Constellations by seasons

Winter constellations

To see the constellations that come and go with the seasons, we need to turn our backs on the north circumpolar constellations and face south. If the winter sky seems alive with stars, it’s no illusion. Besides the obvious facts that the air is clear and dry then, we’re looking at a star-rich region that defines one of the spiral arms of our Milky Way Galaxy. Of the twenty-one brightest stars in the entire night sky (so-called 1st-magnitude stars),seven are in this area.

On a winter evening, the sky is home to what most astronomers agree is the grandest of all constellations — Orion the Hunter. A rectangle of bright stars, which includes, at opposite corners, 1st-magnitude Betelgeuse and Rigel, is bisected by a diagonal row of three bright stars (the “belt”). Beneath the belt hangs a row of three stars — Orion’s “sword.” Don’t be fooled by their uninspiring naked-eye appearance; the middle star in the sword isn’t a star at all. The Orion Nebula is a captivating sight, resembling a fuzzy patch of light in binoculars, where stars are born.

Winter Constellation Image — This map shows the winter sky at 2 a.m. on December 1; midnight on January 1; and 10 p.m. on February 1.

Orion serves as the centerpiece for a dazzling group of stars and constellations. Follow Orion's belt to find Sirius, the brightest star, leading Canis Major. It shimmers beautifully near the horizon during winter. Continuing from Orion's belt, locate the V-shaped Hyades representing Taurus the Bull's "head" and the Pleiades cluster nearby. Taurus's uppermost horn connects to Capella in Auriga the Charioteer, situated above Orion. Orion's companions include Gemini the Twins, found by extending a line from Rigel through Betelgeuse. In 2005, Saturn joins Gemini. Midway between Sirius and Pollux and Castor, you'll spot the 1st-magnitude star Procyon, representing Canis Minor, the Little Dog.

Spring constellations

As the days lengthen and the weather warms, Orion and his wintry retinue process slowly into the western sky. Leo the Lion now assumes center stage high in the south. Leo’s most noticeable feature is an asterism (a grouping of stars) that reminds observers of a sickle or a backward question mark. The period on the question mark is the 1st-magnitude star Regulus. To the left of the Sickle are three stars that form a right triangle. We see the Lion from the side; the Sickle outlines his head, and the triangle, his hindquarters. Viewed with a little imagination, Leo definitely sports a feline profile.

Spring Constellation Image — 1 a.m. on March 1; 11 p.m. on April 1; 9 p.m. on May 1. Add one hour for daylight-saving time.

During spring, the Big Dipper appears nearly overhead from mid-northern latitudes. If you follow the handle of the Dipper away from the bowl, you’ll “arc to Arcturus,” a golden-yellow 1st-magnitude star in theconstellation Boötes the Herdsman. The constellation itself is shaped like a huge kite, with Arcturus at its base. Continuing the arc, you’ll “sprint to Spica.” This blue-white 1st-magnitude star is in Virgo, which is a huge, sprawling constellation. If you look below and to the right of Spica, you’ll spot a neat little group of four bright stars that resembles the outline of a sail.

This is the constellation Corvus the Crow. I’m always impressed at how stately this little constellation looks, perched above the treetops to the south on a clear spring evening.

Summer constellations

Summer is a season of mixed blessings for astronomers. The nights are warm but short and often hazy. As that weren’t bad enough, we have to contend with swarms of blood-sucking mosquitoes! Haze and insects aside, the summer sky is a veritable gallery of cosmic masterpieces. The Milky Way arches high across the sky, which is richer than its winter counterpart because we now look toward the heart of our galaxy. Dominating the evening sky are three 1st-magnitude stars forming the Summer Triangle. Vega is the brightest of the three and is located in a nifty little constellation called Lyra the Lyre.

Deneb, the second star in the Summer Triangle, serves as the celestial tail of Cygnus the Swan, and, along with four other prominent stars of the Swan, collectively composes the striking asterism known as the Northern Cross, which is intricately woven within the ethereal tapestry of the Milky Way, with Deneb majestically adorning the pinnacle of the cross while Albireo, a renowned double star, graces its base with its captivating hues of radiant golden yellow and mesmerizing sapphire blue, a remarkable spectacle that demands the power of a telescope to fully appreciate.

Summer Constellation Image — 1 a.m. on June 1; 11 p.m. on July 1; 9 p.m. on August 1. Add one hour for daylight-saving time.

Farther south on the Milky Way is the bright star Altair and its parent constellation, Aquila the Eagle. If you follow the Milky Way from Aquila toward the southern horizon, you should find a group of stars that looks like a teapot. This asterism is part of Sagittarius the Archer. This constellation marks the location of our galaxy’s center. The area teems with deep-sky treasures — especially bright nebulaeand star clusters. To the right of the teapot is the ruddy 1st-magnitude star Antares, the “heart” of Scorpius the Scorpion. Like the winter star Betelgeuse, Antares is a red supergiant star in the last stages of its life. A fishhook-shaped row of stars trailing down and to the left of Antares forms the Scorpion’s tail and stinger, while an upright row of three stars to Antares’s right marks the location of its claws.

Autumn constellations

As the nights begin to lengthen and a chill pervades the air, the summer Milky Way exits center stage (although the Summer Triangle remains visible in the west until early winter). Following the Summer Triangle is one of the night sky’s prettiest constellations — Delphinus the Dolphin. Four stars, arranged like a diamond, form the Dolphin’s head, while a fifth creates the tail. You can imagine a dolphin leaping out of the water as you gaze at this constellation.

Autumn Constellation Image — 1 a.m. on September 1; 11 p.m. on October 1; 9 p.m. on November 1. Add one hour for daylight-saving time.

In its wake is a rather barren expanse of sky whose most prominent feature is the Great Square of Pegasus the Winged Horse. Alpheratz is at the top left corner of the Great Square. From here, two rows of stars branch out and up. This is the constellation Andromeda the Princess. And yes, it is home to the great Andromeda Galaxy. At a distance of 2.7 million light-years from Earth, it’s the most remote object readily visible to the naked eye. Through binoculars, however, you’ll see an elliptical glow (the galaxy’s bright nucleus), which appears larger in small telescopes.

Now that I’ve introduced you to some of the constellations, it’s time to head out and make your own friends. The expansive night sky will become more familiar to you after spending quality time learning the “faces” of the constellations.