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

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...

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''. Messier's purpose f ...

in 1780. The famous

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

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

light year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s away from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

and around from the

Galactic Center The Galactic Center or Galactic Centre is the rotational center, the barycenter, of the Milky Way galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a compact rad ...

. It is roughly the same size and

luminosity Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a st ...

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 proportional relative change in the other quantity, inde ...

. There are two distinct stellar populations in the cluster, with each displaying unique abundance 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 with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as ...

s lie within the broadest radius, the tidal radius, of it, 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 and ...

s. The cluster may have two

blue straggler A blue straggler is a main-sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams ...

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

Gallery

See also

References and footnotes

External links