Slashdot is powered by your submissions, so send in your scoop

 


Forgot your password?
Close
typodupeerror
×
Space Science

Hubble finds Mass of White Dwarf 126

Posted by CowboyNeal 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.'"
This discussion has been archived. No new comments can be posted.

Hubble finds Mass of White Dwarf More

Hubble finds Mass of White Dwarf

Comments Filter:

  • More on White Dwarfs... (Score:5, Informative)

    by Cherita Chen ( 936355 ) on Friday December 16, 2005 @05:58AM (#14270777) Homepage
    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 [harvard.edu]

    additionally, more can be found on the white dwarfs in general Here [nasa.gov].

  • It'll be more interesting when they find.. (Score:5, Funny)

    by Anonymous Coward on Friday December 16, 2005 @06:01AM (#14270781)
    Mass of RED Dwarf
    • Already found it at the end of series 7...
    • It's near the Galactic Rimmer
    • 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?

      • Re:It'll be more interesting when they find.. (Score:5, Informative)

        by phlegmofdiscontent ( 459470 ) on Friday December 16, 2005 @11:17AM (#14272126)
        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.

  • It's a shame... (Score:5, Interesting)

    by chrstphrb ( 885917 ) on Friday December 16, 2005 @06:03AM (#14270786)
    It is a shame that Hubble is on borrowed time...

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

    • Re:It's a shame... (Score:5, Insightful)

      by luvirini ( 753157 ) on Friday December 16, 2005 @06:24AM (#14270831)
      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....

  • Shame (Score:1, Insightful)

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

  • Hubble (Score:5, Insightful)

    by jurt1235 ( 834677 ) on Friday December 16, 2005 @06:16AM (#14270808) Homepage
    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.
    • 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, rathe
      • 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 bet

    • Re:Hubble (Score:5, Insightful)

      by bhima ( 46039 ) <Bhima,Pandava&gmail,com> on Friday December 16, 2005 @06:42AM (#14270876) Journal
      What's worse is that, with the Hubble Origins Probe: http://www.pha.jhu.edu/hop/ [jhu.edu], 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.

      • Re:Hubble (Score:4, Insightful)

        by Rich0 ( 548339 ) on Friday December 16, 2005 @11:36AM (#14272286) Homepage
        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!
      • We'll figure out how to put people back in space just as soon as China does it. Coincidence? Hardly.
    • 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.

  • Interesting Background... (Score:5, Informative)

    by guygee ( 453727 ) on Friday December 16, 2005 @06:22AM (#14270828)

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

    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."

    • 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.
      • 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 graivtati
      • 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
    • 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?
      • 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.

        • 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

          • 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 Tel
      • Perhaps you meant the cool proposed spontaneous photon blueshifting [aas.org] 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.
        • 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?

          • 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 [ucla.edu] 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.metaresear [metaresearch.org]

  • 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

  • redshift (Score:2, Informative)

    by t0ddsh3rman ( 933033 )
    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 [newscientist.com] Other info on redshit can be found here: http://en.wikipedia.org/wiki/Redshift [wikipedia.org]
    • 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.
      • 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

  • Sirius? (Score:3, Funny)

    by cdn2k1 ( 908657 ) on Friday December 16, 2005 @08:03AM (#14271045)
    Perhaps this is some cleverly disguised viral marketing to promote Howard Stern's move to satellite radio?
  • they are decommissioning Hubble. It hasn't ammounted to anything anyway.
    • 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
  • White Dwarf needs food badly.
    • 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.
  • how do they know it was measured 'accurately'?

  • Get the paper here (Score:1, Informative)

    by Anonymous Coward
    Their paper [arxiv.org].
  • ...dark elfs?

  • The Dogon Mystery (Score:4, Interesting)

    by writerjosh ( 862522 ) on Friday December 16, 2005 @01:00PM (#14272996) Homepage
    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 [dreamscape.com]

    • Excellent article [wikipedia.org] on this topic.

    • Re:The Dogon Mystery (Score:3, Informative)

      by serutan ( 259622 )
      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 amate
  • According to the MSNBC article [msn.com], 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?
    • 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,

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

Slashdot Top Deals

My sister opened a computer store in Hawaii. She sells C shells down by the seashore.

Close