Night Sky Photography -- 03-20-2023 -- The March Equinox & Locating The Spring Triangle & Great Diamond Constellations

Happy Spring Equinox, Y'all!

Today is the first official day of spring equinox 2023 here in the Northern Hemisphere. Goodbye to those long, cold winter nights and hello to longer daytime hours and warmer weather.

The equinox refers to the moment when Earth's rotation axis is directly perpendicular to the Sun, or from our perspective here on Earth when the Sun travels just over the Earth's equator. This occurs twice a year in March and September when the axis of the Earth tilts and turns one hemisphere of the Earth towards the sun in our orbit.

In the Northern Hemisphere this is referred to as the March Vernal Equinox (or spring equinox). In the Southern Hemisphere below the equator this is actually the first day of autumn.

For us amateur stargazers, it also means that the constellations of the Winter Circle (Winter Hexagon) will be setting in the west earlier after dark and new constellations will begin to appear in our evening sky dome.

The first day of spring and the next few months will be the perfect opportunity to see the amazing stars of the Spring Triangle asterism and its spring time constellations in the evening sky.

The Spring Triangle connects three major stars: Arcturus, Spica, and Regulus -- as well as their constellations: Bootes The Heardsman, Virgo The Virgin, and Leo The Lion  -- into a sort of isosceles triangle. A smaller and more equilateral Spring Triangle can also be formed using the star Denebola which is also a part of the Constellation Leo.

The following photos were taken in the late evening after midnight on Monday, March 20th and in the late evening before midnight of the same day of the Spring Triangle stars and their respective constellations.

The first star in the Spring Triangle is the large, orange-colored red giant star, Arcturus (or Alpha Bootes), the third-brightest star in the night sky visible in the Northern Hemisphere, and the brightest star in the Constellation Bootes The Heardsman. Arcturus is relatively the closest to us at about 36.7 light-years (or 11.2 parsecs) from the Sun.

The next is the binary star Spica (or Alpha Virginis) the brightest star in the Constellation Virgo The Virgin (or Virgo The Maiden). The brightest of these binaries is a blue giant star located about 261 light-years (or 80 parsecs) from the Sun. Spica is the 16th brightest star in the night sky.

The third star in the Spring Triangle is Regulus (or Alpha Leonis) the brightest star in the Constellation Leo The Lion, which is in reality a quadruple star system composed of four stars that are organized into two pairs. This system lies approximately 79 light-years (or 24.2 parsecs) from the Sun. Regulus is also known as the "Heart of the Lion" and is the 21st brightest star in the night sky.

The fourth star which comprises the smaller triangle is Denebola (or Beta Leonis), a A-type main sequence dwarf star and the second brightest star in Leo. The star is located at a distance of 36 light-years (or 11 parsecs) from the Sun -- also pretty close to us astronomically speaking.

Locating each of the Spring Triangle stars and their respective constellations is actually not all that hard even for those starting out learning about astronomy. In fact, its quite easy if you can locate the Big Dipper asterism in the evening sky.

The Big Dipper (or Plough) is an asterism of seven bright stars in the larger Constellation Ursa Major The Great Bear and its located near the Spring Triangle stars.

Using the Big Dipper as a guide to the Spring Triangle, you just need to remember three classical mnemonic phrases to navigate your way to their location:

(1) Using the bottom of the Big Dipper below the handle, draw a straight line in the sky using the two stars as a guide to "Make A Reach To Regulus."

(2) Use the end of the handle of the Big Dipper and draw another straight line to "Make An Arc To Arcturus." 
 
(3) Finally, make another straight line using Arcturus to "Drive A Spike To Spica." 

The smaller Spring Triangle stars are also included by a fourth star Cor Caroli in the small Constellation Canes Venatici to form yet another asterism known as the Great Diamond of Virgo -- Or Great Diamond. The Great Diamond connects four constellations and is slightly large than the nearby Big Dipper itself.

That is my presentation and photographic offerings for the beginning of the 2023 spring season. More will be coming soon. Until then, have a wonderful Dixie Day and keep your eyes to the night skies, y'all hear!