The brightest stars are roughly 50 times the size of our sun.
Up to a million times brighter than our sun, Class O (oh) stars can be between 15 and 100 times the mass of our sun and boast surface temperatures of 30,000 to 50,000 degrees Kelvin, or 50,000 to 90,000 degress F. There may be as many as 15,000 of these in the Milky Way galaxy. O-type stars also expel massive amounts of radiation in the ultraviolet spectrum.
Betelgeuse is not an O-type, it is one of the brightest in our sky because it is one of the closest stars. It is a red giant, with a mass between 5 and 30 times that of our sun. Estimates put its temperature around 3300 degrees Kelvin and it has been observed contracting in recent years. Red giants are pulsating stars, meaning that they will expand and contract in size, but some scientists believe Betelgeuse is due to burn out in less than a million years. The uncertainty is so great thought that some say it may already have exploded as a type II super nova, but the light has not reached earth. Around 500 light years away, that is a mathematical possibility.
500 light years, or 150 parsecs from earth, even a super nova explosion would not have a great impact on earth. Betelgeuse is part of the Orion constellation, an evening winter to spring zodiacal display which also contains Rigel, Bellatrix and Alnilam. Orion is roughly between and below Gemini and Taurus, the late April and late May constellations. In North America, Gemini is a february constellation, remember that the astrological time periods came from Greece and Italy.
To find an O-type supergiant, one can loook to the Monoceros constellation, a faint display directly below Gemini in the North American Sky. Dificult to see with the naked eye, but the star Monocerotis is over 2400 light years distant with a mass roughly 60 times that of our sun.
The Milky Way galaxy is thought to contain around 250 billion stars. Reaching 100,000 light years across, and with stars beyond 1,000 light years being difficult to observe with the naked eye, many light patterns we observe in the Milky Way are the sum of multiple stars.