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bystander
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by bystander » Wed Nov 25, 2015 7:37 pm
The Hottest White Dwarf in the Galaxy
Eberhard Karls Universität Tübingen | 2015 Nov 25
Astronomers in Tübingen and Potsdam identify dying star, intergalactic gas entering Milky Way
[img3="Diagram of the Milky Way showing our Sun, the white dwarf, and the gas
cloud relative to our neighbor galaxy, the Large Magellanic Cloud (adajcent
to it the Small Magellanic Cloud). The white dwarf RX J0439.8-6809 and
the gas cloud are between us and the Large Magellanic Cloud.
Credit: Philipp Richter/University of Potsdam"]http://www.uni-tuebingen.de/fileadmin/U ... _dwarf.png[/img3][hr][/hr] Astronomers at the Universities of Tübingen and Potsdam have identified the hottest white dwarf ever discovered in our Galaxy. With a temperature of 250,000 degrees Celsius, this dying star at the outskirts of the Milky Way has already even entered its cooling phase. The researchers also were the first to observe an intergalactic gas cloud moving towards the Milky Way - indicating that galaxies collect fresh material from deep space, which they can use to make new stars. These findings are published in the latest
Astronomy & Astrophysics.
Relatively low-mass stars - like our Sun - get extremely hot towards the end of their lives. The Sun’s surface temperature has been fairly constant at around 6000 degrees Celsius since its birth 4.6 million years ago. Immediately before its source of nuclear energy is exhausted in about five billion years, the Sun will reach thirty times that temperature, going to 180,000 degrees before cooling down as a white dwarf. Computer simulations suggest that stars can become even hotter than that. The highest temperature of an observed dying star was measured to be 200,000 degrees.
The researchers’ evaluation of ultraviolet spectra taken by the Hubble Space Telescope points to a new record of 250,000 degrees - a temperature which can only be reached by a star some five times more massive than our Sun. The white dwarf, RX J0439.8-6809, has already entered the cooling phase. It appears to have reached its maximum temperature of 400,000 degrees about a thousand years ago. Its chemical composition is not yet understood. Analyses show that carbon and oxygen are present on its surface - the products of the nuclear fusion of helium, a process which normally takes place deep in the core of a star. ...
Analysis of HST/COS spectra of the bare C-O stellar core H1504+65 and a high-velocity twin in the Galactic halo - K. Werner, T. Rauch
High-velocity gas towards the LMC resides in the Milky Way halo - P. Richter, K.S. de Boer, K. Werner, T. Rauch
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Ann
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Post
by Ann » Thu Nov 26, 2015 12:41 am
bystander wrote:The Hottest White Dwarf in the Galaxy
Eberhard Karls Universität Tübingen | 2015 Nov 25
Astronomers in Tübingen and Potsdam identify dying star, intergalactic gas entering Milky Way
[img3="Diagram of the Milky Way showing our Sun, the white dwarf, and the gas
cloud relative to our neighbor galaxy, the Large Magellanic Cloud (adajcent
to it the Small Magellanic Cloud). The white dwarf RX J0439.8-6809 and
the gas cloud are between us and the Large Magellanic Cloud.
Credit: Philipp Richter/University of Potsdam"]http://www.uni-tuebingen.de/fileadmin/U ... _dwarf.png[/img3][hr][/hr] Astronomers at the Universities of Tübingen and Potsdam have identified the hottest white dwarf ever discovered in our Galaxy. With a temperature of 250,000 degrees Celsius, this dying star at the outskirts of the Milky Way has already even entered its cooling phase. The researchers also were the first to observe an intergalactic gas cloud moving towards the Milky Way - indicating that galaxies collect fresh material from deep space, which they can use to make new stars. These findings are published in the latest
Astronomy & Astrophysics.
Relatively low-mass stars - like our Sun - get extremely hot towards the end of their lives. The Sun’s surface temperature has been fairly constant at around 6000 degrees Celsius since its birth 4.6 million years ago. Immediately before its source of nuclear energy is exhausted in about five billion years, the Sun will reach thirty times that temperature, going to 180,000 degrees before cooling down as a white dwarf. Computer simulations suggest that stars can become even hotter than that. The highest temperature of an observed dying star was measured to be 200,000 degrees.
The researchers’ evaluation of ultraviolet spectra taken by the Hubble Space Telescope points to a new record of 250,000 degrees - a temperature which can only be reached by a star some five times more massive than our Sun. The white dwarf, RX J0439.8-6809, has already entered the cooling phase. It appears to have reached its maximum temperature of 400,000 degrees about a thousand years ago. Its chemical composition is not yet understood. Analyses show that carbon and oxygen are present on its surface - the products of the nuclear fusion of helium, a process which normally takes place deep in the core of a star. ...
Analysis of HST/COS spectra of the bare C-O stellar core H1504+65 and a high-velocity twin in the Galactic halo - K. Werner, T. Rauch
High-velocity gas towards the LMC resides in the Milky Way halo - P. Richter, K.S. de Boer, K. Werner, T. Rauch
I'm surprised by the suggestion that low-mass (make that intermediate-mass) stars like the Sun get extremely hot towards the end of their lives. Surely it is only the star's
cores that get extremely hot? Young white dwarfs are so hot because they are the naked cores of former red giant stars, which have shed their outer layers and exposed their hot interiors.
Ann
Color Commentator
