, very large globular cluster of about 83 light-years across that lies some 14,300 light-years away from Earth in the central region of the constellation of Ophiuchus (the Serpent-Bearer), while it is receding from us at 69 kilometers per second. The brighter core is only less than half as large, about 35 light-years. It contains only 4 variable stars.
This large ball of stars with a mass of around 200,000 solar masses is estimated to be 11.39 billion years old. It is currently located about 16,000 light-years from the Galactic Center, and completes an orbit around the Milky Way galaxy about every 140 million years, during which it crosses the plane of the galactic disk every 53 million years.
Many stars aren’t alone but live their lives in binary systems. Because binary stars are, on average, more massive than normal stars, the binaries tend to migrate toward the center of the cluster. The core region therefore also contains a concentration of blue straggler stars, most of which formed 2 to 5 billion years ago.
A blue straggler is an old star that appears younger than it should be: it burns hot and blue. This is probably due to a collision of two older (binary) stars that merge and become one star with most of the mass from both stars.
In terms of the abundance of elements other than hydrogen and helium – the so-called metallicity – Messier 10 is “moderately metal–poor”. The abundance of iron is only 3.5% of the abundance found at the surface of the Sun. The cluster shows evidence of being enriched by supernovae.
Messier 10 should appear about two thirds the size of the full Moon in the night sky. However, its outer regions are extremely diffuse, and even the comparatively bright core is too dim to see with the naked eye.
This image is made up of observations made in visible and infrared light using the Advanced Camera for Surveys on the Hubble Space Telescope. The observations were carried out as part of a major Hubble survey of globular clusters in the Milky Way. Hubble, which has no problems seeing faint objects, has observed the brightest part of the center of Messier 10 in this image (released on June 18, 2012), a region which is about 13 light-years across.
A version of this image was entered into the Hubble’s Hidden Treasures Image Processing Competition by contestant Flashenthunder. Hidden Treasures is an initiative to invite astronomy enthusiasts to search the Hubble archive for stunning images that have never been seen by the general public.