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Topic: White dwarf


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In the News (Fri 24 Nov 17)

  
  SPACE.com -- White Dwarf Hints at Our Solar System's End
White dwarfs are the dead stellar remains of relatively small stars like our
The chemical signature of light from the white dwarf suggested it was girdled by some kind of rotating gas disk, he said.
The discovery of this disk around the white dwarf is good evidence of the existence of planets, according to Gänsicke.
www.space.com /scienceastronomy/061222_wdwarf_disk.html   (687 words)

  
  White Dwarf
A white dwarf which exceeds this limit (known as the Chandrasekhar limit), typically by mass transfer from a companion star, may explode as a Type Ia supernova via a process known as "carbon detonation".
As a class, white dwarfs are fairly common; they comprise roughly 6% of all stars and brown dwarfs within 10 parsecs of the Sun.
Many white dwarfs are approximately the size of the Earth, typically 100 times smaller than the Sun; their average mass is about 0.5-0.6 solar masses, though there is quite a bit of variation.
www.juliantrubin.com /encyclopedia/astronomy/whitedwarf.html   (1486 words)

  
 white dwarf
White dwarfs form from the collapse of stellar cores in which nuclear fusion has stopped, and are exposed to space following the loss of the old star's bloated outer envelope, typically as a planetary nebula.
White dwarfs consist of electron degenerate matter, which provides the pressure needed to prevent further collapse, providing that the mass of the dwarf doesn't exceed the Chandrasekhar limit of about 1.4 solar mass.
White dwarfs that consume matter from their companions can explode as type 1a supernovae, which are used as standard candles to measure cosmic distances.
www.daviddarling.info /encyclopedia/W/whitedwarf.html   (455 words)

  
 White dwarf - Wikipedia, the free encyclopedia
Sirius B, which is a white dwarf, can be seen as a faint dot to the lower left of the much brighter Sirius A. white dwarf is an astronomical object which is produced when a low or medium mass star dies.
A white dwarf which approaches this limit (known as the Chandrasekhar limit), typically by mass transfer from a companion star, may explode as a Type Ia supernova via a process known as carbon detonation.
In the 1930s this was explained as a quantum mechanical effect: the weight of the white dwarf is supported by the pressure of electrons (electron degeneracy), which only depends on density and not on temperature.
en.wikipedia.org /wiki/White_dwarf   (1995 words)

  
 White Dwarf Stars
The defining characteristics of white dwarf stars are presented and interpreted in an evolutionary context.
White dwarfs are the cooling naked cores of the most highly evolved stars which have mostly consumed their fusionable elements and undergone gravitational collapse.
White dwarfs are not classifiable by ordinary rules.For example, more massive white dwarfs are usually less luminous because their higher gravity contracts the stars, reducing the surface area.
www.peripatus.gen.nz /Astronomy/WhiDwa.html   (587 words)

  
 White dwarf - Memory Alpha
A white dwarf is a star formed when a red giant runs out of helium fuel after losing most of its mass into space.
The resulting white dwarf is extremely hot and dense, although not as dense as neutron stars or fl holes.
In 2364, the USS Tsiolkovsky was observing the formation of a white dwarf when its crew succumbed to polywater intoxication.
memory-alpha.org /en/wiki/White_dwarf   (270 words)

  
 StarsIntro
White dwarfs, the remains of stars that began their lives between 0.8 and 10 solar masses, no longer have any source of energy generation and are destined only to cool.
When the giant becomes a white dwarf we are left with a seemingly single star (main sequence or evolved giant) with an odd chemical composition.
If the white dwarf and main sequence remnant of a close double are close enough, the white dwarf can raise tides in the main sequence star, and mass will flow the other way, from the main sequence star to the white dwarf.
www.astro.uiuc.edu /~kaler/sow/star_intro.html   (5419 words)

  
 Educational Observatory - White Dwarfs   (Site not responding. Last check: 2007-11-07)
The Structure and Evolution of Hot White Dwarfs are among the oldest objects in the galaxy and are the remnants of the earliest phases of star formation.
When white dwarfs are born the are incredibly hot (about 200,000 degrees C) and then cool down slowly over thousands of millions of years.
Study of the distribution and physical characteristics of the white dwarf population is an essential part of understanding the early history of the galaxy.
www.edu-observatory.org /eo/white_dwarfs.html   (565 words)

  
 Zoom Astronomy Glossary: W
A white dwarf is a small, very dense, hot star near the end of its life.
The companion of Sirius is a white dwarf.
A white giant is a rare, huge white star of spectral type A. A white super giant is a rare, enormous white star of spectral type A. Deneb is a super white giant.
www.enchantedlearning.com /subjects/astronomy/glossary/indexw.shtml   (1090 words)

  
 Universe Today - White Dwarf Theories Get More Proof
Theory that describes how white dwarf stars can exist emerged in the early 1930s, when Subramanyan Chandrasekhar — or Chandra, as he was known — calculated the limit to a white dwarf's mass by applying Einstein's theory of special relativity.
Unlike most white dwarfs, Sirius B is part of a binary system, and astronomers can determine the mass of stars in a binary system.
Sirius B is 10,000 times dimmer than Sirius A. Astronomers can’t even see the white dwarf companion when it comes closest to the primary star during its 50-year, very elongated orbit around Sirius A. For the post several years, Holberg and colleagues have observed Sirius B with the Voyager and Extreme Ultraviolet Explorer spacecrafts.
www.universetoday.com /am/publish/white_dwarf_theory.html?1212005   (825 words)

  
 White Dwarf
White dwarfs are embers of dying stars shrunken to planetary dimensions.
White dwarfs in close binary systems that feed hydrogen-rich matter from a main-sequence type star filling its Roche lobe, and then transfers the gas with the proper angular momentum to form an accretion disk that enshrouds the white dwarf.
The inner region of the accretion disk onto a rotating magnetized central star (neutron star, white dwarf, or T Tauri star) is subjected to magnetic torques that induce warping and precession of the disk.
business.fortunecity.com /rowling/167/SuperNovae/WhiteDwarf.html   (1195 words)

  
 Lives and Deaths of Stars
White dwarfs shine simply from the release of the heat left over from when the star was still producing energy from nuclear reactions.
Analysis of the white dwarfs may provide an independent way of measuring the ages of the globular clusters and provide a verification of their very old ages derived from main sequence fitting.
White dwarfs in binary systems where the companion is still a main sequence or red giant star can have more interesting futures.
www.astronomynotes.com /evolutn/s11.htm   (854 words)

  
 white dwarf concept from the Astronomy knowledge base   (Site not responding. Last check: 2007-11-07)
A typical white dwarf has 60 percent of the Sun's mass but is little larger than the Earth.
White dwarfs are common, accounting for 10 percent of all stars in the Galaxy; the nearest is Sirius B, just 8.6 light-years away.
DA white dwarfs are hydrogen-rich; DB white dwarfs are helium-rich; DC are carbon rich; DF are calcium-rich; DP are magnetic stars.
www.site.uottawa.ca:4321 /astronomy/whitedwarf.html   (450 words)

  
 LOT of digital editing and rearranging, they slowly merged into one somewhat spurious whole.   (Site not responding. Last check: 2007-11-07)
Using the cooling rate of white dwarfs as a stepping stone to the age of the Universe is an entirely independent approach, and is useful as a reality check.
White dwarfs shine dwarf because they are hot; although a white dwarf has no internal power source, it takes billions of years for a white dwarf to cool down.
The density of a white dwarf is approximately siberian dwarf hamster a ton per cubic centimeter..
debtpop.sitesled.com   (2803 words)

  
 NASA - Orbiting Stars Flooding Space With Exotic Gravitational Waves
White dwarfs are remnants of stars like our Sun that have used up all their fuel.
White dwarfs, along with neutron stars and fl holes, are called compact objects because they pack a lot of mass into a small volume.
This white dwarf pair is similar to the orbiting neutron stars leaking gravitational waves discovered by Russell Hulse and Joseph Taylor, who won the 1993 Nobel Prize in Physics.
www.nasa.gov /vision/universe/starsgalaxies/collide_whitedwarf.html   (868 words)

  
 ESA Science & Technology: Astronomers use Hubble to 'weigh' Dog Star's companion [heic0516]
White dwarfs are also the source of Type Ia supernova explosions that are used to measure cosmological distances and the expansion rate of the universe.
Light from the surface of the hot white dwarf has to climb out of this gravitational field and is stretched to longer, redder wavelengths of light in the process.
Despite being the brightest white dwarf known, Sirius B is about 10 000 times fainter than Sirius itself, making it difficult to study with telescopes on the Earth's surface because its light is swamped in the glare of its brighter companion.
hubble.esa.int /science-e/www/object/index.cfm?fobjectid=38420   (794 words)

  
 Supporting Cast (White Dwarf)
White Dwarf followed the man to the desert, where it was explained that he worked for Replicon, an old foe.
White Dwarf was tricked into hurling the a bomb into space, which is what activated it.
White Dwarf is pretty conscientious of collateral damage, so he tries to not break any thing during battle, but if he needs to he knows that ocean freighters make spiffy area effect attacks.
www.patric.net /morpheus/cast/hero/whitedwarf.html   (1694 words)

  
 White Dwarfs and Electron Degeneracy
The white dwarf Sirius-B was not seen until 1862, but was predicted in 1844 from the motion of Sirius-A.
This maximum mass for a white dwarf is called the Chandrasekhar limit.
The star Sirius, referred to as Sirius-A, is perhaps most notable for the study of the "companion of Sirius" or Sirius-B which was the first example of a white dwarf star to be studied.
hyperphysics.phy-astr.gsu.edu /hbase/astro/whdwar.html   (729 words)

  
 White Dwarfs and Novae
Subrahmanyan Chandrasekhar predicted while a very young man in the 1930s that there was a limiting mass for white dwarf stars: no white dwarf could be stable against gravitational collapse if it exceeded this mass, which is about 1.4-1.5 solar masses, depending on the detailed composition of the white dwarf.
Matter accretes in a thin layer on the surface of the white dwarf and eventually ignites in a thermonuclear explosion under degenerate conditions.
The white dwarfs in the field are circled; as expected, they are quite faint compared with the other stars.
csep10.phys.utk.edu /astr162/lect/novae/novae.html   (415 words)

  
 Spaceflight Now | Breaking News | White dwarf explodes inside a dense circumstellar disk
The most widely accepted Type Ia models assume that the white dwarf -- roughly the size of Earth but packing most of the mass of the sun -- accretes matter from an orbiting companion until it reaches 1.4 solar masses, known as the Chandrasekhar limit.
Other schemes include the merger of two white dwarfs or even a lone white dwarf that re-accretes the matter shed by its younger self.
Thus it's more likely that a white dwarf companion in the SN 2002ic system was already busily collecting matter long before the nebula formed.
www.spaceflightnow.com /news/n0403/24whitedwarf   (1988 words)

  
 White Dwarfs
A white dwarf is what stars like our Sun become after they have exhausted their nuclear fuel.
A typical white dwarf is half as massive as the Sun, yet only slightly bigger than the Earth.
But in a white dwarf, all of the electrons are forced close together; soon all the energy levels in its atoms are filled up with electrons.
imagine.gsfc.nasa.gov /docs/science/know_l2/dwarfs.html   (758 words)

  
 White Dwarfs - Introduction
The white dwarf is surrounded by an expanding shell of gas in an object known as planetary nebula.
The first white dwarf to be discovered was found because it is a companion star to Sirius, a bright star in the constellation Canis Major.
The white dwarf HZ 43 was observed by the
imagine.gsfc.nasa.gov /docs/science/know_l1/dwarfs.html   (1317 words)

  
 Pulsating white dwarf star
Being a white dwarf star, Kawaler said, BPM37093 has burned its nuclear fuel and all that remains is ash of carbon and oxygen.
Crystallized white dwarf stars have been theorized to exist for 30 years, but because these stars are rare and exist under very extreme conditions, proving their existence has been a challenge.
A pulsating white dwarf star that is snowing inside will be roughly 11 to 12 billion years old, rather than the currently estimated 9 billion years, Kawaler said.
www.xs4all.nl /~carlkop/diamond.html   (854 words)

  
 White Dwarfs   (Site not responding. Last check: 2007-11-07)
Therefore, the path a white dwarf star would trace on the HR diagram would proceed diagonally down and to the right (decreasing luminosity and temperature).
Once a white dwarf has radiated off all of its residual heat, it emits no light and is referred to as a fl dwarf.
The more massive a white dwarf is, the smaller its radius will be (since a more massive star has a higher gravity and is therefore compressed to a smaller size).
www.astro.umd.edu /education/astro/stev/wdwarf.html   (439 words)

  
 ScienceDaily: FUSE Observations Strengthen White Dwarf Theory
Theory that describes how white dwarf stars can exist emerged in the early 1930s, when Subramanyan Chandrasekhar or Chandra, as he was known calculated the limit to a white dwarf's mass by applying Einstein's theory of special relativity.
Unlike most white dwarfs, Sirius B is part of a binary system, and astronomers can determine the mass of stars in a binary system.
Sirius B is 10,000 times dimmer than Sirius A. Astronomers can't even see the white dwarf companion when it comes closest to the primary star during its 50-year, very elongated orbit around Sirius A. For the post several years, Holberg and colleagues have observed Sirius B with the Voyager and Extreme Ultraviolet Explorer spacecrafts.
www.sciencedaily.com /releases/2005/01/050125084745.htm   (1922 words)

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