Tau1 Serpentis, Latinized from τ1 Serpentis, is a singlestar in the Caput (Head) segment of the
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
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** equatorial mount, of telescopes
* equatorial ...
Serpens
Serpens ( grc, , , the Serpent) is a constellation in the northern celestial hemisphere. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations designated by the International ...
. It is a red hued star that is dimly visible to the naked eye with an
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 5.16. Based upon parallax measurements, this star is located at a distance of approximately 990 light years from the Sun, while it is drifting closer with a radial velocity of −16.5 km/s.
This object is an aging red giant star, currently on the asymptotic giant branch, with a stellar classification of M1III. Having exhausted the supply of hydrogen at its
core
Core or cores may refer to:
Science and technology
* Core (anatomy), everything except the appendages
* Core (manufacturing), used in casting and molding
* Core (optical fiber), the signal-carrying portion of an optical fiber
* Core, the centra ...
, it has cooled and expanded until it now has around 99 times the girth of the Sun. It is a suspected
variable star
A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as e ...
with a brightness that has been measured varying from magnitude 5.13 down to 5.20. The '' Hipparcos'' data for Tau1 Serpentis shows brightness variations with a period of 6.4675 days, and an amplitude of 0.0066 magnitudes. The star is radiating 2,158 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 ...