Hobbies And Interests
Size and Mass
Astronomers classify stars as either "dwarfs" or "giants," based on their sizes. The sun is a dwarf star, but even though it is small compared to giants, more than 1 million Earths could fit within the sun. Most of the matter in the solar system --- more than 99.9 percent --- is contained within the sun. Most of that matter is in the form of hydrogen and helium, weighing more than 333,000 times the weight of Earth.
Temperature and Luminosity
Scientists classify the sun's brightness and temperature as "G2V," which places it in the lower-mid-range compared to other stars. Hotter stars appear more blue, and cooler stars more red, but the sun's surface temperature of around 6,000 degrees Kelvin gives its light a yellow color. Although the sun's luminosity is not very great compared to other stars, from Earth it appears more than 300,000 times brighter than a full moon.
Life Cycle
Stars are formed from clouds of dust and gas in space, like the Great Nebula in the constellation Orion. Scientists estimate that the sun was formed 4.5 billion to 5 billion years ago, and is about halfway through its life cycle. In the last 2 billion years of the sun's life cycle, astrophysicists believe that the sun will expand into a red giant, similar to the star known as Arcturus. Then, at the very end of its life, the sun will disperse, leaving only its core to burn as a small white dwarf.
Earth-Like Planets
Planet hunters have discovered several sun-like stars orbited by planets that could be similar to Earth. A star called 61 Virginis, which is visible from Earth as part of the constellation Virgo, has three such planets, which could be habitable. The 61 Virginis star is similar to the sun in age and mass, and is located only 28 light-years away. Another similar star, HD 1461, is 75 light-years from Earth, and is orbited by two or three planets, one of which might be able to support life.