Thursday, September 17, 2020

ALS REVIEWER - Module "Beyond the Stars" - Things & Terms to Remember | SCIENCE

 This module tells us that:

 

          Stars can differ in terms of magnitude, color and temperature, composition, proper motion, radial velocity, size and stellar distance.



          Stars can be classified as variable stars, binary stars, novae, supernovae, dwarfs, neutron stars, pulsars and black holes.

 

          There are two kinds of star clusters, namely, globular clusters and open or galactic clusters.

 

          There are ten stages in the evolution of stars. These are:

 

1.        the interstellar medium stage;

 

2.        the contraction of the cloud stage;

 

3.        the protostar stage;

 

4.        the young star stage


              5.    the mature star stage;

 

6.   the red giant stage;

 

7.   the helium flash stage;

 

8.   the helium star stage;

 

9.   the white dwarf or supernova stage; and

 

10.  the black dwarf, pulsar, neutron star or black hole stage.


          Interstellar matter refers to dust and gases in space from which stars and planets are formed.

 

          The Milky Way is the galaxy to which our solar system belongs together with at least 200 billion other stars and their planets.

 

          There are three types of galaxies, namely, elliptical, spiral and irregular galaxies.

 

          The steady state theory states that the universe is always expanding but maintaining a constant average density.

 

          The big bang theory states that the universe was created by a gigantic explosion.

 

          The following projects contributed to the development of space exploration at present:

 

1.        Apollo Lunar Missions;

 

2.        Near Earth Asteroid Rendezvous (NEAR);

 

3.        Skylab Project;

 

4.        Galileo Project;

 

5.        Mars Polar Lander; and

 

6.        International Space Station.

Binary stars - a system of two stars that share and orbit around the same center of mass and are held together by gravitational attraction.

 

Black hole = a region in space, believed to be formed when a large star has collapsed on itself at the end of its life, with such a strong gravitational pull that not even light waves can escape from it.

 

Dwarf = a kind of star designated by color.

 

Globular cluster = a symmetrical cluster into which many thousands of stars are gathered.

 

Magnitude = the degree of brightness of a star.

 

Neutron star = a star of very small size and very great density which has almost reached the end of its evolutionary life.

 

Nova  = a  normally faint star that suddenly flares into brightness and then fades again.

 

Open cluster = a cluster of several hundred to several thousand relatively young stars that are usually loosely distributed; also known as galactic cluster.

 

Proper motion - the movement of a fixed star in space relative to the sun.

 

Pulsar = a source of electromagnetic radiation emitted in brief regular pulses, mainly at radio frequency, believed to be a rapidly revolving neutron star.

 

Radial velocity = ahe velocity, along the observer’s line of sight, of a star or other body.

 

Supernova = a vast stellar explosion which takes a few days to complete making the star temporarily millions of times brighter than it originally was.

Variable star= a star whose brightness changes over a period of time.

The steady state theory is a view that the universe is always expanding but maintaining a constant average density.

The big bang theory. Gamow proposed that the universe was created in a gigantic explosion and that its various elements observed today were produced within the first few minutes after the big bang, when the extremely high temperature and density of the universe fused subatomic particles into chemical elements.

1.                     Variable stars are those that vary in brightness over certain periods of time.

 

2.                     Binary stars are pairs of stars that share and orbit around the same center of mass and are held together by gravitational attraction.

 

3.                     Novae are stars that suddenly flare into brightness and then normally fade again.

 

4.                     Supernovae are vast stellar explosions which take a few days to complete making the stars temporarily millions of times brighter than they originally were.

 

5.                     Dwarfs are extremely small stars determined by their colors.

 

6.                     Neutron stars are those of very small sizes and very great densities which have already reached the end of their evolutionary lives.

 

7.                     Pulsars are rapidly revolving neutron stars.

 

Black holes are very massive star cores, remnants of supernovae, that can exert such tremendous gravitational forces that not only solid objects but even atoms cannot escape from their surfaces.

The color of a star can be determined based on luminosity and temperature. The hottest star is blue-white.

 

Temperature and color are  two properties of stars that are interrelated

 

Proper motion is the ability of stars to move over long periods of time

 

The composition of a star determine its elements.

 

Stellar distance can be measured in terms of light years.



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