Characteristics of the Universe
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.
Welcome!
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Please complete the pre-assessment
It’s for us—it’s not about you
What are we going to cover?
 Our
Place in the Universe
 Scale and Distance
 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?
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
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

Open Clusters
dozens to thousands of young
stars
 located in the spiral arms of a
galaxy
 example: Pleiades

Globular Clusters
millions to hundreds of millions
of stars, clumped closely
together
 old! 6 to 13 billion years
 surround our disk as a halo

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
 Many different types, sizes, composition

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
Next Up
 Our
Place in the Universe
 Scale and Distance
 The Electromagnetic Spectrum
 Classifying Stars
 Classifying Galaxies
 History of the Universe
Measuring Distances
 What


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




is a Light Year?
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 centimeters 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.
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?

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.
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
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
Next Up
 Our
Place in the Universe
 Scale and Distance
 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
 Now
let’s examine the invisible parts—
using our cell phones and a solar cell.
Radiation
 All


stars emit radiation
Radio, infrared, visible, ultraviolet, x-ray and even some gamma
rays
Most of the sunlight is yellow-green visible light or close to it
The Sun at X-ray wavelengths
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.
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
A Star is Born
Movie at http://www.stsci.edu/EPA/PR/95/44/M16.mpg
Regular/ Small Star
On the “Main Sequence”
Red Giant
White Dwarf
Small, but very hot
Massive
Stars
On the “main Sequence” but
not for long
Betelgeuse—Red Supergiant
Supernova—Massive Star
Explodes
Neutron Star or Pulsar
Image at http://hubblesite.org/newscenter/archive/releases/nebula/supernova-remnant/2002/24/results/50/
Black Hole
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
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
Galaxies
Spiral galaxy--Andromeda
Elliptical Galaxies
group of galaxies
interacting
Interacting
Cluster
Origin of the Universe
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Big Bang
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Dominant scientific theory about the
origin of the universe
Occurred ~13.7 billion years ago
How do we know????
http://www.esa.int/esaCP/ESAKD7G18ZC_FeatureWeek_1.html
Building a Universe
.
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Infinitely dense point
not governed by our
physical laws or time
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All matter and energy
contained in one point
Building a Universe
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The Big Bang
Instantaneous filling
of space with all
matter
Edwin Hubble
http://en.wikipedia.org/wiki/File:Edwin_Hubble_with_pipe.jpg
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Showed that universe is
continuously expanding
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Galaxy’s velocity is proportional
to its distance (galaxies that
are twice as far from us move
twice as fast)
• taken every galaxy the
same amount of time to
move from a common
starting position to its
current position
Hubble’s Evidence
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Doppler shifting - wavelength emitted by
something moving away from us is shifted to a
lower frequency
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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.
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When we observe the redshift of galaxies outside
our local group, every galaxy appears to be
moving away from us - Universe is expanding.
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
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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
Feedback, Questions
Reach us online at http://www.lpi.usra.edu/education/
For more information, contact
Christine Shupla
Lunar and Planetary Institute
3600 Bay Area Blvd
Houston, TX 77058
(281) 486-2135
shupla@lpi.usra.edu