Complex sentence: The largest star within ten light years is Sirius, a bright main-sequence star roughly twice the Sun's mass and orbited by a white dwarf called Sirius B and lies 8.6 light years away.
Split into simpler sentences: The largest star within ten light years is Sirius. A bright main-sequence star roughly twice the Sun's mass, Sirius is orbited by a white dwarf called Sirius B and lies 8.6 light years away.