Apparent magnitude is a measure of the brightness of a star or other astronomical object to an observer on Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance, and any extinction of the object's light caused by interstellar dust along the line of sight to the observer.
Asteroid 65 Cybele and two stars, with their magnitudes labeled
Image of 30 Doradus taken by ESO's VISTA. This nebula has a visual magnitude of 8.
A star is a luminous spheroid of plasma held together by self-gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixed points of light. The most prominent stars have been categorised into constellations and asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated 1022 to 1024 stars. Only about 4,000 of these stars are visible to the naked eye—all within the Milky Way galaxy.
Image of the Sun, a G-type main-sequence star, the closest to Earth
A star-forming region in the Large Magellanic Cloud
Stars in the night sky
Infrared image from NASA's Spitzer Space Telescope showing hundreds of thousands of stars in the Milky Way galaxy
