HD 145457 is a

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

located 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 ...

of Corona Borealis (The Northern Crown) at a distance of around 443 light-years from the Sun, as determined through

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. It has been formally named Kamuy by the

IAU The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

, after a spiritual or divine being in Ainu mythology. With an apparent magnitude of 6.57, it is barely visible to the unaided eye on dark nights clear of light pollution. It is drifting closer to the Sun with a

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

of −3.2 km/s. HD 145457 is an aging giant star with 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 K0 III that has cooled and expanded off the

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 ...

after exhausting its core hydrogen supply. It is a lithium-rich giant, unusual since lithium is rapidly destroyed once a star becomes a

red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...

. One explanation for the excess lithium in these stars has been a recent engulfment of a planet, but it is now thought more likely to be due to nucleosynthesis in the star. It is generally assumed that these lithium-rich giants are members of the red clump, core helium burning stars at the cool end of the

horizontal branch The horizontal branch (HB) is a stage of stellar evolution that immediately follows the red-giant branch in stars whose masses are similar to the Sun's. Horizontal-branch stars are powered by helium fusion in the core (via the triple-alpha process) ...

. With the assumption that it is a helium-burning object, the properties of HD 145457 can be derived by comparison with

evolutionary Evolution is change in the heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene expression, expressions of genes, which are passed on from parent to ...

tracks. With an age of 5.2 billion years old, it is around 1.57 times as massive as the Sun and has swollen to around 10 times its diameter. It is radiating 50 times the luminosity of the Sun from its enlarged

photosphere The photosphere is a star's outer shell from which light is radiated. The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...

at an

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 4,738 K.

Companion

HD 145457 has a companion called HD 145457 b discovered in 2010. 2.9 times as massive as

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 ...

, it orbits about every 176 days with an

orbital eccentricity In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values betwee ...

of . Its

semimajor axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longe ...

is 0.76 AU. HD 145457 b was discovered by precise Doppler measurements with the Subaru Telescope. As part of the

NameExoWorlds project in 2019, HD 145457 b has been formally named Chura. The name was selected by

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. Chura is a word in the Ryukyuan/ Okinawan language meaning natural beauty.

References

{{DEFAULTSORT:HD 145457 K-type giants Planetary systems with one confirmed planet Corona Borealis Durchmusterung objects 145457 079219 Stars with proper names