To celebrate Pi Day tonight, seek out the circular constellation Corona Borealis

March 14 (3/14) is the yearly celebration of the mathematical constant Pi, which permeates the sciences.
By | Published: March 14, 2019 | Last updated on May 18, 2023
A semicircle of stars make up the small constellation Corona Borealis the Northern Crown. Tonight, being Pi Day, makes for the perfect night to seek out this circular sight.
Till Credner/Wikimedia Commons
By pinpointing this brilliant star Arcturus tonight, you can begin tracing a constellation perfectly suited for observation on March 14 — also known as Pi Day.

Pi day, which was designated by the U.S. House of Representatives in 2009, celebrates the well-known mathematical constant Pi (π). For you non-geeks, Pi Day is 3/14 because the first three digits of the mathematical constant pi, which is the ratio of a circle’s circumference to its diameter, are 3.14.

As midnight approaches tonight, look to the east for the bright star Arcturus. At magnitude 0.0, it is the second-brightest star visible from mid-northern latitudes.

If you scan about 20° to the left and a little below this luminary, you should see a conspicuous semicircle of stars: the constellation Corona Borealis the Northern Crown.

This small constellation is the most prominent group of stars having a shape reminiscent of a circle, and it makes it an ideal target for Pi Day — a day where we celebrate all things circular.

For more quick and easy observing tips, check out The sky this week for March 8 to 17.