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The Summer Triangle - Deneb
> This is the last of our trilogy on the starry points of the Summer Triangle. Our first two visits took us to bright blue Vega and her companion across the Milky Way, Altair. Now we will sail upstream, along the Milky Way to Deneb, the main star in the constellation Cygnus the Swan, and the northernmost of our triad.
Cygnus is also known as the Northern Cross. (You'll never guess why.) But not only does our constellation look like a cross, it also, surprisingly, looks like a swan! Remember, not many constellations actually look like their namesake; Cygnus is an exception.
If you go out tonight you can see the cross overhead, with the top of the cross in the north, the foot of the cross more southerly and almost overhead. One can imagine the pole of the cross as the swan's body, with is tail on the north end, and head at the south. The two perpendicular stars are its outspread wings.
There are several stories that accompany the Swan. But one is a story that remains fresh especially in today's culture with our fair share of wild youth.
Helios, the sun god, had an ungodly son named Phaethon. As is the nature of many young sons, he decided to take his dad's Sun Chariot for a spin one day. Big mistake. Phaethon was not the best driver and apparently had little respect for the houses of the gods and their peaceful existence above. His hellish driving put the heavenly hosts in immortal danger.
Jupiter was not amused. He finally decided he had had just about enough of this young whippersnapper, and chucked him from the chariot. Thrown to earth in a flash, Phaeton fell fatally into the river Eridanus. Enter Cycnus.
Cycnus was a friend of Phaeton. Devastated by the turn of events that resulted in his friend's death, he felt it his duty to collect every body part of his charred, dismembered friend for a proper burial. He made several arduous dives into the Eridanus to gather all his remains.
Seeing all this devotion, Jupiter and his minions were moved. So Jupiter decided to reward Cycnus for his act of selflessness, although the reward by today's standards may not be a welcome one.
Jupiter thought it would be nice to turn Cycnus into a waterfowl! And since he ruled the heavens there was no discussion about it. Behold! Cycnus metamorphosed into a swan. And his name was now Cygnus. And, as an added bonus, he was placed into the starry dome above where we see him still today.
Let's focus now on our star of the week, Deneb, the brightest star in Cygnus. Deneb is the top of the cross, the tail of the swan. Its name, like so many other stars, is from the Arabic. Al Dhanab al Dajajah is its full name, which means "the hen's tail."
Deneb is one of the brightest stars in the summer sky, but it is also very, very far away. Vega and Altair are just tens of light years away, Deneb is over 3000 light years beyond that!
What does this tell us? For Deneb to shine that brightly at that great distance makes him a monster big star. How big? Our best estimates put him at over 250 times the size of our sun!
Deneb may have a claim as Cygnus' brightest, and it may be one member of our very elite Summer Triangle club, but for a beautiful sight through the telescope, and a favorite at star parties, go to the foot of the cross. There, like two brilliant starry diamonds are Albireo, a double-star system containing a striking blue star and its reddish companion.
In fact, take a telescope and, using the Summer Triangle as a reference, scan the skies in the region and farther south down the Milky Way. You will find nebulae and double stars and what seems like sparkling dust, which is the star-studded Milky Way itself. It is an awesome trip. But don't scan too quickly, Jupiter might object and we know what happens to those who race through the Milky Way!
Until next time, clears skies.
Posted by Mark Ritter at 2007.08.19 09:08 PM | Comments (0)
