On Thu, Aug 25, 2016 at 07:59:55PM +0000, Phil Pugliese (via tml list) wrote:
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>
> Let's talk a little about the new earth-like planet planet that's been discovered recently, right next door.
>
> From what I've seen & heard, it's orbiting Proxima Centauri & is so far from Alpha Centauri A&B that they would appear as a single star to an observer in orbit around the planet.
> I must say I was surprised to see such a planet discovered around a red dwarf but, assuming that it is in fact 'earth-like', I wonder what it would be like on the surface.
>
> How would the reddish light affect vision?

Hardly at all.  It would be a bit whiter than most incandescent
lights, and not really distinguishable from our sunlight unless one
saw them side by side.

> How bright would the 'dwarf appear to be to the naked eye from the
> surface?

Too dazzlingly bright to look at for long without risking eye damage.
Visually much the same brightness would be spread over a somewhat
larger disc in the sky, but this wouldn't make very much difference.

> What, if any, would be the effect of the 'redness?' (a more
> infra-red compared to Sol) of the of the dwarf's radiation be?
> Would it possible to get a 'sunburn'?

The biggest difference would be far less ultraviolet from the star,
but still ample to get a very nasty sunburn very quickly in the
absence of an ozone layer in an oxygen atmosphere.

One counterintuitive effect is that the reduced UV output would not
maintain as great a concentration of ozone in an Earthlike atmosphere,
so the amount of UV reaching the surface could actually be greater.
This is dependent upon many other variables, though.

> Also, as I recall, Proxima actually orbits A&B.

We still don't know for sure.  It seems likely.

> How far away is that orbit compared to our solar system?
> Is it farther away than Uranus?

About 800 times farther.  Far enough that they would just appear as
stars, but close enough that Alpha Centauri A and B would be by far
the two brightest stars in the night sky (magnitudes -6 and -5) and
even visible during the day.  They would normally be visually distinct
from one another, but only up to 6 arcminutes apart -- about 1/5 the
visual diameter of the Moon.

- Tim