The Night Sky

Young Astronomers Blog, Volume 29, Number 9.

The stars follow a very regular pattern when viewed from the Earth. They appear to move from east to west. This pattern repeats itself over the course of a night (Earth’s rotation) and over the four seasons of the year (Earth’s orbit).

The constellations that dominate the night sky depend on the season as you look to the South in the evening after sunset.

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

In the Summer, look for Scorpius the Scorpion, with its orange heart Antares, followed by Sagittarius the Archer low in the horizon. Note the “teapot” shape of Sagittarius. Higher in the sky and to the east is the Summer Triangle consisting of Altair (Aquila the Eagle), Vega (Lyra the Harp) and Deneb (the tail of Cygnus the Swan). Find the yellow/blue “double star” Albireo at the head of the Swan.

Draw a line from the center star of Cygnus (wings and body) through Vega to Hercules. Find the Keystone with four stars representing his body and the Hercules Globular Cluster (M13) on the far side of the keystone from Vega. Hercules is upside down and is kneeling with his other foot on the head of Draco the Dragon.

During the Fall, find the Great Square of Pegasus. Add a few more stars to find Pegasus itself, the upside-down flying horse, high in the sky. Off to the east of Pegasus is Andromeda and the faint Andromeda Galaxy (M31). To find the Andromeda Galaxy, start with the upper left corner of Pegasus. Count one, two stars to the left. Then, count one, two to the north.

Central to the cool and clear Winter sky is Orion the Hunter with his bright belt of 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).

Up from Orion’s belt is the V-shaped head of Taurus the Bull with the reddish star Aldebaran (the Bull’s right eye). On the Bull’s back is the open star cluster the Pleiades (M45 / The Seven Sisters / Subaru).

Down from Orion’s belt is the bright “Dog Star” Sirius in Canis Major the Greater (Large) Dog. Above the Large Dog, is Procyon in Canis Minor the Lesser (Small) Dog. A bit higher is Pollux and Castor, the heads of the Gemini twins. High in the sky is the Charioteer Auriga looking like a trapezoid or pentagon with the bright star Cappella.

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

As you turn to the North, the stars appear to rotate around the “fixed” star Polaris (The North Star). Polaris is found at the tip of the handle of the Little Dipper, which is part of Ursa Minor the Lesser (Small) Bear.

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

You can always follow Merak and Dubhe, “the pointer stars”, at the end of the Big Dipper’s bowl to find Polaris (The North Star). The Little Dipper is always found curving in toward the Big Dipper.

For detailed maps of the constellations, see “The Constellations” by the International Astronomical Union and Sky & Telescope.

The position of the Moon in the evening sky changes as it travels through its 27 days orbit about the Earth and goes through a set of phases every 29½ days. If you watch the Moon from night to night, you will notice that it slowly moves from west to east across the sky while its hourly movement is from east to west as the Earth rotates. The Old Farmer’s Almanac has information about the current Moon phases for the Winston-Salem area.

• A new moon is found high at noon when the far side of the moon is completely illuminated by the Sun.
• The moon is waxing as the light appears after a new moon (waxing crescent…1^st quarter…waxing gibbous).
• A full moon is high at midnight when the near side is fully illuminated by the Sun.
• The moon is waning as the light disappears after a full moon (waning gibbous…3^rd quarter…waning crescent).
• A 1^st (first) 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 is illuminated.

The planets, or “wanderers” in Greek, move from west to east against the background of the stars. The planets generally follow the “ecliptic”, which is the annual path of the Sun through the sky. Use the resources below to find the current location of each planet.

Mercury is always low in the horizon and alternates between the evening and morning sky. Venus looks like a very bright “star” appearing either in the morning or evening sky. As viewed from the Earth, both will travel from superior conjunction (appearing as a small round disk while behind the Sun) to inferior conjunction (appearing as a large crescent in front of the Sun) and back again. While in the evening, the planets are moving toward us (SC to IC). While in the morning, they are moving away from us (IC to SC).

Mars moves across the ecliptic from west to east. Although from time to time it will follow a retrograde motion from east to west for a short period of time.

Jupiter and Saturn move slowly west to east from constellation to constellation along the ecliptic. In 2021, they both can be found below the Summer Triangle and between the constellations Sagittarius and Pegasus.

There are many smart phone and tablet apps available to help you find the stars, planets, and Moon. Most have augmented reality which allows you to hold your phone or tablet up and the app will show you the night sky as it appears above you. SkySafari (Simulation Curriculum) is one of the more popular apps. It is available as a basic, plus, and pro version. You might also consider Planets (Q Continuum) and Sky Guide (Fifth Star Labs LLC). There are a few online articles listed below with some suggestions. You could also talk with friends who stargaze, and they might have a few additional suggestions.

There are several on-line guides which will help you navigate the night sky.

• “This Week’s Sky at a Glance.” Sky & Telescope. https://skyandtelescope.org/observing/sky-at-a-glance/
• “The Sky this Week.” Astronomy. https://astronomy.com/observing/sky-this-week
• “The Sky this Month.” Astronomy. https://astronomy.com/magazine/sky-this-month
• “The Night Sky This Month.” Cosmic Pursuits. https://cosmicpursuits.com/night-sky-this-month/
• “Night Sky Planner.” NASA Night Sky Network. https://nightsky.jpl.nasa.gov/planner.cfm
• “Constellation Guide: A Guide to the Night Sky.” https://www.constellation-guide.com/
• “Monthly Star Chart.” Orion Telescopes. https://www.telescope.com/content.jsp?pageName=Monthly-Star-Chart
• “What’s Out Tonight.” Ken Graun/Kenpress. http://www.kenpress.com/index.html

If you’re a bit old fashioned, try a planisphere. It won’t help you find the planets, but it will provide a nice map of the stars and constellations for any time of the year. Match the current time with the current date. Hold the planisphere above your head and it will show you the current sky. Like apps, there are many to choose from including “Guide to the Stars”, which has some useful information about star gazing printed on the front and back.

You can’t stargaze without clear skies. For a quick look at the quality of the night sky in the Winston-Salem area, check out the Pilot Mountain Clear Sky Chart.

If you want to travel a bit, you might look for a site with little light pollution. Unfortunately, artificial light is everywhere, and it is difficult, particularly for those of us on the east coast, to find dark skies. The International Dark-Sky Association has more information about this.

When you first go outside, it will take several minutes for your eyes to adjust to the dark. To maintain your night vision, don’t forget to take a red flashlight with you. Avoid using a white flashlight or bright flashlight (of any color). Some prefer green light because you can see more detail than red, and you can get by with a lower intensity light.

For more information see the FAS Navigate The Night Sky webpage.

“Light Pollution.” International Dark-Sky Association. (accessed May 3, 2021). https://www.darksky.org/light-pollution/