When Giovanni Riccioli used a telescope like this one to observe a star in the handle of the Big Dipper, he discovered two stars that orbit each other. - PowerPoint PPT Presentation

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When Giovanni Riccioli used a telescope like this one to observe a star in the handle of the Big Dipper, he discovered two stars that orbit each other.

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When Giovanni Riccioli used a telescope like this one to observe a star in the handle of the Big Dipper, he discovered two stars that orbit each other. – PowerPoint PPT presentation

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Title: When Giovanni Riccioli used a telescope like this one to observe a star in the handle of the Big Dipper, he discovered two stars that orbit each other.


1
  • When Giovanni Riccioli used a telescope like this
    one to observe a star in the handle of the Big
    Dipper, he discovered two stars that orbit each
    other.

Red Sea
2
  • A group of stars that appear to form a pattern as
    seen from Earth is called a constellation.
  • The stars in a constellation are generally not
    close to one another. They just happen to lie in
    the same general direction of the sky as seen
    from Earth.

3
Star Systems
4
Star Systems
  • Most stars occur in groups of two or more.
  • A star system is a group of two or more stars
    that are held together by gravity.
  • A star system with two stars is called a binary
    star. The two stars orbit each other.

5
Star Systems
  • Sometimes the smaller star in a binary star is
    too dim to be seen easily from Earth but can
    still be detected from the motion of the other
    star.
  • If one star passes in front of the other,
    blocking some of the light from reaching Earth,
    the star system is called an eclipsing binary.
  • The brightness of an eclipsing binary varies over
    time in a regular pattern.

6
Star Clusters
7
Star Clusters
  • Studying star clusters is useful because all the
    stars formed together in the same nebula, so they
    are about the same age and the same distance from
    Earth.
  • Astronomers plot the stars of a cluster on an H-R
    diagram to estimate the clusters age.

8
Star Clusters
  1. The Pleiades are an open star cluster that is
    visible to the unaided eye.

9
Star Clusters
  1. The Pleiades are an open star cluster that is
    visible to the unaided eye.
  2. 47 Tucanae is a spectacular globular cluster that
    is visible in southern skies.

10
Star Clusters
  • An open cluster has a disorganized or loose
    appearance and contains no more than a few
    thousand stars that are well spread out.
  • Open clusters often contain bright supergiants
    and gas and dust clouds.
  • Associations are temporary groupings of bright,
    young stars. In time, gravity from nearby stars
    breaks these groups apart.
  • Associations are typically larger than open
    clusters.

11
Star Clusters
  • A globular cluster is a large group of older
    stars.
  • Globular clusters usually lack sufficient amounts
    of gas and dust to form new stars. They are
    spherical and have a dense concentration of stars
    in the center.

12
Star Clusters
  • Globular clusters can contain more than a million
    stars. Globular clusters usually do not have
    short-lived blue stars because these stars have
    already died out.
  • Astronomers estimate that the oldest globular
    clusters are about 12 billion years old. Thus,
    the universe must be at least that old.

13
Galaxies
14
Galaxies
  • A galaxy is a huge group of individual stars,
    star systems, star clusters, dust, and gas bound
    together by gravity.
  • There are billions of galaxies in the universe.
  • The largest galaxies consist of more than a
    trillion stars. Galaxies vary widely in size and
    shape.

15
Galaxies
  • Spiral and Barred-Spiral Galaxies
  • Spiral galaxies have a bulge of stars at the
    center, with arms extending outward like a
    pinwheel.
  • These spiral arms contain gas, dust, and many
    bright young stars.
  • The Milky Way is a spiral galaxy.

16
Galaxies
  • Some spiral galaxies have a bar through the
    center with the arms extending outward from the
    bar on either side. These are called
    barred-spiral galaxies.

17
Galaxies
  • Elliptical Galaxies
  • Elliptical galaxies are spherical or oval, with
    no trace of spiral arms.
  • Elliptical galaxies come in a wide range of
    sizes.
  • Elliptical galaxies have very little gas or dust
    between stars. They contain only old stars.

18
Galaxies
  • Irregular Galaxies
  • A small fraction of all galaxies are known as
    irregular galaxies.
  • Irregular galaxies have a disorganized
    appearance. They have many young stars and large
    amounts of gas and dust.
  • Irregular galaxies come in many shapes, are
    typically smaller than other types of galaxies,
    and are often located near larger galaxies.

19
Galaxies
  1. A spiral galaxy in the constellation Coma
    Berenices

20
Galaxies
  1. A spiral galaxy in the constellation Coma
    Berenices
  2. A barred-spiral galaxy in the Fornax cluster

21
Galaxies
  1. Elliptical galaxy M87

22
Galaxies
  1. Elliptical galaxy M87
  2. An irregular galaxy with many areas of star
    formation

23
Galaxies
  • The Milky Way Galaxy
  • The Milky Way galaxy has an estimated 200 to 400
    billion stars and a diameter of more than 100,000
    light years.
  • Every individual star that you can see with the
    unaided eye is in our galaxy.
  • The solar system lies in the Milky Ways disk
    within a spiral arm, about two thirds of the way
    from the center.

24
Galaxies
  • In a side view, the Milky Way appears as a flat
    disk with a central bulge. An overhead view of
    the Milky Way shows its spiral shape.

About 100,000 light-years
25
Galaxies
  • The Milky Ways flattened disk shape is caused by
    its rotation.
  • The sun takes about 220 million years to complete
    one orbit around the galaxys center.
  • Recent evidence suggests that there is a massive
    black hole at our galaxys center.
  • Stars are forming in the galaxy's spiral arms.

26
Galaxies
  • Quasars
  • By studying their spectra, astronomers have
    determined that quasars are the enormously bright
    centers of distant, young galaxies.
  • Quasars produce more light than hundreds of
    galaxies the size of the Milky Way.
  • What makes a quasar so bright? The most likely
    explanation involves matter spiraling into a
    super-massive black hole with the mass of a
    billion suns.

27
Assessment Questions
  • A constellation is
  • two stars that orbit each other.
  • a star system with more than two stars.
  • an open cluster of stars that are close to one
    another.
  • a group of stars that appear to form a pattern.

28
Assessment Questions
  • A constellation is
  • two stars that orbit each other.
  • a star system with more than two stars.
  • an open cluster of stars that are close to one
    another.
  • a group of stars that appear to form a
    pattern. ANS D

29
Assessment Questions
  • A large group of older stars without sufficient
    gas and dust to form new stars is a(n)
  • open cluster.
  • galaxy.
  • association.
  • globular cluster.

30
Assessment Questions
  • A large group of older stars without sufficient
    gas and dust to form new stars is a(n)
  • open cluster.
  • galaxy.
  • association.
  • globular cluster. ANS D

31
Assessment Questions
  • What type of galaxy is the Milky Way?
  • spiral galaxy
  • barred-spiral galaxy
  • elliptical galaxy
  • irregular galaxy

32
Assessment Questions
  • What type of galaxy is the Milky Way?
  • spiral galaxy
  • barred-spiral galaxy
  • elliptical galaxy
  • irregular galaxy ANS A
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