In article ,
"Mike Dworetsky" writes:
I'm not sure how you are doing this calculation. The absolute magnitude of
Sirius B is (from references) about +11.5, so at 31.5 AU, log(d) = -3.82 (d
in parsec). The usual distance modulus formula m - M = 5logd -5 then gives
apparent magnitude m = -12.6, roughly as bright as the average full moon
from Earth. At 8 AU it should be about 15 times brighter than that.

Looks right to me. Worth noticing is that Sirius B would be a point
of light, not extended. Looking at it with human eyes would probably
burn a blind spot in one's retina. A single spot would be tiny and
therefore unnoticed in normal life, but an accumulation of blind
spots would significantly decrease vision. Presumably the
inhabitants of such a planet would have evolved some protection
against this danger, though I'm not sure quite what. Maybe just a
reflex aversion to looking at bright lights would suffice.

Incidentally, Sirius is around 25 times more luminous than the Sun, so if
the supposed planet of the OP is meant to have Earthlike conditions, it
needs to be about 5 AU from the primary, so the distance to Sirius B would
range from around 3 AU to 26.5 AU at opposition (if the orbit is roughly
circular).

Hard to imagine a planet 5 AU from Sirius A having a stable orbit.
There must be some calculation of how small the orbit would have to
be, but I don't know where to find it. Even 1 AU, where mean
temperature would be about 330 deg_C, seems dubious to me.

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