16 Sep 2019

Gravitation plays a vital role in star formation

How Stars are formed?


Have you ever question yourself, how these "bulbs of universe" (Stars) formed?

They are present in number of millions and billions hence, they are forming each and every second because the process of star formation is time consuming. Star formation is the process in which the dense region of interstellar space which is also referred as "stellar nurseries" collapses and form stars.

Lets know more about interstellar clouds first:

In the universe, lots of stellar remnants, and diffuse interstellar medium of gases and dusts are present. Our milky way galaxy is composed of about 70% of hydrogen gas and in rest 30% a huge amount of helium is present. But our interstellar medium is also rich in heavy elements released from stars.

These regions of heavy density take a shape of cloud which is further referred as diffuse nebulae which later converts into nebulas with high density and this is the site for formation of a star.

These dense nebulas are also called molecular nebula because most of the Hydrogen content in these nebulas exist in molecular form(H2).
The main reason of star formation is, cloud collapse.

But the question rises in mind is, what lead these cloud to collapse?

This question can be answered by using virial theorem. This theorem states that to maintain equilibrium, the gravitational potential energy must equal twice the internal thermal energy.

In large clouds, the kinetic energy of gas pressure is insufficient to support it then the phenomenon of gravitational collapse takes place. The mass above which a cloud will go under such gravitational collapse is known as jeans mass which depends on the temperature and density of cloud.

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During cloud collapse dozens to ten thousands of stars form more or less simultaneously which is observable in so-called embedded clusters.

The end product of a core collapse is an open cluster of stars. As the cloud collapses, the material at the centre begins to heat up, Known as a protost, it is this hot core at the heart of the collarapsing cloud that will one day become a star.

Molecular clouds may collide with each other, or a nearby supernova explosion can be a trigger, sending shocked matter into the cloud at very high speeds. (The resulting new stars may themselves soon produce supernovae, producing self-propagating star formation).

Alternatively, galactic collisions can trigger massive starbursts of star formation as the gas clouds in each galaxy are compressed and agitated by tidal forces.

The black holes present in the centre of the galaxy also show its effects on star formation.

In newly formed galaxies, the black hole is small hence the process of star formation is faster as compare to those old galaxies in which a huge black hole is sitting in the centre of the galaxy ejecting radio-frequency-emitting particles at near-light speed can also block the formation.

Star formation takes approximately a billion years and between this time that start goes into different phases. One of the most longest and famous phase is formation of a protostar.

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A protostellar cloud will continue to collapse as long as the gravitational binding energy can be eliminated. This excess energy is primarily lost through radiation.

However, the collapsing cloud will eventually become opaque to its own radiation, and the energy must be removed through some other means.

The dust within the cloud becomes heated to temperatures of 60–100 K, and these particles radiate at wavelengths in the far infrared where the cloud is transparent. Thus the dust mediates the further collapse of the cloud.

Here one noticeable point is that the mechanism of formation of low mass and high mass star is totally different in comparison.

Major discoveries about star formation in the far reaches of the Universe. This is important as far away galaxies are seen far back in time, because of the huge distances their light has needed to reach us.

Studying starlight from the most distant objects Hubble has observed gives clues about how stars formed in the early years of the Universe, and how they have changed over time.

Nowadays, scientists are trying to find the oldest star of universe because by studying these oldest star we can predict the early time of our universe.

Today we are capable to see the formation of stars with the help of evolved telescopes and hence we can know anything about Stars now.


2 comments:

  1. Thanks for sharing this article here about the star formation. Your article is very informative and I will share it with my other friends as the information is really very useful. Keep sharing your excellent work. Physics homework help online

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