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The opposite change, a decrease in wavelength and increase in frequency and energy, is known as a blueshift, or negative redshift. The terms derive from the colours red and blue which form the extremes of the visible light spectrum .
The first one to address the problem of an infinite number of stars and the resulting heat in the Cosmos was Cosmas Indicopleustes, a 6th-century Greek monk from Alexandria, who states in his Topographia Christiana: "The crystal-made sky sustains the heat of the Sun, the moon, and the infinite number of stars; otherwise, it would have been full of fire, and it could melt or set on fire."
Novae are stars that undergo dramatic explosions, but unlike supernovae, these do not result in the destruction of the original star. The likely rate of novae in the Milky Way is about 40 per year, [ 1 ] but of these only about 10 per year are discovered by observers as of the 2000s (decade). [ 2 ]
Main-sequence stars vary in surface temperature from approximately 2,000 to 50,000 K, whereas more-evolved stars – in particular, newly-formed white dwarfs – can have surface temperatures above 100,000 K. [3] Physically, the classes indicate the temperature of the star's atmosphere and are normally listed from hottest to coldest.
The first list shows a few of the known stars with an estimated luminosity of 1 million L ☉ or greater, including the stars in open cluster, OB association and H II region. The majority of stars thought to be more than 1 million L ☉ are shown, but the list is incomplete. The second list gives some notable stars for the purpose of comparison.
Closest star to the Sun with exactly six [29] exoplanets, and closest K-type main sequence star to the Sun with a multiplanetary system. One of the oldest stars with a multiplanetary system, although it is still more metal-rich than the Sun. None of the known planets is in the habitable zone. [30] 61 Virginis: Virgo: 13 h 18 m 24.31 s: −18 ...
John Michell calculated in 1767 that the probability of a chance alignment of so many bright stars was only 1 in 500,000, and so surmised that the Pleiades and many other clusters must consist of physically related stars. [54] When studies were first made of the proper motions of the stars, it was found that they are all moving in the same ...
The huge luminosity of quasars results from the accretion discs of central supermassive black holes, which can convert between 5.7% and 32% of the mass of an object into energy, [40] compared to just 0.7% for the p–p chain nuclear fusion process that dominates the energy production in Sun-like stars.