How big are stars?

The sun is quite a small star, measuring 1,392,530 km across, which is 109 times more than the Earth's diameter. Some stars are known as supergiants, such as Antares which is 700 times bigger than the sun. There is also a star in Aurgia constellation which has a diameter of 3,000 million km or 4,000 times bigger than the sun. There are also stars which are smaller than the sun, such as the neutron star. Neutron stars may measure only 20 km, after the explosion of a supernova. But, it has enormous mass. It it weighs more than 2 or 3 times that of the sun, it begins to collapse to become a black hole.

The minimum size for a star is believed to be near 0.04 times the mass of the Sun; an object called a brown dwarf which is really a large planet which was not massive enough for thermonuclear fusion to get ignited in the core. The largest star is probably about 150-200 times the mass of the Sun. There are probably only a handful of these hyperstars in our own Milky Way which has over 200 billion stars in it.