How To Spot Constellations

Stars and Constellations

Even if you are new to astronomy, you have probably heard of constellations, but have you ever wondered what makes them different to stars?

Stars are giant balls of flaming gas, which are the pinpricks of light you see in the sky at night. We call groups of stars which appear to form a pattern of constellations. The word constellation means ‘sea of stars’, from the Latin cōnstellātiō. The Greek word for constellation is ἄστρον, in English ‘astron’, which is where we get the word astronomy.

The patterns we perceive in the night sky exist only from our limited perspective here on Earth. When we form constellations, we connect stars based on their apparent brightness, often linking distant, luminous stars while overlooking nearer, dimmer ones. In other words, constellations are patterns we created because we recognised shapes that weren’t really there, a reflection of a phenomenon known as apophenia, our tendency to find patterns in randomness.

Did you ever play connect-the-dots as a child? You would start with a sheet of paper covered with dots. By drawing lines between them, the image would reveal itself. That’s what constellations are – imaginary lines drawn between the stars to create shapes and symbols. You can even navigate by using the stars.

Constellations and Asterisms

You might think you know the names of some easy-to-find constellations. Have you heard of Orion’s Belt? Or the Big Dipper? These are not actually constellations but asterisms.

In astronomy, constellations are technically how we divide up the night sky. This helps astronomers more easily identify where objects are located. The International Astronomical Union officially recognises 88 constellations.

Asterisms are the familiar shapes we see in the stars, and they may overlap with, or be partially formed from, constellations.

Traditionally, constellations are perceived to form animals and mythological figures. You might also be familiar with the twelve famous zodiac constellations. Although the popularity of different constellations has changed throughout history, some can be dated back to Babylonian times or earlier.

How to Spot Constellations

Finding constellations can be easy, but you need to be in the right place at the right time.

• If you are in the northern hemisphere, you will only be able to see half of the night sky. Constellations like the Southern Cross will be hard to find when there is a planet in the way!
• Depending on the season, constellations which are close to the horizon can be harder to see because the Earth wobbles slightly as it spins around the sun.
• The time of day (or night) is important. Some constellations travel high up in the sky, but those closer to the horizon may only be visible for a few hours or less.
• The moon might be in the way of important details.
• The direction you are facing is important too. Constellations are all around the sky, so make sure you look around.

Other Tips

• The weather is an important detail. You won’t see many stars behind the clouds, so cloudless nights are best for stargazing.
• Getting away from the light pollution of cities and towns will help you spot the faint details in the sky.
• Bring a coat. Even summer nights can get chilly, especially if you are in the open.
• Bring a telescope, but don’t zoom in too close. Constellations are much bigger than the individual stars. Telescopes can be very helpful in finding stars within a constellation to get you started. (Did you know who invented the telescope?)
• Bring a compass, so you can check that you are oriented correctly.

Easy Constellations to Spot

If you are just getting started with astronomy, you might already know that the constellations visible in the northern hemisphere are different from those you can see in the southern hemisphere. Also, due to the rotation of the earth, seasonal changes, and of course, the weather, the best time to see one constellation over another could differ.

These are some of the easiest constellations to spot in the Northern Hemisphere.

Constellation: Ursa Major (UMA), Asterism: Big Dipper

Best time to see it

Ursa Major is visible all year round, but in spring it is higher in the sky.

How to find Ursa Major

The easiest way to find Ursa Major is to begin with the Big Dipper, as this is an easily recognised shape. It rotates around the North Star, Polaris, so in the Spring, the Big Dipper will appear upside down. Look for three stars in a line which forms the ‘handle’ of the Big Dipper. These stars are called Alcor, Alioth and Megrez. Megrez is also the corner of the roughly squarish shape which forms the Dipper.

To be sure you have found the right shape, look carefully at the two stars which form the other end of the square. These are Merak and Dubhe. They should form a line which points at Polaris. If you have found all of these, then you should be able to identify the rest of Ursa Major. The brightest star in Ursa Major is Alioth and is 82 light-years away from Earth.

Orion (ORI), Asterism: Orion’s Belt

Best time to see it

In the Northern Hemisphere, Orion is most visible from November to February.

How to find Orion

Orion’s Belt is the most distinctive part of Orion, making this one of the easiest constellations to find. Look for a line of three bright stars. They are easy to find with the naked eye, and they are named Alnitak, Alnilam, and Mintaka. Begin closer to the horizon and scan up as you turn to find it. Fortunately, Orion always appears the right way up in the northern hemisphere. Now look for the hourglass shape above and below the line of the belt. This forms Orion’s body.

Down and to the right of Mintaka is Rigel, which forms the bottom corner of Orion’s body. Up and to the left of Alnitak is Betelgeuse, which forms his shoulder. If you continue this line, you will see his arm and upraised ‘hand’, which is shaped like a crude letter ‘v’. If you look up and to the right of the belt, you will see a group of stars that approximate the shape of a bow.

The brightest star in Orion is Rigel, and it is a staggering 860 light-years away.

Gemini (GEM)

Best time to see it

Gemini is most clearly visible from November to February.

How to find Gemini

If you have already found Orion, then Gemini is a good next step. Gemini is named for the twin half-brothers Castor and Pollux in Greek and Roman mythology. Gemini sits above and to the left of Orion’s shoulder, and roughly forms a letter ‘n’.

Draw a line from Orion’s left foot (Rigel) to his right shoulder (Betelgeuse), and you will come to a star named Tejat Posterior. From here, you can trace up one side of the ‘n’ to Castor. Left and below Castor is Pollux. These stars form the shoulders of the constellation. From here, you should be able to trace a parallel line back toward Orion.

The brightest star in Gemini is Pollux and is 34 light-years away from Earth. Castor is not actually a star but a system of six stars which appear to be one when viewed with the naked eye.

Identifying stars and constellations accurately is a valuable navigational skill. You can learn navigation and other survival and adventurous skills as part of the Army Cadets Adventurous Training Course. They are a fantastic way to get outdoors, learn more, and make new friends. Знайдіть найближчий загін сьогодні.

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All star charts are from the IAU, published under Creative Commons.

Hero image photo by Marc Sendra Martorell на Вимкнути сплеск