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Hubble finds Mass of White Dwarf

Posted by CowboyNeal on from the gully-dwarf-mass-still-unknown dept.

Chris Bradshaw writes "The mass of the nearest white dwarf star to Earth has been measured accurately for the first time. from the article: 'Sirius B is just 12,000 km (7,500 miles) in diameter, similar to Earth, but its mass is 98% that of the Sun. Studying Sirius B has been difficult because of the bright light coming from its neighbour Sirius A, the "Dog Star." The results, published in the Monthly Notices of the Royal Astronomical Society, come from astronomers using the Hubble Space Telescope.'"

126 comments

  1. More on White Dwarfs... by Cherita+Chen · · Score: 5, Informative
    It's important to note that with out supplemental information from other sources, this would not have been possible. another space-born observatory that has aided greatly in the study of white dwarfs Here

    additionally, more can be found on the white dwarfs in general Here.

    --
    I'm not fat, just big boned...
    1. Re:More on White Dwarfs... by Anonymous Coward · · Score: -1, Offtopic

      Wow that's almost as dense as George Bush...

    2. Re:More on White Dwarfs... by omeg · · Score: 2, Informative

      And here.

    3. Re:More on White Dwarfs... by doza · · Score: 1

      and here? http://www.britannica.com/search?query=White+Dwarf &ct=

      --
      ---
  2. It'll be more interesting when they find.. by Anonymous Coward · · Score: 5, Funny

    Mass of RED Dwarf

    1. Re:It'll be more interesting when they find.. by AccUser · · Score: 1, Insightful

      Already found it at the end of series 7...

      --

      Any fool can talk, but it takes a wise man to listen.

    2. Re:It'll be more interesting when they find.. by Spacejock · · Score: 0

      It's near the Galactic Rimmer

      --
      Hal Spacejock: Science Fiction with Nuts
    3. Re:It'll be more interesting when they find.. by IAmTheDave · · Score: 1

      Does anyone else want to take "measured accurately for the first time" with a grain of salt? I'm not a physicist or anyone that can make any truely accurate statements about how we measure the mass of objects light-years away from earth, but we constantly find that certain measuring devices we use are slightly off - like older, now debunked versions of carbon/radiation dating of fossils, etc.

      Is there anyone that can comment intelligently on this?

      --
      Excuse my speling.
      Making The Bar Project
    4. Re:It'll be more interesting when they find.. by phlegmofdiscontent · · Score: 4, Informative

      It's all relative. For years, astronomers have known that Sirius B was about 1 solar mass, plus or minus maybe a tenth. They found this by observing the size of its orbit and its period. This time, using spectroscopy, they can estimate the surface gravity of Sirius B, which will give its radius and mass. There's still uncertainty in the measurement, as in all measurements, but that uncertainty is smaller than previous measurements. Who knows, 20 years from now new techniques could give an even more accurate measure of Sirius B's mass, but one could still say "measured accurately for the first time" since it's better than previous measurements. This is not revolutionary, it's evolutionary.

  3. It's a shame... by chrstphrb · · Score: 5, Interesting
    It is a shame that Hubble is on borrowed time...

    http://washingtontimes.com/upi-breaking/20050420-1 25927-9641r.htm

    1. Re:It's a shame... by luvirini · · Score: 4, Insightful

      That is the way NASA works, ost of the money is spent on admninstration and other things only vaguely related to space and spaceresearch, thus they do not have money to maintain and build actual things.. but then.. NASA sees to be like most goverment agencies, mainly a jobs program and a way to divide contracts to the districts of congressmen. Too bad they lost their way somewhere....

  4. Shame by Anonymous Coward · · Score: 1, Insightful

    To bad they are going to plough it into earths atmosphere.

  5. More on Karma Whoring... by Anonymous Coward · · Score: 3, Funny

    http://en.wikipedia.org/wiki/Karma_whoring

    1. Re:More on Karma Whoring... by Anonymous Coward · · Score: -1, Offtopic

      From the article:

      Karma whores

      Karma is a scoring system on Slashdot meant to reward "good" posting and punish "bad" posting. The goal is that people who repeatedly post offensive, offtopic, or otherwise unwanted messages will be punished with a lower visibility of their messages, and those who post informative, insightful, or otherwise desirable messages are rewarded with a higher visibility. Karma whores are individuals, or messages themselves, that attempt to receive feedback in the form of karma points. Often these will be needless information (such as a link to a Wikipedia article relevant to the subject being discussed), or a message of a political nature that is in alignment with the groupthink so that it will be moderated upwards by people who agree with the stance expressed in the message.

    2. Re:More on Karma Whoring... by Anonymous Coward · · Score: -1, Offtopic

      Good work posting that. We wouldn't want people to miss out now that wikipedia has been slashdotted.

    3. Re:More on Karma Whoring... by Anonymous Coward · · Score: -1, Offtopic

      I guess if you post as an AC, you're a Karma Slut because you're doing it for no points?

    4. Re:More on Karma Whoring... by buraianto · · Score: 1

      Boy, that article gives way too much credit to the Slashdot crowd. "Bizarre and complex subculture"? "Highly developed and artistic attempts to provoke outraged responses"? Right...

    5. Re:More on Karma Whoring... by ceoyoyo · · Score: 1

      Well, it's definitely a bizarre subculture. Complex is in the eye of the beholder. Maybe they meant "Highly developed and AUTISTIC attempts to provoke...."

    6. Re:More on Karma Whoring... by lorelorn · · Score: 1
      Boy, that article gives way too much credit to the Slashdot crowd. "Bizarre and complex subculture"? "Highly developed and artistic attempts to provoke outraged responses"? Right...

      Relax, it's Wiki. If you don't like it, just change it yourself.

      Something like "predictable, emotive knee-jerk reactions mixed with the kind of homogenous racism and misogyny we have learned to expect from the internet."

      It will be months before anyone notices, then Wired will have something else to write articles on to make themselves look relevant and topical.

  6. Hubble by jurt1235 · · Score: 5, Insightful

    Although NASA (or the US goverment, it is all politics) does not want to fund Hubble anymore, the telescope proves that it is valuable every time again. Astronomers just need more time with the equipment to take more readings of an object so that they can catch the details. Is it an idea that a commercial company adopts the Hubble telescope and rents the time on the telescope out again to different agencies around the globe? The price for the adoption could be the operational cost of keeping Hubble in orbit in working order.

    --

    My wife's sketchblog Blob[p]: Gastrono-me
    1. Re:Hubble by penguin-collective · · Score: 1

      Although NASA (or the US goverment, it is all politics) does not want to fund Hubble anymore, the telescope proves that it is valuable every time again.

      I don't even want to defend NASA's decision (I really don't know the tradeoffs well enough), but merely observing that Hubble is still useful tells you little about whether it makes sense to continue funding it. The real question is whether the cost/benefit calculations work out overall. In particular, is it worth trying to fix Hubble again and again, rather than saving up for a new space-based telescope?

    2. Re:Hubble by jurt1235 · · Score: 1

      So far multiple space telescopes have been scrapped (EOL) while new data was still being gathered. Those telescopes were not in space maintenable like Hubble proved to be. It is a tough job to repair/upgrade Hubble, that is why I made my commercial venture suggestion. The enterprise taking this on itself will have to do those calculations and see what will happen. NASA than can save for a new telescope. The bad part about this will be that the company taking over Hubble will probably not be happy with a better competitor if it comes within a certain period (lets say 3 years: One maintenance run now will keep Hubble running for this period (If nothing unexpected happens).
      So adjusting my view to: Short term (~3 years) intermediate solution.

      --

      My wife's sketchblog Blob[p]: Gastrono-me
    3. Re:Hubble by bhima · · Score: 4, Insightful
      What's worse is that, with the Hubble Origins Probe: http://www.pha.jhu.edu/hop/, an extremely high value, achievable alternative plan exists.

      The shuttle is not necessary, nor is the not yet designed or built robotic servicing capability. The Hubble Origins Probe could be in orbit by the time the original fails, continuing and extending the original mission while the James Webb mission design, construction, and launch is completed.

      Additionally, if the US ever figures out how to put people back in space, or really does design robotic satellite repair capability the is nothing preventing the Hubble Origins Probe from having an extremely long and productive life.

      --
      Nothing in the world is more dangerous than sincere ignorance and conscientious stupidity.
    4. Re:Hubble by argStyopa · · Score: 1

      No, because any commercial entity (even a non-profit) is going to do the same analysis that NASA did, and probably come to the same conclusion: cost > return.

      If it's such a boon to mankind, convince some multigajillionaire to buy it for naming rights. Instead of the "Hubble Space Telescope" we could be getting this sort of data from the U2 Space Telescope or the Bjorn Bayley Space Telescope.

      --
      -Styopa
    5. Re:Hubble by Rich0 · · Score: 3, Insightful

      Somebody mod parent up. Why does the hubble have to be an either-or solution (vs James Webb/etc)? Just make a new one and launch it - most of the costs of a space probe are for design, and we already have that done - just put the right mirror in, put the consumables in an easily serviced module, etc.

      It has to be cheaper just to build another one than to build a robotic telescope repair system, and launch that!

    6. Re:Hubble by robogun · · Score: 1

      The new Hubble should be in Shuttle-serviceable orbit. Or dockable to ISS.

  7. Time to update Wikipedia? by mattwarden · · Score: 0

    Time to update the Wikipedia entry?

    "The core, no longer supported against gravitational collapse by fusion reactions, becomes extremely dense, with a typical mass of about half that of the sun contained in a volume about equal to that of the Earth."

    Still probably has less errors than Britannica...

    1. Re:Time to update Wikipedia? by mattwarden · · Score: 1

      Actually, I may have spoken too soon:

      Many white dwarfs are approximately the size of the Earth, typically 100 times smaller than the Sun. They may have the same mass as the Sun and so are very compact.

      Do they really vary in density that much?

    2. Re:Time to update Wikipedia? by Vo0k · · Score: 1

      Not necessarily. Is Sirius B a -typical- white dwarf or is it half the typical white dwarf size?
      Does anyone know?

      --
      Anagram("United States of America") == "Dine out, taste a Mac, fries"
    3. Re:Time to update Wikipedia? by The+Wannabe+King · · Score: 2, Informative
      Yes. If you read on, you'll find the mass of Sirius B given as approximately that of the Sun.

      The upper limit, known as the Chandrasekhar limit, for a white dwarf is 1.4 solar masses (more or less).

    4. Re: Time to update Wikipedia? by Black+Parrot · · Score: -1, Offtopic

      > Time to update the Wikipedia entry?

      You could have done it for about the same amount of effort it took you to post the question.

      --
      Sheesh, evil *and* a jerk. -- Jade
    5. Re:Time to update Wikipedia? by meringuoid · · Score: 2, Informative
      Many white dwarfs are approximately the size of the Earth, typically 100 times smaller than the Sun. They may have the same mass as the Sun and so are very compact.

      Do they really vary in density that much?

      Yes. White dwarfs vary in density a whole lot; degenerate gases behave quite oddly. If you add matter to a white dwarf, it actually gets a little smaller. The limit is about 1.4 solar masses, at which point the white dwarf collapses to form a neutron star.

      --
      Real Daleks don't climb stairs - they level the building.
    6. Re:Time to update Wikipedia? by $RANDOMLUSER · · Score: 1
      > The upper limit, known as the Chandrasekhar limit, for a white dwarf is 1.4 solar masses (more or less).

      Just to expand that a bit, if the mass of a white dwarf goes over 1.4 solar masses, the gravitational collapse is strong enough to trigger a supernova explosion. In other words, at masses greater than the Chandrasekhar limit, the (inward) gravitational pressure overcomes the (outward) thermal/fusion pressure, thus causing a collapse and the ignition of most of the remainder of the stars fuel, thus the supernova explosion.

      --
      No folly is more costly than the folly of intolerant idealism. - Winston Churchill
    7. Re:Time to update Wikipedia? by meringuoid · · Score: 5, Informative
      if the mass of a white dwarf goes over 1.4 solar masses, the gravitational collapse is strong enough to trigger a supernova explosion. In other words, at masses greater than the Chandrasekhar limit, the (inward) gravitational pressure overcomes the (outward) thermal/fusion pressure, thus causing a collapse and the ignition of most of the remainder of the stars fuel, thus the supernova explosion.

      Right idea, wrong mechanism.

      A white dwarf is not supported by thermal pressure, or by nuclear fusion; it is supported by degeneracy pressure between electrons, a consequence of the exclusion principle in quantum mechanics that forbids two electrons from occupying the same quantum state.

      1.4 solar masses is correctly given as the critical point at which gravity prevails over the internal pressure; at this point, the star switches from degeneracy pressure between electrons to degeneracy pressure between neutrons, in the process dropping considerably more than the weight of the Sun from the size of the Earth to something more like the size of Belgium, through an enormously strong gravitational field. This releases an awful lot of energy, and is the main power source for such a supernova.

      There's another type of supernova which is driven by fusion, but that's more typical of accretion systems in which the infalling matter has heated the white dwarf sufficiently to reignite fusion processes; then the fusion reaction is an uncontrolled runaway and can wholly disrupt the star.

      --
      Real Daleks don't climb stairs - they level the building.
    8. Re:Time to update Wikipedia? by Detritus · · Score: 1

      I don't think the Chandrasekhar limit has anything to do with gravity overcoming the forces of thermal energy. According to the wikipedia article, it's the amount of mass required to overcome electron degeneracy pressure, producing a neutron star or a black hole.

      --
      Mea navis aericumbens anguillis abundat
    9. Re:Time to update Wikipedia? by Anonymous Coward · · Score: 0

      Wrong. When in binary mass transfer systems white dwarves do gain mass from their companion star. How else would they reach Chendrasekar's(sp?) limit and explode in a type I supernova? Furthermore, when they do reach that magical 1.4 solar masses they explode leaving nothing behind. White dwarves never become neutron stars.

    10. Re:Time to update Wikipedia? by J_Darnley · · Score: 0, Informative
      When the grandparent said smaller he meant in terms of diameter/radius. The mass they pick up from a companion star causes them to shrink in diameter, a small amount though until they hit the Chandrasehkar limit and explode. From Wikipedia:
      "For some white dwarfs the accreted material, which is usually hydrogen rich, will light up in a nuclear explosion and leave the core of the star intact. This phenomenon can be repeated as long as accretion material is available."
      So obviously they don't just dissapear. The core must remain to regather what ever material is left.
    11. Re:Time to update Wikipedia? by ajpr · · Score: 2, Informative

      I think Neutron stars are around 20km diameter (size of a small city), quite a bit smaller than Belgium. Plus, they often spin very quickly due to the conservation of angular momentum (think of the ice skaters spinning with arms stretched compared to closed thing).

    12. Re:Time to update Wikipedia? by JetJaguar · · Score: 1

      What you are referring to is a nova. Not a supernova. White dwarfs can in fact go through several nova events, as long as their total mass remains below the limit. A nova explosion is usually fueled by nuclear reactions in the outer portion of the star, in the accretted material. As the material acretes recurring nova can happen almost periodicaly. However, a Type I supernova is a different beast entirely, and results from the amount of acreted material raising the density and pressure in the core of the white dwarf enough to reinitiate nuclear fusion in the core. When this happens, the reaction is catastrophic and blows the star apart.

      --

      Shop Smart, Shop S-mart!

    13. Re:Time to update Wikipedia? by Phanatic1a · · Score: 2, Informative

      This releases an awful lot of energy, and is the main power source for such a supernova.

      What type of supernova? Simply collapsing to a neutron star doesn't *cause* a supernova, although a neutron star can be a supernova remnant.

      It sounds like you're saying that if you have a white dwarf sitting there, and it accretes mass from some other source, like a binary companion, when its mass grows to be greater than the C-limit, it collapses into a neutron star, and that the energy released in the collapse generates a supernova.

      That's not the case. If you have a white dwarf sitting there, and it accretes enough mass to go over that limit, then basically what happens is that carbon begins to fuse. It happens everywhere, throughout the star, and you wind up with a carbon detonation supernova, a Type 1a supernova. It's not the energy of gravitational collapse which blows the star apart, it's the new fusion reactions.

    14. Re:Time to update Wikipedia? by phlegmofdiscontent · · Score: 1

      Sirius B is pretty typical, though there is still a lot of variation. If I remember correctly, their masses can range from about half solar to 1.4 solar with a radius similar to Earth's.

    15. Re:Time to update Wikipedia? by qeveren · · Score: 1

      Well, I don't think it's a typical scenario for a white dwarf star to collapse into a neutron star due to mass accretion; that usually leads to a Type Ia supernova. Neutron stars form from the core of their progenitor star directly, do they not, skipping the white dwarf stage?

      --
      Don't just stand there, get that other dog!
    16. Re:Time to update Wikipedia? by Galahad2 · · Score: 1

      Something doesn't add up for me with that description of a 1a supernova. There's a hell of a lot of gravitational potential held in a white dwarf -- something like 10^44 joules. This is also incidentially approximately the same as the energy released in the fusion process, assuming 0.1% of rest mass is converted to energy. So either I'm missing something, or about half the energy of a 1a supernova comes from fusion, and the other half from gravitational collapse. It's not clear to me that one would dominate, in the way you describe.

    17. Re:Time to update Wikipedia? by Anonymous Coward · · Score: 0

      D = m/v
      mass of sun = ~ 1.99 x 10^33 g
      volume of sphere = 4/3 X (pi) X r^3
      radius of Sirius B = ~6000 km = 6^3 km X 1000 m/km X 100 cm/m
      volume = ~9.01 x 10^26 cm^3
      D = ~2.2 x 10^6 g/cm^3

    18. Re:Time to update Wikipedia? by Viadd · · Score: 4, Informative
      Right idea, wrong mechanism.

      No, white dwarfs do become fusion-powered supernovae, not gravity-powered. IAAA (I am an astrophysicist.)

      A white dwarf becomes a Type Ia supernova when, at around 1.4 solar masses, the pressure at the center reaches the point where it can burn by fusion the carbon-nitrogen-oxygen left over from previous rounds of burning. This leads to a fusion-driven explosion that gets no net energy from gravitational collapse, leading to an expanding gas cloud that is largely hot iron-group elements.

      There is another class of supernova that is gravitationally driven. Core collapse supernovae are produced when a massive star (>8 solar masses, last I heard) has burned 1.4 solar masses at its center to iron. (The 1.4 solar mass value is semi-coincidental with that in the previous paragraph, based on similar but not identical physics.) This is a gravity-powered supernova that blows the outer parts of the core away, leaving a neutron star or black hole where the core was.

      There is no way for a white dwarf to become a core collapse supernova, the fusion kicks in and blows it apart before that happens.
    19. Re:Time to update Wikipedia? by Viadd · · Score: 3, Informative

      You are right that the gravitational binding energy of a white dwarf is comparable to the fusion energy of its combustion from carbon to iron. However, comparable doesn't mean equal and if you work it out, the fusion energy dominates. The gravitational energy is negative, so it reduces the amount of available energy for the supernova (i.e. the ejecta are moving more slowly because it has to climb out of its own gravity well), but it is still energetically favorable to go from a dense chunk of carbon to an expanding diffuse cloud of iron.

    20. Re:Time to update Wikipedia? by Galahad2 · · Score: 1

      The gravitational energy is negative, so it reduces the amount of available energy for the supernova

      No, that's not right. If the dwarf collapses to, say, a neutron star, energy will be liberated when the radius of the star decreases. The change in gravitational potential is negative, so that extra energy has to go somewhere. This fuels Type 2 supernovas. I'm just not sure where that energy fits into the Type 1a.

      I've heard that it might be that no neutron star is formed in 1a supernovas (the star is just blown apart), so there is no liberation of gravitational potential. That's probably the answer.

    21. Re:Time to update Wikipedia? by Impy+the+Impiuos+Imp · · Score: 1

      There is no way in holy Hell that the Hulk can ever stand up even to the weakest, post-John Byrne incarnation.

      Very recently, Superman was able to easily support 200 quintillion tons with one arm, no straining. This is roughly 1/30,000th of the mass of the Earth itself. (Hence he could, with effort, actually move the earth, and without taking eons to slowly accelerate it.) Yes, he was over-amped on sun juice, and may be "dying", but his strength was only up by 3x over its normal level according to the poindexter examining him.

      Meanwhile, the Hulk's greatest feat, lifting a 150 billion ton mountain, was not even that great. The Secret Wars issue involved clearly states inside he was merely supporting a tiny section of it, under a hollow created by Iron Man after the Molecule Man dropped the mountain range on the heroes.

      --
      (-1: Post disagrees with my already-settled worldview) is not a valid mod option.
    22. Re:Time to update Wikipedia? by Viadd · · Score: 1

      Just a terminology thing: Gravitational potential energy is measured relative to the system dispersed out to infinity. A white dwarf has negative potential energy, and so combined with the positive energy release by fusion will diminish the energy of this Type Ia supernova, relative to what you would get if you jcoudl just ignore gravity.

      The iron core of a core-collapse supernova progenitor (similar to a white dwarf in size and mass, but made of un-fusable iron) has negative gravitational energy. The 12-km radius neutron star it becomes as it collapses has a much much more negative gravitational energy, by of order -1e46 Joules (-1e53 ergs). As you'd expect, this means that there's about 1e46J of positive energy suddenly liberated. 99% of that comes out in neutrinos, which have almost no effect once they get out of the star. The remaining 1e44 ergs comes in the form of supernova light and kinetic energy of the exploding ejecta.

      The non-neutrino portion of the energy of a core collapse supernova is comparable to the total energy of a Type Ia supernova (which does not produce much in the way of neutrinos).

  8. Mods wake up by CaptainFork · · Score: -1, Offtopic

    Why is the parent marked a troll?

    1. Re:Mods wake up by Shihar · · Score: -1, Offtopic

      I imagine it got modded as a troll because it is an uninformative one line post that adds nothing to the conversation. A dozen other people have mentioned that Hubble, but have done so while taking the time to at least use the world "Hubble" in their post. No, it probably isn't a troll, but it doesn't deserve any positive mods.

    2. Re:Mods wake up by guygee · · Score: 3, Funny

      Perhaps the Mod thought the parent post was suggesting that "the advanced Siriusian aliens were planning to hit the Earth with Sirius B. Obviously the Siriusians are an advanced corporate culture, and are intent on "downsizing" their system, cutting their aging former stars loose, in an attempt to get lean and (very) mean, and to eliminate possible future competition from other evolving corporatized systems."

    3. Re:Mods wake up by Anonymous Coward · · Score: -1, Redundant

      I, for one, welcome our new Siriusian alien overlords.

    4. Re:Mods wake up by guygee · · Score: 1

      Sorry , Funny. Now Please mod us all down some more because on of the Official Slashdot Mods (OSM) originally zinged the parent before he had his coffee. Oh, BTW, cooperate with the DIA, much? Not so much? Much too much!

    5. Re:Mods wake up by WormholeFiend · · Score: 1

      Shouldn't the aliens from Sirius be called the Nommos

    6. Re:Mods wake up by Anonymous Coward · · Score: 0

      Ironic, ain't it. You got modded down to -1 for posting an apology for a bad moderator, and the ambiguous AC parent got modded up twice, after first being modded as a "troll".

    7. Re:Mods wake up by guygee · · Score: 1

      The Nommo are ancestral spirits (sometimes referred to as deities) worshipped by the Dogon tribe of Mali, Africa. The word Nommos is derived from a Dogon word meaning, "to make one drink"

      Considering how the slashdot mods tapped into this thread and harvested 2-3 Karma pints^^^^^points from every contributor, yes, it does seem appropriate

      The Dogon reportedly related to Griaule and Dieterlen a belief that the Nommos were inhabitants of a world circling the star Sirius

      Oh, yeah and that too.

    8. Re:Mods wake up by CaptainFork · · Score: 0

      Why is my comment modded off topic? Bad modding is *always* on topic, since it happens on every thread!

  9. Interesting Background... by guygee · · Score: 5, Informative

    not mentioned in the article, at http://columbia.thefreedictionary.com/Sirius

    Selected excerpt:

    "Sirius A is about twice the size of the sun and about 20 times as luminous. It is also one of the nearest stars, lying at a distance of 8.7 light-years, so that it has been studied extensively. From an analysis of its motions, F. W. Bessel concluded (1844) that it had an unseen companion, which was later (1862) confirmed by observation. The companion, Sirius B, is a white-dwarf star and has also been the object of considerable study because it is the first white dwarf whose spectrum was found to exhibit a gravitational red shift, as predicted by the General Theory of Relativity."

    1. Re:Interesting Background... by anandsr · · Score: 1, Informative

      I have just a little bit of trouble with the Red Shift Prediction. Actually GR does not unambiguously predict a Red Shift. Actually the /\ factor was added before to have a static universe, then it was removed when the Red Shift was observed, and now it has been readded with a reversed sign to account for an accelarating expansion. So it is a case of fine tuning.

    2. Re:Interesting Background... by MasterPlaid · · Score: 3, Insightful

      I think you're referring to cosmological redshift here - the redshift that makes objects farther away seem redder. You're correct that GR doesn't predict cosmological redshift a priori; cosmological redshift is caused by the expansion of the universe, and GR allows for an expanding universe, a contracting universe, or even a static universe. But GR does demand that gravitational redshift exist. This redshift is caused by the curvature of spacetime by matter which lies at the heart of GR itself, so graivtational redshift is tightly connected to GR, and its observation an important piece of evidence for the theory.

    3. Re:Interesting Background... by miller701 · · Score: 1

      I wikipedia'd redshift to gain some insight as to the gravitional red shift, and I can understand how that works (thanks to the nice diagram), but how does a gravitational blueshift work?

    4. Re:Interesting Background... by ceoyoyo · · Score: 1

      If the star emitting the light has a really strong gravitational field, light climbing out of that gravity well will show a red shift. If you had your telescope sitting in a big gravity well, light falling into that well (and being detected by your telescope) would show a blue shift.

    5. Re:Interesting Background... by miller701 · · Score: 1
      If the star emitting the light has a really strong gravitational field, light climbing out of that gravity well will show a red shift. If you had your telescope sitting in a big gravity well, light falling into that well (and being detected by your telescope) would show a blue shift.

      OK, so would that mean that to some degree, light leaving the sun is slightly red shifted on the way out, and slightly blue shifted when we see it on earth? Would a telescope at one of the Lagrange points not have that blue shift? Has this been detected/Is it enough to be detected? (I don't even know if there are observatories at the L points yet)?

      Brian - not an astronomer

    6. Re:Interesting Background... by SpiritStranger · · Score: 1

      Perhaps you meant the cool proposed spontaneous photon blueshifting where light is actually blue-shifted according to the strenght of the gravitational potential. This is based on the subquantum kinetics theory rather that GR.

    7. Re:Interesting Background... by ceoyoyo · · Score: 1

      Light from the sun would be red shifted a little bit, and light reaching the Earth would be a bit blue shifted. I expect the effect is far too small to detect though. This white dwarf has the mass of the sun packed into a volume the size of the Earth so it's surface gravity is tremendous.

      I guess a telescope at an L-point would indeed not show blueshift of incoming light, but the effect is so small for gravity wells like Earth's that I suspect the difference is undetectable.

      I think the James Webb Space Telescope is scheduled to be deployed to one of the L points. SOHO is at an L-point as well, I think.

    8. Re:Interesting Background... by hector1965 · · Score: 1

      You are confusing doppler red shift, the one we observe due to the expansion of the universe (which is produce whenever a light souce is moving toward the observer), with gravitational red shift is due to space-time curvature

    9. Re:Interesting Background... by miller701 · · Score: 1

      I've heard of the Pioneer anomaly before. Could it be that Pioneer isn't really slowing down, but it's just the signal being blueshifted?

    10. Re:Interesting Background... by SpiritStranger · · Score: 1
      Could it be that Pioneer isn't really slowing down, but it's just the signal being blueshifted?
      According to that guy it seems so. Also there seems to be this notion of "tired light" floating around in various articles trying to falsify the red-shift/distance relation. These theories seems to have problems though. I don't know the weak spots in LaViolette's gravity/light model, but it sure was very interesting. Maybe there's some cosmological paradigm shift sneaking upon us. See e.g., http://www.metaresearch.org!
  10. Red Dwarf Move Mass by Anonymous Coward · · Score: 0

    If they try to measure the mass of the Red Dwarf Movie they will need a pretty big set of scales, what with all that bullshit flying about. An air freshener might be an idea too.

  11. RETARD!!! by Anonymous Coward · · Score: -1, Offtopic

    It is a shame that Hubble is on borrowed time...

    Dude, there are much more important things than watching the stars.

    Like saving our world from the evil. You better go to church and pray for our troops who do everything to give the children of Irak back their hopes.

    Hubble doesn't fight terrorism.

    1. Re:RETARD!!! by Anonymous Coward · · Score: -1, Offtopic

      ...but by spreading false fear of terrorism, people like you help create it.

      The War on Terrorism is only a fig leaf for the U.S. Government's War on American Citizens

    2. Re:RETARD!!! by Billygoatz · · Score: -1, Flamebait



      Tell that to the people in the World trade buildings

    3. Re:RETARD!!! by Anonymous Coward · · Score: 0

      Yeah, and tell it to all the the dead and maimed soldiers who are bravely fighting the wrong enemy in the wrong country. And tell it to their families, their mothers and fathers, their wives, their children.

      Osama bin Who?

      "...the process of transformation, even if it brings revolutionary change, is likely to be a long one, absent some catastrophic and catalyzing event - like a new Pearl Harbor."

      From Project for the New American Century (PNAC)Report, ""Rebuilding America's Defenses: Strategies, Forces and Resources for a New Century", September 2000.

    4. Re:RETARD!!! by Billygoatz · · Score: 0

      I would never tell the "families, their mothers and fathers, their wives, their children." of our brave soldiers, "...but by spreading false fear of terrorism, people like you help create it." Your a real piece of crap to dishonor our fighting men and women and their families to even suggest it. Shame on you

    5. Re:RETARD!!! by Anonymous Coward · · Score: 0

      The biggest terror incident in this country lately was two Air Marshals gunning down some poor guy who was afraid of flying, then lying about some imaginary bomb threat. None of the 9-11 hijackers were Iraqis, and Saddam Hussein was a mortal enemy of Osama bin Laden. Hussein, brutal despot that we was, was a secularist, bin Laden is an Islamic Fundamentalist. There cannot be a "War on Terror", because terror is not a country, or a group, but a criminal act. But Bush has declared an endless war, without any metrics for what constitutes victory. In the process, we create more terrorist, while the United States is viewed as a terrorist country by the rest of the world, in favor of torture, carrying out a preemptive invasion of a weak country, being lead by War Criminals, and nearing bankruptcy. Our constitutional freedoms are being taken away, and we are becoming a police state. We sold our soul while Bush looted our treasury and distributed it to the Chinese and his rich cronies, and for what? So people like you could puff out their chests, and stick little yellow ribbons on your car, and otherwise feel good about your stultifying, impotent, drone-like existence? Good luck!

    6. Re:RETARD!!! by Billygoatz · · Score: 0

      Thank for the "good luck"

      Good Americans need it.

    7. Re:RETARD!!! by Anonymous Coward · · Score: 0

      There, we are agreed!

  12. update? by penguin-collective · · Score: -1, Offtopic

    I'm sorry, but I don't get it. In what way does Wikipedia need to be updated in light of this result?

  13. More on Anonymous Coward... by HoneyBunchesOfGoats · · Score: 2, Funny

    http://en.wikipedia.org/wiki/Anonymous_Coward

  14. A White Hole... by Anonymous Coward · · Score: 0, Funny

    So what is it?

  15. Ba-ba-booey by Azreal · · Score: -1

    Ahh now it makes sense. Michael Powell must've been behind the 500 million paid to Howard Stern to send him to Sirius.

    --
    $sys$droids
  16. An operation of public communication by 4D6963 · · Score: 1, Interesting
    It sounds like they mention alot that it was done using Hubble to make people hear that the HST is still usefull and can be used to find real results, as more and more people think the HST is only good at making nice looking color images but not getting any important scientifical discovery.

    I still keep thinking the HST isn't really needed anymore

    --
    You just got troll'd!
    1. Re:An operation of public communication by Anonymous Coward · · Score: -1, Offtopic

      What's the Harmonized Sales Tax got to do with it?

  17. redshift by t0ddsh3rman · · Score: 2, Informative

    The BBC article cited in the main post has no mention of the redshift associated with this whitedrawf. It just says "The mass calculations are based on how the star's light is distorted by its neighbour's intense gravitational field." This New Scientist article reporting on the same news does mention redshift - I like redshift: http://www.newscientist.com/article.ns?id=dn8460&f eedId=space_rss20 Other info on redshit can be found here: http://en.wikipedia.org/wiki/Redshift

    1. Re:redshift by LiquidCoooled · · Score: -1, Offtopic

      I would recommend seeking medical attention if you have redshit, wikipedia is not qualified to give diagnosis.

      --
      liqbase :: faster than paper
    2. Re:redshift by Keith+McClary · · Score: 1
      I sent them this via their contact page:

      Re: Hubble finds mass of white dwarf (Science/nature website)
      "The mass calculations are based on how the star's light is distorted by its neighbour's intense gravitational field."

      This is incorrect. They measured the gravitational red shift due to the dwarf's own gravity.

      The Universe Today and New Scientist websites got it right.
    3. Re:redshift by Keith+McClary · · Score: 1
      I got a reply:

      Keith
      I have asked that the page be corrected.

      I am indebted to your time and interest.

      Jonathan Amos
      Assistant Editor, Science and Nature
      BBC News Interactive
  18. Santa Claus rided in front of Hubble by La+Gris · · Score: -1, Offtopic

    Mass white dwarves and maybe imps, but the story don't tell.

    That's Santa Claus riding near Hubble.

    --
    Léa Gris
  19. When by OreoCookie · · Score: 0

    they're still finding large objects in our own solar system http://science.slashdot.org/article.pl?sid=05/12/1 4/1836202&tid=160&tid=99 that we didn't know where there. It doesn't seem too likely that ANYTHING in another solar system could be measured with any accuracy. It seems to me that if our science was that precise then large objects would not go undetected fantastically closer to home.

    1. Re:When by stevelinton · · Score: 2, Informative

      Detectig and studying non-luminous objects like Buffy is a lot harder than luminous ones like Sirius B.

  20. Sirius? by cdn2k1 · · Score: 3, Funny

    Perhaps this is some cleverly disguised viral marketing to promote Howard Stern's move to satellite radio?

    1. Re:Sirius? by Fishstick · · Score: 1

      I figured there had to be a Stern radio joke in here somewhere.

      I was wrong. ;-)

      --

      There is much cruelty in the universe, John.
      Yeah, we seem to have the tour map.

    2. Re:Sirius? by Anonymous Coward · · Score: 0

      I am sirius... and don't call me Shirley.

  21. An African White Dwarf or a European White Dwarf? by Anonymous Coward · · Score: -1

    Or perhaps two running together with a strand of creeper?

  22. Mass of Snow White by Anonymous Coward · · Score: -1

    It'll be fun trying to figure that one out.

  23. Hubble finds Mass of White Dwarf by Anonymous Coward · · Score: 0

    And, as always, it was the last place hubble looked...

  24. Could this be.... by Churla · · Score: 0

    Could this be where they all went to sulk when they found out that they had no shot at being in the Willy Wonka remake?

    --
    I'm a fiscal conservative, it's a pity we don't have a political party anymore
  25. White dwarf? by fusto99 · · Score: -1, Redundant

    The politically correct term for this would be "Caucasian little person"

    1. Re:White dwarf? by Anonymous Coward · · Score: 2, Funny
      The politically correct term for this would be "Caucasian little person"


      Or "Caucasian vertically challenged person"
    2. Re:White dwarf? by pianoman113 · · Score: 1

      Actually "caucasian" has gone out of vouge. "White" is now the accepted term.

      --

      Free as in speech, free as in beer, or free as in lunch?
    3. Re:White dwarf? by Anonymous Coward · · Score: 0

      Funny story: when Willem Luyten applied for federal funding to host the first conference on White Dwarf Stars, the application got bounced, since he hadn't filled out all the proper forms for doing scientific studies of human subjects!

      They're actually called "white dwarfs" not "white dwarves" to help avoid confusion.

      For all kinds of Ph.D. theses and more, visit http://whitedwarf.org/

      Cheers,
      Matt Wood, Professor
      Dept Physics & Space Sciences
      Florida Institute of Technology
      Melbourne, FL 32935
      wood@fit.edu

    4. Re:White dwarf? by Anonymous Coward · · Score: 0

      And it's a star, not a person. So that might go as "caucasian/white vertically challenged star/cosmic body".

      (Slashes always give it a nice touch!)

  26. The title should be: by kirk26 · · Score: -1

    Hubble finds Hank the Angry Dwarf.

    --
    Linux sucks. It is an underground OS that is completely unstandardized. Linux geeks, get the fuck over yourselves.
  27. Good thing... by mattyohe · · Score: 1

    they are decommissioning Hubble. It hasn't ammounted to anything anyway.

    --
    - what is the definition of simultanagnosia?! I've been meaning to look it up!
    1. Re:Good thing... by TheAwfulTruth · · Score: 1

      Hubble has had a good run, but in it's lifetime a dozen or more extremely high quality ground scopes with much more sophisticated imaging gear have been built here on earth. Using adaptive optics and imaging solutions (similar to the ones that "fixed" the hubbels blurry main mirror btw) they are even besting it for image clarity and with much larger aperatures are able to go even deeper than hubble in a shorter amount of exposure time.

      Every available scope IS useful, but the Hubble has reached a point where it's maintenence is far more costly than the amount of service it is currently providing.

      We whould celebrate Hubble for it's ground breaking discoveries, but not become so emotionally attached that it blinds us to it's current age, cost and other limitations.

      --
      Contrary to popular belief, coding is not all free blow-jobs and beer. Those things cost MONEY!
  28. White Dwarf... by WolfZombie · · Score: 2, Funny

    White Dwarf needs food badly.

    --
    Cheesy Movie Night
    1. Re:White Dwarf... by jd · · Score: 1

      Food no use to White Dwarf. Thrud the Barbarian and some Call of Cthulhu articles would be good, along with a total ban on anything by Games Workshop. That's what caused it to gravitationally collapse in the first place.

      --
      It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
  29. More on Wikipedia... by raynet · · Score: 0

    http://en.wikipedia.org/wiki/Wikipedia

    --
    - Raynet --> .
  30. just curious... by zxnos · · Score: 1

    how do they know it was measured 'accurately'?

    --
    always mosh clockwise
  31. Luminous? by tepples · · Score: 1

    Detectig and studying non-luminous objects like Buffy is a lot harder than luminous ones like Sirius B.

    What about detecting and studying Lumines itself? And, if you value Freedom, what about Luminesweeper?

  32. No Gully Dwarf response? by Anonymous Coward · · Score: 0

    Me want gully dworf speak say. No got nothin'. Two speaks and no gully? Glubphulgers!

  33. Get the paper here by Anonymous Coward · · Score: 1, Informative

    Their paper.

  34. Satellite? by Anonymous Coward · · Score: 0

    But how many stations do you get on this Sirius B? I can't live without my 70s gold.

  35. what about.. by nazsco · · Score: 1

    ...dark elfs?

  36. More on the Slashdot effect... by drn8 · · Score: 0

    http://en.wikipedia.org/wiki/Slashdotted

  37. Moron on Wikipedia... by p3d0 · · Score: 0, Offtopic

    http://en.wikipedia.org/wiki/Moron

    --
    Patrick Doyle
    I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
  38. The Dogon Mystery by writerjosh · · Score: 4, Interesting

    The Dogon, a tribe in West Africa, are believed to be of Egyptian descent. After living in Libya for a time, they settled in Mali, West Africa, bringing with them astronomy legends dating from before 3200 BCE. In the late 1940s, four of their priests told two French anthropologists of a secret Dogon myths about the star Sirius (8.6 light years from the earth). The priests said that Sirius had a companion star that was invisible to the human eye. They also stated that the star moved in a 50-year elliptical orbit around Sirius, that it was small and incredibly heavy, and that it rotated on its axis.

    All these things happen to be true. But what makes this so remarkable is that the companion star of Sirius, called Sirius B, was first photographed in 1970. While people began to suspect its existence around 1844, it was not seen through a telescope until 1862 -- and even then its great density was not known or understood until the early decades of the twentieth century. The Dogon beliefs, on the other hand, were supposedly thousands of years old.

    http://www.dreamscape.com/morgana/thalass2.htm

    --
    Health Insurance Quotes
    1. Re:The Dogon Mystery by serutan · · Score: 2, Informative

      I'm glad somebody mentioned the Dogon mystery. It's one of those fascinating things that won't go away. Robert Temple's famous book "The Sirius Mystery" is based mainly on the work of anthropologists Marcel Griaule and Germaine Dieterlen, who lived among the Dogon for more than 30 years starting in 1931. Critics such as Carl Sagan dismissed the conclusions in Temple's book, theorizing that the Dogon had obtained their astronomical information from modern outside sources. Griaule himself was in fact an amateur astronomer. Dieterlen countered these criticisms by displaying Dogon artifacts that dated back hundreds of years.

      More recently another team of anthropologists led by Walter Van Beek did a 10-year study of the Dogon, beginning in 1991. Van Beek, who managed to speak to some of the same individuals who had known Griaule and Dieterlen, said these Dogon disagreed completely with each other as to which star was meant. Some said it was an invisible star, others said it was Venus. But all of them agreed that they learned about the star from Griaule.

  39. Sirius B a potential Type 1a Supernovae? by Anonymous Coward · · Score: 0

    I'm glad to hear the mass of Sirius B has been accurately measured to be 0.98 solar masses. But I'm more interested in the rate of mass change. If Sirius B can suck in enough matter to hit the Chandrasekar limit of 1.4 solar masses, we all will have a very bad day 8.7 years after this event.

    Sirius A is 20 AU away from Sirius B. Any idea of the rate of mass transfer from A to B?

    "I don't know, but it keeps me up at night."

  40. That's easy. by jd · · Score: 1

    They went to a comic/magazine collector and asked them how much that issue weighed.

    --
    It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
  41. Super nova remnant? by Gorimek · · Score: 1

    According to the MSNBC article, white dwarfs are the result of "Type Ia supernovas".

    Is that really true?

    It seems like an event like that only 8 light years away would have fried our little pitiful planet in a away that would be very noticeble today, or more likely exterminate all life.

    Anyone know?

    1. Re:Super nova remnant? by spanklin · · Score: 1
      Actually, the MSNBC article gets it right -- they didn't say that white dwarfs are the result of Type Ia supernovas, they said:
      " ...white dwarfs are involved in explosions called Type Ia supernovas."

      White dwarfs are the remnant of Sun-like stars -- they are not formed in supernova explosions. However, some white dwarfs in binary star systems can accumulate mass from their companion and explode in a nova or in some cases a Type Ia supernova.

      The nearest star most likely to go supernova (and not Type Ia, but Type II), is eta Carina.

  42. Wiki to the rescue by robogun · · Score: 1

    Excellent article on this topic.

  43. So that's where they went... by faloi · · Score: 1

    I knew my wife did something my collection. Who would've thought game magazines would do so well in space?

    --
    "It is a miracle that curiosity survives formal education." -Albert Einstein
  44. Figure by umbrellasd · · Score: 1

    We'll figure out how to put people back in space just as soon as China does it. Coincidence? Hardly.