About the Object Object Name: NGC 6397 Object Description: Globular Cluster Position (J2000): R.A. 17h 40m 41s.36 Dec. -53° 40' 25".3 Constellation: Ara Distance: 8,200 light-years (2.5 kiloparsecs) Dimensions: This image is roughly 2 arcminutes (3.8 light-years or 1.2 parsecs) wide. About the Data Data Description: These images were created from HST data from the following proposals: 9313: K. Noll (STScI), A. Cool (SFSU), J. Anderson (Rice), I. King (U. Washington), L. Frattare, H. Bond, C. Christian, F. Hamilton, Z. Levay, T. Royle (STScI); 7335: J. Grindlay (Harvard U.), A. Cool (SFSU), C. Bailyn (Yale U.), H. Cohn and P. Lugger (Indiana U.); and 5929: I. King (U. Washington), A. Cool (SFSU), C. Sosin (UCB), H. Cohn and P. Lugger (Indiana U.), J. Grindlay (Harvard U.), P. Callanan (UCC), and C. Bailyn (Yale U.). Significant contributions to the science were also made by A. Bolton (MIT), J. Taylor (Harvard U.), and P. Edmonds (CfA). Instrument: WFPC2 Exposure Date(s): March 6/7, 1996; April 3/4 1999; November 4, 2001 Exposure Time: 7 hours Filters: F336W("I"), F439("B"), F814W("U") About the Image Image Credit: NASA and the Hubble Heritage Team (STScI/AURA) Release Date: August 7, 2003 Orientation: Too Close for Comfort [ http://imgsrc.hubbl…]
Fast_Facts
Technical facts about this news release:
About the Object Object Name: NGC 6397 Object Description: Globular Cluster Position (J2000): R.A. 17h 40m 41s.36 Dec. -53° 40' 25".3 Constellation: Ara Distance: 8,200 light-years (2.5 kiloparsecs) Dimensions: This image is roughly 2 arcminutes (3.8 light-years or 1.2 parsecs) wide. About the Data Data Description: These images were created from HST data from the following proposals: 9313: K. Noll (STScI), A. Cool (SFSU), J. Anderson (Rice), I. King (U. Washington), L. Frattare, H. Bond, C. Christian, F. Hamilton, Z. Levay, T. Royle (STScI); 7335: J. Grindlay (Harvard U.), A. Cool (SFSU), C. Bailyn (Yale U.), H. Cohn and P. Lugger (Indiana U.); and 5929: I. King (U. Washington), A. Cool (SFSU), C. Sosin (UCB), H. Cohn and P. Lugger (Indiana U.), J. Grindlay (Harvard U.), P. Callanan (UCC), and C. Bailyn (Yale U.). Significant contributions to the science were also made by A. Bolton (MIT), J. Taylor (Harvard U.), and P. Edmonds (CfA). Instrument: WFPC2 Exposure Date(s): March 6/7, 1996; April 3/4 1999; November 4, 2001 Exposure Time: 7 hours Filters: F336W("I"), F439("B"), F814W("U") About the Image Image Credit: NASA and the Hubble Heritage Team (STScI/AURA) Release Date: August 7, 2003 Orientation: Too Close for Comfort [ http://imgsrc.hubbl…]
Fast Facts
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*Image Type:*: Astronomical/Illustr ation
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*Image Type:*: Astronomical/Illustr ation
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*Release Date*:August 7, 2003 09:00 AM (EDT)
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*Release Date*:August 7, 2003 09:00 AM (EDT)
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*News Release Number:*: STScI-2003-21b
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*News Release Number:*: STScI-2003-21b
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*Title*:Too Close for Comfort
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*Title*:Too Close for Comfort
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*Description*:
Four types of stars reside within the center of the globular cluster NGC 6397. They have been identified in the accompanying image as: 1) helium white dwarfs; 2) blue stragglers; 3) normal white dwarfs; and 4) cataclysmic variables.
1) Helium white dwarfs (blue squares): Three faint blue stars that do not vary in brightness can be seen near the center of the cluster. These stars may be very-low-mass white dwarfs, formed in the cores of giant stars whose evolution is somehow interrupted by a stellar collision or an interaction with a binary companion. When a giant star interacts with another star, it can lose its outer layers prematurely, exposing its hot, blue core.
2) Blue stragglers (blue circles): A blue straggler is a hot, bright, young star that is the result of a direct collision between two stars that have merged together to form a new star. They stand out among the old stars that make up the vast majority of stars in a globular cluster.
3) Normal white dwarf (purple circle): These stars appear throughout the cluster and form through the normal stellar evolution processes, when outer layers have been burned off of the star. Since they don't involve any stellar interactions, which occur predominantly near the cluster center, there are very few visible in this close-up image of NGC 6397. Nearly 100 such burned-out stars were identified in the entire image.
4) Cataclysmic variables (red triangles): A cataclysmic variable is a pairing of a normal, hydrogen-burning star and a burned-out star, or white dwarf. In this binary system, material pulled off the surface of the normal star by the white dwarf will encircle the white dwarf in an "accretion disk," and eventually falls onto it. The result of this accretion process is that cataclysmic variables vary in brightness.
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*Description*:
Four types of stars reside within the center of the globular cluster NGC 6397. They have been identified in the accompanying image as: 1) helium white dwarfs; 2) blue stragglers; 3) normal white dwarfs; and 4) cataclysmic variables.
1) Helium white dwarfs (blue squares): Three faint blue stars that do not vary in brightness can be seen near the center of the cluster. These stars may be very-low-mass white dwarfs, formed in the cores of giant stars whose evolution is somehow interrupted by a stellar collision or an interaction with a binary companion. When a giant star interacts with another star, it can lose its outer layers prematurely, exposing its hot, blue core.
2) Blue stragglers (blue circles): A blue straggler is a hot, bright, young star that is the result of a direct collision between two stars that have merged together to form a new star. They stand out among the old stars that make up the vast majority of stars in a globular cluster.
3) Normal white dwarf (purple circle): These stars appear throughout the cluster and form through the normal stellar evolution processes, when outer layers have been burned off of the star. Since they don't involve any stellar interactions, which occur predominantly near the cluster center, there are very few visible in this close-up image of NGC 6397. Nearly 100 such burned-out stars were identified in the entire image.
4) Cataclysmic variables (red triangles): A cataclysmic variable is a pairing of a normal, hydrogen-burning star and a burned-out star, or white dwarf. In this binary system, material pulled off the surface of the normal star by the white dwarf will encircle the white dwarf in an "accretion disk," and eventually falls onto it. The result of this accretion process is that cataclysmic variables vary in brightness.
