One of the best ways to confirm the arrival of summer is to gaze at the eastern sky after nightfall. A prominent group of stars known as the Summer Triangle emerges above the horizon during this time, forming a vast yet simple arrangement of three incredibly bright, but distinct stars. Its appearance in the night sky not only signals the beginning of summer in the Northern Hemisphere but also winter in the Southern Hemisphere, where it is known as the Winter Triangle. This celestial triangle serves as a guide, indicating the direction to look for the Milky Way when under dark skies.
The Summer Triangle is not a constellation, but rather an asterism, a simple pattern formed by stars from official constellations. It comprises one bright star from each of three constellations – Vega in Lyra, Deneb in Cygnus, and Altair in Aquila.
The Summer Triangle star that ascends in the east after dusk is Vega. It is one of the most renowned and brightest stars in the night sky, largely due to its immense size and close proximity to Earth – a mere 25 light-years away. If you have a telescope, initially focus it on Vega, then adjust slightly towards the northeast, and you will spot Epsilon Lyrae, a spectacular double star. However, with larger telescopes, each star within Epsilon Lyrae is also revealed as a double star, earning it the nickname “the Double Double.”
Rising below and to the right of Vega on the horizon is Altair, the 12th brightest star in the night sky. Similar to Vega, its brightness stems from its proximity to Earth, located just 17 light-years away. Like Vega, Altair is about twice the mass and radius of our sun.
This is not the case for the third star in the Summer Triangle, Deneb, which rises in the northeast. It is the 19th brightest star in the night sky, but situated much further away than Vega and Altair at a distance of 2,600 light-years. Its brilliance is attributed to its status as a supergiant star, 20 times the mass and around 200 times the radius of our sun. It is one of the farthest stars visible to the naked eye.
The Summer Triangle is well worth locating and observing throughout the summer as it climbs higher into the sky each night. It traverses a rich field of the Milky Way, so if you find yourself in a dark sky park or any location with low light pollution, locate the Summer Triangle, and you will witness the Milky Way running through it, from Deneb to Altair.
