From Simple English Wikipedia, the free encyclopedia
Arcturus
(or α Boo, α Bootis,
Alpha
Bootis) of the
constellation
Bootes
is the brightest
star
in the northern
celestial hemisphere
. With an
apparent magnitude
of −0.04, it is the
fourth brightest star
in the night sky, after −1.46 magnitude
Sirius
, −0.86 magnitude
Canopus
, and −0.27 magnitude
Alpha Centauri
.
[1]
It is a relatively close star at only 36.7
light-years
from Earth, and, together with
Vega
and Sirius, one of the most luminous stars in the
Sun
's neighborhood.
Arcturus is a
type
K1.5 IIIpe
red giant
star, with an
absolute magnitude
of ?0.30. It has likely exhausted its
hydrogen
from the core and is now in its active
red giant
phase. It will continue to expand before entering the horizontal branch stage of its life cycle.
[2]
The diameter of Arcturus is around 35 million kilometers.