On a clear evening in an area with little light pollution we can see millions of stars above our heads. It is a cosmic sight to behold. With the naked eye we can see some may shine brighter than others but which is the brightest star in the sky?
In this article we will learn more about stars, what affects how bright they are and ultimately which of these known and named stars shines the brightest. The answers may surprise you but they will certainly teach you something you maybe didn’t already know.
What Are Stars?
When discussing something relating to the universe it is always wise to start at the beginning because sometimes things can seem complicated. So what exactly is a star? As mentioned we see millions of stars in the night sky so they are likely our most familiar astronomical body.
These bright heavenly bodies represent the most fundamental building blocks of galaxies with some being billions of years old. They are huge energy producing balls of gas which through nuclear fusion also produce heavy elements such as carbon, nitrogen and oxygen.
How Are Stars Formed?
Hundreds of thousands of years after the Big Bang the gases released into our universe were not spread out evenly. Two main gases, hydrogen and helium, would clump together into dense clouds of gas. As these clumps grew they would become denser and more compact. At the center of these dense clumps temperatures became hotter eventually leading to nuclear fusion.
The cloud collapses inward causing the material at the center to heat up. This is known as a protostar and the gradual build up of heat and pressure creates a star. Sometimes these clouds which also include dust may break into blobs creating multiple stars. This is why you may see stars grouped together in the night sky.
Our Own Star
There is a very simple answer to the question “which star is the brightest in the skies of earth?” Although some people may not be aware of this. There is one star so bright that when it shines we can not see any of the others. This star is our own sun.
Around 93 million miles away from earth the sun is indeed a star and is considered a yellow dwarf. Without this star there would be no life on our planet. However if we just settle on the sun as an answer here that would be too easy. So read on to find out which star is the brightest in our skies after the sun has dipped below the horizon.
What Affects a Star’s Brightness?
The brightness of a star as we see it from earth is expressed by the term magnitude. This is a function of its luminosity, distance from earth, effects of dust/gas, and the effects of earth’s atmosphere. The measurement of absolute magnitude for a star is a unit that assesses the star’s luminosity if it were 10 parsecs from earth. A parsec equates to roughly 32.6 lightyears.
A difference of one magnitude unit equates to a brightness variation of about 2.5 times. This means that a magnitude of +1.00 is about 2.5 times brighter than a magnitude of +2.00. As a reference the faintest stars visible to the naked eye are +6.00 magnitude which is about 100 times less bright than a magnitude +1.00.
The brightness of a star can vary greatly based on how near it actually is to earth. The closest star other than the sun to earth is Proxima Centauri 4.2465 light-years away. Although this is a very small star comparatively speaking. You can not see it with the naked eye as it has an apparent magnitude of +11.13.
Proxima Centauri is a dwarf red star about 12.5% the mass of our own sun. If it were a bigger star it might be more prominent in the night sky based on its relative closeness to planet earth.
Without question the size of a star has a huge impact on its luminosity. This is because of a much larger surface area producing more light and energy that eventually reaches earth as visible light. Light energy can dissipate over vast stellar distances however so if a large star is far enough away its light may not be visible to the naked eye on earth.
A large star that is close to earth will generally be more prominent in the night skies.
What Is the Brightest Star in the Night Sky?
Also referred to as the Dog Star, Sirius is currently the brightest star in the skies that can be seen over our planet. It has an apparent magnitude of -1-46 which is almost twice as bright as the next brightest Canopus. It is relatively close to earth at just 8.6 light-years.
Compared to our own sun it is about twice the size and 25 times more luminous. It is only the proximity of the sun to earth that allows it to far outshine Sirius in our unassisted vision of the skies.
It is a prominent star in the skies thanks to its brightness and has been recorded in some of the earliest astronomical records. It had adorned the night sky far before the hominids left the trees and started to walk on two feet.
Stellar models suggest that Sirius formed during the collapse of a molecular cloud. After 10 million years, its internal energy generation is still derived entirely from the nuclear reactions caused by this collapse.
Based on its size and other dimensions astronomers have estimated it will have burned through the fuel in its core within a billion years of its formation. This means it will likely adorn our skies for hundreds of thousands of years to come.
There are really two answers to the question of which is the brightest star in the sky. It all depends whether it is day or nighttime. During the day our own solar system’s star which we refer to as the sun is without question the brightest. However once the sun starts the day on the other side of our planet the Dog Star also known as Sirius picks up the brightness mantle.
If our sun and Sirius however were placed next to one another Sirius would be the brighter of the two due to its sheer size. It is 25 times brighter than our own sun but because it is over 8 light-years away from earth it can only show its luminosity after the sun goes down.