12 Ophiuchi
Encyclopedia
12 Ophiuchi is a variable star
in the constellation
Ophiuchus
. No companions have yet been detected in orbit around this star, and it remains uncertain whether or not it possesses a dust ring.
This star is categorized as a BY Draconis variable
, with variable star designation V2133. The variability is attributed to large-scale magnetic activity on the chromosphere
(in the form of starspot
s) combined with a rotational period that moved the active regions into (and out of) the line of sight. This results in low amplitude variability of 12 Ophiuchi's luminosity. The star also appears to display rapid variation in luminosity, possibly due to changes in the starspots. Measurements of the long-term variability show two overlapping cycles of starspot activity (compared to the Sun's single, 11-year cycle.) The periods of these two cycles are 4.0 and 17.4 years.
This star is among the top 100 target stars for NASA
's planned Terrestrial Planet Finder
mission http://www.solstation.com/stars/12ophiu.htm. However, the mission is now postponed indefinitely.
Its abundance of heavy elements (elements heavier than helium
) is nearly identical to that of the Sun. The surface gravity is equal to
, which is somewhat higher than the Sun's. The space velocity is 30 km/s relative to the solar system. The high rotation period and active chromosphere are indicative of a relatively young star.
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching 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....
Ophiuchus
Ophiuchus
Ophiuchus is a large constellation located around the celestial equator. Its name is from the Greek "serpent-bearer", and it is commonly represented as a man grasping the snake that is represented by the constellation Serpens. Ophiuchus was one of the 48 constellations listed by the 2nd-century...
. No companions have yet been detected in orbit around this star, and it remains uncertain whether or not it possesses a dust ring.
This star is categorized as a BY Draconis variable
BY Draconis variable
BY Draconis variables are main sequence variable stars of late spectral types, usually K or M. The name comes from the archetype for this category of variable star system, BY Draconis. They exhibit variations in their luminosity due to rotation of the star coupled with star spots, and other...
, with variable star designation V2133. The variability is attributed to large-scale magnetic activity on the chromosphere
Chromosphere
The chromosphere is a thin layer of the Sun's atmosphere just above the photosphere, roughly 2,000 kilometers deep....
(in the form of starspot
Starspot
Starspots are equivalent to sunspots but located on other stars. Spots the size of sunspots are very hard to detect since they are too small to cause fluctuations in brightness...
s) combined with a rotational period that moved the active regions into (and out of) the line of sight. This results in low amplitude variability of 12 Ophiuchi's luminosity. The star also appears to display rapid variation in luminosity, possibly due to changes in the starspots. Measurements of the long-term variability show two overlapping cycles of starspot activity (compared to the Sun's single, 11-year cycle.) The periods of these two cycles are 4.0 and 17.4 years.
This star is among the top 100 target stars for NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's planned Terrestrial Planet Finder
Terrestrial Planet Finder
The Terrestrial Planet Finder was a proposed project by NASA to construct a system of telescopes for detecting extrasolar terrestrial planets. TPF was postponed several times and finally cancelled...
mission http://www.solstation.com/stars/12ophiu.htm. However, the mission is now postponed indefinitely.
Its abundance of heavy elements (elements heavier than helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
) is nearly identical to that of the Sun. The surface gravity is equal to
, which is somewhat higher than the Sun's. The space velocity is 30 km/s relative to the solar system. The high rotation period and active chromosphere are indicative of a relatively young star.