The Milky Way Triangle, also called the Summer Triangle, is currently high overhead in the early evening. Formed by three of the night sky’s bright stars — Vega, Altair, and Deneb — the triangle is easy to identify.
Vega, the brightest overhead star, is a little to the northwest of the sky’s straight-up point, called the zenith. Then with your hand held at arm’s length, Deneb, the faintest of the triangle stars, is two fist-widths to the northeast of Vega. Altair, to the south, is four fist-widths from Deneb and three from Vega.
Although easily recognizable, the Milky Way Triangle is not an official constellation but rather is an asterism — an informal pattern of stars. Each star of the triangle is the brightest star of its own constellation.
Vega, the night sky’s fifth brightest star, is part of Lyra, the Musical Lyre, one of the smallest constellations. It’s most distinctive feature is a small parallelogram hanging from Vega.
Deneb is the tail of Cygnus, the Swan. Under dark skies, Cygnus is seen flying generally southward down the middle of the Milky Way with its wings spanning the width of the Milky Way. The swan’s head, a fainter star, is two fist-widths from its tail.
Altair is the head of Aquila, the Eagle, which is flying along the eastern edge of the Milky Way in the opposition direction of Cygnus.
As with many things in nature, appearances can be deceiving. Our Sun is blindingly bright to us, yet it is much fainter than any of the triangle stars. It seems so bright because it is so close, a mere 8 light minutes (93 million miles) away.
While Deneb appears as the faintest star in the triangle, its true brightness is greater than that of Vega, Altair, and our Sun combined. A white supergiant star, Deneb only seems fainter because it is so much further away. Whereas Altair and Vega are virtual neighbors at 16 and 25 light years, respectively, Deneb is a whopping 1,500 light years away making it one of the most distant bright stars we can see with our naked eyes.
In a future column we’ll tell the story of Vulpecula, the sly but foolish fox lurking in the Milky Way Triangle.
• Sky Calendar:
- Oct. 8th, Thurs. morning: Saturn is less than a moonwidth to the upper left of brighter Mercury and well below brilliant Venus low in the east at dawn.
- Oct. 11th, Sun.: The Moon is at 3rd quarter.
- Oct. 12th, Mon. morning: Mars is above the bright Moon high in the east before dawn.
- Oct.13th, Tues. morning: Saturn is a moonwidth to the left of much brighter Venus low in the east as they rise well before the Sun.
- Oct. 14th, Wed. morning: Leo’s brightest star Regulus is to the upper left of the crescent Moon before dawn.
- Oct. 16th, Fri. morning: The crescent Moon is to the right of Venus with Saturn above and Mercury well below Venus.
- Oct. 18th, Sun.: The Moon is new.
- Oct. 20th/21st Tue./Wed. all night: This could be a good year for the Orionid meteor shower with no Moon interference.
• Naked-eye Planets. Evening: Jupiter dominates in the south southeast. Morning: Saturn and Mercury are near the eastern horizon at dawn, below brilliant Venus with much fainter Mars high in the east.
• Astro Milestones. Oct. 4, 1957, Russia launched Sputnik I, beginning the Space Age and the Cold War space race.
Paul Derrick is an amateur astronomer who lives in Waco. Contact him at 918 N. 30th, Waco, 76707, (254) 753-6920 or email at firstname.lastname@example.org.
Visit the Stargazer Web site at www.stargazerpaul.com.