Transcript No Slide Title - Indiana State University

Insert:
Beyond our Solar
System
Deployment of the Hubble Space
Telescope in Earth orbit, April 24, 1990
The 300-meter
radio telescope
at Arecibo,
Puerto Rico
Hertzsprung-Russell diagram
Shows the relation between stellar
Brightness (absolute magnitude) and
Temperature
Diagram is made by plotting (graphing)
each star's
Luminosity (brightness) and
Temperature
Hertzsprung-Russell diagram
Parts of an H-R diagram
Main-sequence stars
• 90% of all stars
• Band through the center of the H-R diagram
• Sun is in the main-sequence
Giants (or red giants)
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•
•
•
Very luminous
Large
Very large giants are called supergiants
Only a few percent of all stars
Hertzsprung-Russell diagram
Parts of an H-R diagram
White dwarfs
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•
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•
Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars
Hertzsprung-Russell diagram
The Orion Nebula is a well-known
emission nebula
A faint blue
reflection
nebula in the
Pleiades star
cluster
Stellar evolution
Two opposing forces in a star are
Gravity – contracts
Thermal nuclear energy – expands
Stages
Birth
Main-sequence stage
• 90% of a star's life is in the main-sequence
Red giant stage
Burnout and death
• white dwarf, neutron star, or a black hole
Evolutionary stages
Stellar evolution
Stellar remnants
White dwarf
Small and Dense
• Spoonful weighs several tons
Neutron star
Gravitational force collapses atoms
• Electrons combine with protons to produce neutrons
• Pea size sample weighs 100 million tons
• First one discovered in early 1970s Crab nebula
(remnant of an A.D. 1054 supernova)
Crab Nebula in the constellation Taurus
Stellar remnants
Black hole
More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
• Becomes very hot
• Emits x-rays
Likely candidate is Cygnus X-1, a strong x-ray
source
Binary Pair with a Red Giant and a Black Hole
Galaxies
Other galaxies
Existence was first proposed in mid-1700s by
Immanuel Kant
Four basic types of galaxies
• Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• e.g., Milky Way
Face-on view of the Milk Way Galaxy
Edge-on view of the Milk Way Galaxy
Great Galaxy, a spiral galaxy, in
the constellation Andromeda
Galaxies
Other galaxies
Four basic types of galaxies
• Barred spiral galaxy
• Elliptical galaxy
• Irregular galaxy
The study of light
Doppler effect
The apparent change in wavelength of radiation
caused by the relative motions of the source and
observer
Used to determine
• Direction of motion
• Increasing distance – wavelength is longer
("stretches")
• Decreasing distance – makes wavelength shorter
("compresses")
The Doppler effect
Red shifts
Doppler effect
Change in the wavelength of light emitted by an
object due to its motion
• Movement away stretches the wavelength
• Light appears redder
• Movement toward “squeezes” the wavelength
• Light shifted toward the blue
Expanding universe
Most galaxies exhibit a red Doppler shift
Raisin bread analogy of an
expanding universe
Big Bang theory
Accounts for galaxies moving away from us
Universe was once confined to a "ball" that
was
Supermassive
Dense
Hot
Big Bang theory
Big Bang marks the inception of the
universe
Occurred about 15 billion years ago
All matter and space was created
Matter is moving outward
Fate of the universe
Two possibilities
• Universe will last forever
• Outward expansion sill stop and gravitational;
contraction will follow
Big Bang theory
Fate of the universe
Final fate depends on the average density of the
universe
• If the density is more than the critical density, then
the universe would contract
• Current estimates point to less then the critical
density and predict an ever-expanding, or open,
universe
End of Chapter 16