STAR IS BORN

Jason Duria BEEd III-A

How the Star is Born?

Stars are formed in nebulae, interstellar clouds of dust and

gas (mostly hydrogen). These

stellar nurseries are abundant in the

arms of spiral galaxies.

In these stellar nurseries, dense parts

of these clouds undergo gravitational

collapse and compress to form a rotating gas

globule.

The globule is cooled by emitting radio waves and infrared radiation. It is

compressed by gravitational forces and also by shock waves of pressure from

supernova or the hot gas released from nearby bright stars. These forces cause

the roughly-spherical globule to collapse and rotate. The process of collapse takes

from between 10,000 to 1,000,000 years.

A Central Core and a Protoplanetary Disk:As the collapse proceeds, the temperature

and pressure within the globule increases, as the atoms are in closer proximity. Also, the globule rotates faster and faster. This spinning action causes an increase in centrifugal forces (a radial force on spinning objects) that causes the globule to have a central core and a surrounding flattened disk of dust (called a protoplanetary disk or accretion disk). The central core becomes the star; the protoplanetary disk may eventually coalesce into orbiting planets, asteroids, etc.

Protostar:The contracting cloud heats up due to friction and forms a glowing protostar; this stage lasts for roughly 50 million years. If there is enough material in the protostar, the gravitational collapse and the heating continue.

If there is not enough material in the protostar, one possible outcome is a brown dwarf (a large, not-very-luminous celestial body having a mass between 1028 kg and 84 x 1028 kg).

A Newborn Star:

When a temperature of about

27,000,000°F is reached, nuclear fusion

begins. This is the nuclear reaction in

which hydrogen atoms are converted to

helium atoms plus energy. This energy

(radiation) production prevents further

contraction of the star.

Young stars emit jets of intense radiation that

heat the surrounding matter to the point at

which it glows brightly. These narrowly-focused

jets can be trillions of miles long and can travel

at 500,000 miles per hour. These jets may be

focused by the star's magnetic field.

The protostar is now a stable main sequence

star which will remain in this state for about 10

billion years. After that, the hydrogen fuel is depleted and the star begins to die.

Life span:

The most massive stars have

the shortest lives. Stars that are 25

to 50 times that of the Sun live for

only a few million years. Stars like

our Sun live for about 10 billion

years. Stars less massive than the

Sun have even longer life spans.

SUMMARY OF THE BIRTH OF

THE STAR

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