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Light-year
A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in a vacuum in one year. While there is no authoritative decision on which year is ... > more -
Supergiant
Supergiants are the most massive stars. Supergiants can have masses from 10 to 70 solar masses and brightness from 30,000 up to hundreds of thousands times the solar luminosity. They vary greatly in ... > more -
Orion Nebula
The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a glowing emission nebula with a greenish hue and is situated below Orion's Belt. It is one of the brightest nebulae visible to the ... > more -
Blue supergiant
Blue supergiants are supergiant stars (class I) of spectral type O. They are extremely hot and bright, with surface temperatures of between 20,000 - 50,000 degrees Celsius. The best known example is ... > more -
Nicolaus Copernicus
Nicolaus Copernicus (February 19, 1473 - May 24, 1543) was the astronomer who formulated the first modern heliocentric theory of the solar system. His epochal text, De revolutionibus orbium ... > more -
Doppler effect
The Doppler effect, named after Christian Andreas Doppler, is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. The ... > more -
Gravitational wave
In physics, in terms of a metric theory of gravitation, a gravitational wave is a fluctuation in the curvature of space-time which propagates as a wave, traveling outward from a moving object or ... > more
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