What’s up in the sky – August 2010

Fred Barrett | Jul 29, 2010

By Fred Barrett

The Summer Triangle - note that straight up is North East.

This month we’re off to rummage around the asterism known as the Summer Triangle. It’s made up of three bright stars Vega, Deneb and Altair in three constellations, Lyra, Cygnus and Aquila. Prominent high above at twilight from May through to early fall, the Triangle stretches across some 38 degrees.

To find the Triangle, go out just after sunset and face east. Look almost straight up and watch for the first star to appear. Voila! That’s Vega! It is the first star of the three that make up the Summer Triangle. It’s about three times larger than our Sun and 50 times brighter. Now, look to the right (or southeast) of Vega to find Altair, and to the left (or northeast) of Vega to find Deneb. To make sure that you have picked Vega, keep watching as it gets darker. As more stars appear you will see that Vega is above a parallelogram of stars that mark the constellation Lyra, the Harp.

Deneb, which is Arabic for tail, marks the tail feathers of Cygnus, the Swan. It is a supergiant star that’s 200 times the diameter of the Sun and shines as bright as 85,000 Suns. It’s about 1500 light years away. That’s 60 times farther than Vega yet they are both equally bright in the sky. Deneb is one of the largest stars in our Milky Way! Cygnus has the shape of a cross with Deneb as the top star of the cross. It is also known as the Northern Cross.

Altair is part of the head of Aquila, the Eagle. Altair is only one and a half times larger than our Sun and about 17 light years away. An interesting fact about Altair is that it rotates so fast that it is flattened! It completes a rotation in nine hours versus 25 days for our Sun. The diameter at its equator is 25 percent greater than its diameter from pole to pole.

You can use the Summer Triangle as a key to finding other beautiful objects in the summer sky. Cygnus appears to be flying through the star clouds of the Milky Way with Aquila as wing partner.

A dark band of dust that hides more distant stars appears as a dark, swirling cloud slicing through the Milky Way in the region of the Summer Triangle. It is also known as the Great Rift.

One of the best double stars in the sky can be found at the opposite end of Cygnus from Deneb, at the base of the cross shape of Cygnus. Albireo shows two stars, one yellow and one blue. It’s a truly beautiful sight when viewed through binoculars or a small telescope. This binary star system is about 380 light-years away from Earth.

Two of my favorite nebulae can be found in the Triangle. M57, in Lyra, also known as the Ring Nebula, sits half way between the two stars that are at the opposite end of the parallelogram from Vega. The other nebula, known as the Dumbbell Nebula or M27, lies about two thirds of the way along an imaginary line connecting Deneb to Altair. They are both Planetary Nebula and their nebulosity is provided by gases blown off by a dying star at their centre. I really don’t have the space to describe how much there is to see. Grab a pair of binoculars, go outside and kick back in a lawn chair and tour this fabulously populated region of the Milky Way. You won’t be disappointed.

METEORS: The Perseids – August 12 & 13

Look to the constellation Perseus as the point of origin or radiant of this shower. If you can’t find Perseus don’t worry because the meteors will appear in all parts of the sky. This year the waxing Moon will set early, leaving a nice dark sky. The best times to catch the shower are after midnight on the peak mornings of the 12th and 13th but the Perseids should put on a good show all week! I’m really looking forward to an excellent shower with many meteors. Don’t miss it!

THE MOON AND PLANETS

I hope you all had a good look at the 4 planets in a line during July just after sunset in the southwest. This month on August 7th about an hour after sunset, Saturn, Mars and Venus actually group within a circle about 4.8 degrees across – a planetary trio! Follow the dance of these planets during August. Watch the slim crescent Moon slide past them between August 11th and 13th. Jupiter rises about 9PM by the middle of the month and is a truly awe-inspiring sight through binoculars with its moons strung around its globe. It rises higher in the South as the night passes. It’s huge and is getting larger as it approaches opposition (closest orbital position). You can be sure that I will be out trying to get a good picture of it through my telescope.

The full Moon this month is August 24th and is the smallest full Moon of 2010. That happens when it is at its most distant point in its orbit around the Earth. The name of this full Moon is the Sturgeon Moon. Fishing tribes found that the easiest time to catch this Great Lakes fish was in August.

STARGAZE 2010: There will be an Astronomy night at Charleston Lake Provincial Park (Take the Highway 3 exit off of the 401 east of Gananoque and go north 20 Km to Woodvale Rd. and turn right). It starts at 7:30PM on Thursday, August 12. It's called Star Gaze 2010 and Terence Dickinson, editor of Sky News and author of several Astronomy books, will be giving a presentation. Usually about 10 telescopes or so are set up for viewing after the presentation. Ask at the entrance of the park for directions to Stargaze 2010. Hope to see you there.

MARS HOAX: If you receive an email with the sensational headline that Mars will be larger than the Moon and closer to us than it has been in thousands of years, don't believe it!  Mars is closest to the Earth when at or near opposition, that is, when the Earth passes between it and the Sun. This happened on January 29 this year and happens roughly every 2 years and 2 months. However, at no time is Mars ever as large or larger than the Moon, except maybe in the eyepiece of a telescope. Right now Mars is about 250 million km away. Leading up to and after August 12, Mars is part of the beautiful planetary trio of Venus, Saturn and Mars. Venus is the brightest, then a dimmer Saturn, with Mars showing up quite visible but somewhat small and faint.

If you have questions or suggestions, Fred Barrett may be contacted at This email address is being protected from spambots. You need JavaScript enabled to view it.

The Beginner’s Observer’s Guide by Leo Enright is available at the Sharbot Lake Pharmacy or by contacting the Royal Astronomical Society of Canada www.rasc.ca/publications, subscriptions for our very own excellent Canadian astronomy magazine, Sky News, are also available from RASC..