Posted: 05 December, 2008
Like a shaken snow globe of sparkling snow flakes frozen in time, Hubble has captured an instantaneous glimpse of the thousands of glittering stars moving about the globular cluster M13.
M13 is a densely packed globular cluster located 25,000 light years away. Image: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).
M13 is one of the brightest and best-known globular clusters in the northern sky, and is easily located in the winter sky in the constellation Hercules. It is home to a metropolis of over 100,000 stars that are packed so closely together, especially in the central regions where the density of stars is about a hundred times greater than the density in the neighborhood of our Sun, that they occasionally slam into each other and form a new star, known as a blue straggler.
Blue stragglers are hotter and bluer than any other blue stars of the same luminosity in a given cluster, leading astronomers to believe that they underwent an unusual evolution. Since they are frequently observed in densely packed globular clusters, their genesis was attributed to stellar collisions. In contrast, the brightest red stars in the cluster are ancient red giants, aging stars that have expanded to many times their original diameters and subsequently cooled.
Globular clusters can be found in a vast halo around our Galaxy and M13 is one of nearly 150 known globular clusters surrounding our Milky Way. Globular clusters contain some of the oldest stars in the Universe. They likely formed before the disc of our Milky Way, so they are older than nearly all other stars in our galaxy. Studying globular clusters therefore tells us about the history of our Galaxy.
The newly released image is a composite of archival Hubble data taken with the Wide Field Planetary Camera 2 and the Advanced Camera for Surveys. Observations from four separate science proposals taken in November 1999, April 2000, August 2005, and April 2006 were used to construct the image, which includes broadband filters that isolate light from the blue, visible, and infrared portions of the spectrum.
Hubble has been in operation for over 18 years, and this week NASA officials announced that the delayed mission to repair and replace vital components on the troubled space telescope has been rescheduled for 12 May 2009.