(GED Science/Earth And Space Science; Lesson 5)-The Expanding Universe

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The Expanding Universe

The sun is a medium size yellow star, which consists of a globe of helium and hydrogen gas. It creates, its own heat and light through nuclear reactions. 

The sun started its lives as protostars, which are being formed from clouds of condensing gases and dust called nebulae. When the protostars reaches a certain density and temperature, nuclear reactions begins to take place releasing large amount of energy which is known as main sequence star. This stars begins to run out of hydrogen fuel, after billions of years (it may become a red giant).

With time it may become unstable and then collapses, either exploding as a supernova and leaving behind a neutron star. It could also loose mass slowly to become a giant dwarf. It may collapse as a result of gravity i.e the neutron star become very dense which creates a black hole.

Formation of star

Source: www.en.wikipedia.org 

The milky way galaxy is just one star (the sun) in a huge group of stars. Galaxies can be defined as about one million to one trillion stars, along with clouds of gas and dust, which are being held together by force of gravity. 

Note that there are about 27 known galaxies in the local group. Local group consists of  milky way galaxy, the Andromeda galaxy etc.

Source: www.wallpaperflare.com 

The universe is known as an empty space with galaxies scattered throughout. The universe also consists of other Bodies: 

  1. Brown dwarfs; consists of objects that are less massive than a star but more massive than a planet
  2. Pulsars; it is known as a rotating neutron stars that emit pulses of energy at same intervals.
  3. Quasers; it has the shape of a starlike objects. It emits more energy than a hundred galaxies.

The study of the origin, properties and evolution of the universe is known as cosmologist. The big bang is a theory that has to do with the beginning of the universe. In this theory the big bang theory helps explain the origin of the universe. From this theory it is ascertain that the universe began as a compact spot of matter that exploded. Cosmologist do not have any idea of what resulted to the explosion that resulted to the big bang theory, but from the current rate of expansion of the universe, it is being estimated that it age should be between 10 to 20 billions years ago.


1. The sun is a …….. size yellow …….?

A. Medium/yellow

B. Large/yellow

C. Medium/white

D. Large/white

Ans= A

2. The earth contains a globe of ……… and ………?

A. Helium/ hydroxide gas

B. Helium/ hydroxyl gas

C. Helium/ hydrogen gas

D. Helium/ hydrogen

Ans= C

3. The sun started its lives as ……..?

A. Proton star

B. Star

C. Protostars

D. Photostat

Ans= C

4……… is known as rotating neutron stars that emit pulses of energy?

A. Pulses

B. Pulsars

C. Quasers

D. Pulse star

Ans= B

5. In the big bang theory it talks about the ……. Universe?

A. Theory

B. Origin

C. Location

D. Properties

Ans= B