Alpha Doradus
Encyclopedia
Alpha Doradus is the brightest star
in the constellation
of Dorado. It is actually a binary
system of two stars, and has an overall apparent visual magnitude which varies between 3.26 and 3.30. The binary star consists of a subgiant with spectral type B revolving around a giant star
with spectral type A in an eccentric orbit
with a period of about 12 years. The orbital separation varies from 2 astronomical unit
s at periastron to 17.5 astronomical units at apastron. The primary, α Doradus A, is a chemically peculiar star whose atmosphere has a high concentration of silicon
.
, CCDM J04340-5503C, located 77 arcseconds away. It has no physical relation to the other two stars.
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Dorado. It is actually a binary
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
system of two stars, and has an overall apparent visual magnitude which varies between 3.26 and 3.30. The binary star consists of a subgiant with spectral type B revolving around a giant star
Giant star
A giant star is a star with substantially larger radius and luminosity than a main sequence star of the same surface temperature. Typically, giant stars have radii between 10 and 100 solar radii and luminosities between 10 and 1,000 times that of the Sun. Stars still more luminous than giants are...
with spectral type A in an eccentric orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
with a period of about 12 years. The orbital separation varies from 2 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s at periastron to 17.5 astronomical units at apastron. The primary, α Doradus A, is a chemically peculiar star whose atmosphere has a high concentration of silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
.
Visual companion
The binary star has an optical visual companionDouble star
In observational astronomy, a double star is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope. This can happen either because the pair forms a binary star, i.e...
, CCDM J04340-5503C, located 77 arcseconds away. It has no physical relation to the other two stars.