Alpha Coronae Borealis

Starbox begin
name=Alpha Coronae Borealis A/B Starbox observe
epoch=J2000
ra=15^h 34^m 41.3^s
dec=+26° 42′ 53″
appmag_v=2.21 (2.24 / 7.1)
constell=Corona Borealis Starbox character
class=A0 V / G5 V
b-v=−0.02 /
u-b=−0.02 /
variable=Eclipsing binary Starbox astrometry
radial_v=+1.7
prop_mo_ra=120.38
prop_mo_dec=−89.44
parallax=43.65
p_error=0.79
absmag_v=0.18 / 5.0 Starbox detail
mass=3/0.9
radius=2.7/1.0
luminosity=60/0.7 | temperature=9,750/5,400
metal=?
rotation=133 km/s
age=3.14 × 10⁸Starbox catalog
names=Gemma, Alphekka, Alphecca, Gnosia, Ashtaroth, The Jewel, "Gnosia Stella Coronae", 5 CrB, HR 5793, BD +27°2512, HD 139006, GCTP 3519.00, SAO 83893, FK5 578, HIP 76267. Starbox reference
Simbad=HD+139006

Alpha Coronae Borealis (α CrB / α Coronae Borealis) is a binary star in the constellation Corona Borealis. It also has the traditional names Gemma or Alphekka or Alphecca.

α CrB is an eclipsing binary system similar to Algol (β Per). Its period is 17.36 days, with magnitude varying from +2.21 to +2.32, which is hardly noticeable to the unaided eye.

α CrB is believed to be a stream star member of the Ursa Major Moving Group.

A large disc of dust and material has been shown to exist around Alphecca, prompting speculation of a similar planetary/proto-planetary system to that currently assumed around Vega. How the binary-star dynamic would affect such a system is the subject of intense debate.

The name "Gemma" is Latin for "jewel". The other traditional name comes from Arabic "al-fakkah", "the broken" (ring of stars), from فكّ "fakk" "unsealed"). In astrology it is one of the Behenian fixed stars and has the symbol .

References

* Tomkin, J.; Popper, D. M., 1986, "Rediscussion of eclipsing binaries. XV - Alpha Coronae Borealis, a main-sequence system with components of types A and G", "Astronomical Journal", vol. 91, June 1986.