Summer Triangle and Constellations
The Summer Triangle is the main asterism used in the summer night sky to identify constellations. The asterism included the 3 prominent stars in the summer night sky. The triangle links the 3 bright stars of Altair, Deneb and Vega in the constellations of Aquila, Cygnus, Lyra respectively. From this asterism stargazers are able to orient themselves in the summer night sky and locate many of the constellations in this area of the sky. The asterism is a simple triangle linking 3 points but as it is intended to orient oneself in the sky and includes the 3 brightest it is easy to find.
The summer triangle is not a constellation itself and rather an asterism used to locate constellations. The stars are part of the constellations of Lyra, Aquila & Cygnus which are all among the original 48 constellations listed by the Egyptian mathematician Ptolemy, who lived under Roman rule in Alexandria in the 2nd century. These constellations formed the basis for the modern list agreed by the IAU. Constellations from the southern hemisphere, unable to be seen from the Mediterranean, represent the majority of additions to the list.
As the earth moves in its orbit around the sun, each night you are looking at a different portion of the sky. When looking at stars it is important to be aware of what is within your view. Northern hemisphere stargazers can group constellations into 3 groups; circumpolar, summer and winter constellations. The circumpolar constellations are in the north sky, appear to move around the north star and are visible throughout the year. The constellations in the south sky are only visible for part of the year and are grouped as either summer or winter constellations. Each is visible from between 4 to 10 months.
It is important to be aware of the specific time of year and hour of the night when deciding what to look for. These pages below show the constellations in each group so you can find the constellations that interest you.
CIRCUMPOLAR (year around) – Ursa Major – Cassiopeia – Ursa Minor – Draco – Cepheus
WINTER – Pegasus – Pisces – Aries – Auriga – Taurus – Orion – Canis Major – Canis Minor – Gemini – Lynx – Cancer – Leo – Winter Hexagon
SUMMER – Virgo – Libra – Scorpius – Bootes – Hercules – Lyra – Ophiuchus – Sagittarius – Aquila – Cygnus – Capricornus – Aquarius – Summer Triangle
Or use this guide to easily see which constellations are easiest to find right now:
Summer Triangle Quick Facts:
Brightest star: Vega, +0.03 magnitude (5th brightest star in the night sky)
Stars brighter than 3 magnitude: 3
Primary stars: 3 (Vega in Lyra constellation, Altair in Aquila constellation, Deneb in Cygnus constellation)
Latitude: 45 degrees north – 10 degrees north
Northern Hemisphere Season: Summer (February – December)
Which months can you see the Summer Triangle?
The Summer Triangle can be seen from February to December but can be found high in the sky at 21:00 during the month of September:
- Early evening viewers (before 21:00) can find the constellation from July in the eastern sky until December in the western sky. Summer Triangle will be visible overhead in October.
- Mid evening viewers (21:00-23:30) can find the constellation from June in the eastern sky until November in the western sky. Summer Triangle will be visible overhead in September.
- Late evening viewers (after 23:30) can find the constellation from May in the eastern sky until September in the western sky. Summer Triangle will be visible overhead in July.
- Early morning viewers can find the constellation from February in the eastern sky to July in the western sky. Summer Triangle will be visible overhead in May.
As time passes the constellation will gradually appear earlier in the night with ranges below showing the window of opportunity in each month. Summer Triangle is between 45 degrees north – 10 degrees north latitude. Therefore, the further south your position the further north it will appear in the sky. At its maximum range it is possible to see the Summer Triangle at latitudes between +90 and -45.
Best time to see Summer Triangle and related constellations:
Best visible at 21:00 in September
February: visible on the south east horizon before sunrise from 03:30. It will reach 30 degrees above the south east horizon by sunrise.
March: appear on the south east horizon at 01:30. It will reach 45 degrees above the south east horizon by sunrise.
April: appear on the south east horizon at 00:30. It will reach 60 degrees above the south east horizon by sunrise.
May: appear on the south east horizon at 23:30, reaching its peak 65 degrees above the southern horizon at 05:00.
June: appear on the south east horizon at 21:30, reaching its peak 65 degrees above the southern horizon at 03:00. It will continue moving west until sunrise when it will be 55 degrees above the south west horizon.
July: 25 degrees above the south east horizon at sunset, reaching its peak 65 degrees above the southern horizon at 01:00. It will continue moving west until sunrise when it will be 30 degrees above the western horizon. Making it is visible throughout the night.
August: 45 degrees above the south east horizon at sunset, reaching its peak 65 degrees above the southern horizon at 23:00. It will continue moving west until 04:00 when it will begin to be only partially visible on the western horizon.
September: 60 degrees above the south east horizon at sunset, reaching its peak 65 degrees above the southern horizon at 21:00. It will continue moving west until 02:00 when it will begin to be only partially visible on the western horizon.
October: 65 degrees at its peak trajectory above the southern horizon at sunset. It will continue moving west until 00:00 when it will begin to be only partially visible on the western horizon.
November: 60 degrees above the south west horizon at sunset. It will continue moving west until 22:00 when it will begin to be only partially visible on the south west horizon.
December: 40 degrees above the south west horizon at sunset. It will continue moving west until 20:00 when it will begin to be only partially visible on the south west horizon.
Trajectory: The constellation is between 15 degrees north – 5 degrees south which means that for those in low latitudes of the northern hemisphere it will pass high in the southern sky. For those in higher latitudes of the northern hemisphere it will appear low in the southern sky for a shorter time each night. Its peak trajectory in Wadi Rum is 65 degrees above the southern horizon from May through October.
Not the right time for Summer Triangle? Have a look what constellations you can see tonight.
How to find Summer Triangle and constellations?
Refer to the timings above and provided you are looking at the correct time the 3 brightest visible stars will form the triangle.
Identifying with the Summer Triangle
The summer triangle which is a prominent asterism in the night sky throughout summer for northern hemisphere viewers. It is useful to be familiar with and helps locate many constellations throughout summer. The triangle links the 3 bright stars of Altair, Deneb and Vega in the constellations of Aquila, Cygnus, Lyra respectively.
The Summer Triangle is easy to locate as it connects the 3 brightest stars in the northern hemisphere summer sky. The band of the Milky Way passes through the Summer Triangle. Therefore if you can not observe the band of the milky way it may not be the correct time to locate the Summer Triangle.
Vega is the brightest star, while the other 2 stars are within the band of the milky way. They are the three brightest star in this area of the sky and are prominent and easy to identify. Altair the second brightest star is furthest west and marks the head of the eagle. It is slightly north east of the core of the milky way.
Learn how to form the shape of Winter Triangle
The shape of the Summer Triangle is a simple geometric shape and is not connected to ancient myth. It is intended to be an easy grouping of stars to identify that can be subsequently used to identify other constellations.
Summer Triangle in the Ancient World
The 3 stars that form the summer Triangle are all among the 20 brightest stars and a very prominent within their own region of the sky. Vega in particular is one of the most studied stars and has remained a focus throughout the ancient world.
Significance of Vega in history
Vega was the Polar star in 12,000BC and is the second brightest star in the northern hemisphere. Vega is also used as the reference point for determining the brightness of all objects in the sky.
Vega was prominent for early astronomers with prominent names given by the Assyrian, Akkadian and Babylonians. The star was used across many ancient civilizations to identify the changing of the seasons. The early ancient Polynesians used the appearance of Vega as a signal of the arrival of Spring and when they would plant their crops. The Roman empire used the setting of Vega to identify the arrival of Autumn.
Ancient Chinese mythology recognised Vega as a mother ‘Niulang the weaver girl’ separated from her family by the river of the milky way. The Japanese still celebrate this folklore with the Tanabata festival.
Vega has references in both ancient Hindu and Zoroastrian faith. It has also been identified with oral history in cultures in Australia.
Main stars in the Summer Triangle
Vega (+0.03m, 25ly, 13 suns, #5)
Vega is a Greek pronunciation from the Arabic for ‘falling’ from the phrase ‘the falling eagle’. It is the 5th brightests star with an apparent magnitude of +0.03. The distance from earth is 25 light years. It is 13 times the size of the sun.
Altair (+0.77m, 17ly, 5 suns, #12)
Altair is from the Arabic phrase ‘flying eagle’. It is the 12th brightest star with an apparent magnitude of +0.77. The distance from earth is 17 light years. It is more than 5 times the size of the sun and noted for having a very rapid rotation.
Deneb (+1.24m, 2,615ly, 8m suns, #19)
Deneb is from Arabic meaning ‘tail’. It is the 19th brightest star with an apparent magnitude of +1.24. The distance from earth is 2,615 light years. It is over 8 million times the size of the sun.
Wadi Rum is one of the best locations in the world to see the full beauty of the stars. Combining high altitudes, clear skies and no light pollution. You may be surprised how many stars are visible to the naked eye. Come with us and spend a night under the stars.