Messier 56 (also known as M56 or NGC 6779) 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 ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Lyra Lyra (; Latin for lyre, from Greek ''λύρα'') is a small constellation. It is one of the 48 listed by the 2nd century astronomer Ptolemy, and is one of the modern 88 constellations recognized by the International Astronomical Union. Lyra was ...

. 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 1779. It is angularly found about midway between

Albireo Albireo is a double star designated Beta Cygni (β Cygni, abbreviated Beta Cyg, β Cyg). The International Astronomical Union uses the name "Albireo" specifically for the brightest star in the system. Although designated ' beta', ...

(Beta (β) Cygni) and Sulafat (Gamma (γ) Lyrae). In a good night sky it is tricky to find with large (50–80 mm) binoculars, appearing as a slightly fuzzy star. The cluster can be resolved using a telescope with an

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An opt ...

of or larger. M56 is about 32,900

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 measures roughly 84 light-years across, containing 230,000

solar mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

es (). It is about 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 ...

and above the

galactic plane The galactic plane is the plane on which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles. In actual usage, the terms ''galactic plane'' and ''galactic poles'' usual ...

. This cluster has an estimated age of 13.70 billion years and is following a retrograde orbit through the Milky Way. The properties of this cluster suggest that it may have been acquired during the merger of a

dwarf galaxy A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is ...

, of which

Omega Centauri Omega Centauri (ω Cen, NGC 5139, or Caldwell 80) is a globular cluster in the constellation of Centaurus that was first identified as a non-stellar object by Edmond Halley in 1677. Located at a distance of , it is the largest-known globular c ...

forms the surviving nucleus. For Messier 56, the abundance of elements other than hydrogen and helium, what astronomers term the

metallicity In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...

, has a very low value of e/H= –2.00 dex which is of the abundance in the Sun. The brightest

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

s in M56 are of 13th

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

, while it contains only about a dozen 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, such as V6 ( RV Tauri star; period: 90 days) or V1 (

Cepheid A Cepheid variable () is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude. A strong direct relationship between a Cepheid varia ...

: 1.510 days); other variable stars are V2 (irregular) and V3 (semiregular). In 2000, a diffuse X-ray emission was tentatively identified coming from the vicinity of the cluster. This is most likely

interstellar medium In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...

that has been heated by the passage of the cluster through the galactic halo. The relative velocity of the cluster is about 177 km s⁻¹, which is sufficient to heat the medium in its wake to a temperature of 940,000 K. M56 is part of the

Gaia Sausage The Gaia Sausage or Gaia Enceladus is the remains of a dwarf galaxy (the Sausage Galaxy, or Gaia-Enceladus-Sausage, or Gaia-Sausage-Enceladus) that merged with the Milky Way about 8–11 billion years ago. At least eight globular clusters wer ...

, the hypothesised remains of a merged dwarf galaxy.

Gallery

References and footnotes

External links

Messier 56, SEDS Messier pages

Messier 56, Galactic Globular Clusters Database page

Hubble snaps a collection of ancient stars
August 26, 2012, ''TG Daily'' * * {{NGC70 Messier 056 Messier 056 056 Messier 056 Gaia-Enceladus Astronomical objects discovered in 1779

Gallery

See also

References and footnotes

External links