equatorial Equatorial may refer to something related to:
*Earth's equator
**the tropics, the Earth's equatorial region
**tropical climate
*the Celestial equator
** equatorial orbit
**equatorial coordinate system
** equatorial mount, of telescopes
* equatorial ...
Ophiuchus
Ophiuchus () is a large constellation straddling the celestial equator. Its name comes from the Ancient Greek (), meaning "serpent-bearer", and it is commonly represented as a man grasping a snake. The serpent is represented by the constella ...
. It is visible to the naked eye as a faint, white-hued point of light with a combined
apparent visual magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...
of 3.73. It is located approximately 86.9 light years away from the Sun based on parallax, but is moving closer with a heliocentric radial velocity of -23.9 km/s.
As of 2008, the pair had an angular separation of . According to Gray et al. (2003), the primary component has a stellar classification of A5 V, matching an
A-type main-sequence star
An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between ...
. Cowley et al. (1969) had assigned it to a class of A4 IVs, suggesting it is a sharp- lined (s)
subgiant star
A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution o ...
. The latter class is still in use by some sources.
The primary is 250 million years old with double the mass of the Sun and is spinning with a moderate
projected rotational velocity
Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface.
The rotation of a star produces an equatorial bulg ...
of 65 km/s. It is radiating 20 times the
luminosity of the Sun
The solar luminosity (), is a unit of radiant flux ( power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun.
One nominal ...
infrared excess
An infrared excess is a measurement of an astronomical source, typically a star, that in their spectral energy distribution has a greater measured infrared flux than expected by assuming the star is a blackbody radiator. Infrared excesses are oft ...
, suggesting a
debris disk
A debris disk (American English), or debris disc (Commonwealth English), is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris di ...
is orbiting the star with a mean separation of and temperature of 60 K. The system is a source of X-ray emission, which is most likely coming from the 14th magnitude companion.
There are additional visual companions: component C with magnitude 11.5 lies at an angular separation of from the primary, while component D, has magnitude 14.8 and separation 24".