Delta Eridani, which is Latinized from δ Eridani, 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 ...

in the equatorial

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 Eridanus. The star is visible to the naked eye and has been observed to vary in slightly brightness between magnitudes 3.51 and 3.56, although subsequent observations did not bear this out. It is relatively near to the Sun, with a distance of about 29.5

light year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s as determined from

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 ...

. The star is drifting closer 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 −6 km/s. Delta Eridani is sometimes called Rana: ''

Rana Rana may refer to: Astronomy * Rana (crater), a crater on Mars * Delta Eridani or Rana, a star People, groups and titles * Rana (name), a given name and surname (including a list of people and characters with the name) * Rana (title), a histor ...

'' means "the frog" in Latin, but derivation of this name is uncertain. The name was approved by the International Astronomic Union on 4 April 2022.

Structure

The

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 this star is K0 IV, matching a subgiant star that has exhausted its core hydrogen. This has caused the star to expand and become cooler than a comparable main sequence star. Stellar modelling indicates it is near the end of the subgiant stage and about to transition into a giant. It is an estimated six billion years old with 33% more mass than the Sun. The star has 2.3 times the girth of the Sun and is radiating three times the Sun's luminosity from its

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 4,986 K. Delta Eridani is catalogued as a suspected RS Canum Venaticorum variable in 1983, but the activity level for the star is so low that this is considered doubtful. This class of variables occurs in close binary systems. A low projected rotational velocity of under 1 km/s and the lack of radial velocity variation suggests that this putative variable is being viewed from nearly pole-on. However, an examination of the star using

interferometry Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opt ...

does not detect the presence of a companion at the expected distance.

Chinese name

In Chinese, (), meaning '' Celestial Meadows'', refers to an asterism consisting of δ Eridani, γ Eridani, π Eridani, ε Eridani, ζ Eridani, η Eridani, π Ceti, τ¹ Eridani, τ² Eridani, τ³ Eridani, τ⁴ Eridani, τ⁵ Eridani, τ⁶ Eridani, τ⁷ Eridani, τ⁸ Eridani and τ⁹ Eridani. Consequently, the Chinese name for δ Eridani itself is (, en, the Third Star of Celestial Meadows.)

References

External links

* *
nStars entry
{{DEFAULTSORT:Delta Eridani K-type subgiants Eridani, Delta Suspected variables Eridanus (constellation) Eridani, Delta BD-10 0728 Eridani, 23 0150 023249 017378

1136 Year 1136 ( MCXXXVI) was a leap year starting on Wednesday (link will display the full calendar) of the Julian calendar. Events By place Levant * Spring – Raymond of Poitiers, son of the late Duke William IX of Aquitaine, arri ...

Structure

Chinese name

See also

References

External links