Transcript Stars and Galaxies

Stars and Galaxies
Created by the
Lunar and Planetary Institute
For Educational Use Only
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/