m10 – globular cluster


Lupe Rioné, Amateur astronomer (Spain)


Globular cluster


Constellation of Ophiuchus


14,300 light-years


83 light-years

Globular clusters: Globular clusters are concentrations of thousands to millions of stars joined gravitationally. They all orbit in the halo of a galaxy, although some of them can be located near the center of the Milky Way.

Do you want to know more about stellar clusters?

History and Discovery

Also known as NGC 6254, M10 was discovered by Charles Messier on May 29, 1764, one night after observing the globular cluster M9. At that time he defined it as a “starless nebula” near the belt of the constellation Ophiuchus and was struck by its extremely round shape. There are not many notes by Messier about M10, only its position in the firmament and a brief description.

With a larger and more accurate telescope, the German astronomer William Herschel observed M10 in much greater detail and found it to be a grouping of individual stars. He described it as “a beautiful cluster of stars compressed together.” Later, Harlow Shapley was the first to calculate an approximate distance to the globular cluster, estimating about 33,000 light-years. We now know that this estimate was off, and the data indicate that the star cluster is 14,300 light-years away.

M10 Globular cluster. Credit: Verónica Casanova, (Valladolid) R80 F/5 telescope.

M10 Globular cluster. Credit: Jesús Sanabria


M10 is a very bright and star-rich cluster. Located in the constellation Ofiuco, it is estimated to be approximately 16,000 light-years from the center of our galaxy. An analysis of its radial velocity allows us to deduce that it is moving away from Earth at more than 271,440 km/h. This velocity originates from the combination of its orbital velocity around the Milky Way’s nucleus and the velocity of the Sun and the Earth.

We know that M10 takes about 140 million years to complete its orbit around the galaxy, and about 53 million years to cross the plane of the Milky Way. For comparison, the Sun takes about 250 million years to complete an orbit around the galaxy and about 70 million years to cross the galactic plane.

The data indicate that M10 contains approximately 100,000 stars, and about 15% of these are binary stars located in the core. Binary stars tend to be located in the center of the cluster because of their mass. Consequently, the core of M10 contains a huge concentration of blue straggler stars, most of them formed 2-5 billion years ago. They are called stragglers because they appear to be much younger than the cluster to which they belong. M10 is a cluster very poor in variable stars. Only four stars of this type have been catalogued; a curious fact, since in other globular clusters they are found in much greater numbers.

M10 has a diameter of about 83 light-years, and its central region, the most striking of this celestial body, measures 35 light-years. Its apparent magnitude is 6.4, which makes it difficult to see with the naked eye unless we have very dark skies. Its spectral type is F3, which means that in photographs it appears golden due to the large number of red giant stars (yellowish or orange) that it contains.

On the other hand, it belongs to class VII in the Shapley-Sawyer Concentration Classification. This is a classification system on a scale of one to twelve that uses Roman numerals for globular clusters according to their concentration. The most concentrated clusters are classified as Class I, decreasing to Class XII as the concentration decreases. In addition, it is a cluster with a fairly low metallicity (metallicity is the amount of elements that can be found in a star beyond hydrogen and helium). This data is relevant because it allows us to calculate the age of the globular cluster, approximately 11.4 billion years.

M10 Globular Cluster. Credit: NASA/ESA /Hubble


It is not strange that among the first objects catalogued and discovered by Charles Messier there were so many globular clusters, since many of them could resemble the scalp of a comet. M10, for example, is only 3 degrees 20′ southeast of M12, another globular cluster, and Messier may have identified them as 2 simultaneous comets. In fact, the astronomer drew up his famous catalog to differentiate these objects (which remained stationary and did not move against the background of stars) from comets.

With astronomical binoculars, M10 appears close to M12, farther south and much brighter. To locate it we will start from the 1st magnitude star Antares (Scorpius alpha) and head north, about 25 degrees, until we find M10.

With a telescope the process is the same, but the cluster can be seen in much more detail, and its dense core can be distinguished. With a 200+ telescope, M10 will dazzle us with its thousands of stars, from the outer halo to the dense core. In addition to this spectacle, there is the rich stellar background that populates the vicinity of this beautiful globular cluster.


Location of M10. Credit: ESO, IAU and Sky &Telescope

Don’t miss our astronomy videos on youtube (English and Spanish subtitled)

Somewhere, something incredible is waiting to be known

Carl Sagan 

M10 – Globular Cluster | Cúmulo Globular

M10 is a very bright and star-rich cluster. Located in the constellation Ofiuco, it is estimated to be approximately 16,000 light-years from the center of our galaxy. An analysis of its radial velocity allows us to deduce that it is moving away from Earth at more than 271,440 km/h.

M9 – Globular Cluster | Cúmulo Globular

Like all globular clusters, M9 is a spectacle in itself, and one of the oldest and most intriguing objects in our galaxy. M9 stands out as one of the closest globular clusters to the center of our galaxy, only 5,500 light-years away.

M8 – Lagoon Nebula | Nebulosa de la Laguna

Like all emission nebulae, M8 or NGC 6523 is a gigantic HII region, that is, a spectacular cradle of stars. With a magnitude of 5.8, this incredible nebula boasts many large, hot stars, whose ultraviolet radiation sculpts the gases and cosmic dust, giving it its characteristic shape.

M7 – Open Cluster | Cúmulo Abierto

Also known as NGC 6475, M7 is an open cluster, that is, a group of gravitationally bound stars formed by the same molecular cloud. It is a very sparse cluster, located in a very rich region of the Milky Way.

M6 – Open Cluster | Cúmulo Abierto

This beautiful cluster comprises more than 200 stars and has a diameter of about 12-20 light-years. It is estimated that its stars were formed about 100 million years ago, which means that while dinosaurs roamed the planet, M6 was just beginning to shine in the sky.

M5 – Globular Cluster | Cúmulo Globular

The globular cluster M5 is probably one of the most interesting because it is one of the oldest, largest, and brightest clusters. It is located in the constellation of The Serpent (Serpens) at a distance of approximately 24,500 light-years.

M4 – Globular Cluster | Cúmulo Globular

Also called NGC 6121, M4 is the closest globular cluster to the Earth. M4 contains about 100,000 stars, and like most globular clusters, it is a very old structure, about 12-13 billion years old.

M3 – Globular Cluster | Cúmulo Globular

M3, also called NGC 5272, is one of the largest and most spectacular clusters that we can observe in our galaxy. In fact, M3 was the first original discovery by Charles Messier.

M2 – Globular Cluster | Cúmulo Globular

M2 is a globular star cluster and the second object in the Messier catalog. Also called NGC 7089, it was discovered in 1746 by French astronomer Jean-Dominique Maraldi.

M1 – Crab Nebula | Nebulosa del Cangrejo

M1 is the remnant of a supernova explosion that was observed by Chinese astronomers during the Song Dynasty in the 11th century.


Pin It on Pinterest

Share This