Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

White Dwarfs, > Chandra Mass?

  1. Feb 8, 2006 #1


    User Avatar
    Science Advisor

    Other posts and discussion have left at least one thing clear. That is that only Carbon-Oxygen white dwarf stars will become Type Ia supernovae if enough mass is accreted to exceed MChandra, about 1.39 solar masses. Others can use the more common 1.44 Msolar since it isn't important to detail here.

    But, the composition of any white dwarf will depend on the mass (and some other factors) of the progenitor star. (The bolded highlights in the following were inserted by Labguy to emphasize certain phrases)"&hl=en&gl=us&ct=clnk&cd=49&lr=lang_en
    So, for the many white dwarfs that formed from the far more numerous small stars there must be a large number of He white dwarfs. And the larger stars also do not form not carbon-oxygen rich dwarfs. Therefore:
    and: http://chandra.harvard.edu/chronicle/0400/sirius.html
    And: http://online.itp.ucsb.edu/online/gravity_c03/lindblom/pdf/Lindblom.pdf
    Therefore, from the handy links and quotes provided I would conclude that:

    (1) Since smaller stars are far more numerous in the universe than large stars, more white dwarf stars are formed with an He composition.

    (2) The largest white dwarf progenitors also do not lead to a carbon-oxygen composition.

    (3) Regardless of mass accreted, most white dwarfs will not result in a Type Ia supernova even if MChandra is exceeded.

    (4) For all white dwarf stars existing, the required C-O composition needed for a Type Ia supernova could be considered "rare" regardless of accreted mass.

    I am very interested in this and related stellar evolution subjects, so if any of this seems unclear or invalid please provide me with a link or two for consideration.
    Last edited: Feb 8, 2006
  2. jcsd
  3. Feb 8, 2006 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Given their rarity, it's possible we've never observed an explosion from a helium white dwarf passing the chandrasekhar limit. However, if it did occur, it would almost certainly have a different spectral signature, so you're right that it wouldn't be classified as a Type Ia.

    Think a little harder about this one. Helium white dwarfs are thought to form from progenitors with M <~ 0.4 Msun. How long do those stars live on the main sequence? How old is the universe?

    Helium white dwarfs can, however, form from binary systems.

    You should know better than to quote Wikipedia for these discussions.

    The AIC scenario might happen, but population synthesis models suggest that it occurs a factor of >~ 20 times less frequently than Type Ia supernovae. (Dessart et al. 2006)

    From what I've read, we can check your points:




    Last edited: Feb 8, 2006
  4. Feb 8, 2006 #3


    User Avatar
    Science Advisor

    Obviously there won't be any agreement on this subject. My opinion is:
    (1) Yes
    (2) Yes
    (3) Yes
    (4) Yes

    Did you know also that every large star with a "short" lifetime always becomes a Type II supernova.:zzz:

    That's a broad statement, I'm sure that there couldn't possibly be any exceptions. But like you said elsewhere, you post yours and I'll post mine, but not here again. If I see obvious errors I'll just post my objections/corrections anyway. I have no doubt whatsoever that you will do the same. Odd how so many threads end with the same name, even when the topic has already been discussed, agreed upon and settled..:confused:
  5. Feb 8, 2006 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    This isn't a matter of opinion; in fact, I'm relatively certain that your claims are wrong since your references are vague (they don't even directly support your statements) and are mostly from pop-sci websites. In the future, if you think something I say is wrong or want to expand on it, just address it directly in the thread, don't get all hostile and rant about how I'm always ignoring important details. I'm not always right, but I can assure you that I know what I'm doing.

    I don't know what you're getting at here, but the reason topics are repeated has to do mostly with the fact that new posters don't search the entire post database before asking a question. I can understand this, so if something has been addressed before, I have no problem with linking to the old discussion.
  6. Sep 20, 2006 #5


    User Avatar

    Staff: Mentor

    Dr. Andy Howell has discovered a distant supernova, or exploded star, so large that it will force scientists to question their understanding of how certain older stars disintegrate. Howell and co-authors Peter Nugent and Richard Ellis will be publishing results and analysis of the discovery in Nature this week.

    Supernova leads to questions about death of stars
    'Champagne supernova' challenges understanding of how supernovae work
    A type Ia supernova breaks Chandrasekhar limit, astronomy's 'standard candles' suddenly variable
    Snls-03d3bb: An Overluminous, Low Velocity Type Ia Supernova Discovered At Z=0.244

    Elsewhere -

    Towards a Cosmological Hubble Diagram for Type II-P Supernovae

    Authors: Peter Nugent (1), Mark Sullivan (2), Richard Ellis (3), Avishay Gal-Yam (3 and 4), Douglas C. Leonard (3 and 5), D. Andrew Howell (2), Pierre Astier (6), Raymond G. Carlberg (2), Alex Conley (2), Sebastien Fabbro (7), Dominique Fouchez (8), James D. Neill (9), Reynald Pain (6), Kathy Perrett (2), Chris J. Pritchet (9), Nicolas Regnault (6) ((1) Lawrence Berkeley National Laboratory, (2) University of Toronto, (3) California Institute of Technology, (4) Hubble Postdoctoral Fellow, (5) NSF Astronomy and Astrophysics Postdoctoral Fellow, (6) LPNHE, CNRS-IN2P3 and University of Paris VI & VII, (7) CENTRA, (8) CPPM, CNRS-IN2P3 and University Aix Marseille II, (9) University of Victoria)
    Comments: 36 pages, 16 figures, accepted for publication in ApJ

    Last edited: Sep 20, 2006
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: White Dwarfs, > Chandra Mass?
  1. White dwarfs (Replies: 2)

  2. White dwarf (Replies: 1)