Since the beginning of civilization, man has been curious about the fascinating nature of the sky. Even though it looked like the movement of celestial objects was chaotic, he soon realized its unique patterns and how it could help him understand more about the earth and in a sense the universe itself.
One of the earliest applications that used the movements of these objects in the sky was navigation. The sun, the moon and the stars were the guides for man to know where he’s and to travel from a location to another over land or water. The celestial navigation for trade ships & vehicles was instrumental in connecting major trade hubs around the world in the pre-industrial era. Let’s know more about these stars in the sky that have helped navigation for centuries.
Where do you start?
Look for 7 bright stars, that look like a kite in the northern sky. This also looks like a pan with handle (4 stars forming the pan and 3 stars in an arc making the handle). These 7 stars are part of a constellation called the ‘Big Dipper’ and this is your starting point in exploring the night sky.
Draw a path using the stars on the far edge of the Big Dipper, through A and B in the above map to arrive at the first bright star. This is Polaris. Also called the North Star, it has been very important for navigation as facing it from anywhere on the northern hemisphere means you are always looking due north. Polaris is the last tail-end star of the constellation, the Little Dipper. This constellation looks very similar to the Big Dipper but inverted.
If you failed to find the Big Dipper and instead start from Polaris/the Little Dipper, you can arrive at the Big Dipper using the diagonal stars in the Little Dipper’s pan.
The Big Arc through Polaris!
Now that you found the Polaris, let’s locate 5 major and bright stars in the sky using a simple arc. Create an arc passing through Polaris and the farthest star from Polaris in the Little Dipper. The Big Dipper should lie inside the arc (the centre of the arc should be towards the Big Dipper).
The first bright star on the arc on the Polaris side is Capella. The sixth-brightest star in the night sky, Capella is actually a quadruple star system. There are two binary stars in this system. In the same path of the arc after Capella comes the Betelgeuse. Betelgeuse, a red supergiant star, is in the top ten brightest stars in the night sky and also the second brightest in the constellation of Orion. Continuing on the arc, you find Sirius next. Sirius is the brightest star in the night sky. Sirius is also a binary star. While one star of the Sirius star system is a main-sequence star another is a white dwarf.
On the other side of the arc from Polaris, you see Arcturus. It’s the fourth brightest star in the night sky. Arcturus, also being the brightest star in the northern celestial hemisphere, was an important star for celestial navigation. Next on the arc after Arcturus, you’ll see Spica. This is a binary star system with an orbit period of 4 days around each other and also among the top-20 brightest stars of the night sky. Because of the binary star characteristics, it flashes red and blue in the sky.
The Spring Triangle
From the Big Dipper, instead of drawing a path from A to B to find Polaris, if we draw the path in the opposite direction, we see Regulus. It’s the brightest star in the constellation Leo. Regulus along with the earlier identified stars Arcturus and Spica forms the Spring Triangle. These 3 stars are visible throughout the night sky during spring months from March to May. Some sources use the less bright Denebola (also from Leo constellation) as part of the summer triangle. This forms more of an equilateral triangle compared to the one with Regulus.
The Spring Triangle along with another star called Cor Caroli forms the Great Diamond in the night sky. Another bright star visible close to the spring triangle is Antares. Create an arc from Regulus through Denebola and the first star you see on the path is Antares. Belonging to the Scorpius constellation, it’s a reddish appearing star and is in the top-20 brightest stars of the night sky.
The Summer Triangle
In the Little Dipper’s pan, if you draw a path using the diagonal stars as above in the first image to find the Big Dipper and move in the opposite direction, you find Deneb as the first bright star. Deneb is the brightest star of the Cygnus constellation, that looks like a flying swan with Deneb as its beak. Close to Deneb, there are two more stars Vega and Altair. These 3 stars, together, form the Summer triangle. These stars are visible throughout the night sky during the summer months from June to August.
The Winter Triangle
We’ve already identified Betelgeuse and Sirius earlier. These stars are also part of the Winter Triangle along with Procyon. Orion, a prominent constellation that looks like a hunter and easily recognizable across the world, is also visible right next to the winter triangle. Orion’s belt is a major feature of the constellation which helps identify the constellation very easily.
Other major stars that are visible around the Winter Triangle and are in the top-20 brightest stars of the night sky include Rigel (Orion’s brightest), Canopus (2nd brightest in the night sky) and Aldebaran (14th brightest, and a red giant). Just around the Winter Triangle, one can identify 7 of the top-20 brightest stars of the night sky.
Triple Planetary Conjunction
Apart from the stars, we can also see the planets in our solar system regularly. Venus, appearing white, is the brightest planet visible to the naked eye and is usually seen just before the sunrise and after the sunset similar to Mercury.
Other planets that we can see with naked eye include Mars, Jupiter and Saturn. And currently, there’s an interesting phenomenon happening. All these 3 planets are very close to each other with Mars and Saturn in almost in conjunction and Jupiter very close by. On March 4, 2020, all three planets were equally spaced, with 8° separating each of these. You can see them next to each other throughout April 2020 in early mornings. Mars appears red whereas Jupiter and Saturn look orange and yellow respectively.
The stars and planets that are visible in the night sky on a given day depend on the location of the observation and the visibility of the sky varies with the weather conditions.