Constellations: All You Want to Know

~3 min
Constellations in the sky

In today’s article, we’ll briefly answer the most popular questions about constellations. You can also check out our infographic on seven constellations everyone can find!

What do astronomers mean by a constellation?

A constellation is a group of stars that appears to form a pattern when viewed from the Earth. Constellations are completely imaginary – most of them were invented by ancient astronomers and used as memory aids for navigating the night sky.

What is the difference between a constellation and an asterism?

Asterisms differ from constellations in that they are not officially registered. Most asterisms are easily recognizable patterns of stars within a constellation. For example, the most well-known asterism is undoubtedly the Big Dipper in Ursa Major; another famous one is the Teapot in Sagittarius. Sometimes, an asterism can comprise stars from multiple constellations – like the Summer Triangle that includes the stars located in Cygnus, Lyra, and Aquila.

How many constellations are there?

The International Astronomical Union (IAU) officially recognizes 88 constellations that cover both northern and southern skies. Each constellation is a region of the sky, bordered by arcs of right ascension and declination. Any given point on a celestial sphere lies in one of the constellations.

How many zodiac constellations are there?

The zodiac is a set of constellations that lie along the annual path of the Sun across the sky called the ecliptic. Over the year, the Sun seems to pass through all of the zodiac constellations.

From an astronomical point of view, there are 13 zodiac constellations. The constellations are Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius, Capricornus, Aquarius, Pisces, and Ophiuchus. Why do astrologers mention only 12 constellations then? The zodiac was invented by the Babylonians, who wanted the constellations to match the number of months in the calendar. For this reason, they simply omitted the 13th constellation, Ophiuchus, although it also lies in the path of the ecliptic.

How to find constellations?

The easiest way to find constellations (as well as individual stars, planets, and other celestial bodies) is to use stargazing mobile apps – like Star Walk 2. Simply point your phone up to the sky, and Star Walk 2 will show you the name and shape of any constellation above your head. Tap on the constellation’s name to view its interactive 3D model, learn some astronomical facts and discover the mythology behind it.

Why do constellations not look like their names?

Don’t forget that constellations are products of ancient people’s imagination. The human brain has a tendency to see meaningful patterns in random structures, and the final result is highly individual. Where the Greeks saw Orion the Hunter, ancient Chinese astronomers saw the White Tiger and Vermilion Bird. If you were to name constellations, you’d probably come up with totally different shapes and names.

What is the biggest constellation?

The largest of 88 constellations is Hydra – it measures 1,303 square degrees and takes up 3.16% of the night sky. It is also the longest constellation, spanning over 100 degrees in length. If you live in the Southern Hemisphere, you can find this constellation by looking for the Head of Hydra asterism, located between bright stars Regulus and Procyon. Or you can simply use a stargazing app!

Which constellation holds the brightest star in the northern sky?

The brightest star in the night sky is Sirius; it can be seen from both the Northern and Southern Hemispheres. Sirius resides in the constellation Canis Major and shines with a visual magnitude of -1.44.

What are three stars in a row called?

The famous asterism of three stars in a straight line is the Orion’s Belt situated in the constellation of Orion. It consists of the three bright stars Alnitak, Alnilam, and Mintaka. Looking for Orion’s Belt in the night sky is the easiest way to find the constellation of Orion.

We hope you’ve learned some interesting facts from our article and maybe cleared up some misconceptions about constellations. If some of your questions were left unanswered, don’t hesitate to ask them in the comments on our social media!

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Image Credit:Vito Technology
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