The Hubble Space Telescope has taken a picture of the star Proxima Centauri, the closest to the Sun, using its Wide Field and Planetary Camera 2 (WFPC2) instrument. It’s in the neighborhood in astronomical terms, just over 4 light-years from Earth, but generally its light is very dim. Occasionally, however, Proxima Centauri is particularly brilliant.
Proxima Centauri is a red dwarf of spectral type M5.5 Ve with a mass about one-eighth that of the Sun. For this reason, despite its relative closeness to Earth is invisible to the naked eye. It’s part of the triple star system Alpha Centauri, along with two stars a little smaller than the Sun.
It was only in 1915 that astronomer Robert Innes discovered Proxima Centauri, noting that it had the same proper motion as Alpha Centauri. It was the dimmest star star discovered at the time. Today it’s possible to study its characteristics much better, in particular the variations in its brightness.
Proxima Centauri is a flare star, a type of variable star subject to sudden increases in brightness across the electromagnetic spectrum of very short duration. The phenomenon of convection within the star generates a magnetic field with an occasional blasting.
Even under these optimal conditions and with the sophisticated instruments of the Hubble Space Telescope, Proxima Centauri is rather dim. Generally, its companions in the Alpha Centauri system are the ones who are observed since they are more similar to the Sun but there are reasons for astronomers to be interested in this little star as well.
The same convection processes that cause its flares, in this case combined with other factors such as its reduced mass which determines a slow consumption of hydrogen, will also allow Proxima Centauri to have an extremely long life in its main sequence. The estimated duration of this life is around 4 trillion years.
That’s an incredibly long life expectancy, also thinking that a star like the Sun remains in the main sequence “only” for about ten billion years.
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