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This is an accepted version of this page This is the latest accepted revision, reviewed on 8 February 2025. Discrepancy of the lack of evidence for alien life despite its apparent likelihood This article is about the absence of clear evidence of extraterrestrial life. For a type of estimation problem, see Fermi problem. Enrico Fermi (Los Alamos 1945) The Fermi paradox is the discrepancy ...
These names of stars that have either been approved by the International Astronomical Union or which have been in somewhat recent use. IAU approval comes mostly from its Working Group on Star Names, which has been publishing a "List of IAU-approved Star Names" since 2016. As of February 2025, the list included a total of 492 proper names of stars.
The following is a list of particularly notable actual or hypothetical stars that have their own articles in Wikipedia, but are not included in the lists above. BPM 37093 — a diamond star Cygnus X-1 — X-ray source
This implies that at least one step in this process must be improbable. Hanson's list, while incomplete, describes the following nine steps in an "evolutionary path" that results in the colonization of the observable universe: The right star system (including organics and potentially habitable planets) Reproductive molecules (e.g. RNA)
Stability, luminosity, and lifespan are all factors in stellar habitability. Humans know of only one star that hosts life, the G-class Sun, a star with an abundance of heavy elements and low variability in brightness. The Solar System is also unlike many stellar systems in that it only contains one star (see Habitability of binary star systems).
A star's life begins with the gravitational collapse of a gaseous nebula of material largely comprising hydrogen, helium, and trace heavier elements. Its total mass mainly determines its evolution and eventual fate. A star shines for most of its active life due to the thermonuclear fusion of hydrogen into helium in its core.
In the Steady state theory the universe is infinitely old and uniform in time as well as space. There is no Big Bang in this model, but there are stars and quasars at arbitrarily great distances. The expansion of the universe causes the light from these distant stars and quasars to redshift, so that the total light flux from the sky remains finite.
The active life of a magnetar is short compared to other celestial bodies. Their strong magnetic fields decay after about 10,000 years, after which activity and strong X-ray emission cease. Given the number of magnetars observable today, one estimate puts the number of inactive magnetars in the Milky Way at 30 million or more.