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Astronomy Unit 2

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Title: Astronomy Unit 2


1
Astronomy Unit 2
  • Telescopes
  • Celestial Spheres/Constellations
  • Apparent Motion of the Stars
  • Motion of the Planets

2
Telescopes
  • Vocab Words for this section are
  • Reflecting Telescope
  • Refracting Telescope
  • Radio Telescope
  • Space Telescope

3
Telescopes
  • Hans Lippershey was the inventor of the telescope
    in 1608.
  • Galileo was the first to use a telescope to study
    the sky in 1609.
  • The invention and use of the telescope began a
    huge number of discoveries in the field of
    astronomy.

4
Telescopes
  • 3 types of telescopes
  • Optical Telescopes study visible light.
  • Reflecting telescopes use mirrors to bounce light
    from an objective lens to an eyepiece lens
  • Refracting telescopes use lens to bend light and
    magnify images coming through an objective lens.
  • Radio Telescopes study radio waves from earth.
  • Space Telescopes travel out of Earths atmosphere
    to study the other types of radiation not visible
    to the naked eye, and the radiation that cannot
    make it through earths protective atmosphere.

5
Telescopes
  • Optical Telescopes study the visible light
    section of the electromagnetic spectrum.
  • They uses mirrors and/or lenses to magnify the
    light.

6
Telescopes
  • One type of Optical Telescope is the Reflecting
    Telescope
  • Within this telescope there are mirrors to bounce
    the light traveling through.

7
Telescopes
  • Another type of Optical telescopes is the
    Refracting Telescope
  • Within this telescope there are lenses to bend
    the light traveling through.

8
Telescopes
  • Radio Telescopes use a parabolic antenna and a
    receiver to study radio waves.
  • Radio Waves are a type of radiation that is not
    normally visible to the naked eye.

9
Telescopes
  • Space telescopes travel out of earths atmosphere
    to study all different types of radiation that
    can not make it through earths atmosphere.
  • Examples are the Hubble Space Telescope and the
    Chandra Space Telescopes

10
Celestial Sphere/Constellations
  • Vocab words for this section are
  • Celestial Sphere
  • Declination
  • Right Ascension
  • Constellation
  • Circumpolar Constellation
  • North Circumpolar Constellation
  • South Circumpolar Constellation
  • Zodiac
  • Ecliptic

11
Celestial Sphere/Constellations
  • A celestial sphere is similar to a globe of the
    sky.
  • It is an imaginary sphere where the sun, the
    moon, and all the other stars appear to be
    combined.

12
Celestial Sphere/Constellations
  • To locate on the celestial sphere, you use
    declination and right ascension.
  • Declination measures angular distance North or
    South of the celestial equator
  • Between 0 and 90 degrees
  • Right Ascension measures distances eastward,
    along the celestial equator from the vernal
    equinox
  • Goes up to 360 degrees

13
Celestial Sphere/Constellations
  • The 88 recognized constellations by the
    International Astronomical Union are plotted on
    the Celestial Sphere.
  • Some constellations are close enough to a
    celestial pole that they are visible in certain
    locations on earth all year long. These
    constellations are called Circumpolar
    Constellations.

14
Celestial Sphere/Constellations
  • Constellations close to the N. Celestial Pole are
    North Circumpolar Constellations
  • They are visible from the North Pole all year
    long!
  • Constellations close to the S. Celestial Pole are
    South Circumpolar Constellations.
  • They are visible from the South Pole all year
    long!

15
Celestial Sphere/Constellations
  • These are the North Circumpolar Constellations

16
Celestial Sphere/Constellations
  • These are the South Circumpolar Constellations

17
Celestial Sphere/Constellations
  • The ecliptic is the apparent path the sun traces
    out in the sky throughout the year.
  • It is visible on the celestial sphere!
  • Along the ecliptic there is a band of 12
    constellations. They are called the zodiac
    constellations
  • These are where astrological signs come from.
    The constellation that rises and sets during the
    month of your birthday is supposedly your sign.

18
Celestial Sphere/Constellations
  • The 12 constellations of the zodiac are

19
Apparent Motion of the Stars
  • Vocab Words for this section are
  • Constellation
  • Circumpolar Constellation
  • Diurnal Circles
  • Parallax

20
Apparent Motion of the Stars
  • We have previously discussed circumpolar
    constellations.
  • This concept deals with how stars appear to move
    throughout the year.

21
Apparent Motion of the Stars
  • If you trace the path a star makes each day, it
    would trace out a Diurnal Circle.
  • This the circular path a star appears to take
    each day.
  • We cant see stars during the daytime because of
    the sun, so we dont actually see the circle.

22
Apparent Motion of the Stars
  • Diurnal Circles

23
Apparent Motion of the Stars
  • Stars also display parallax.
  • Parallax is the apparent movement of an object
    due a change in the viewers position.
  • You can try it with your finger.
  • Hold your finger in front of your face. Close
    your left and view your finger from your right
    eye. Quickly switch eyes. Go back and forth a
    few times. Your finger should appear to move
    even though it isnt actually moving.
  • As the earth moves around the sun, it changes our
    viewing position of stars. This causes them to
    display parallax!

24
Apparent Motion of the Stars
  • We use a stars parallax (or apparent shift)
    relative to fixed background stars, to
    determine the distance to stars.
  • Stars that are further away display less of a
    parallax, than stars that are close to us.

25
Motion of the Planets
  • Vocab Words for this section are
  • Sidereal Motion
  • Prograde
  • Retrograde
  • Keplers 1st Law of Planetary Motion
  • Keplers 2nd Law of Planetary Motion
  • Ellipse

26
Motion of the Planets
  • A sidereal day actually takes 23 hours, 56
    minutes and 4.09 seconds
  • This is the amount of time it takes the earth to
    get back to the same location it was at
    previously.
  • We dont use this as a day because the earth not
    only rotates, but it moves a little bit around
    the sun in its revolution during each rotation.
    This is where we get the 24 hour day from.

27
Motion of the Planets
  • As we watch planets move across the sky, they
    move relative to their background fixed stars.
  • Planets normally move westward across the night
    sky. This is called Prograde motion.
  • Sometimes planets appear to begin moving
    backward or eastward across the night sky.
    This is called Retrograde motion.
  • Please not that if you look these words up, the
    directions will be backwards because Astronomers
    pretend like you are living on the planet looking
    out. For our purposes we define the word as how
    it looks in the night sky!

28
Motion of the Planets
  • The planets dont actually switch directions.
  • What is happening is our orbits around the sun
    (the earths and whichever planet we are looking
    at) are catching up with each other.
  • This makes the planet appear to move backwards
    for a small portion of time.
  • See the animation at the following website to
    help you understand prograde vs. retrograde
    motion
  • Prograde vs. Retrograde Motion

29
Motion of the Planets
  • Johannes Kepler developed 3 laws for how the
    planets move around the sun. He did this after
    making detailed studies and observations as to
    how the planets are moving.
  • We are going to study the first 2!
  • These laws dont only apply to planets, but they
    also apply to how moons orbit their parent
    planets!

30
Motion of the Planets
Keplers First Law of Planetary Motion
Planets follow elliptical orbits, with the Sun at
one focus of the ellipse.
31
Motion of the Planets
  • The planets move around the sun in an elliptical
    shape with the sun at one of the foci.
  • An ellipse appears as a squashed circle.
  • It is defined as a closed loop where the sum of
    the distances from 2 points (the foci) to every
    point on the line is constant.

32
Motion of the Planets
  • This means there are times throughout the year
    where the earth is closer and further from the
    sun.
  • The earth is actually closer to the sun in
    December, our winter!
  • It is about 147,450,000 km from the sun
  • The earth is further from the sun in June, our
    summer!
  • It is about 152,400,000 km from the sun

33
Motion of the Planets
Keplers 2nd Law of Planetary Motion
As a planet moves in its orbit, it sweeps out an
equal amount of area in an equal amount of time.
34
Motion of the Planets
  • Keplers 2nd Law implies that when a satellite is
    closer to its parent object, it actually travels
    faster than when it is further away!
  • When we are closer to the sun we travel slightly
    faster than when we are further away.
  • This is due to the gravitational pull the parent
    object has on the satellite.
  • The pull the sun has on the earth
  • On average the earth travels at 29.78 km/s

35
Motion of the Planets
  • Keplers Laws apply to ALL the planets that orbit
    the sun.
  • Keplers Laws also apply to how every moon orbits
    its parent planet!
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