What diameter should the satellite of Sirius be if it is 10 magnitudes fainter in absolute value than Sirius, the distance between these stars is 20.4 AU. and if it shone with light reflected from Sirius, like a planet. The absolute magnitude of Sirius is +1.3.
Its diameter is 630 times larger than Jupiter, or 63 times larger than the Sun, that is, 35 times larger than Sirius itself – which is incredible. Hence we conclude that the satellite is a self-luminous body.
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