HD 12661

Properties

The star has an apparent visual magnitude of 7.42, too faint for naked-eye viewing but observable with a small telescope of 6 cm aperture or more. Parallax measurements place HD 12661 at a distance of about 123.3 light-years from Earth. Its stellar classification is G6 V, a main sequence star fusing hydrogen at its core. The effective temperature of the outer envelope is about 5,754 K, giving it a yellow hue typical of G-type stars.

Stellar models estimate its radius between 107% and 112% of the Sun's radius and its mass between 107% and 110% of the Sun's mass. Chromospheric emission indicates the star is older than the Sun, with an estimated age of roughly seven billion years, though the technique becomes less accurate beyond about 5.6 billion years. The star has a low projected rotational velocity of 1.20 km/s, consistent with older age. Lithium abundance provides a separate age estimate of 4.4 billion years, though this method is less accurate.

The metallicity—abundance of elements heavier than hydrogen and helium—is unusually high compared to the Sun. High metallicity correlates statistically with multi-planet systems; one planet may have been scattered and accreted by the star, possibly explaining the high surface metallicity.

Planetary system

Astronomers first detected a planet around HD 12661 in 2001 by measuring tiny shifts in the star's light at Lick and Keck observatories. The same team found a second planet two years later.

Both worlds are heavier than Jupiter. In 2025, astrometry revealed the true mass and orbital tilt of the outer planet. The system is dynamically unstable, suggesting either we are seeing it in an unusual phase or unseen planets are influencing its motion.