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(OTHER FACTS (When you look at stars you are literally look back in time.,…
CLASSIFICATION
HERTZSPRUNG - RUSSELL DIAGRAM
SPECTRAL CLASSES
O (e.g. 10 Lacertra)
Singly ionized helium lines (H I) either in emission or absorption. Strong UV continuum.
Blue in color
Approximate surface temperature is over 25, 000 K
Average mass (The Sun=1) is 60
Average radius (The Sun=1) is 15
Average luminosity (The Sun=1) is 1, 400, 000
G (e.g. The Sun)
Absorption lines of neutral metallic atoms and ions (e.g. once-ionized calcium).
White to Yellow in color
Approximate surface temperature is 5, 000 - 6, 000 K
Average mass (The Sun=1) is 1.1
Average radius (The Sun=1) is 1.1
Average luminosity (The Sun=1) is 1.2
B (e.g. Rigel)
Neutral helium lines (H II) in absorption.
Blue in color
Approximate surface temperature is 11, 000 - 25, 000 K
Average mass (The Sun=1) is 18
Average radius (The Sun=1) is 7
Average luminosity (The Sun=1) is 20, 000
K (e.g. Aldebaran)
Metallic lines, some blue continuum.
Orange to Red in color
Approximate surface temperature is 3, 500 - 5, 000 K
Average mass (The Sun=1) is 0.8
Average radius (The Sun=1) is 0.9
Average luminosity (The Sun=1) is 0.4
A (e.g. Sirius)
Hydrogen (H) lines strongest for A0 stars, decreasing for other A's.
Blue in color
Approximate surface temperature is 7, 500 - 11, 000 K
Average mass (The Sun=1) is 3.2
Average radius (The Sun=1) is 2.5
Average luminosity (The Sun=1) is 80
M (e.g. Betelgeuse)
Some molecular bands of titanium oxide.
Red in color
Approximate surface temperature is under 3, 500 K
Average mass (The Sun=1) is 0.3
Average radius (The Sun=1) is 0.4
Average luminosity (The Sun=1) is 0.04 (very faint)
F (e.g. Procyon)
Ca II absorption. Metallic lines become noticeable.
Blue to White in color
Approximate surface temperature is 6, 000 - 7, 500 K
Average mass (The Sun=1) is 1.7
Average radius (The Sun=1) is 1.3
Average luminosity (The Sun=1) is 6
DEFINITION
A star is a luminous ball of gas, mostly hydrogen and helium, held together by its own gravity.
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A star is a huge sphere of very hot, glowing gas. Stars produce their own light and energy by a process called nuclear fusion.
Stars are enormous spheres of ignited gas that light the cosmos, and seed it with the materials for rocky worlds and living beings.
TYPES
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GIANT STARS
Blue Giant Star
Blue giants blaze with a surface
temperature of 20,000 Kelvin or more
that can reach up to -5 to -6 absolute magnitude.
It has a life span of only 10,000 - 100, 000 years.
Red Giant Star
Reg giant star is super cold and has a surface temperature under 6,500 Kelvin. It reaches a sizes of 100 million to 1 billion kilometers in diameter, 100 to 1,000 times the size of the sun. It lasts only for a few thousand to 1 billion years.
SUPER GIANT STARS
Red Supergiant Star
Red super giant star has a radius between 200 and 800 times the radius of the Sun. It is known as the largest star. It is cold and has a surface temperature of 3,500 - 4,500 Kelvin.
Blue Supergiant Star
Blue super giant star blaze with surface temperatures of 20,000 – 50,000 Kelvin. It has a life span of up to few hundred million years only.
OTHER TYPES
Neutron Star
Young neutron stars before they cool
can also produce pulses of X-rays
when some parts are hotter than others.
neutron stars have jets of materials
streaming out of them at nearly the speed
of light X-ray pulsars capture the
material flowing from more massive companions.
Binary Star
A binary star is a system of two
stars that rotate around a common
center of mass
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Eclipsing Binary
An eclipsing binary is two close
stars that appear to be a single
star varying in brightness.
X-ray Binary
X-ray binary stars are a special type of binary star in which one of the stars is a collapsed object such as a white dwarf, neutron star, or black hole.
Variable Star
Stars that Vary in Luminosity
Cepheid Variable Stars
Cepheid variables are stars that regularly
pulsate in size and change in brightness.
As the star increases in size,
its brightness decreases;
then, the reverse occurs.
Mira Variable Stars
A Mira variable star
is a variable star whose
brightness and size cycle
over a very long
time period,
in the order
of many months.
Black Hole A black hole is a region of space
where matter has collapsed on itself.
At its center, matter is squeezed
into tiny , incredibly dense point.
Supermassive black hole :green_cross:Supermassive black holes lie
at the center of most galaxies,
including our own.
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OTHER FACTS
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The bigger the star, the shorter is its life.
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Proxima Centauri is the closest star to Earth, 4.2 light-years away
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