NGC 6397
A Hubble Space Telescope (HST) image of NGC 6397. The Hubble Space Telescope ( HST; also known colloquially as "the Hubble" or just "Hubble" is a space telescope that was carried into Credit: HST/NASA/ESA. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member
Observation data (J2000 epoch)
Class	IX
Constellation	Ara
Right ascension	17h 40m 41. In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. The Shapley–Sawyer Concentration Class is a classification system on a scale of one to twelve using Roman numerals for Globular clusters according to their concentration In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture Ara ( Altar) is a southern Constellation situated between the constellations Scorpius and Triangulum Australe. Right ascension (abbrev RA; symbol α) is the Astronomical term for one of the two Coordinates of a point on the Celestial sphere 36s[1]
Declination	−53° 40′ 25. In Astronomy, declination (abbrev dec or δ) is one of the two coordinates of the Equatorial coordinate system, the other being either 3″[1]
Distance	7. 2 kly[2] (2. A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by 2 kpc)
Apparent magnitude (V)	+6. History The first direct measurements of an object at interstellar distances were undertaken by German Astronomer Friedrich Wilhelm Bessel in 1838 The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value 68[1]
Apparent dimensions (V)	32′. 0
Physical characteristics
Mass	presently unknown kg ( M)
Radius	34 ly[3]
VHB	14. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. 2
Estimated age	13. 4 ± 0. 8 Gyr[2]
Notable features	Second closest globular to Earth
Other designations	GCl 74,[1] Lacaille III. 11, Dunlop 366, Bennett 98
See also: Globular cluster, List of globular clusters
This box: view • talk • edit

NGC 6397 is a globular cluster in the Ara constellation. A globular cluster is a spherical collection of Stars that orbits a galactic core as a Satellite. This is a list of Globular clusters. The apparentmagnitude does not include an extinction correction A globular cluster is a spherical collection of Stars that orbits a galactic core as a Satellite. Ara ( Altar) is a southern Constellation situated between the constellations Scorpius and Triangulum Australe. In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture It is located about 7,200 light-years from Earth, making it one of the two nearest globular clusters to Earth (the other one being Messier Object 4). A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Messier 4 (also known as M4 or NGC 6121) is a Globular cluster in the Constellation Scorpius. NGC 6397 is one of the at least 20 globulars of our Milky Way Galaxy which have undergone a core collapse^[2], meaning that its core has contracted to a very dense stellar agglomeration. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply In the study of human settlements an agglomeration is an extended City or Town area comprising the built-up area of a central place ( usually a Municipality The cluster contains around 400,000 stars. ^[2]

Contents 1 Astronomical research 1.1 Estimating the age of the Milky Way 1.2 Lower mass limit for stars 2 References

Astronomical research

Estimating the age of the Milky Way

In 2004, a team of astronomers^[2] focused on the cluster to estimate the age of the Milky Way. A team comprises a group of people or Animals linked in a common purpose Historically Astronomy was more concerned with the classification and description of phenomena in the sky while Astrophysics attempted to explain these phenomena The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply The team consisted of Luca Pasquini, Piercarlo Bonifacio, Sofia Randich, Daniele Galli, and Raffaele G. Gratton. They used the UV-Visual Echelle Spectrograph of the Very Large Telescope to measure, for the first time, the beryllium content of two stars in the cluster. An echelle grating (from French échelle, meaning stairs or ladder is a type of Diffraction grating which is characterised by a relatively low grooves density but The Very Large Telescope ( VLT) is a system of four separate Optical telescopes (the Antu telescope, the Kueyen telescope, the Melipal Measurement is the process of estimating the magnitude of some attribute of an object such as its length or weight relative to some standard ( unit of measurement) such as Beryllium (bəˈrɪliəm is a Chemical element with the symbol Be and Atomic number 4 A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth This allowed them to deduce the time elapsed between the rise of the first generation of stars in the entire Galaxy and the first generation of stars in the cluster. For other uses see Time (disambiguation Time is a component of a measuring system used to sequence events to compare the durations of A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth They added in the estimated age of the stars in the cluster to arrive at an age for the Galaxy (about 13. 6 billion years, which is nearly as old as the universe itself). A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun The age of the Universe is the time elapsed between the theory of the Big Bang and the present day

Lower mass limit for stars

In 2006, a study of NGC6397 using the Hubble Space Telescope was published that showed for a clear lower limit in the brightness of the cluster's population of faint stars. The Hubble Space Telescope ( HST; also known colloquially as "the Hubble" or just "Hubble" is a space telescope that was carried into In Astronomy, absolute magnitude (also known as absolute visual magnitude) is the Apparent magnitude an object would have if it were at a standard The authors deduce that this indicates a lower limit in mass for stars to develop a core that is capable of fusion, and obtain a value of approximately 0. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus 083 times the mass of the Sun. The Sun (Sol is the Star at the center of the Solar System. ^[4]

References

---

© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic