A star is an astronomical object consisting of a luminous spheroid of plasma. Stars are held together by gravity. They are huge in size and have very high temperatures. They give out heat and light because they are very hot. Sun is also a star.


The stars twinkle in the night sky. When starlight enters the atmosphere, it is affected by winds in the atmosphere and by areas with different densities, and temperatures that cause light from the star appear to twinkle when seen from the ground.


There are different types of stars. Some of them are,


 A red giant star is a star that has low surface temperature and a diameter that is large relative to the sun. A red giant will expand outward many times its original size. Betelgeuse (Alpha Orionis) is a well-known example of a Red Giant Star.


A white dwarf is what stars like the Sun become after they have exhausted their nuclear fuel. A white dwarf is very dense. White dwarf stars, so-called because of the white color of the first few that were discovered, are characterized by a low luminosity, a mass on the order of that of the Sun, and a radius comparable to that of Earth.


Supergiant is among the most massive and most luminous stars. A star classed as a supergiant may have a diameter several hundred times that of the Sun and a luminosity nearly 1,000,000 times as great. The temperature range of supergiant stars spans from about 3,400 K to over 20,000 K.


Neutron stars are the smallest and densest stellar objects, excluding black holes and hypothetical white holes, quark stars, and strange stars. The properties of neutron stars are utterly out of this world — a single teaspoon of neutron-star material would weigh a billion tons. Neutron stars have a radius on the order of 10 kilometers (6.2 mi) and a mass of about 1.4 solar masses.


A G-type main-sequence star often called a yellow dwarf, or G dwarf star is a main-sequence star of spectral type G. Such a star has about 0.84 to 1.15 solar masses and a surface temperature of between 5,300 and 6,000 K., Tables VII, VIII. Yellow dwarf stars live for about 10 billion years, and at 4.5 billion years old, our middle-age sun is about halfway through its lifetime. Once its hydrogen supply is depleted, the sun will start consuming its heavier elements. 7.5% of stars are yellow dwarfs and they are brighter than 90% of all other stars.


A blue giant is a hot star with a luminosity class of III (giant) or II (bright giant). Rigel is a blue giant star close to zero magnitudes in Earth’s sky, making it a bright star, and is best visible in the winter northern sky. It also has somewhere between 265 and 315 solar masses, making it the most massive star yet discovered.


A brown dwarf is a type of substellar object that has a mass between the most massive gas giant planets and the least massive stars, approximately 13 to 80 times that of Jupiter ( M J).


When a white dwarf exhausts its own supply of carbon, oxygen, and free-flowing electrons, it will slowly burn out, transforming into a black dwarf. A black dwarf is a theoretical stellar remnant, specifically a white dwarf that has cooled sufficiently that it no longer emits significant heat or light. Black dwarfs take quadrillions of years to form.

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