CHARA (Beta Canum Venaticorum).
A lovely name for a northern star that vaults the heavens
in northern spring, "Chara" from Greek meaning "joy." Not terribly
bright, not quite making third magnitude, Chara (the Beta star of
the constellation) is the fainter of the pair of stars that
dominates the modern constellation Canes
Venatici, the Hunting Dogs, invented by Hevelius in the mid-
1600s. The dogs are held by Bootes as he
pursues Ursa Major around the pole, Chara
and Cor Caroli (the Alpha star)
helping make the "southern dog," the "northern dog" represented by
a small group of stars to the northeast of Cor Caroli. Chara was
originally the name for the southern dog itself, the northern
called "Asterion" for "Little Star." But with the brighter of the
those that make the southern dog called "Cor Caroli," little Chara
got the name to itself. Chara's most interesting aspect is its
similarity to the Sun.
The principal component of Alpha Centauri,
the third brightest star in the sky, is also similar, but it has a
bright companion. Chara, on the other hand, like the Sun, seems to
be single. The majority of bright naked eye stars are considerably
more luminous than the Sun, some vastly so, a natural result of
their intrinsic brilliance, such stars visible over great
distances. However, our Sun, a modest star in the middle of the
full range of stellar brightness, would be invisible to the eye if
only 70 light years away. At a distance of 27 light years, Chara
provides a good chance to see what the Sun would look like at
stellar distances. It is a warm class G star with a temperature of
5860 Kelvin (only 80 degrees hotter than the Sun), a mass only four
percent smaller, and a radius but four percent larger, though it is
25 percent more luminous. Since main sequence hydrogen-fusing
stars brighten and swell somewhat as they age, Chara may be one or
two billion years older than the Sun. Chara is also detected in
the X-ray part of the spectrum, implying that it too has a
surrounding hot corona, as expected. Extending the solar
similarity, Chara even rotates at a similar speed. The biggest
difference, other than luminosity, seems to be a metal content less
than solar, the star having only about 60 percent as much iron. So
if you want to see the Sun from afar, take a look at Canes
Venatici's "southern dog." Could Chara have planets too? We do
not know, and for now is not on observing lists that will check the
possibility. If it does, our Sun would look almost the same from
there as Chara does to us.