Castor and Pollux
Observing >
March puts above our wondering heads the mythological Gemini twins – Castor and Pollux. Let’s do a little mythological background check to see how the Twins got there.
Once upon a time, according to Greek myth, Zeus, long
known for his out-of-control infidelity, “visited” a certain
beauty named Leda on her wedding day. To make a long and naughty story
short, Leda ended up simultaneously giving birth to two sets of twins
– one set fathered by Zeus, one set by her husband. One of the Zeus
twins was Pollux, while Castor was a twin from Leda’s husband.
No matter that they were of different fathers, or that Pollux was immortal
and Castor not – the “twins” got along just like the best
of friends.
Together they saved the Argo fleet, fought valiantly in battle, stole
some women on their wedding day, engaged in cattle thieving – all
the typical exploits of Greek heroes. Sadly, the cattle coveting incident
lead to the killing of Castor.
Pollux was upset to say the least. Trying to be a sympathetic dad, Zeus
told Pollux to come on up to Olympus. But Pollux would not. How could
he enjoy Olympus if his best “twin” buddy was imprisoned with
mortals in the underworld?
So Zeus compromised and allowed the brothers to spend alternating days
in Hades and on Olympus.
Later Greek writers, the ancient ancestors of today’s
happy-ending American television writers, rewrote the script and had Zeus
put the Twins in the starry abode where we see them now. (Note: Some astrophysicists
do not accept this explanation of how the two stars got there.)
So where are The Twins exactly? They are the two bright stars above your
head in the early evening. (On Monday night, the Moon is right next to
them.)
Castor
is the bright star slightly more northwest than the other, with a slight
bluish tint. A decent telescope reveals that Castor is really a “visual
binary” – called Castor A and Castor B - the first of its kind
discovered. Regular readers here will remember that binaries are two stars
that are gravitationally bound and revolve around each other.
Castor A is itself another binary system whose two huge stars are so close
they are almost in contact! In fact, they are so close that even our best
telescopes can make out only one star there.
Castor B is also a binary (!) made of two huge stars that are even closer
and take a mere three days to go around each other.
Beyond these pair of pairs is yet another faint pair! All these stars
are gravitationally bound to each other, making what we call “Castor”
a six-star system.
Castor’s brother, Pollux, is the rather pinkish star next door. It’s
that faint orangey sort of color because it is in its red giant stage.
That is when a star is about ready to shuffle off its mortal coil and
expands out to enormous proportions. When it expands, the surface cools
down and takes on a reddish color.
And – surprise! - this twin is also a binary system. It appears Castor
and Pollux were put by early mythologists in the perfect place, an area
full of twins, some related, some not.
The downside for these starry twins is that they, and all the stars in
their systems are, unlike their mythological namesakes, not immortal.
Most of them will blow out or blow up in the next millions of years.
Posted by Administrator at 2001.03. 4 08:45 AM | Comments (0)
