The Night Sky

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The darkest nights produce the brightest stars John Green

The night sky is a beautiful place. Us humans have become advanced enough to venture far beyond into the night sky than where our ancestors could go. When you look up at night, what do you see? In most cases it must be a ceiling above your head, but if you step outside, there is a whole other world(s) out there.

Credit: Alexey Elfimov

When we peer into the night sky with the unaided eye, the most we can see are stars. However, there is much more to the night sky, galaxies, nebulae and more. So why can’t we see them? The answer lies in one of the fundamentals of optics. It is known as exposure. Exposure is the amount of light we are exposed to. Our eyes, being made to use mainly during the day, can’t offer a lot of exposure, making us unable to look at the night sky in it's full glory. That is why we use cameras and telescopes. Cameras are behind most galaxy and nebulae pictures as their exposure can be adjusted to the point that the entire night sky becomes viewable.

The Andromeda Galaxy

Catalogs

In the night sky, there is a huge assortment of heavenly bodies. There are galaxies, nebulae, star clusters and constellations. So in order for it to be easy to identify them, we have astronomical catalogs.

An astronomical catalog is a list of astronomical objects, grouped together because they share something in common like origin, shape size etcetera. There are two popular catalogs, known as Messier catalog and New General Catalog (NGC). The Messier catalog was created by Charles Messier, a french astronomer, and consists of 110 objects.

Funnily enough, Charles Messier created the Messier Catalog of deep sky objects by accident. He was a comet hunter, and created the catalog to make not of objects that were not comets so that other comet hunters wouldn't waste their time looking at deep sky objects. In doing so, Messier created the best catalogs of deep sky objects of his century

The NGC was compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxies, star clusters and nebulae. Astronomical objects in a catalogue are often named after the catalogue name in order to make it easier to study them and avoid confusion. Like the Orion Nebula, known as both M42 in the Messier catalogue and NGC 1976 in the New General Catalogue.

Messier Catalog Credit: Michael A. Phillips

Some notable galaxies and Nebulae are the Whirlpool galaxy, the Andromeda galaxy, the Ring nebula, Orion nebula and Horse-head nebula.

Catalogs are the method used to identify galaxies and nebulae. But there are so many stars in the night sky. Stars are identified by their color, which indicates their temperature. They are divided into what are known as spectral classes. These classes are O, B, A, F, G, K, and M. Class O stars are the hottest and are blue in color. However, stars are often identified by the constellation they are in as well.

Constellations of the Night Sky

Constellations cover the night sky, they were imaginary shapes made by joining stars in the night sky to form shapes and today used to locate astronomical objects like stars and nebulae.

Some of the popular stars in the night sky are Sirius, Procyon, Arcturus, Vega and Betelgeuse. Sirius is the brightest star. Or should I say stars? You see, Sirius is a double star, which means that Sirius is not one star but two, orbiting each other relatively closely. This doesn’t affect it’s brightness though, because the second str is very small. The stars brightness is because of the fact that it is relatively close to Earth. Sirius is made up of two stars, Sirius A and Sirius B. Sirius falls into the A spectral type.

Now let’s talk about our own Solar system. Our ancestors could differentiate planets from stars because of a very specific reason. the planets orbited around the sun. This caused them to appear to move over the course of days or weeks, which led to our ancestors to call them ‘wanderers of the night sky’ from where the term ‘planet’ was derived.

There are 7 planets observable from our Earth, well, 8 if you want to include the fact that Earth is observable from Earth. Jupiter, despite its enormous size, is not the brightest viewable planet from Earth. It is actually Venus. Venus is known as the morning and evening star as it is most often seen just before sunrise or right after sunset. The cause of Venus’ brightness is the fact that it is closes to Earth in terms of orbits and has a yellowish-white atmosphere that reflects almost all the light.

Mercury is seldom visible from Earth as it is often close to the Sun and not very bright. Mars appears as a tiny red dot in the night sky and Saturn appears slightly elongated because of its rings. Then of course, we have the Moon, Earth's only satellite and the brightest object in the night sky. It is also the most studied object in the night sky. These are the objects visible in the night sky.

Thanks for reading!