A glance at the night sky above Earth shows that some stars are much brighter than others. ... Astronomers define star brightness in terms of apparent magnitude — how bright the star appears from Earth — and absolute magnitude — how bright the star appears at a standard distance of 32.6 light-years, or 10 parsecs.
The brightness of a star in the sky is determined by how close it is to the planet and what its composition is.
What is Star?In astronomy, a star is a luminous gas spherical object that is kept together by gravitational force. It is an organic glowing body that can be seen in the night sky with open eyes or a telescope.
In every direction, light is constantly emitted by stars. Energy is a component of the photons. Since stars are so bright, it is more practical to estimate their luminosities in units of the Sun's luminosity.
We determine that stars have a wide variety of photon energies by calculating the apparent luminosity and distance of the stars in our immediate area. The Sun is one million times as bright as the stars in our galaxy which are the most luminous.
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