HD 12661 is a G-type main sequence star in the northern

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Aries Aries may refer to: *Aries (astrology), an astrological sign *Aries (constellation), a constellation of stars in the zodiac Arts, entertainment and media * ''Aries'' (album), by Luis Miguel, 1993 * ''Aries'' (EP), by Alice Chater, 2020 * "Aries" ...

. The star is slightly larger and more massive than the Sun, with an estimated age of seven billion years. It has two known extrasolar planets.

Properties

The apparent visual magnitude of this star is 7.42, making it too faint to be viewed by the naked eye even under ideal viewing conditions. However, it can be readily observed using a small

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

with an

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An opt ...

of or more.

Parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...

measurements of HD 12661 place it at a distance of about from the Earth, with a margin of error of ±0.2 light years. It has a

stellar classification In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

of G6 V, indicating that it is a

main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...

star that is generating energy through the

thermonuclear fusion Thermonuclear fusion is the process of atomic nuclei combining or “fusing” using high temperatures to drive them close enough together for this to become possible. There are two forms of thermonuclear fusion: ''uncontrolled'', in which the re ...

of hydrogen at its core. The

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

of the star's outer envelope is about 5,754 K, giving it the characteristic yellow hue of a G-type star. Based on stellar models, estimates of the radius of this star range from 107% to 112% times Sun's radius, while the mass is likely in the range from 107% to 110% of the Sun's mass. As a star ages it slows its

rotation Rotation, or spin, is the circular movement of an object around a '' central axis''. A two-dimensional rotating object has only one possible central axis and can rotate in either a clockwise or counterclockwise direction. A three-dimensional ...

and diminishes the amount of magnetic activity in its

chromosphere A chromosphere ("sphere of color") is the second layer of a star's atmosphere, located above the photosphere and below the solar transition region and corona. The term usually refers to the Sun's chromosphere, but not exclusively. In the Su ...

. Hence the measured emission from the chromosphere can be used to estimate the age of a star, particularly for F and G-type dwarf stars with an age of less than two billion years. However, this technique becomes less accurate for ages beyond about 5.6 billion years. Based upon the chromosphere emission of HD 12661, it is older than the Sun with an estimated age of roughly seven billion years. It has a low

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 bulge ...

of 1.20 km/s, consistent with it being an older star. The age of a star can also be estimated by the abundance of lithium, as this element is destroyed through

at the core. However, this is less accurate technique. For HD 12661, the lithium abundance gives an age estimate of 4.4 billion years. The abundance of elements other than hydrogen and helium, what astronomers term the

metallicity In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...

, is unusually high in this star when compared to the Sun. High metallicity has been found to be statistically correlated with the presence of a multi-planet system around a star. It is possible that a planet in this system may have been scattered and ended up being accreted by the star, which may account for the large surface metallicity.

Planetary system

The first planet was discovered in 2001 from the Lick and Keck observatories using precision measurements of the star's radial velocity variations. The periodicity in this variation allowed astronomers to extract information about the planet's orbit and minimum mass. A second planet was discovered by the same team two years later. Both planets are greater in mass than

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

. The system is dynamically unstable. "Either this system is being observed during a relatively rare state, or additional planets are affecting the observed radial velocities and/or the system’s secular eccentricity evolution."

References

External links

* *
Extrasolar Planet Interactions
by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona
Local Sky Map
{{DEFAULTSORT:HD 12661 009683 Aries (constellation) 012661 G-type main-sequence stars Planetary systems with two confirmed planets Durchmusterung objects

Properties

Planetary system

See also

References

External links