Skip to main content

Stars sparkle and shine in Hubble image of a distant globular cluster

Another week, another beautiful image of space captured by the Hubble Space Telescope. This week’s image shows the globular cluster NGC 6717, located over 20,000 light-years away in the constellation of Sagittarius.

A global cluster is a dense group of stars, often thousands or even millions of stars strong, which is bound together by gravity. The clusters form roughly spherical shapes and mostly consist of less massive stars, each one typically less than the mass of our sun. As you can see in the image below, the stars are packed closer together nearer the center of the cluster and are more spaced out around its edges.

A star-studded image from the NASA/ESA Hubble Space Telescope depicts NGC 6717, which lies more than 20,000 light-years from Earth in the constellation Sagittarius.
This star-studded image from the NASA/ESA Hubble Space Telescope depicts NGC 6717, which lies more than 20,000 light-years from Earth in the constellation Sagittarius. NGC 6717 is a globular cluster, a roughly spherical collection of stars tightly bound together by gravity. Globular clusters contain more stars in their centers than their outer fringes, as this image aptly demonstrates; the sparsely populated edges of NGC 6717 are in stark contrast to the sparkling collection of stars at its center. ESA/Hubble and NASA, A. Sarajedini

As well as the globular cluster, you can see a few very bright stars shining out near the center of the image. These stars aren’t actually a part of the cluster, but rather are located between it and Earth.

Studying globular clusters is important to astronomers because they are some of the oldest objects in the universe, so looking at them can reveal how early stars and galaxies formed. However, imaging this globular cluster was a challenge because of where it is located. The constellation of Sagittarius is located in the same portion of the sky as the center of the Milky Way, where many stars in our galaxy shine brightly. The center of our galaxy is also full of dust and gas which absorb light and obscure the view behind it.

To capture this image through the dust and gas, Hubble used two of its instruments in combination: The Wide Field Camera 3 and the Advanced Camera for Surveys.

Editors' Recommendations

Georgina Torbet
Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…
Hubble gets festive with a string of cosmic Christmas lights
The billion stars in galaxy UGC 8091 resemble a sparkling snow globe in this festive Hubble Space Telescope image from NASA and ESA (European Space Agency). The dwarf galaxy is approximately 7 million light-years from Earth in the constellation Virgo. It is considered an "irregular galaxy" because it does not have an orderly spiral or elliptical appearance. Instead, the stars that make up this celestial gathering look more like a brightly shining tangle of string lights than a galaxy.

Researchers using the Hubble Space Telescope are getting into the festive spirit with a holiday image showing a dwarf irregular galaxy called UGC 8091. Located 7 million light-years away in the constellation of Virgo, this region is a hotbed of star formation, with bright young stars illuminating the gas around them to create a sparkling mass reminiscent of Christmas lights.

It is designated an irregular galaxy because of its nonuniform shape, and a dwarf galaxy because of its small size. Unlike spiral galaxies, such as our Milky Way, or elliptical galaxies, which are smooth and have a elliptical shape, irregular galaxies can come in a variety of shapes. Often, these galaxies have been pulled into odd shapes due to gravitational forces, such as when two galaxies come close to each other and interact.

Read more
Hubble captures a formation of galaxies neatly lined up
An interacting galaxy system known as Arp-Madore 2105-332, that lies about 200 million light-years from Earth in the constellation Microscopium.

Sometimes, Hubble or other telescopes will capture two or more galaxies that are in the process of merging -- called interacting galaxies. These huge collisions can warp one or both of the galaxies, twisting them into strange shapes. The results of such collisions can be catastrophic, with one of the galaxies being destroyed. Or they can be creative, with one larger galaxy being formed from the two merging galaxies.

However, sometimes galaxies that appear very close in images are not actually interacting. Sometimes, they merely appear to be close when seen from Earth, but they can actually be thousands of light-years apart. That's the case with a previous Hubble image showing two overlapping galaxies.

Read more
James Webb spots tiniest known brown dwarf in stunning star cluster
The central portion of the star cluster IC 348. Astronomers combed the cluster in search of tiny, free-floating brown dwarfs.

A new image from the James Webb Space Telescope shows a stunning view of a star cluster that contains some of the smallest brown dwarfs ever identified. A brown dwarf, also sometimes known as a failed star, is an object halfway between a star and a planet -- too big to be a planet but not large enough to sustain the nuclear fusion that defines a star.

It may sound surprising, but the definition of when something stops being a planet and starts being a star is, in fact, a little unclear. Brown dwarfs differ from planets in that they form like stars do, collapsing due to gravity, but they don't sustain fusion, and their size can be comparable to large planets. Researchers study brown dwarfs to learn about what makes the difference between these two classes of objects.

Read more