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LIFE CYCLE OF A STAR (TYPES: (GIANT (is a star with substantially larger…
LIFE CYCLE OF A STAR
TYPES:
GIANT
is a star with substantially larger radius and luminosity than a main-sequence (or dwarf) star of the same surface temperature.They lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzsprung–Russell diagram and correspond to luminosity classes II and III.[
MEDIUM-SIZED STAR
For stars heavier than 1.4 solar masses but lighter than about 3-4 solar masses (the calculations are still a bit uncertain), the electron pressure is not strong enough to balance gravity. The contraction then goes crushing the electrons together and braking apart the Iron nuclei into their constituents. These constituents, neutrons and protons, also detest being close to each other and, as mentioned above, produce a (degenerate) pressure which opposes gravity.
SUPERGIANT
Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8 with temperatures spanning from about 3,500 K to over 20,000 K.
DWARF STAR
s a star of relatively small size and low luminosity. Most main sequence stars are dwarf stars. The term was originally coined in 1906 when the Danish astronomer Ejnar Hertzsprung noticed that the reddest stars
NEUTRON STAR
A neutron star is the collapsed core of a large star which before collapse had a total of between 10 and 29 solar masses. Neutron stars are the smallest and densest stars, not counting hypothetical quark stars and strange stars.
BLACKBODY
Stars are considered blackbody radiators. Blackbody radiators emit and absorb energy perfectly. When the energy from a star is plotted on a graph, a smooth curve, known as a blackbody curve, is formed.
MAIN SEQUENCE
The main sequence is where most stars spend the majority of their “lives.” Most main-sequence stars take a billion years or more to complete their life cycles.
END OF STAR
All stars eventually lose their nuclear fuel and die out. As the star continues to burn, fusion creates internal pressure that pushes out from within the star. As hydrogen atoms combine to form helium, the amount of hydrogen decreases; at the same time, the center of the star becomes increasingly heavy.
BRIGHTNESS
Perhaps the most important characteristic of a star is its luminosity—the total amount of energy at all wavelengths that it emits per second. Earlier, we saw that the Sun puts out a tremendous amount of energy every second. (And there are stars far more luminous than the Sun out there.) To make the comparison among stars easy, astronomers express the luminosity of other stars in terms of the Sun’s luminosity.
TEMPERATURE
You might be surprised to know that the color of stars depends on their temperature. The coolest stars will look red, while the hottest stars will appear blue.
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