Messier 70 or M70, also known as NGC 6681, is a

globular cluster A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards its center. It can contain anywhere from tens of thousands to many millions of member stars, all orbiting ...

of stars to be found in the south of Sagittarius. It was discovered by

Charles Messier Charles Messier (; 26 June 1730 – 12 April 1817) was a French astronomer. He published an astronomical catalogue consisting of 110 nebulae and star clusters, which came to be known as the ''Messier objects'', referred to with th ...

in 1780. The famous

comet Hale–Bopp Comet Hale–Bopp (formally designated C/1995 O1) is a long-period comet that was one of the most widely observed of the 20th century and one of the brightest seen for many decades. Alan Hale (astronomer), Alan Hale and Thomas Bopp disc ...

was discovered near this cluster in 1995. It is about 29,400

light year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by t ...

s away from

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

and around from the

Galactic Center The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a ...

. It is roughly the same size and

luminosity Luminosity is an absolute measure of radiated electromagnetic radiation, electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electroma ...

as its neighbour in space, M69. M70 has a very small core radius of and a half-light radius of . This cluster has undergone core collapse, leaving it centrally concentrated with the luminosity distribution following a

power law In statistics, a power law is a Function (mathematics), functional relationship between two quantities, where a Relative change and difference, relative change in one quantity results in a relative change in the other quantity proportional to the ...

. There are two distinct stellar populations in the cluster, with each displaying unique abundances. These likely represent different generations of stars. Five known

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...

s lie within its broadest radius, the tidal radius, all of which are

RR Lyrae variable RR Lyrae variables are periodic variable stars, commonly found in globular clusters. They are used as standard candles to measure (extra) galactic distances, assisting with the cosmic distance ladder. This class is named after the prototype a ...

s. The cluster may have two

blue straggler A blue straggler is a type of star that is more luminous and bluer than expected. Typically identified in a stellar cluster, they have a higher effective temperature than the main sequence turnoff point for the cluster, where ordinary stars b ...

s near the core.

Gallery

File:Messier 70 Hubble WikiSky.jpg, Image by Hubble Space Telescope File:M70map.png, Map showing M70, against a conventional (southern) horizon

References and footnotes

External links

Messier 70, Galactic Globular Clusters Database page
* {{DEFAULTSORT:Messier 070 Globular clusters Sagittarius (constellation) 070 NGC objects Astronomical objects discovered in 1780 Discoveries by Charles Messier

Gallery

See also

References and footnotes

External links