The Summer Triangle - Altair
05 Aug 2007
To most humans throughout history the stars have been more than mere points of light. We connect the dots and see the obvious shapes and figures, and if we look deeper, with our mind's eye, we see stories all over. It's the way we were designed, to see beyond the obvious - if we choose to look.
In our last time together we looked at some stories surrounding Vega, the great blue star directly above our heads in the evening, and one point in our Summer Triangle. Today we look closer at our second featured star in this trilogy, the star Altair in the constellation Aquila.
The bright star located to the south and east of Vega, just across the Milky Way, Altair together with Vega played a primary role in an ancient Chinese myth.
There are variations of this story, to be sure, but basically it goes like this. The Sun Emperor has a daughter, Tchi-niu, an expert weaver. Reliable sources say she could weave some amazingly colorful sunrises and sunsets.
But she is lonely, which in the old stories means romance is soon to follow. Sure enough, Tchi-nui looks out the window one day toward the river that we call the Milky Way and her eyes meet those of the herdsman, Kien-nou. Fireworks go off and they are in love.
The herdsman is very good at his job and so the Emperor has no problem with his daughter marrying this fine, young Kien-nou.
Things go well for a while, but soon the two begin neglecting their duties. Tchi-niu is not weaving her sunsets with the usual rich colors and Kien-nou's cows are wandering all over the place. What to do!
The Emperor is not pleased. After repeatedly telling them to get their proverbial act together, he finally banishes his heedless herdsman son-in-law to the other side of the Milky Way.
The star-crossed lovers cannot convince dad to change his mind. The now crestfallen Tchi-niu, try as she may, just cannot overcome her grief enough to weave out a nice sunset. The Emperor has to do something!
So he summons all the magpies in China to spread their wings into a bridge once a year, on the seventh day of the seventh month, across the Milky Way, so the couple can spend one day together.
We still see the two in the skies during the summer months, with Vega in the role of the weaver princess, and Altair as the herdsman. Sadly, our modern civilization with all its light pollution has all but dried up the Milky Way. Weaving any myth today about the two would require no magpie bridge; there is barely a river to cross.
To cold science, Altair is a type A star. That means it is about twice the size of our sun, with a surface temperature about 2000 kelvins hotter than our sun. It pours out more than ten times the amount of energy than our own star does. Again, not to beat the dead star, but Altair is another big, nasty star best kept at a distance.
Which is actually its standout characteristic. Altair is a mere 17 light years away, almost 100 trillion miles away. That, believe it or not, is very, very close as star distances go, just at the end of the block.
Altair is part of the great constellation Aquila, the Eagle. In our next time together we fly over to another great bird in the sky, Cygnus the Swan. Nested there is our third and last of the Summer Triangle, its northernmost star, Deneb.
Until then, clear skies!