[Physics Class Notes] on Stars Pdf for Exam

Stars And Constellations

The origin of the star takes place in the form of a nebula. The nebula is a cloud of dust and gas. Example: hydrogen. The gravity supports the process of clumping together of dust and gas. Other factors such as temperature, density, and pressure facilitate nuclear fusion, conversion of hydrogen into helium, which ultimately leads to the birth of a star. A star can be born dwarf or dead when the optimum temperature is not reached. When the stars seem to appear in a particular pattern or in groups, then it is called a constellation. These patterns are recognizable in every night sky. 

Stars

The larger the star in size, hotter and higher temperatures exists in the star. The Sun is the example of a star. In reality, the Sun is a yellow dwarf star. Nuclear fusion, also present in the Sun, causes the release of heat and light energy. In the case of large stars, helium itself fuels the star by releasing an even higher amount of energy. 

Another concept related to stars and celestial bodies is a supernova. A supernova is an event in the space that takes place when a star explodes. When this event occurs, the matter of the exploded star is blown away into space. The exploded matter then forms a nebula and the birth of other stars begins. Theorists, such as Subrahmanyam Chandrasekhar,  have also established that a star must continue to collapse under its own gravity. 

There are so many stars in the universe and several of them have been named by astrophysicists and other scientists. Polaris, Sirius, Alpha Centauri System, Betelgeuse, Rigel, Vega, Pleiades, Antares are names of stars. The 2nd nearest star to the earth, after the Sun, is the Proxima Centauri. 

Polaris, Aldebaran, Castor, Spica, Betelguese, and Pollux are names of some very bright stars that have been discovered in the galaxy. One can easily spot Polaris (Dhruv), the pole star, and Sirius in the night sky. 

Constellations

Constellations are not a new discovery, rather they were devised by ancient people, who used to use them for following directions at night. Ursa Major is the name of a constellation that is popular. It can be easily seen in the early parts of the night during summertime and it may consist of  five to ten stars or even more. The bright stars of the constellation can be visible with naked eyes. 

The stars in the patterns appear closer together in the sky, but in reality, they can be billions of miles apart. The stars are also named after the constellation in which they appear. An example of this is the star called “Proxima Centauri”, 2nd nearest star to the earth. The name of the constellation of this star is “Centaurus”. 

Ursa Major is also known by other names such as the Big Dipper, the Great Bear, or the Saptarshi. The pattern of the stars in this constellation appears like a big ladle in the night sky. The Polaris or the Pole star is one of the stars in this constellation. Some parts of this constellation, as well as the Pole Star, might not be visible in the southern hemisphere. Due to earth’s rotation, Ursa Major appears to move from east to west direction across the sky. 

Another common constellation of stars in Orion, also known as the Hunter. Unlike Ursa Major, Orion is visible during late evenings of winters. It consists of seven or eight bright stars. Four of the star forms a quadrilateral in the center of which three stars represent the belt of the hunter. Sirius, a bright star, is usually located close to this constellation. 

Names of Stars And Constellations

The universe is infinite and consists of clouds of dust and gas. When the dust and gas gravitate together, a star is born. Stars can also differ in size, distance, and brightness. Moreover, it is a common tendency of a star to implode and cause a supernova. On the earth, the stars appear closer to each other and form particular patterns which are called constellations. There are as many constellations as many patterns stars create when in the night sky. Polaris, Sirius, Ursa Major, Ursa Minor, and Orion are popular names of stars and constellations.