The size of some star (white dwarf) is close to the size of the Earth, and the surface temperature is 10,000 K. Estimate how far this star can be seen with the eye through a 20-centimeter telescope. Consider that 6 ^ m stars are visible at the limit with the naked eye with a pupil of 6 mm.
10 pc (in the indicated telescope at the limit, stars of 13.6 ^ m will be visible, and the star has an absolute magnitude of ~ 13 ^ m).
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