Star

From Vinidia

A star is any massive gaseous celestial body in outer space. Stars appear as shining points in the nighttime sky that twinkle because of the effect of the atmosphere and their distance from us. Many stars are between 1 billion and 10 billion years old. They range in size from the tiny neutron stars (which are actually dead stars) no bigger than a city, to supergiants which have a diameter about 1,000 times larger than the sun-about 1.6 billion kilometers.

Scientifically, stars are defined as self-gravitating spheres of plasma in hydrostatic equilibrium , which generate their own energy through the process of nuclear fusion. The energy produced by stars radiates into space as electromagnetic radiation (mostly visible light), and as a stream of neutrinos. The apparent brightness of a star is measured by its apparent magnitude. Many stars are gravitationally bound to other stars, forming binary stars. Larger groups called star clusters also exist. Stars are not spread uniformly across the universe , but are typically grouped into galaxies . A typical galaxy contains hundreds of billions of stars.

Stellar classification

Spectral classification

Class Temperature Star Color
O >30,000 Blue
B 10,000 - 30,000 K Blue-white
A 7,300 - 10,000 K White
F 6,000 - 7,300 K Yellow-white
G 5,300 - 6,000 K Yellow (like the Sun)
K 3,900 - 5,300 K Yellow-orange
M 2,300 - 3,900 K Red
L 1,300 - 2,300 K Dark red
T 500 - 1,300 K Magenta
Y <500 K Dark purple


Spectral Type

Category Description Radius
Ia Luminous supergiant >50
Ib Supergiant >50
II Luminous giant 15-50
III Giant 15-50
IV Sub giant 10-15
V Dwarf 0.1-10
VI Sub dwarf <0.1
VII White Dwarf 0.01
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