Part 2: Formation of the Universe STARS AND GALAXIES 1
Slide 3
What is the current theory of how the universe was formed that
is accepted by most scientists? What evidence is there to support
this theory? 2
Slide 4
Every object in the universe is moving, from electrons to
galaxies. Scientists can calculate how fast galaxies are moving
away from us or toward us using spectrographic measurements.
Remember a spectroscope separates visible light into the colors
that make it up STARS ON THE MOVE Spectrograph of a Star 3
Slide 5
THE DOPPLER EFFECT The change in frequency of a wave for an
observer moving relative to its source For sounds, this change in
frequency is heard as a change in pitch. Approaching = wavelength
shorter Moving away = wavelength longer 4
Slide 6
An effect similar to the Doppler effect is seen in light from
stars in other galaxies. For almost all galaxies the shift is
toward longer wavelengths, meaning the galaxies must be moving away
from Earth. For visible light, red has the longest wavelengths, so
the shift is toward the red end of the spectrum and is therefore
called the red shift. RED SHIFT AND BLUE SHIFT 5
Slide 7
For a very few galaxies the shift is toward shorter
wavelengths, meaning the star or galaxy must be moving toward
Earth. For visible light, blue has short wavelengths, so the shift
is toward the blue end of the spectrum and is therefore called the
blue shift. The galaxy Andromeda exhibits a blue shift. RED SHIFT
AND BLUE SHIFT 6
Slide 8
Most galaxies are moving away from us. In addition, scientists
have found that the further a galaxy is from us, the faster it is
moving away from us. Conclusion: The Universe is expanding.
Analogy: Raisons in rising bread dough. This knowledge that the
universe is expanding has led to the development of the Big Bang
Theory. WHAT DOES RED SHIFT TELL US? 7
Slide 9
THE BIG BANG THEORY The Big Bang Theory is a theory for the
origin and evolution of our universe. Remember: a theory is a
logical explanation of events observed in nature. The Big Bang
Theory says that 12 to 14 billion years ago*, the universe existed
in a hot, dense, place that was only a few millimeters across and
that it exploded and has since expanded, and continues to expand,
into the vast and much cooler cosmos of today. *Most recent
estimates by NASA put the age of the universe at about 13.7 0.13
billion years! http://map.gsfc.nasa.gov/universe/uni_age.html
http://map.gsfc.nasa.gov/universe/uni_age.html 8
Slide 10
THE BIG BANG THEORY The Big Bang Theory is a theory for the
origin and evolution of our universe. Remnants of this hot dense
matter can be measured as the now very cold cosmic microwave
background radiation which still pervades the universe and is
visible to microwave detectors as a uniform glow across the entire
sky. *Most recent estimates by NASA put the age of the universe at
about 13.7 0.13 billion years!
http://map.gsfc.nasa.gov/universe/uni_age.html
http://map.gsfc.nasa.gov/universe/uni_age.html 9
Slide 11
Gravity is the force of attraction between objects. The more
mass something has the great the force of gravity it exerts. After
the Big Bang, the force of gravity began to pull matter together
into clumps that would then become the stars, planets, and
galaxies. Gravity is also why Andromeda is moving toward the Milky
Way rather than away. THE ROLE OF GRAVITY 10
Slide 12
SO WHAT DO SCIENTISTS THINK WILL BE THE FUTURE OF THE UNIVERSE?
In the universe, the momentum of expansion and the force of gravity
oppose one another leading to two possibilities: Expansion wins and
the universe keeps expanding forever and slowly cools (Open or Flat
Universe); sometimes called the Big Chill or Big Freeze Gravity
wins and collapses the universe (Closed Universe) referred to as
the Big Crunch this could then lead to another Big Bang 11
Slide 13
An enormously bright object at the edge of our universe (12
billion light years away) which emits massive amounts of energy. In
an optical telescope, they appear point-like, similar to stars.
QUASAR 12 The X-ray image of the quasar PKS 1127-145, about 10
billion light years from Earth, shows an enormous X-ray jet that
extends at least a million light years from the quasar. Picture
from the CHANDRA X-ray Observatory
Slide 14
First detected by looking at point sources of radio waves. Thus
Quasar = quasi-stellar radio source Current theories hold that
quasars are one type of active galaxy nucleus(AGN.) QUASAR 13 The
X-ray image of the quasar PKS 1127-145, about 10 billion light
years from Earth, shows an enormous X-ray jet that extends at least
a million light years from the quasar. Picture from the CHANDRA
X-ray Observatory
Slide 15
Active Galaxy Nuclei (AGN): The centers of a class of galaxies
which spew massive amounts of energy from their centers, far more
than ordinary galaxies. Many astronomers believe supermassive black
holes may lie at the center of these galaxies and power their
explosive energy output. Include quasars, blazars, and Seyferts.
ACTIVE GALAXIES 14