As we near the end of summer, there is still a great opportunity to view some very neat objects in the night sky. The Summer Triangle contains a small variety of celestial objects for your viewing pleasure. If you head outside around 9pm and look overhead, you can see it. The Triangle is formed by 3 bright stars: Altair, Deneb, and Vega. Each star is part of a different constellation, but the Triangle is easier to spot because Altair, Deneb, and Vega are so bright, even in heavy light pollution.
We’ll begin our tour near Altair. Altair is part of the constellation Aquila, the eagle. Altair makes a good guide star while using a telescope, which you will need to spot the objects being discussed here. Aim your telescope at Altair, and move to the right. You will find Messier 71, which is a globular star cluster. It lies around 12,000 light years away, and is nearly 27 light years across. Most globular clusters appear the same through a telescope, but are still neat to look at nonetheless, as there are so many stars packed into such a relatively small space. M71 lies in the center of a small constellation called Sagitta, the arrow (not to be confused with Sagittarius the archer). But Sagitta is difficult to see unless you have very dark skies, so use Altair as your guide!
To the right of the “tip” of the arrow of Sagitta is the planetary nebula Messier 27, also known as the Dumbell Nebula. It will appear as a dumbell or hourglass shape smudge. As with most objects viewed in a telescope, not a lot of color can be made out. Contrary to its classification, M27 is not a planet forming nebula, as the class was named before it was understood. Instead, it’s formed by a star shedding its outer layers into space in its death throes. It’s fairly unmistakable, and a large telescope is not required to view, but as always, the darker the sky, the better it can be seen.
The next star in the Summer Triangle is Deneb. Deneb forms the top of the triangle, and the top (and tail) of the cross-shaped constellation Cygnus, the swan. The center of Cygnus runs right through the Milky Way, and points towards Sagittarius. Finding Deneb will allow you to find Cygnus easier. At the bottom of the cross (or the “beak” of the swan) is Albireo, the beautiful double star consisting of a larger, golden color star and a smaller, blue companion. Cygnus also contains Cygnus X-1, the first black hole discovered. The black hole cannot be seen, however. A radio telescope would be required to detect the X-ray emissions that are given off by it.
Next to the star below Deneb in Cygnus is the open star cluster Messier 29. This box-shaped cluster is estimated at 6,000 light-years distance from Earth. M29 can be spotted using binoculars, but a telescope is necessary to appreciate it to the fullest, as it is quite small in binoculars.
Completing the Summer Triangle is Vega, a bright blue star in the constellation Lyra, the lyre. Vega can be used as a guide to find two more stellar objects in the night sky, Messiers 56 and 57, both of which lie to the left of Vega. Messier 56 is another globular cluster that lies nearly 33,000 light years from Earth. M56 can be found between Albireo in Cygnus and the left-most star in Lyra.
The most tricky of all these objects to find is Messier 57, the Ring Nebula. It’s rather small and can be mistaken for another star without sufficient magnification. At least 40x magnification is needed to find this nebula. Located in between the two left-most stars in Lyra, it will appear as a small, hollow ring. Greater magnification will reveal a wispy ring, with some dim color visible. The Ring Nebula is another planetary nebula, located nearly 2,300 light years away, and is around 1.5 light years in diameter. It is another star shedding outer layers of gas in its final stages, similar to M27. The star in the center is visible, but a 10 inch telescope is required to spot it.
Wrapping up our tour of the Summer Triangle is Brocchi’s Cluster, also known as the Coathanger. It’s much too small to be seen with the naked eye, but binoculars or a wide field eyepiece with low magnification and a telescope reveals this asterism. The Coathanger is located below Albireo in Cygnus, and can be used to help find M27 and M56 as well. It’s interesting to view, as it is a nearly perfectly shaped coathanger.
As summer draws to a close, the Summer Triangle is aptly placed overhead in the early evening sky. This gives a great opportunity to examine some unique nebulae, as well as a variety of star clusters and some very bright stars. Don’t miss out on the opportunity to view these wonderful and amazing objects!
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