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I Do stars have any lower mass limit?

  1. Jul 11, 2017 #1

    Sid

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    Just read an article about a discovery of the smallest/least massive star in the Milky Way galaxy. The star has 85 times the mass of Jupiter and is known as EBLM J0555-57Ab located about 600 light-years from Earth.

    The entire article here - http://www.cbc.ca/news/technology/smallest-star-discovered-1.4199325
     
    Last edited by a moderator: Jul 11, 2017
  2. jcsd
  3. Jul 11, 2017 #2

    davenn

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    hi th

    Hi there welcome :smile:

    I am surprised that that star could be so small and star nuclear fusion ... pretty amazing

    Dave
     
    Last edited by a moderator: Jul 11, 2017
  4. Jul 11, 2017 #3

    Ken G

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    In answer to the title question, that star is just about as small as the mass can get and still have fusion. They didn't say what type of fusion though, but I presume it's hydrogen fusion because I think if it's only deuterium they call it a brown dwarf.
     
  5. Jul 12, 2017 #4

    DrSteve

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    The theoretical limit to a main sequence star's mass is about 80 times the mass of Jupiter, or 0.08 the mass of the sun. Otherwise degeneracy pressure prevents pp fusion from occurring. This is described in most any introductory astronomy textbook.
     
    Last edited: Jul 12, 2017
  6. Jul 12, 2017 #5
    What is particularly interesting about this star is that it was discovered in transit, and because it was only the size of Saturn they incorrectly classified it as an exoplanet. They also recently estimated the minimum mass for a star at 6.7% of Sol, or 70.2 solar masses assuming the same solar metallicity. However, the 6.7% of Sol is theoretical, whereas EBLM J0555-57Ab is observational.

    Source:
    Individual Dynamical Masses of Ultracool Dwarfs - arXiv free preprint, March 2017
     
  7. Jul 12, 2017 #6

    Ken G

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    Those numbers seem inconsistent with each other, perhaps it's a typo. I'm more familiar with the numbers found in the Wiki on Main Sequence stars: "The lower limit for sustained proton–proton nuclear fusion is about 0.08 M☉ or 80 times the mass of Jupiter.[30]" So the 0.08 is right, but not the 13 times, making this star about the smallest mass you can have and still be a main sequence star.
     
  8. Jul 12, 2017 #7

    DrSteve

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    My mistake. It's thought to be around 80 times the mass of Jupiter. Just like the upper limit, I imagine that the lower limit has considerable wiggle room. I have edited my post to correct the number. Thanks
     
  9. Jul 12, 2017 #8
    There is new observational work that suggests the dividing line between red dwarfs and brown dwarfs is not 8% solar but 6.7% solar: See New Scientist and Physics Forums
     
  10. Jul 12, 2017 #9

    DrSteve

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    Yes, the lower limit was never meant to be set in stone (nor is the upper limit).
     
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