Stars and Galaxies
Created by the
Lunar and Planetary Institute
For Educational Use Only
LPI is not responsible for the ways
in which this powerpoint may be used or altered.
Space Science for Middle School at HCDE
February 20, 2009
Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2009/07/image/g/results/50/
Welcome!
Please complete the pre-assessment
It’s for us—it’s not about you
Please let us know how much YOU know,
not how much your friends sitting next to
you know
What are we going to cover?
Our Place in the Universe
The Electromagnetic Spectrum
Classifying Stars
Classifying Galaxies
History of the Universe
First up…
Our Place in the Universe
What is our Universe made of?
How big are things? How far away?
How do we know?
What is our Universe made of?
What was in your drawing?
 Stars and planets
 Gas and dust
 Organized into star clusters
 Organized into nebulae
 Organized into galaxies
 Other things:
 Black holes
 Dark matter
 Dark energy
Image from
http://galileo.rice.edu/lib/student_work/astronomy95/orionpleiades.html
Activity!!
Use the Venn diagrams to place the
stickers—where does everything go?
After you’re finished, let’s discuss…
Examining the Components
Stars
Gas and dust (Nebulae)
Star clusters
Galaxies
Different
types of
stars
Image from
http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/2003/21/image/a/results/50/
Types of Stars
Big
Small
Red
Blue
Yellow
In groups
Alone
More later
What is a “star cluster”?
stars formed together at
same time
stars may be
gravitationally bound
together
two types: open
(galactic) and globular
Image at
http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/2007/18/image/a/format/web/results/50/
Open Clusters
dozens to thousands of stars
young stars! only a few
million years old
may still be surrounded by
nebula from which they formed
located in the spiral arms of a
galaxy
example: Pleiades
Image at http://hubblesite.org/newscenter/archive/releases/star%20cluster/open/2004/20/image/a/results/50/
More open star clusters
Image from http://hubblesite.org/newscenter/archive/releases/star%20cluster/open/2006/17/image/a/results/50/
Globular Clusters
 millions to hundreds of millions of
stars
 old! 6 to 13 billion years
 mostly red giants and dwarfs
 stars are clumped closely together,
especially near the center of the
cluster (densely)
 surround our disk as a halo
Image at
http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/1999/26/image/a/results/50/
What is a “nebula”?
A cloud in space
Made of gas and dust
 Can have stars inside
Most of the ones we see are inside our Milky
Way Galaxy
Different types
Orion image at http://hubblesite.org/newscenter/archive/releases/2006/01/image/a/results/50/
Large, massive, bright nebulae
Emission Nebula
•The hot gas is emitting light
Orion image at http://hubblesite.org/newscenter/archive/releases/2006/01/image/a/results/50/
Colder, darker nebulae
Dark dust blocking the hot
gas behind it
NOAO/AURA/NSF Image from
http://hubblesite.org/newscenter/archive/releases/nebula/dark/2001/12/image/c/results/50/
Leftovers from an Explosion
Supernova remnant
(smaller, less gas)
Image at http://hubblesite.org/newscenter/archive/releases/nebula/supernova-remnant/2005/37/results/50/
What is a “galaxy”?
A large group of stars outside of our own Milky Way
Made of billions to trillions of stars
Also may have gas and dust
Spiral, or elliptical, or irregular shaped
Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2007/41/results/50/
Spiral galaxy--Andromeda
NOAO/AURA/NSF Images at http://www.noao.edu/image_gallery/html/im0606.html and
http://www.noao.edu/image_gallery/html/im0685.html
Elliptical Galaxies
Images at http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/2007/08/image/a/format/large_web/results/50/
and http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/1995/07/results/50/
Irregular Galaxies
NASA and NOAO/AURA/NSF Images at
http://hubblesite.org/newscenter/archive/releases/galaxy/irregular/2005/09/results/50/ ,
http://www.noao.edu/image_gallery/html/im0560.html , and http://www.noao.edu/image_gallery/html/im0993.html
Our Galaxy: the Milky Way
has about 200 billion stars, and lots of gas
and dust
is a barred-spiral (we think)
about 100,000 light-years wide
our Sun is halfway to the edge, revolving at
half a million miles per hour around the
center of the Galaxy
takes our Solar System about 200 million
years to revolve once around our galaxy
The Milky Way
Image at http://news.nationalgeographic.com/news/bigphotos/1945371.html
Mapping the Milky Way
How do we know what our Galaxy
looks like?
We can see stars
 star clusters
 nebulae
 Galaxies
 Let’s try to Map our Galaxy
Measuring Distances
Parallax (let’s model it)
 As Earth orbits the Sun, we see nearby stars move relative to more distant stars
 How many degrees did the plate move, relative to the background?
 Can you calculate the distance to the plate?
 Sine of the parallax (angle) x Earth’s distance to the Sun = Distance to the star
 The angles involved for strellar observations are very small and difficult to
measure. Proxima Centauri, has a parallax of 0.77 arcsec. This angle is
approximately the angle subtended by an object about 2 centimeters in diameter
located about 5.3 kilometers away.
Measuring Distances
What is a Light Year?
 A light year is the distance light travels in a year. Light moves at a
velocity of about 300,000 kilometers (km) each second; how far
would it move in a year?
 About 10 trillion km (or about 6 trillion miles).
Why do we use light years?
 Show me how far 5 centimeters is.
 Now show me 50 centimeters.
 Now tell me (without thinking about it, or calculating it in meters) how far
500 centemeters is. 2000? 20,000?
 We need numbers that make sense to us in relationship to objects; we scale
up and use meters and kilometers for large numbers.
Time for a Break! Next Up
Our Place in the Universe
The Electromagnetic Spectrum
Classifying Stars
Classifying Galaxies
History of the Universe
Let’s check your knowledge
Please draw an electromagnetic spectrum
on a sheet of paper, and label the parts.
You can work in groups.
Radiation
There are lots of types of light (radiation),
including visible and invisible
Electromagnetic spectrum
http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/what_is_ir.html
.
Let’s Observe A Spectrum
What will the spectrum look like with a red
filter in front of your eyes? A blue filter?
Hypothesize and test your hypothesis.
Now let’s examine the invisible parts—
using our cell phones and a solar cell.
There are different types of spectra
Continuous
Emission or Bright Line (from ionized gas, like
a nebula or a neon sign)
Absorption or dark line (from stars)
Illustration at http://imagine.gsfc.nasa.gov/docs/science/how_l1/spectra.html
Radiation
All stars emit radiation
 Radio, infrared, visible, ultraviolet, x-ray and even some gamma
rays
 Most sunlight is yellow-green visible light or close to it
The Sun at X-ray wavelengths
Image at
http://imagine.gsfc.nasa.gov/docs/sc
ience/know_l1/sun.html
Image and info at
http://imagine.gsfc.nasa.gov/docs/teachers/gammaraybursts/imagine/page18.html
Using a Star’s Spectrum
We can use a star’s spectrum to classify it.
NOAO/AURA/NSF image at http://antwrp.gsfc.nasa.gov/apod/ap010530.html
Stellar Evolution
Time to Create a Stellar Graph
Everyone will receive several “stars”
Place them on the large paper, according to
their color and their brightness
This is a version of the Hertzsprung-Russell
diagram.
Hertzsprung-Russell Diagram
Images from
http://www.nasa.gov/centers/goddard/news/topstory/2007/spectrum_plants.html and
http://sunearthday.gsfc.nasa.gov/2009/TTT/65_surfacetemp.php
Young
stars
form in
nebulae
from Small
Magellanic
Cloud
Image at
http://hubblesite.org/newscenter/archive/releases/2007/04/image/a/results/50/
Star-forming region in the Large Magellanic Cloud:
http://hubblesite.org/newscenter/archive/releases/2008/31/image/a/results/50/
Orion image at http://hubblesite.org/newscenter/archive/releases/2006/01/image/a/results/50/
Interstellar “eggs”
Movie at http://www.stsci.edu/EPA/PR/95/44/M16.mpg
Our Sun is a Regular/ Small Star
On the “Main Sequence”
Image at http://www.gsfc.nasa.gov/topstory/20011210insidesun.html
In a few Billion years… Red
Giant
Image at http://hubblesite.org/newscenter/archive/releases/1997/26/image/a/
Our Sun’s Habitable Zone
Billions of years ago, things may have
been different
 The Sun was cooler (by up to 30%!)
 Earth’s atmosphere was different (thicker,
carbon dioxide)
 Conditions will be different in the
future
 By many accounts, increases in the Sun’s
temperature will make Earth uninhabitable
in 1 billion years or less
 These changes will also affect other
planets… Mars?
Animation at
http://www.nasa.
gov/97994main
_BHabitableZon
e.MPG
By 5 billion years… White
Dwarf
Small, but very hot
Image at http://hubblesite.org/newscenter/archive/releases/nebula/planetary/1998/39/results/50/
Image at
http://hubblesite.org/newscenter/archive/releases/nebula/planetary/2000/28/image/a/format/web_print/results/50/
Image at http://hubblesite.org/newscenter/archive/releases/nebula/planetary/2004/27/image/a/format/large_web/results/50/
Massive
Stars are
different
On the “Main
Sequence” but
not for long
Image from
http://hubblesite.org/newscenter/archive/releases/nebula/emission/1997/33/results/50/
Betelgeuse—Red Supergiant
Image from http://hubblesite.org/newscenter/archive/releases/star/massive%20star/1996/04/image/a/results/50/
Supernova—Massive Star
Explodes
Images at
http://hubblesite.org/newscenter/archive/releases/star/supernova/2004/09/results/50/
http://hubblesite.org/newscenter/archive/releases/nebula/supernova-remnant/2005/37/results/50/
http://chandra.harvard.edu/photo/2009/casa/
Neutron Star or Pulsar
Image at http://hubblesite.org/newscenter/archive/releases/nebula/supernova-remnant/2002/24/results/50/
Black Hole
Image at http://hubblesite.org/newscenter/archive/releases/2002/30/image/a/results/50/
Classifying Galaxies
Galaxies
come in different sizes (dwarf, large, giant)
come in different shapes and classifications
Spirals
Ellipticals
Lenticulars
Irregulars
are fairly close together, relative to their
sizes
Spiral Galaxies
have flat disk, spiral arms, central bulge, and a
surrounding halo
some have a “barred” bulge
are fairly large (no dwarf spirals)
have lots of gas and dust and younger stars in their
arms, but older stars and little gas or dust in their
halos and central bulges
Galaxies
Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2005/01/results/50/
Spiral galaxy--Andromeda
NOAO/AURA/NSF Images at http://www.noao.edu/image_gallery/html/im0606.html and
http://www.noao.edu/image_gallery/html/im0685.html
Spiral
Galaxy
on
Edge
Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2006/24/image/a/results/50/
Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2007/41/results/50/
Elliptical galaxies
range from spherical to football shaped
range from very small to giant
have very little gas or dust
mostly old stars
similar to the central bulge of a spiral galaxy
Elliptical Galaxies
Images at http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/2007/08/image/a/format/large_web/results/50/
and http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/1995/07/results/50/
Lenticular
have a disk but no arms
have little or no excess gas and dust
Image at http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/2002/07/results/50/
Irregular Galaxies
any galaxy that isn’t a Spiral, Elliptical, or
Lenticular
usually have lots of gas and dust and young
stars
may have a distorted shape from interaction
with another galaxy
Irregular Galaxies
NASA and NOAO/AURA/NSF Images at
http://hubblesite.org/newscenter/archive/releases/galaxy/irregular/2005/09/results/50/ ,
http://www.noao.edu/image_gallery/html/im0560.html , and http://www.noao.edu/image_gallery/html/im0993.html
Collisions!
We now think that galaxies in groups and
clusters often collide
The Milky Way is moving at 300,000 mph
toward the Andromeda Galaxy
They may collide in about 5 billion years
Stars don’t usually collide
New orbits, gas piles up to form new stars
Interacting
Image from http://hubblesite.org/newscenter/archive/releases/galaxy/interacting/2000/34/results/50/
the Antennae or Mice
Information at http://hubblesite.org/newscenter/archive/releases/galaxy/interacting/1997/34/results/50/
The occasional results of two
galaxies colliding: ringed
galaxies
Images from http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2002/21/image/a/results/50/ and
http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/1999/16/image/a/results/50/
Various galaxies
(can you identify types?)
Image at
http://hubblesite.org/newscenter/archive/releases/galaxy/cluster/1999/31/results/50/
Supermassive black holes
almost every medium to large galaxy we’ve check
has a supermassive black hole at the center
the larger the galaxy, the more massive the black
hole
we don’t know which comes first, the galaxy or
the black hole
we think that these black holes are responsible for
some of the galaxies with jets and lobes which
give off radio waves, x-rays, etc.
Active
galaxy
Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2000/37/results/50/
at the center of a large galaxy
Image at http://hubblesite.org/newscenter/archive/releases/exotic/black-hole/1998/22/results/20/ and
http://hubblesite.org/newscenter/archive/releases/exotic/black%20hole/2000/21/image/a/format/web_print/results/20/
Galaxy Clusters
the Local Group
includes the Milky Way, the Andromeda, and over
30 other smaller galaxies
the Virgo Cluster
hundreds to thousands of galaxies, 60 million lightyears away
giant elliptical at center, formed by galactic
cannibalism
the Local Group is “falling” toward the Virgo
Cluster at 60 to 250 miles per second!
Coma Cluster
Image at http://hubblesite.org/newscenter/archive/releases/galaxy/cluster/2008/24/image/a/results/20/
Superclusters!
clusters are bound together in larger structures, called
superclusters
these superclusters have been mapped, and are grouped
into long strings
300 million to a billion light-years long
100 to 300 million light-years wide
and only 10 to 30 million light-years thick
in between these strings are huge voids of galaxies,
although some astronomers may have detected hot gas
Evolution of Galaxies
Image at http://www.galex.caltech.edu/media/glx2007-05f_img01.html
Origin of the Universe
Big Bang
Dominant scientific theory about the
origin of the universe
Occurred ~13.7 billion years ago
What is the Big Bang?
How do we know?
What is the Big Bang?
Infinitely dense point
not governed by our
physical laws or time
All matter and energy
contained in one point
Image from http://www.newscientist.com/articleimages/dn11799/0-didantimatter-factory-spark-brightest-supernova.html
Building a Universe
Instantaneous filling of
space with all matter
History of the
Universe
•10-43 seconds - gravity separates from other forces
•10-35 to 10-32 seconds - fundamental particles - quarks and electrons
•10-6 seconds - quarks combine into protons and neutrons
•1 second - electromagnetic and weak nuclear forces separate
•3 minutes - protons and neutrons combine into atomic nuclei
•105 years - electrons join nuclei to make atoms; light is emitted
•105-109 years - matter collapses into clouds, making galaxies and stars
Orion Nebula - http://stardate.utexas.edu/resources/ssguide/planet_form.html
History of the Universe
Image from http://dsc.discovery.com/space/top-10/strange-universe/space-10-weirdest-things-universe-10.html
Later History
Image at http://www.galex.caltech.edu/media/glx2004-01r_img02.html
Big Bang Theory
 In 1915, Albert Einstein concluded that the
universe could not be static based on his
recently-discovered theory of relativity and
added a "cosmological constant" to the
theory of relativity because astronomers
assured him that the universe was static
 Aleksandr Friedmann and Abbe George
LeMaitre are credited with developing the
basics of the Big Bang model between 1922
and 1927; their calculations suggested that
universe is expanding, not static.
 Years later, Einstein called his cosmological
constant the biggest mistake of his career
Image at http://map.gsfc.nasa.gov/universe/bb_theory.html
Expanding Universe
 In 1929, Edwin Hubble showed that most
galaxies are red-shifted (moving away
from us), and that a galaxy’s velocity is
proportional to its distance (galaxies that
are twice as far from us move twice as
fast)
Image from http://imagine.gsfc.nasa.gov/docs/science/mysteries_l1/origin_destiny.html
Hubble’s Evidence
 Doppler shifting - wavelength emitted by something moving away
from us is shifted to a lower frequency
 Sound of a fire truck siren - pitch of the siren is higher as the fire
truck moves towards you, and lower as it moves away from you
 Visible wavelengths emitted by objects moving away from us are
shifted towards the red part of the visible spectrum
 The faster they move away from us, the more they are redshifted.
Thus, redshift is a reasonable way to measure the speed of an
object.
 When we observe the redshift of galaxies, almost every galaxy
appears to be moving away from us – the Universe is expanding.
Predictions for the Big Bang
Model
The expansion of the Universe
 Edwin Hubble's 1929 observation that galaxies were generally
receding from us provided the first clue that the Big Bang theory
might be right.
The abundance of the light elements H, He, Li
 The Big Bang theory predicts that these light elements should have
been fused from protons and neutrons in the first few minutes after
the Big Bang.
The cosmic microwave background (CMB) radiation
 The early universe should have been very hot. The cosmic
microwave background radiation is the remnant heat leftover from
the Big Bang.
Evidence for Big Bang
 Red shift - as light from distant galaxies approach earth there is an
increase of space between earth and the galaxy, which leads to
wavelengths being stretched
 In 1964, Arno Penzias and Robert Wilson, discovered a noise of
extraterrestrial origin that came from all directions at once radiation left over from the Big Bang
 In June 1995, scientists detected helium in the far reaches of the
universe - consistent with an important aspect of the Big Bang
theory that a mixture of hydrogen (75%) and helium (25%) was
created at the beginning of the universe
When Did the Universe Form?
Cosmic background radiation
temperature on celestial sphere
 ~13.7 billion years ago
 How do we know?
Spreading (Red Shift) know distances, rates of
retreat, relative positions
Pervasive background
radiation of 2.7°C above
absolute zero - afterglow
of the Big Bang
http://timeline.aps.org/APS/resources/85_06a.jpg
Feedback, Questions
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Lunar and Planetary Institute
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shupla@lpi.usra.edu