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11 de feb. de 2015 · Polaris: Also known as the North Star (as well as the Pole Star, Lodestar, and sometimes Guiding Star), Polaris is the 45th brightest star in the night sky. It is very close to the north...
Arcturus. (Alpha Boötis) Arcturus is the brightest star in the constellation Boötes (the herdsman). It is a red giant (spectral type K1.5IIIp) that is the fourth brightest star in the sky. Arcturus is 34 light-years from Earth. It has an apparent magnitude of -0.04 and an absolute magnitude of 0.2. Betelgeuse.
Along with their brightness (apparent magnitude), the spectral class of a star can tell astronomers a lot about it. There are seven main types of stars. In order of decreasing temperature, O, B, A, F, G, K, and M. O and B are uncommon, very hot and bright. M stars are more common, cooler and dim.
The universe’s stars range in brightness, size, color, and behavior. Some types change into others very quickly, while others stay relatively unchanged over trillions of years.
Astronomers estimate that the universe could contain up to one septillion stars – that’s a one followed by 24 zeros. Our Milky Way alone contains more than 100 billion, including our most well-studied star, the Sun. Stars are giant balls of hot gas – mostly hydrogen, with some helium and small amounts of other elements.
This diagram shows most of the major types of stars. The vast majority of stars are main sequence stars - these are star like the Sun that are burning hydrogen into helium to produce their energy. Most stars spend 90% of their life as main sequence stars.
20 de mar. de 2019 · Most of the stars in our galaxy, including the sun, are categorized as main sequence stars. They exist in a stable state of nuclear fusion, converting hydrogen to helium and radiating x-rays....
