City of sparkling stars

Messier 107

Astronomers have found roughly 150 globular star clusters—giants 'cities' of stars—surrounding our Milky Way galaxy…such as this one, known as Messier 107. Photo courtesy ESO.

MESSIER 107 IS A BUSTLING METROPOLIS—thousands of stars concentrated into a space that is only about twenty times the distance between our Sun and it’s nearest stellar neighbour, Alpha Centauri.

The sharp new image above, captured by the Wide Field Imager on the 2.2-metre telescope at the European Southern Observatory’s (ESO) La Silla Observatory in Chile, displays the structure of Messier 107 in exquisite detail.

Also known as NGC 6171, the compact and ancient family of stars about 21,000 light-years from Earth is an example of what astronomers call a globular star cluster, so-called because of their round shape.

Astronomers know of about 150 of globular star clusters orbiting our galaxy, the Milky Way.

ESO 2.2m telescope

The ESO 2.2m telescope at La Silla, Chile. Photo courtesy ESO / H.H.Heyer.

In Messier 107, a significant number of these stars have evolved into red giants, one of the last stages of a star’s life, and have a yellowish colour in this image.

Globular clusters are among the oldest objects in the Universe. And since the stars within a globular cluster all formed from the same cloud of interstellar matter at roughly the same time—typically over 10 billion years ago—they are all low-mass stars, since lightweights burn their hydrogen fuel supply much more slowly than stellar behemoths.

Globular clusters formed during the earliest stages in the formation of their host galaxies and therefore studying these objects can give significant insights into how galaxies, and their component stars, evolve.

See the full-size, high-resolution image here (will open in a new window or tab).

M107 is not visible to the naked eye, but it can easily be seen from a dark site with binoculars or a small telescope. It is found in the constellation of Ophiuchus, north of the pincers of Scorpius.

Roughly half of the Milky Way’s known globular clusters are actually found in the constellations of Sagittarius, Scorpius and Ophiuchus, in the general direction of the centre of the Milky Way. This is because they are all in elongated orbits around the central region and are on average most likely to be seen in this direction.

Messier 107 was discovered by French astronomer Pierre Mechain in April 1782 and it was added to the list of seven Additional Messier Objects that were not originally included in the final version of countryman Charles Messier’s catalogue of “deep sky” objects, which was published the previous year.

On 12 May 1793, it was independently rediscovered by English astronomer William Herschel, who was able to resolve this globular cluster into stars for the first time. But it was not until 1947 that this globular cluster finally took its place in Messier’s catalogue as M107, making it the most recent star cluster to be added to this famous list.

Adapted from information issued by ESO.

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