A
star is a massive luminous spheroid
astronomical object made of
plasma that is held together by its own
gravity. Stars exhibit great diversity in their properties (such as
mass,
volume,
velocity, stage in
stellar evolution, and
distance from
Earth) and some of the outliers are so disproportionate in comparison with the general population that they are considered extreme. This is a list of such stars.
Records that are regarded as authoritative and unlikely to change at any given point are recorded on a white background, while those that could change with new information and/or discoveries are recorded on a grey background.
Also called Alpha Centauri C, it is the outlying star in a
trinary star system that includes
Alpha Centauri A (Rigil Kentaurus) and
Alpha Centauri B (Toliman). This is currently the nearest known neighbouring star to our own Sun. This star was discovered in 1915, and its parallax was determined at the time, when enough observations were established.
Commonly nicknamed Methuselah as a result of its extreme age, this
subgiant star demonstrates a slight
blueshift, indicating that it is moving in a direction towards the Earth.
Stars are being formed constantly in the universe so it is impossible to tell which star is the youngest. For information on the properties of newly formed stars, see Protostar, Young stellar object and Star formation.
This was the third star whose parallax was determined. Before Alpha Centauri, the record was held by
61 Cygni, the first star whose parallax was determined.
The apparent size of the Sun was first measured by
Eratosthenes in the 3rd century BC,[35] who was the second person to measure the distance to the Sun. However,
Thales of Miletus provided a measurement for the real size of the Sun in the 6th century BC, as 1⁄720 the great circle of the Sun (the orbit of the Earth)[36]
Consistent with the upper limit for
red supergiants of roughly 1,500 R☉ based on the four largest stars measured in a survey, which is consistent with the current
stellar evolutionary theory.[38]
This exceeds the predicted limit of 150 M☉, previously believed to be the limit of stellar mass, according to the leading star formation theories.
R136a1 considered the most massive known by the scientific community.[46]
Several candidates exist which have a higher mass, however their mass has been measured by less precise methods and as such their mass value is regarded as less certain.
A B3V star orbited by an unknown-type star, both orbited by another unknown star, together orbited by another unknown star, all orbited by a B9III star orbiting a pair of stars which are a B9III and unknown star.
^An "average" star is a normal star which is larger than a
red dwarf, but smaller than a
giant star. Depending on the definition, this can also be called "Sun-like star".
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