The Stars & Constellations (and more)

The Stars

For the most part, to navigate the night sky, you won’t be looking at individual stars, and binoculars or telescopes aren’t that useful. It’s best just to go out and look up. When you do, you will focus on groups and patterns of stars called constellations and asterisms. There are 88 official constellations in the nights sky (e.g., Orion and Leo) and many unofficial asterisms (e.g., the Big and Little Dippers).

Southern Horizon

The constellations (and asterisms) follow a very regular pattern appearing to move from east to west when viewed from the Earth. This pattern repeats itself over the course of a night and over the course of a year. Therefore, as you look to the South in the eventing after sunset, the constellations that dominate the night sky depend on the season.

If you’re just starting out, look for Leo in the Spring, Scorpius and Sagittarius in the Summer, Pegasus in the Fall, and Orion in the Winter. For more, here is a Quick Introduction to the Night Sky.

Spring

High in the sky is Leo, the Lion with the bright star Regulus followed by Corvus, the Crow, and Virgo, the Maiden. Farther to the east is the Boötes, the Herdsman, and Corona Borealis, the Northern Crown.

Find the bright stars Arcturus (Boötes) and Spica (Virgo) by following the handle of the Big Dipper -> “Arc to Arcturus and Speed on to Spica”.

Summer

In early summer, low in the horizon, look for Scorpius, the Scorpion, with the orange star Antares, and Sagittarius, the Archer. Note the “teapot” shape of Sagittarius.

Higher in the sky and to the east is the Summer Triangle of Altair (Aquila the Eagle), Vega (Lyra the Harp) and, Deneb (tail of Cygnus the Swan). Find the yellow/blue “double star” Albireo, the head of the Swan.

Fall

During the fall find the Great Square of Pegasus and Pegasus, the upside down flying horse. Off to the east of Pegasus is Andromeda and the faint Andromeda Galaxy (M31).

Farther to the east is Perseus, looking like an upside down Y.

Winter

Center to the cool and clear Winter sky is Orion, the Hunter, with his bright belt (Alnitak, Alnilam and Mintaka). Don’t miss red Betelgeuse, his right shoulder, and bluish/white Rigel, his left foot. In the center of his sword is the Great Orion Nebula (M42). Bellatrix is his left shoulder and Saiph his right foot.

Up from Orion’s belt is the V-shaped head of Taurus, the Bull, with the reddish Aldebaran, the Bull’s right eye. On the Bull’s back is the open star cluster the Pleiades (M45 / The Seven Sisters / Subaru). Most of the stars in the V-shaped head are a star cluster known as the Hyades.

Down from Orion’s belt is the bright “Dog Star” Sirius in Canis Major, the Greater (Large) Dog. Above the Large Dog, is Canis Minor, the Lesser (Small) Dog, along with Pollux and Castor, the heads of the Gemini twins. High in the sky is the Charioteer Auriga with the bright star Cappella.

Follow the Winter Hexagon (Circle) from Sirius to Procyon to Pollux to Capella to Aldebaran to Rigel.

Northern Horizon

As you look to the North, the stars appear to rotate counterclockwise around the “fixed” star Polaris (The North Star).

Polaris is found at the tip of the handle of the Little Dipper, part of Ursa Minor, the Lesser (Small) Bear.

Follow the two stars (Merak and Dubhe) at the end of the Big Dipper’s bowl to the North Star. The Little Dipper is always found curving in toward the Big Dipper.

Spring Sky

High in the Spring sky is the Big Dipper, the tail and back of Ursa Major, the Greater (Large) Bear. Find the double stars Mizar and Alcor in the middle of the handle.

Between the dippers is the tail of Draco the Dragon. Standing on the head of Draco is Hercules.

The W-shaped Cassiopeia is low in the horizon.

Fall Sky

High in the Fall sky is the M-shaped Queen Cassiopeia. Nearby is the faint King Cepheus.

The Big Dipper is low in the sky this time of year.

A Deeper Dive

The Seasonal Night Skies (FAS Articles)

The Night Sky (One-Minute Astronomer)

Once you know your way around the night sky, you will find that there are plenty of objects worth taking a closer look at with binoculars or telescopes. There are a few interesting double stars and different colored stars that you might view close up (e.g. Mizar/Alcor and Albireo). However, it is the Moon, planets and deep sky objects that garner the most interest.

The Moon

The Moon moves from west to east as it travels through its 27.3 day orbit and goes through a set of phases every 29½ days. It is best to view the Moon during its 1st or 3rd quarters and not during a full moon when it is way too bright. Follow the Moon’s phases with the folks at NASA, timeanddate, and the Farmers’ Almanac. The Planetary Society has a nice map of Moon features.

Phases of the Moon

A new moon is high at noon when the far side of the moon is completely illuminated by the Sun.
A crescent is when the sunlight is just visible before or after a new moon.
A 1^st quarter moon rises mid-day and a 3^rd (Last) quarter moon rises near midnight. Both occur when half of the near side and half of the far side are illuminated.
A gibbous is between a quarter and full moon. This is when you will see a “daytime moon.”
- A waxing gibbous occurs just before a full moon and is visible in the afternoon to the east.
- A waning gibbous occurs just after a full moon and is visible in the morning to the west.
A full moon is high at midnight when the near side is fully illuminated by the Sun.

The moon is waxing as the light appears after a new moon
(new moon -> waxing crescent -> 1st quarter -> waxing gibbous -> full moon).

The moon is waning as the light disappears after a full moon
(full moon -> waning gibbous -> 3rd (Last) quarter -> waning crescent -> new moon).

The Planets

The planets, “wanderers” in Greek, generally move from west to east along the ecliptic against the background of the stars. They will from time to time exhibit a retrograde motion and move in the opposite direction. Check Stellarium Web or your astronomy app such as Sky Guide or SkySafari for their current position. The Famers’ Almanac will tell you when they are visible throughout the year.

Mercury alternates between the evening and morning skies.
Venus looks like a very bright “star” either in the morning or evening sky.
Mars moves around a lot from month to month.
Jupiter is currently (October 2024) between the horns of Taurus.
Saturn is currently (October 2024) found in Aquarius (below Pegasus) and is slowly moving toward Pisces.

Deep Sky Objects

In addition to the stars and planets, there are also deep-sky objects. A hundred or so of the most noticeable are classified as Messier objects. Others are found in the Caldwell Catalogue. Most also have a designation from the New General Catalog and are assigned NGC numbers.

Open Star Clusters are small and younger clusters of stars that formed at approximately the same time (e.g., the Pleiades/M45).
Globular Star Clusters are larger and older clusters of stars found outside the plane of the Milky Way. These clusters are over 10 billion years old and contain hundreds of thousands to millions of stars (e.g., the Hercules Globular Cluster/M13).
Nebulae are gaseous clouds, typically composed mostly of hydrogen, where new stars are being formed (e.g., the Orion Nebula/M42).
Supernova Remnants are nebula composed of material that was ejected during a supernova explosion. (e.g., the Crab Nebula/M01).
Planetary Nebulae are the remnants of stars after they expanded into a red giant where material was blown away from the surviving star core (e.g., the Ring Nebula/M57).
Galaxies are large collections of stars such as the Milky Way and Andromeda (M31).