I was looking up the radius of Proxima Centauri and got a funny result.

Google says it's about 100,000 km, while WolframAlpha says its about 200,000 km. Are the error bars that big, or does someone have some bad numbers?

  • $\begingroup$ I had not realised either were in the business of measuring stellar radii. Were no original sources quoted? $\endgroup$
    – ProfRob
    Feb 23, 2018 at 8:03
  • 3
    $\begingroup$ One answer is half of the other; you're certain no-one has confused radius and diameter? $\endgroup$
    – user10106
    Feb 23, 2018 at 8:42

1 Answer 1


Wikipedia quotes $0.1542\pm 0.0045$ solar radii which is $107276\,km$ with an error of about $3130\, km$.

They also give a reference to a 2017 paper available on Arxiv Proxima's orbit around Alpha Centauri, P. Kervella, F. Thévenin, C. Lovis that gives this value.

Wolfram's estimate is too far off to be an experimental error, IMO, and I think someone has just inadvertently used the diameter (twice the radius) rather than the radius.


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