Messier 70 (M70) is a globular cluster located in the constellation Sagittarius. Discovered by Charles Messier in 1780, it is part of the well-known Messier catalog of deep-sky objects. Like many other globular clusters, M70 is a dense collection of stars bound together by gravity, with an estimated population of hundreds of thousands of stars. It lies approximately 29,300 light-years away from Earth and has been the subject of interest due to its position near the core of the Milky Way.
Description
Messier 70 is a compact, bright globular cluster that appears as a small, concentrated patch of light when viewed through a telescope. The cluster's stars are densely packed toward the center, and it spans about 68 light-years in diameter. The core is extremely bright, but like many globular clusters, it becomes less luminous as you move outward from the center.
M70 is classified as a class V globular cluster on the Shapley-Sawyer Concentration Class scale, meaning it has a medium level of concentration. The stars within the cluster are primarily older, metal-poor stars, which is typical of globular clusters formed early in the history of the universe.
Magnitude
Messier 70 has an apparent magnitude of 7.87, making it too faint to be seen with the naked eye but visible with small telescopes or good binoculars under dark skies. When observed through a larger telescope, individual stars within the cluster can be resolved, especially toward the outskirts of the cluster.
Constellation and Visibility
Messier 70 resides in the constellation Sagittarius, which is rich in deep-sky objects due to its proximity to the center of the Milky Way. Sagittarius is a summer constellation for observers in the Northern Hemisphere, making Messier 70 most prominent during the summer months, especially in July and August.
Sagittarius is located near the southern horizon for observers in mid-northern latitudes, but it appears higher in the sky for those closer to the equator or in the Southern Hemisphere, where it can be observed during winter.
How to Find Messier 70
Finding Messier 70 requires locating the Sagittarius constellation, which is easily recognized by its "Teapot" asterism. The globular cluster lies about 2.5 degrees west-southwest of the star Ascella (Zeta Sagittarii), which forms part of the "handle" of the teapot. The cluster is also about 1.5 degrees east of Messier 69 (M69), another globular cluster in the same region.
For amateur astronomers using a telescope, start by centering Ascella in your finderscope, and then scan the area to the west-southwest. At low magnification, M70 will appear as a faint, round glow. Increasing the magnification will help resolve more detail, allowing you to see the cluster's dense core.
History
Charles Messier discovered Messier 70 on August 31, 1780, during his extensive search for comet-like objects. Messier was a French astronomer who cataloged 110 deep-sky objects that could potentially be confused with comets. M70 was added as the 70th object in his catalog.
Over the years, M70 has been studied in greater detail using modern telescopes. It gained particular attention in 1995 when it was discovered that the globular cluster coincided with the location of Comet Hale-Bopp's perihelion. This means that Comet Hale-Bopp made its closest approach to the Sun near the position of Messier 70, an interesting celestial coincidence.
Globular clusters like M70 are of significant interest to astronomers because they provide insights into the early stages of the Milky Way's formation and the overall structure of our galaxy. M70 is located close to the galactic center, making it an excellent target for studying the dynamics of stars within such dense environments and how they interact with the gravitational forces of the galaxy's core.
Conclusion
Messier 70 is a fascinating globular cluster located in the constellation Sagittarius. With an apparent magnitude of 7.87, it is best viewed during the summer months in the Northern Hemisphere and can be located near the star Ascella in the "Teapot" asterism. While not one of the brightest globular clusters, it offers a compelling view through a telescope and provides astronomers with valuable insights into the early history of the Milky Way.