
Grigori S. answered 08/03/13
Certified Physics and Math Teacher G.S.
The sun is a star because it produces the energy it radiates and makes itself visible. This energy is a result of thermonuclear reactions taking place in the core of the star where the temperature reacxhes at
T = 20,000, 000 0 K - high enough to tirgger thermonuclear reactions (formation of one nucleus of helium from nuclei of hydrogen).
Planets can't produce enough energy that makes them visible in space, they are cold cosmic bodies visible only if there is a star the radiation of which is reflected by the planet back to space.
Stellar masses are arranged from 0.01 - 100 solar masses (theoretical upper limit, while observable is around 46 solar masses). Planets orbit their central stars, while stars orbit the center of the Galaxy (Milky Way).


Grigori S.
I don't have an information about the mass of the object.
100 solar masses is an approximate theoretical limit. More precisely, it' defcined by Eddington's lunimosity limit, at which the radiation pressure is strong enough to overcome gravity (stars with masses above this limit are expected to be unstable). 46 solar masses I used above, is an old data (approximately 20 yeras ago).
08/04/13

Timur C.
It is possible for a star to exceed the 100 solar mass limit, though it would have only been possible for stars in the early universe. Having a near zero metallicity, stars could have grown to be exceedingly large, much larger than any star we have observed to this day.
08/04/13
Mike C.
Uhh...probably more than 100 solar masses as well. What about VY Canis Majoris, for example?
08/04/13