Hubble's View of Messier 68: Like Diamonds in the Sky

By Nancy Atkinson - July 30, 2012 at 1:00 PM UTC | Extragalactic
messier-68.jpg

If you've ever looked at Messier 68 through a telescope, you know what a delightful view it is. But the Hubble Space Telescope offers a spectacular, diamond-studded picture of this crowded stellar encampment, a spherical, star-filled region of space known as a globular cluster. This beautiful grouping of stars has been performing a type of stellar dance for perhaps 10 million years.

At a distance of approximately 33,000 light-years, the M68 globular cluster contains at least 2,000 stars that are visible, including 250 giants and 42 variables. It spans 106 light years in diameter.

Mutual gravitational attraction among a cluster's numerous stars keeps stellar members in check, allowing globular clusters to hang together for many billions of years.

Astronomers can measure the ages of globular clusters by looking at the light of their constituent stars.

The chemical elements leave signatures in this light, and the starlight reveals that stars of globular clusters typically contain fewer heavy elements, such as carbon, oxygen and iron, than stars like the Sun.

Since successive generations of stars gradually create these elements through nuclear fusion, stars having fewer of them are relics of earlier epochs in the Universe.

Indeed, the stars in globular clusters rank among the oldest on record, dating back more than 10 billion years.

More than 150 of these objects surround our Milky Way Galaxy. On a galactic scale, globular clusters are not all that big. In Messier 68's case, its stars span a volume of space with a diameter of little more than a hundred light-years. The disc of the Milky Way, on the other hand, extends over some 100,000 light-years or more.

Image caption: The globular cluster Messier 68. Credit: ESA/Hubble & NASA

Source:

ESA

Nancy Atkinson

Nancy Atkinson

Nancy Atkinson is a space journalist and author with a passion for telling the stories of people involved in space exploration and astronomy. She is currently retired from daily writing, but worked at Universe Today for 20 years as a writer and editor. She also contributed articles to The Planetary Society, Ad Astra (National Space Society), New Scientist and many other online outlets.

Her 2019 book, "Eight Years to the Moon: The History of the Apollo Missions,” shares the untold stories of engineers and scientists who worked behind the scenes to make the Apollo program so successful, despite the daunting odds against it. Her first book “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” (2016) tells the stories of 37 scientists and engineers that work on several current NASA robotic missions to explore the solar system and beyond.

Nancy is also a NASA/JPL Solar System Ambassador, and through this program, she has the opportunity to share her passion of space and astronomy with children and adults through presentations and programs. Nancy's personal website is nancyatkinson.com