Blue Stragglers

This animation is an artist’s rendering of the movement of blue straggler stars in a globular cluster over time. Blue straggler stars are blue, bright stars with a higher-than-average mass for a cluster. Over time, they sink toward the center of a star cluster. Those closest to the cluster core are the first to migrate inwards; more distant blue stragglers move inward over time.

Video Credit: ESA

Messier 13

Messier 13 is a large globular star cluster about 25,000 light years from Earth. It contains several hundred thousand stars and is about 145 light-years in diameter. July is a good month to look for it with a pair of binoculars. About a-third of the way from Vega to Arcturus, four bright stars in the constellation of Hercules form the Keystone asterism. M13 can be seen partway between Zeta Herculis and Eta Herculis, the two star that form the shoulders of the constellation.

Image Credit: NASA / ESA

Messier 56

Messier 56 (or M56) is a globular cluster in the constellation Lyra. It appears to be a slightly fuzzy star in large binoculars or a small telescope, but the cluster can be resolved using a telescope with an aperture of 20 cm or larger.

M56 is at a distance of about 32,900 light-years from Earth and measures around 84 light-years across, with a combined mass some 230,000[4] times that of the Sun. Because the cluster appears to be 13.7 billion years and is following a retrograde orbit through the Milky Way, it is believed to be part of the Gaia Sausage, the remains of a dwarf galaxy that merged with the Milky Way.

Image Credit: NASA / ESA

Messier 75

This is Messier 75. It’s a globular cluster, a spherical collection of stars bound together by gravity. It’s around 67,000 light-years away. The majority of the cluster’s 400,000 stars are in its core, making it is one of the most densely packed clusters ever found. It’s extremely bright,180,000 times brighter than the Sun.

Image Credit: NASA / ESA

A Star Cluster in Another Galaxy

The clump of stars in the center of the picture is the globular cluster NGC 1898. It’s not in our galaxy. It’s near the middle of the Large Magellanic Cloud, a satellite galaxy of The Milky Way which contains a rich population of star clusters, making it an ideal laboratory for investigating star formation.

Image Credit: ESA / NASA


Messier 92 is one of the brightest globular clusters in the northern sky, but it is often overlooked by amateur astronomers because of its proximity to the even more spectacular Messier 13. It is visible to the naked eye under very good seeing conditions. Indeed, M92 is among the brightest clusters in terms of absolute magnitude as well as being one of the oldest clusters in the Milky Way.

Image Credit: ESA / NASA

NGC 3201

NGC 3201 is an oddball among the 150-or-so globular star clusters in the Milky Way. It is moving very rapidly through the galaxy, and its motion is retrograde, that is, it’s orbiting around the galactic core in the opposite direction of most of the stars in the galaxy. That’s led to speculation that it may have come from outside and have been captured.

Also, it contains a black hole which was revealed by the strange movements of a star being quickly flung around the massive, invisible singularity.

Image Credit: ESA / NASA

Messier 5

Messier 5 (aka M5) is a globular star cluster of over 100,000 stars bound by gravity and packed into a region about 165 light-years across. It’s about 25,000 light-years away. Globular star clusters are ancient members of the Milky Way, and M5 is one of the oldest. Its stars are nearly 13 billion years old.

Image Credit: NASA / ESA

A Globular Cluster

Youthful NGC 362Globular clusters offer some of the most spectacular sights in the night sky. These ornate spheres contain hundreds of thousands of stars, and reside in the outskirts of galaxies. The Milky Way contains over 150 globular clusters, and NGC 362 is one of the more unusual ones.

As stars make their way through life they fuse elements together in their cores, creating heavier and heavier elements—astronomers call anything further up the period table than helium a “metal”—in the process. When stars die, they flood their surroundings with the material they have formed during their lifetimes, enriching the interstellar medium with metals. New stars that form from the remnants of older stars contain higher proportions of metals than their older relatives. The stars in NGC 362 contain a surprisingly high metal content, indicating that it is younger, second generation stars. Most globular clusters are much older than the majority of stars in their host galaxy, but NGC 362 bucks the trend, with an age lying between 10 and 11 billion years old. That makes them newbies compared the average age of a star in the Milky Way, 13 billion years.

Image Credit: ESA / NASA

An Old Star Cluster

An ancient globuleThis is NGC 6535, a globular cluster 22,000 light-years away in the constellation of Serpens (The Serpent). It’s about one light-year across.

Globular clusters are tightly bound groups of stars which orbit galaxies. The Latin word globulus, from which these clusters take their name, means a small sphere.  A large mass in the rich stellar centre of a globular cluster pulls the stars inward to form a ball of stars.

Globular clusters are generally very ancient objects that form around the same time as their host galaxy. Thus far, no new star formation has been observed within any globular cluster. The lack of young stars explains the abundance of aging yellow stars in this image, most of them containing very few heavy elements.

Image Credit: NASA

The Riddle of the Missing Stars

Directed by: Georgia Bladon
Visual design and editing: Martin Kornmesser
Written by: Georgia Bladon and Nicky Guttridge
Narration: Sara Mendes da Costa
Images: NASA, ESA/Hubble
Videos: NASA, ESA/Hubble
Animations: Martin Kornmesser, NASA, ESA/Hubble
Music: Jennifer Athena Galatis
Web and technical support: Mathias Andre and Raquel Yumi Shida
Executive producer: Lars Lindberg Christensen

Omega Centauri

omega centauriOmega Centauri is the brightest and largest globular cluster of stars in the sky. This picture shows the central part only. The cluster is actually much larger than the field reproduced here; at a distance of about 16,500 light-years, the diameter of the field shown is about 90 light-years. There are hundreds of thousands of stars in the picture. Omega Centauri is in excess of 5 million solar masses, making it by far the most massive cluster of this type on the Milky Way galaxy.

Image Credit: ESO