Stellar Classification

-

Stars: What are they and how are they classified?

One thing we all have in common is that we all love to stare at the night sky and look at the stars. But when we see thousands of stars in the night sky to accompany us in the middle of the night, how long has it been since you actually thought about stars? Most people know that our sun is a star. But what else do you know about it? Let's find out together! 
A Star is a luminous hot ball of gases (mostly hydrogen and helium) held together by its own gravity. Every star is supported by nuclear fusion where two hydrogen nuclei are merged together to form helium nuclei.

As of now there are seven classifications for stars. These stars are classified under the Morgan-Keenan (MK) system using the letters O, B, A, F, G, K and M, a sequence from the hottest (O type) to the coolest (M type).

1) G - Type Stars

Let us start with a star that comes to all our minds first, the Sun. The Sun is literally part of our daily life and it's one of the reasons why Earth can sustain life. The Sun is a good example of a G-type star. G-type stars are usually very bright but are considered yellow dwarves with surface temperatures of 5,000-6,000 K. The Sun is white even though it can often appear yellow. A G-type main sequence star can keep up nuclear fusion for up to 10 billion years. 














2) O - Type Stars

Now let's start with one of the biggest stars to exist, O - type stars. An O - type star is a hot, blue-white star of spectral type O with temperatures of over 30,000 K. These types of stars are very rare but are extremely bright. Because of their huge mass, they have a very short lifespan and often end up exploding into supernovae, resulting in black holes or neutron stars. 

3) B - Type Stars

Within 100 light years of earth, there are only 4 B-type stars, so calling it rare is a huge understatement. Stars of spectral type B are very hot, bright, and blueish emitting a propotion of their radiations in the ultraviolet wavelengths. Their stellar surfaces range from 9,000 K to 31,000 K. They are normally found near stars of even higher masses like O-type stars. An example of a B-type star is Algol.



4) A - Type Stars

Stars which are of spectral type A are called A-type stars. These stars' spectra are defied by strong Balmer series of hydrogen. They have temperatures ranging from 7,600 K to 10,000 K. They have an approximate main sequence life span of 1 billion years. One of the best-known A-type stars is Sirius, the brightest star in the night sky.


5) F - Type Stars

A F-type main sequence star is a star of spectral type F and luminosity class V. These stars have 1 to 1.4 times the mass of the sun and temperatures between 6,000 K to 7,000 K. This temperature gives a whiteish hue when observed by the atmosphere. Because of that, this class of stars are called yellow-white dwarf.  These stars can support planets like the Tau Bootis and HD 10647. Some studies show that there is a possibility that life could also develop plants. They have a life cycle which is similar to G-type stars.



6) K - Type Stars

K-type stars are of spectral type K and they are normally orange in color. They are normally called as orange dwarf and are said to have a lifespan from 17 billion to 70 billion years. They are nearly half the size of the sun and have temperatures between 3,900 K and 5,300 K. Because of their very long lifespan there is a huge possibility of extra terrestrial life. A great example of a K-type star is the Alpha Centauri B.



7) M - Type Stars

M-type stars are of spectral type M and they are called red dwarfs because they are the smallest and coolest kind of star on the main sequence. They are very common in the Milky Way galaxy and have a surface temperature of about 2,000 K and have only 9% of the sun's radii. They have a lifespan of 1 to 10 trillion years. 


It is really fascinating that there are so many different kinds of stars out there in the distant universe. Each class of a star has completely different properties in which we can go into great detail when it comes to spectral types and masses. I hope you all enjoyed reading it as I did while making it. Let's all fall in love with astronomy together! 



Comments

Post a Comment

Popular posts from this blog

Applications of Astronomy in Daily Life

-
Image
What is Astronomy? When sitting by the window and staring out to the sky, have you ever wondered what else might be out there? Astronomy is an area of study that deals with celestial objects, space, and physical objects as a whole. This branch of science is so vast that there are near infinite possibilities and applications to how it can affect our day-to-day lives. Some instances include: 1) Satellite services in mobiles and communications Mobiles and data communications is one of the fastest developing sectors currently. It has reached a point where imagining a world with no phones, no television, no internet and no GPS is unthinkable, and to some, unlivable. You don’t need to be an expert in the subject to know that satellites are used for data communications and navigation systems. This is done through a portable wireless technology with satellite communications between the satellite and earth stations. 2) Climate Study Has it ever crossed your mind how your phone can magically pr...
Read more

Gravitational Wave Astronomy - Listening to the Universe

-
Image
Gravitational wave astronomy is a relatively new branch in the field of astrophysics that studies the universe using gravitational waves. Gravitational waves are basically ripples in the fabric of spacetime caused by the acceleration of massive objects, such as black holes and neutron stars. It was originally theorized by Einstein in his general theory of relativity back in the year 1915. Even though it was theorized long ago, the first detection of gravitational waves was made in 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO) collaboration.  Do we normal human beings produce gravitational waves when we accelerate? Yes, we do, but the amount of waves produce is so small it is practically impossible to detect them with the current technology. For now, we can only detect them from incredibly massive and dense objects like black holes or neutron stars. In addition to studying black holes and neutron stars, gravitational wave astronomy can also be used to study ...
Read more

Exoplanet Detection Methods

-
Image
Ever since space exploration was a thing, one of the biggest questions asked is about the possibility of someone else out there. Are we alone in this vast universe? Or are there some extraterrestrial lives possible in other galaxies? For all that, we have to find some planets in the first place to know if it is capable for a star to host a planet, and a planet to host life. Here are 5 different ways according to NASA on how to find an exoplanet.  Exoplanet Detection There are many ways to detect the presence of a planet. Radial Velocity and Transit Light Curve methods are the most commonly used methods to detect a planet. Around 5000 planets have been found through these 2 methods alone.  1) Radial Velocity  Why does the Earth move around the Sun? It's because of gravitational pull of the Sun is greater than that of the Earth. But the Earth and other planets also have a gravitational field. So, shouldn't the Sun move a bit as well? Actually, it does, and this event is cal...
Read more