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Extraterrestrial liquid water in the Solar System is likely uncommon, although it has been hypothesized to exist in some of its moons, and to have formerly existed on Mars and Venus. [2] [3] Extrasolar liquid water has not yet been confirmed to exist. The following list contains candidates that meet the following criteria:
Extraterrestrial liquid water. Extraterrestrial liquid water is water in its liquid state that naturally occurs outside Earth. It is a subject of wide interest because it is recognized as one of the key prerequisites for life as we know it and is thus surmised to be essential for extraterrestrial life. [1]
It is an Irr-I category galaxy about 52 Mly distant. An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy. [1] Irregular galaxies do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, with neither a nuclear bulge nor any trace ...
Giant radio galaxies are different from ordinary radio galaxies in that they can extend to much larger scales, reaching upwards to several megaparsecs across, far larger than the diameters of their host galaxies. [119] A "normal" radio galaxy do not have a source that is a supermassive black hole or monster neutron star; instead the source is ...
A dark galaxy is a hypothesized galaxy with no (or very few) stars. They received their name because they have no visible stars but may be detectable if they contain significant amounts of gas. Astronomers have long theorized the existence of dark galaxies, but there are no confirmed examples to date. [1]
The hypothesis of dark matter has an elaborate history. [18] [19] In the appendices of the book Baltimore lectures on molecular dynamics and the wave theory of light where the main text was based on a series of lectures given in 1884, [18] Lord Kelvin discussed the potential number of stars around the Sun from the observed velocity dispersion of the stars near the Sun, assuming that the Sun ...
Dwarf galaxy. A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way 's 200–400 billion stars. [1] The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, [2] is sometimes classified as a dwarf galaxy; others consider it a full-fledged galaxy.
This is an accepted version of this page This is the latest accepted revision, reviewed on 5 October 2024. Discrepancy between lack of evidence of advanced alien life and apparently high likelihood it exists 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 ...