This weekend, during the late evening hours, search for the famous “Summer Triangle” high in the eastern sky.
The triangle consists of three of the brightest stars in the sky, each the brightest in its own constellation. Bluish-white star Vega in Lyra (the lyre) is the brightest in the triangle, with yellow-white Altair in Aquila (the eagle) and white Deneb in Cygnus (the swan), following it as second- and third-brightest in the configuration.
From our viewpoint, Vega appears twice as bright as Altair and more than three times brighter than Deneb. But sometimes things are not always what they seem. We know that Vega clearly is more luminous compared to Altair, because it’s situated at a greater distance from us. Altair is 17 light years away, while Vega is just a little farther out at 25 light years away.
The light you’re seeing from Altair tonight started on its journey to Earth in 1996, and the light from Vega started on its way toward Earth back in 1988. But brilliant Vega actually pales in comparison with Deneb, one of the greatest supergiant stars known.
Deneb’s distance measures 1,467 light-years from Earth with a luminosity computed to be more than 60,000 times that of the sun. Because its light takes nearly 15 centuries to reach us, Deneb merely appears as a fairly conspicuous but by no means particularly notable star.
See the Milky Way
With the moon arriving at new phase on Monday, July 8, and then waxing to just a thin crescent phase by week’s end, there is no better time than now to observe the beautiful summer Milky Way.
Under a dark sky with a good pair of binoculars or a telescope you can now observe millions of sparkling little stars that make up this glowing, irregular belt of luminosity.
It appears to arch from the north-northeast to the south-southeast, with its brightest and most spectacular region running across the summer triangle and beyond toward the south-southeast horizon.
There appears to be a great black rift dividing it into two streams (called the “dark bifurcation”), beginning with Cygnus and extending down toward the south. Also in Cygnus is the black void known as the “northern coal stack.” The coal stack and the rift are not holes in the Milky Way, but rather are vast clouds of dust “floating” out in interstellar space which present a solid and impenetrable curtain between us and the more distant stars.
There have been many stories, myths and legends told about the Milky Way across different cultures.
In a Japanese legend involving the galaxy, the star Vega represented Orihime, the weaving princess, who produced brilliantly colored fabrics. Across the “heavenly river” (the Milky Way), Altair represented the cow herder Hikoboshi, who was also known as Kengyu.
After meeting each other, they received divine permission to marry, whereupon both abandoned their occupations. This angered the gods who consequently separate them and send them back to their original jobs on opposite sides of the heavenly river.
The couple, however, received permission from the gods to get together for one night each year. That special night is July 7 — but only if the sky is clear.
As a result, the evening of July 7 has evolved into a young people’s holiday in Japan called Tanabata, meaning “evening of the seventh.” Prayers are offered for clear skies so that Orihime and Hikoboshi, the star-crossed lovers can be reunited.
Popular customs relating to the festival vary by region, but generally, girls wish for better sewing and craftsmanship, and boys wish for better handwriting by writing wishes on strips of paper. The date of Tanabata also varies by region, but the first festivities begin on July 7 of the Gregorian calendar.
The original Tanabata date was based on the Japanese lunisolar calendar, which is about a month behind the Gregorian calendar. As a result, some festivals are held on July 7, some last for a few days around August 7 and others take place on the seventh day of the seventh lunar month of the traditional Japanese lunisolar calendar, which is usually in August in the Gregorian calendar.
This year, the Gregorian date of “the seventh day of the seventh lunar month of the Japanese lunisolar calendar” will fall on Aug. 13.
Editor’s note: If you snap an amazing picture of the night sky that you’d like to share for a possible story or image gallery send photos, comments and your name and location to Managing Editor Tariq Malik at firstname.lastname@example.org.
Image courtesy of Flickr, Socalastro
This article originally published at Space.com
Read more: http://mashable.com/2013/07/05/summer-triangle/