Stars and Galaxies - PowerPoint - PowerPoint by 4HA1WqpQ

VIEWS: 16 PAGES: 55

									  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!

•   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
   Whatis 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
 Ingroups
 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      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 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

 Thereare 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
 •   Big Bang
     •   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

                 •    Infinitely dense point
                      not governed by our
                      physical laws or time

        .        •    All matter and energy
                      contained in one point
Building a Universe

                      •   Instantaneous filling
                          of space with all
                          matter
    The Big Bang
    Edwin Hubble
                                                               •   Showed that universe is
                                                                   continuously expanding

                                                               •   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
http://en.wikipedia.org/wiki/File:Edwin_Hubble_with_pipe.jpg           move from a common
                                                                       starting position to its
                                                                       current position
Hubble’s Evidence

 •   Doppler shifting - wavelength emitted by
     something moving away from us is shifted to a
     lower frequency
 •   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.
 •   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

    •    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

								
To top