Astronomy Picture of the Day for June 14

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is  featured, along with a brief explanation written by a professional astronomer.

2012 June 14

M13: The Great Globular Cluster in Hercules

Image Credit & Copyright: Martin Pugh  

 

 

Explanation: In 1716, English astronomer Edmond Halley noted, “This is but a little Patch, but it shews itself to the naked Eye, when the Sky is serene and the Moon absent.” Of course, M13 is now modestly recognized as the Great Globular Cluster in Hercules, one of the brightest globular star clusters in the northern sky. Telescopic views reveal the spectacular cluster’s hundreds of thousands of stars. At a distance of 25,000 light-years, the cluster stars crowd into a region 150 light-years in diameter, but approaching the cluster core upwards of 100 stars could be contained in a cube just 3 light-years on a side. For comparison, the closest star to the Sun is over 4 light-years away. Along with the cluster’s dense core, the outer reaches of M13 are highlighted in this sharp color image. The cluster’s evolved red and blue giant stars show up in yellowish and blue tints.

Astronomy Picture of the Day for April 9th

Astronomy Picture of the Day

Discover the cosmos!Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2012 April 9
See Explanation.  Clicking on the picture will download the highest resolution version available.

Blue Straggler Stars in Globular Cluster M53
Image Credit: ESA/Hubble, NASA 

Explanation: If our Sun were part of M53, the night sky would glow like a jewel box of bright stars. M53, also known as NGC 5024, is one of about 250 globular clusters that survive in our Galaxy. Most of the stars in M53 are older and redder than our Sun, but some enigmatic stars appear to be bluer and younger. These young stars might contradict the hypothesis that all the stars in M53 formed at nearly the same time. These unusual stars are known as blue stragglers and are unusually common in M53. After much debate, blue stragglers are now thought to be stars rejuvenated by fresh matter falling in from a binary star companion. By analyzing pictures of globular clusters like the above image taken by the Hubble Space Telescope, astronomers use the abundance of stars like blue stragglers to help determine the age of the globular cluster and hence a limit on the age of the universe. M53, visible with a binoculars towards the constellation of Bernice’s Hair (Coma Berenices), contains over 250,000 stars and is one of the furthest globulars from the center of our Galaxy.