This module tells us that:
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Stars can differ in
terms of magnitude, color and temperature, composition, proper motion, radial
velocity, size and stellar distance.
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Stars can be
classified as variable stars, binary stars, novae, supernovae, dwarfs, neutron
stars, pulsars and black holes.
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There are two kinds of
star clusters, namely, globular clusters and open or galactic clusters.
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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.
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Interstellar matter refers to dust and
gases in space from which stars and planets are formed.
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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.
