Hobbies And Interests
Sizes
The bigger the star, the shorter its life will be. The largest known star, VY Canis Majoris, has a diameter roughly 1,800 to 2,000 times the diameter of our sun, Sol. This is large enough to engulf the orbit of Saturn.
Stars can be much smaller than our own as well. OGLE-TR-122b, the smallest known red dwarf star with a radius of 167,000 km, is 88 percent smaller than our own star. Theory dictates that a star may only need to have 7 percent of our sun's mass to sustain the fusion reactions that take place in all stars. The smallest known neutron star (a dead star) is only 10 km in diameter.
Proximity
The closest star to Earth, besides the sun, is Proxima Centauri, approximately 41.5 trillion km away. Traveling at the speed of light, it would take over four years to reach this star. Current space shuttles are known to reach speeds upwards of 28,000 km/hour, a speed which would put you at Proxima Centauri a mere 169,000 years after your launch from Earth. While the Alpha Centauri system, a series of three stars, is visible from Earth, it is only visible from the southern hemisphere.
The next closest is Barnard's Star, discovered by the famous astronomer E. E. Barnard in 1916. This red dwarf star is approaching our own sun at a rate of about 140 km/second. Recent attempts to discover Earth-like planets orbiting this star have been unsuccessful.
Number of Stars
The number of stars in the Milky Way galaxy is estimated to be in the 200 to 400 billion range. It is possible that there around 500 billion galaxies of equal or greater size in the universe, which would mean there could be 2 x 10^23 stars in the universe. That is more stars than there are atoms on Earth.
Composition of Stars
All stars are comprised of roughly 75 percent hydrogen and 25 percent helium, with other sparse elements included as well. Some stars have heavier concentrations of heavier elements, like iron; these stars have been found to be over five times as likely to have planets orbiting them than stars without heavy metals.