The red dwarf star Proxima Centauri is the closest-known star to the Sun (being about 4.2 ly or 1.3 pc away), however it's not visible to the unaided eye for it is too small and dim. I'd like to know how close one should get to see Proxima well, like most other stars. In Celestia the star would become visible to me at about 0.75 ly away. Is Celestia right?


1 Answer 1


"Back of an envelope" calculation:

Proxima Centauri has an apparent magnitude of about $11$. The faintest objects visible to the unaided eye have magnitudes about $6.5$. So we need to decrease Proxima Centauri's magnitude by about $5$ in round numbers, which corresponds to an increase in brightness of about $100$ times. To achieve this we would have to be about $10$ times closer to Proxima Centuari than we are now, which gives a distance of about $0.4$ ly.

At a distance of $0.75$ ly the apparent magnitude of Proxima Centauri would be about $7.5$, so I think Celestia is being a little optimistic.

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    $\begingroup$ Just to clarify : are you making these calculations exoatmospheric? Both photopic brightness and scene contrast matter. $\endgroup$ Commented Feb 3, 2020 at 20:15

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