star finder

What Types of Stars Exist in Our Galaxies

20 May 2019

The stars shining up above the sky have fascinated astronomers and astrophysicist for centuries. Astronomers left no stones unturned in studying the secrets of our galaxy and the history of stars. Stars appear as multiple luminous bodies on the sky, shining bright and clear.

Astronomers observe the motion of stars in order to determine their mass, age, chemical composition, luminosity and other properties. Stars are either binary or multiple. For so many years, it was believed that no planet can exist in multiple star systems. However, the discovery and existence of exoplanets refuted this assumption.

Division of Stars

Astronomers have divided stars into various types depending on their spectral characteristics such as temperature and color. Most of the stars are classified under Morgan-Keenan system. These stars are marked with the letters O, B, A, F, G, K, and M. They are organized from the hottest (O) to the coolest (M) type of stars.

Types of stars

Blue Stars

— O-Type Stars

They are usually found in the arms of spiral galaxies which are filled with dust and cloud. As a result, they appear bluish white. These stars have a very high surface temperature ranging from 25000 – 50000 K. They are also known as Blue Giants and are extremely luminous and shine ultraviolet. Only about 0.00003% in our solar neighborhood is classified as O-types. Singly ionized helium lines are apparent on these stars which are either emitted or absorbed. These stars are estimated to live for more than 40 million years.

— B-type Stars

These types of stars shine blue and have neutral helium lines in absorption. They have a surface temperature that range from range from 10,000 K to 25,000 K. They have a They are so energetic, that they only live for a relatively short time.

Both B-type and O-type stars are very hot and gigantic and end in violent supernova events. Consequently, neutron stars or black holes are created.

Yellow Dwarfs

G-type Stars

G-type stars are also known as Yellow Supergiants. About 7.5% of the stars in our solar neighborhood are G-class stars. Sun is the best example of G-type star. Sun emits various colors which are all blended together to produce white.

G-type stars have a typical temperature of 5200 to 7500 K. They can live for up to 17 billion years. G-type stars have the ability to convert hydrogen into helium. They appear bright red when supply of hydrogen is exhausted.

Orange Dwarfs

— K-type Stars

They are a bit cooler than the Sun and shine orange. A prominent K-type main- sequence star is Alpha Centauri B.

K-type stars emit lesser amount of UV radiations which are known for damaging DNA. They have a typical temperature of 3700 to 5200 K and can live for up to 30 billion years.

Red Dwarfs

— M-types

They occupy a large are of Milky Way and are the most common stars (about 76% of the main-sequence stars in the solar neighborhood). The brightest known of them is called M0V Lacaille 8760 with the magnitude 6.6.

They are expected to live for trillions of years.

Blue Giants

— A-type Stars

They are one of the most common stars occupying the galaxy. About 0.625% of our neighborhood-stars are classified as an A-type. They shine white or bluish-white and can be seen with the naked eye.

They have a typical temperature of 10,000 to 30,000 K and may live for up to 100 million years.

Neutron Stars

They are the collapsed cores of the gigantic stars that were previously compressed during a supernova event. They are bigger than protons and carry no electrical charge. Pulsars are energetic neutron stars. They also emit large quantities of radiation in various frequencies.

Stars lighten up our galaxies. It is estimated that 150 billion stars are born every year in the entire Universe. This also means that 4200 stars are born per second. Astronomers believe that the process of formation of stars has slowed down and our galaxy has finally got its fair share of luminous stars.