Vega, Deneb, Altair: observing the Summer Triangle

Spotlights and … telescopes aimed at the Summer Triangle!

summer triangle picture
The stars of the Summer Triangle.
Credit: Wikipedia

In the northern skies it is possible to admire, from the beginning of June until the beginning of January, the famous asterism known as the “Summer Triangle”.

Main features

Its isosceles triangle shape is particularly recognizable in the summer skies. Its position (almost at the zenith) allows us to identify it precisely between the lights of the Milky Way.

We can find it in the area of ​​our galaxy called “Slit of the Swan” and between one dark nebula and another, it is possible to observe it from the beginning of June until the end of December / beginning of January. It consists of three main stars that constitute the vertices of the isosceles triangle: Vega, Deneb and Altair.

The stars of the Summer Triangle

Vega

The fifth brightest star in the sky. With its apparent magnitude of 0.3 is at the top vertex of the triangle. Particularly visible, Vega is a blue-white star found in the constellation of the Lira. It is 25 light years away from us. Known since ancient times, it “played” the role of North Star some 12,000 years ago. Because of the precession of the Earth’s axis, in the past it was in a different position from today, where it will be found again in 13700 years.

Deneb

The main star of the Swan constellation, of which it “represents” the tail. It means in Arabic “Hen Tail”. In the past ancients saw the constellation as a bird that took the form of an eagle, a swan, a hen or a pigeon.

It is the nineteenth brightest star in the sky. With its absolute magnitude of -7.1 it is one of the brightest stars in the Galaxy. In relation to this, the fact that it appears to us less luminous than other stars is due to its distance – which has not yet been precisely determined but goes on the order of thousands of light years (from 1500 to 3200). It is a white-blue supergiant of apparent magnitude 1.25.

Altair

Twelfth brightest star in the night sky, is 17 light years away from us. Its apparent magnitude is 0.77 which also makes it the brightest star of its constellation, the Eagle. Its main feature is its high rotation speed: it completes a rotation in eight and a half hours, which makes it more squashed at the poles. It is white in color and we can find it in the north-eastern part of the constellation of Eagle.

The Slit of the Swan and objects from the deep skysky milky way man

The summer triangle includes an area populated by different objects from the deep sky. It is also used to identify the other constellations given its privileged position in the sky. Among the thousand shades of the Milky Way, in the so-called “Swan’s Slit” is an area populated by dark nebulae that crosses the “Milky Way” in two “cutting it”. It is here that we can find the Summer Triangle, the asterism, visible to the naked eye, which stands out in the summer skies.

In the constellation of the Volpetta, between the two stars Vega and Altair we can identify thanks to a telescope or binoculars the planetary nebula M27 the

m57 ring nebula
Ring nebula M57. Image Credit: NASA, ESA

“Handlebar Nebula“. It is known for its “hourglass” shape; is about 1350 light years from us and has an apparent magnitude 7.4.

M57 is instead a visible ring nebula in the constellation of the Lira. Its distance from the Earth is about 2000 light years and has an apparent magnitude of 8.8.

We vcan find the North America Nebula in the constellation of Swan, near its main star Deneb. It is an emission nebula whose shape resembles that of the American continent.

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