Summer Triangle

<h2 id="history">History</h2>
<p>The term was popularized by the American author <a href="/facts/H._A._Rey/0X9R1Ctx">H. A. Rey</a> and the British astronomer <a href="/facts/Patrick_Moore/pwSzBtUg">Patrick Moore</a> in the 1950s.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> The name can be found in constellation guidebooks as far back as 1913.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> The Austrian astronomer <a href="/facts/Oswald_Thomas/EIsXjXdQ">Oswald Thomas</a> described these stars as <i>Grosses Dreieck</i> (Great Triangle) in the late 1920s and <i>Sommerliches Dreieck</i> (Summerly Triangle) in 1934.  The asterism was remarked upon by <a href="/facts/Joseph_Johann_von_Littrow/5UDpqaKU">Joseph Johann von Littrow</a>, who described it as the "conspicuous triangle" in the text of his atlas (1866), and <a href="/facts/Johann_Elert_Bode/32lyc9wP">Johann Elert Bode</a> connected the stars in a map in a book in 1816, although without a label. These are the same stars recognized in the Chinese legend of <i><a href="/facts/The_Cowherd_and_the_Weaver_Girl/0N171NyB">The Cowherd and the Weaver Girl</a></i>, a story dating back some 2,600 years, celebrated in the <a href="/facts/Qixi_Festival/15p5EGLm">Qixi Festival</a>. The stars also bear ceremonial significance in the related celebrations of <a href="/facts/Tanabata/SSzPxVlh">Tanabata</a>, <a href="/facts/Chilseok/azFFtc7y">Chilseok</a>, and Thất Tịch, derived from Qixi. In the mid- to late-20th century, before <a href="/facts/Inertial_navigation_system/UzUTMhK2">inertial navigation systems</a> and other electronic and mechanical equipment took their places in military aircraft, the <a href="/facts/United_States_Air_Force/7MxWBYlc">United States Air Force</a> navigators referred to this asterism as the "Navigator's Triangle".<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a>
</p>
<h2 id="visibility">Visibility</h2>

<p>From <a href="/facts/Middle_latitudes/spJe2FNR">mid</a>-to-tropical <a href="/facts/Northern_Hemisphere/EFwyqL25">northern latitudes</a>:
</p>
<ul><li>the centre of the triangle appears about <a href="/facts/Zenith/ISuRFp05">overhead</a> around <a href="/facts/Solar_midnight/hSw4Jbn3">solar midnight</a> during <a href="/facts/Summer/v3DY22Uq">summer</a>, and exactly so at about the <a href="/facts/27th_parallel_north/fWaWzw3L">27th parallel north</a>. This means it rises at sunset in the east and sets at sunrise in the west.</li>
<li>it is visible in the eastern sky in early mornings during <a href="/facts/Spring_(season)/3UWDpVmx">spring</a>.</li>
<li>In autumn and winter evenings, it is visible in the western sky until January.</li></ul>
<p>From mid-<a href="/facts/Southern_Hemisphere/QfJ4z9L5">southern latitudes</a>, the asterism is in the north during the culmination season described above.
</p>
<h2 id="the-stars-of-the-summer-triangle">The stars of the Summer Triangle</h2>
<p>Both Altair and Vega are bluish-white, rapidly-rotating A-type main sequence stars in the local neighbourhood of the sun. However, Deneb is a white supergiant star over 100 times as distant, and one of the most luminous stars in the entire galaxy.
</p>
<table><tbody><tr><th>Name</th><th>Constellation</th><th><a href="/facts/Apparent_magnitude/7pCTF1Me">Apparent magnitude</a></th><th>Luminosity(<a href="/facts/Solar_luminosity/CLG0r9bP">L☉</a>)</th><th><a href="/facts/Stellar_classification/dYrIuK9H">Spectral type</a></th><th>Distance(<a href="/facts/Light_year/IGc5NdQb">light years</a>)</th><th>Radius(<a href="/facts/Solar_radius/5t1Xavju">R☉</a>)</th></tr><tr><th><a href="/facts/Vega/G3wJwhhl">Vega</a></th><td><a href="/facts/Lyra/gMRhk3ed">Lyra</a></td><td>0.03</td><td>52</td><td>A0 V</td><td>25</td><td>2.36 to 2.82</td></tr><tr><th><a href="/facts/Deneb/L7dTfcog">Deneb</a></th><td><a href="/facts/Cygnus_(constellation)/L1fYe414">Cygnus</a></td><td>1.25</td><td>200,000</td><td>A2 Ia</td><td>3550</td><td>203 ± 17</td></tr><tr><th><a href="/facts/Altair/avsmInG0">Altair</a></th><td><a href="/facts/Aquila_(constellation)/p90KeceQ">Aquila</a></td><td>0.77</td><td>10</td><td>A7 V</td><td>16.6</td><td>1.63 to 2.03</td></tr></tbody></table>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Northern_Cross_(asterism)/zYvw1hxh">Northern Cross</a></li>
<li>Spring <a href="/facts/Great_Diamond/BUGoK7cw">Great Diamond</a></li>
<li><a href="/facts/Spring_Triangle/Ue0N9v4F">Spring Triangle</a></li>
<li><a href="/facts/Winter_Triangle/KqInNfUY">Winter Triangle</a></li>
<li><a href="/facts/Winter_Hexagon/Ve7Rmvj0">Winter Hexagon</a></li>
<li><a href="/facts/Heavenly_Market_enclosure/3resnSpK">Heavenly Market enclosure</a></li></ul>

<h2 id="external-links">External links</h2>

Wikimedia Commons has media related to Summer triangle.

<ul><li><a href="https://web.archive.org/web/20030823181320/http://homepage.mac.com/kvmagruder/bcp/aster/constellations/sumt.htm">Summer Triangle</a> at <a href="https://web.archive.org/web/20031013145549/http://homepage.mac.com/kvmagruder/bcp/">Basic Celestial Phenomena</a> by Kerry Magruder</li>
<li><a href="http://www.astronomy.net/articles/24/">Summer Triangle</a> at <a href="http://www.astronomy.net/">The Astronomy Net</a></li>
<li><a href="http://www.daviddarling.info/encyclopedia/S/Summer_Triangle.html">Summer Triangle</a> at <a href="http://www.daviddarling.info/">DavidDarling.info</a></li>
<li><a href="https://apod.nasa.gov/apod/ap100625.html">NASA Astronomy Picture of the Day: Summer Triangle (25 June 2010)</a></li>
<li><a href="https://apod.nasa.gov/apod/ap170703.html">NASA Astronomy Picture of the Day: The Summer Triangle over the Great Wall (3 July 2017)</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Patrick Moore (20 October 1983). Patrick Moore's History of astronomy. Macdonald. ISBN 978-0-356-08607-1. <a href="978-0-356-08607-1" target="_blank">978-0-356-08607-1</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Alice Mary Matlock Griffiths (1913), The Stars and Their Stories: A Book for Young People. <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Lt. Col. William E. Hubert, USAF (Ret.) (December 1, 2006). "Chapter Eleven: "Triple Rated" Copilot, (Ugh)!". Pilot Here Or Pile It There: A Memoir. AuthorHouse. p. 115. ISBN 978-142595689-9. <a href="978-142595689-9" target="_blank">978-142595689-9</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
</ol>

Summer Triangle open-in-new

Summer Triangle