7 Draconis, also named Tianyi /tiˈɛnjiː/ (or) /ˌtjɛnˈjiː/, is a single star in the northern circumpolar constellation of Draco. It is visible to the naked eye as a faint orange-hued star with a stellar classification of 5.43. Based upon an annual parallax shift of 4.16 mas as seen from the Earth, the star is located approximately 780 light-years from the Sun.
This is an evolved giant star with a stellar classification of K5 III. The measured angular diameter of this star, after correction for limb darkening, is 2.61±0.03 mas. At its estimated distance, this yields a physical size of about 67 times the radius of the Sun. It is radiating about 1,024 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,945 K.
Epoch J2000.0 Equinox J2000.0 (ICRS)
|Right ascension||12h 47m 34.34473s|
|Declination||+66° 47′ 25.0977″|
|Apparent magnitude (V)||5.43|
|Spectral type||K5 III|
|B−V color index||1.567±0.006|
|Radial velocity (Rv)||+11.33 km/s|
|Proper motion (μ)|| RA: 6.674 mas/yr |
Dec.: −6.498 mas/yr
|Parallax (π)||4.1601 ± 0.1056 mas|
|Distance||780 ± 20 ly |
(240 ± 6 pc)
|Absolute magnitude (MV)||−1.35|
7 Draconis is the star's Flamsteed designation.
The star bore the traditional Chinese name of Tianyi, from 天乙 (Tiān Yǐ) or 天一 (Tiān Yī, the Celestial Great One), a deity in Taoism. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Tianyi for this star on 30 June 2017 and it is now so entered on the List of IAU-approved Star Names.
These names of stars that have either been approved by the International Astronomical Union (its Working Group on Star Names has since 2016 been publishing a "List of IAU-approved Star Names", which as of June 2018 included a total of 330 proper names of stars) or which have been in somewhat recent usage. See also the lists of stars by constellation, which give variant names, derivations, and magnitudes.
Of the roughly 10,000 stars visible to the naked eye, only a few hundred have been given proper names in the history of astronomy. Traditional astronomy tends to group stars into asterisms, and give proper names to those, not to individual stars.
Many star names are in origin descriptive of the part of the asterism they are found in; thus Phecda, a corruption of the Arabic -فخذ الدب- fakhth al-dubb "thigh of the bear". Only a handful of the brightest stars have individual proper names not depending on their asterism; so Sirius "the scorcher", Antares "like Mars", Canopus (of uncertain origin), Alphard "the solitary one", Regulus "kinglet"; and arguably Aldebaran "the follower" (of the Pleiades), Procyon "preceding the dog [Sirius]". The same holds for Chinese star names, where most stars are enumerated within their asterisms, with a handful of exceptions such as 織女 "weaving girl" (Vega).
In addition to the limited number of traditional star names, there are some coined in modern times, e.g. "Avior" for Epsilon Carinae (1930), and a number of stars named after people (mostly in the 20th century).Tianyi
Tianyi may refer to:
Tianyi Pavilion, Ningbo, the oldest existing library in China
Tianyi Square, Ningbo
Tianyi Film Company, one of the biggest film production companies in pre-World War II China
Tianyi, the proper name of the star 7 Draconis
Luo Tianyi, Chinese vocaloid character