AB Doradus
Encyclopedia
AB Doradus is a pre-main sequence trinary star system
in the constellation
Dorado
. The primary is a flare star
that shows periodic increases in activity.
The primary star in this system spins at a rate 50 times that of the Sun, and consequently has a strong magnetic field. It has a greater number of star spots
than the Sun. These can cause the luminosity of the star to appear to vary over each orbital cycle. Measurements of the spin rate of this star at its equator have shown that it varies over time due to the effect of this magnetic field.
The system has three components. The binary star AB Doradus B orbits the primary at an average distance of 135 astronomical unit
s (AUs). AB Doradus C, is a close-in companion that orbits the primary at a distance of 2.3 AU, and has an orbital period of 11.75 years. The third star is among the lowest-mass stars ever found. At an estimated mass 93 times Jupiter
's, it is near the limit of 75-83 Jupiter masses below which it would be classified as a brown dwarf
.
This system is a member of the eponymous AB Doradus Moving Group
, a loose stellar association of about 30 stars that are all approximately the same age and moving in the same general direction. It is likely that all of these stars formed in the same giant molecular cloud.
Star system
A star system or stellar system is a small number of stars which orbit each other, bound by gravitational attraction. A large number of stars bound by gravitation is generally called a star cluster or galaxy, although, broadly speaking, they are also star systems.-Binary star systems:A stellar...
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....
Dorado
Dorado
Dorado is a constellation in the southern sky. It was created in the late 16th century and is now one of the 88 modern constellations. Its name refers to the dolphinfish , which is known as dorado in Spanish, although it has also been depicted as a swordfish...
. The primary is a flare star
Flare star
A flare star is a variable star that can undergo unpredictable dramatic increases in brightness for a few minutes. It is believed that the flares on flare stars are analogous to solar flares in that they are due to magnetic reconnection in the atmospheres of the stars. The brightness increase is...
that shows periodic increases in activity.
The primary star in this system spins at a rate 50 times that of the Sun, and consequently has a strong magnetic field. It has a greater number of star spots
Sun SPOT
Sun SPOT is a wireless sensor network mote developed by Sun Microsystems. The device is built upon the IEEE 802.15.4 standard...
than the Sun. These can cause the luminosity of the star to appear to vary over each orbital cycle. Measurements of the spin rate of this star at its equator have shown that it varies over time due to the effect of this magnetic field.
The system has three components. The binary star AB Doradus B orbits the primary at an average distance of 135 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s (AUs). AB Doradus C, is a close-in companion that orbits the primary at a distance of 2.3 AU, and has an orbital period of 11.75 years. The third star is among the lowest-mass stars ever found. At an estimated mass 93 times Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
's, it is near the limit of 75-83 Jupiter masses below which it would be classified as a brown dwarf
Brown dwarf
Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth...
.
This system is a member of the eponymous AB Doradus Moving Group
AB Doradus moving group
AB Doradus Moving Group is a group of about 30 associated stars that are moving through space together with the star AB Doradus. A moving group is distinguished by its members having about the same age, composition and motion through space...
, a loose stellar association of about 30 stars that are all approximately the same age and moving in the same general direction. It is likely that all of these stars formed in the same giant molecular cloud.