Transcript The Sun and Other Stars - Tuslaw Local School District

The Sun and Other Stars
Our Star the Sun
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Center of the Solar System
Our only source of - light, heat, energy
An average star in size, mass, density, temperature
Diameter = 864,000 mi.
Volume = 1.3 million x earth’s
Mass = 332,000 x earth’s *sun contains 99.86% of
the mass of the Solar System
The explosion of a 10 megaton bomb converts 1 lb.
of matter into energy. The sun converts about 5
million tons of matter into energy each second.
2 Theories of Solar Heat Production
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Fusion - a thermonuclear reaction
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H + H = He + energy
2. Gravitational collapse - the sun is shrinking
Other Stars
• Electromagnetic spectrum - energy travels through
space in the form of waves at a speed of 186,000mps
• Wavelength - the distance from the crest of a wave to
the crest of the next wave
• Visible light has a wavelength < 1/1,000,000 m
Telescopes
• Optical - collects visible light
1. refracting - uses convex lenses to collect and
focus light
2. Reflecting - uses a mirror to collect light
*the bigger the diameter the more light gathering capability
• Radio telescopes - used to detect radio waves rather
than visible light
Satellites - orbit the earth above the atmosphere
Spectrographs - breaks light into color; collects info about
stars - chemical composition and temperature
Classifying Stars
• Stars are classified according to size, temperature,
brightness
• Size - range from < 8000 mi. in diameter to > 2300
x’s the diameter of the sun
• Color
blue - white = hottest, yellow = average
red = coldest
brightness
• Apparent brightness - as seen from earth
• Absolute magnitude - the brightness a star would have if
it were a standard distance from earth
Hertzsprung - Russell Diagram ( HR Diagram )
• Shows the relationship between surface temperature
and brightness
The Theory of Stellar Evolution
• Birth - a star is born out of a nebula - a large cloud of
interstellar gas and dust
The cloud condenses, due to gravity, and produces a
protostar ( the earliest stage in a star’s life) and
becomes hot enough for fusion to start
Life of a star
• How long a star lives depends on its mass
*small mass stars use up their fuel more slowly
than large mass stars, so they have much longer
lives
• Medium mass stars like the sun live about 10 by
• Small mass stars may live 200 by
• A large mass star 15 x’s as massive as the sun may
live only about 10 my
Death of a star
• When a star begins to run out of fuel
* center of the star shrinks
* outer part expands
• All main sequence stars eventually become red
giants or supergiants
• What happens next depends on the mass of the star
* small & medium mass stars produce a white dwarf
White dwarfs are about the size of the earth but have
the mass of the sun!
• A dying giant or supergiant can suddenly explode
creating a supernova
• The material expands into space creating a nebula
• The material left behind forms a neutron star which
are smaller and denser than white dwarfs
( 3 x’s mass of the sun, 20 km in diameter )
• Black holes - stars that are > 40 x’s the mass of the
sun become black holes when they die
* 5 x’s the mass of the sun, 30 km in diameter
* the gravity is so strong nothing can escape including
light!
Pulsar - a neutron star that produces radio waves
Quasar - a distant galaxy with a black hole at its
center
Distances to Stars
• Light year - the distance light travels in 1 year
- light travels at a speed of 186,000 mps
(300,000km/s)
- light travels about 6 trillion miles in 1 year
- ( 9.5 million million kilometers)
Parallax - the apparent motion of an object when viewed
from 2 different points in space; can only
measure distances to nearby stars
Star Systems
• More than half of all stars are members of groups of
2 or more stars called star systems
• Binary stars - star systems w/ 2 stars
• Triple stars - 3 stars
Galaxies ( “Island Universe”)
• Contain single, double, triple stars, star systems, lots
of gas and dust between stars
• Milky Way - the name of our galaxy
• Classified into 3 main categories
spiral
elliptical
irregular
Big Bang - theory of the universe formation 10 to 15 bya
Red shift - evidence of an expanding universe