Astronomy 103 Tuesday, Thursday 11:00 am 12:15 pm Tom Burbine tburbinemtholyoke'edu

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Astronomy 103Tuesday, Thursday1100 am 1215
pmTom Burbinetburbine_at_mtholyoke.edu
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Website

• http//www.mtholyoke.edu/courses/tburbine/ASTR103/
  
• Link is also on Ella

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• Put your full name on all HW assignments
• Some people printed out the star charts and
  didnt circle what they saw

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• www.skyandtelescope.com
• Interactive sky chart
• Change hour, day, month, year
• Change location

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HW 5

• Use the interactive sky chart on
  www.skyandtelescope.com

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Summer Sky
Winter Sky
http//wind.caspercollege.edu/marquard/astronomy/
images/star_ch_med.jpg
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• The entire sky appears to turn around imaginary
  points in the northern and southern sky once in
  24 hours.

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Now there are 13 constellations in the zodiac

• Why?
• Originally the zodiac was divided into 12 equally
  spaced signs
• However, some constellations are big, some are
  small
• When the astronomers redid the boundaries, a 13th
  constellation was added to the zodiac

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• The zodiac is divided into 12 signs of 30 each
• Constellations actually all have different sizes

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Terminology for looking at the sky
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Celestial Poles

• The altitude of the celestial pole is equal to
  your latitude
• If the altitude of the celestial pole is 50
  degrees, you latititude is 50 degrees

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Celestial Poles

• The altitude of the celestial pole is equal to
  your latitude
• If the altitude of the celestial pole is 50
  degrees, you latititude is 50 degrees

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Angular size

• We measure distances in the sky using angles
• 180o in the observable sky

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More precise distances

• 1 degree 60 arcminutes (symbol )
• 1 arcminute 60 arcseconds (symbol )
• So something that is 2 degrees, 10 arcminutes, 22
  arcseconds would be written as
• 2o 10 22

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Star positions change versus latitude
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Astrology

• Astrology by birth sign or sun sign means that
  your particular horoscope characteristics are
  based mainly upon the location of the sun's
  astrological position in the zodiac at the time
  of your birth.

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Aries (21 March - 20 April)

• Arians have a tendency to act like a dynamo of
  energy when they set their mind on achieving some
  goal. They can sometimes act so quickly that they
  later discover that they should have put in just
  a little more thought before starting. Action and
  achievement are important and slow pokes that get
  in the way, watch out! Aries may step on your
  toes. Aries enthusiasm rubs off onto others and
  they get involved in something, others are ready
  to follow. Selfishness, which sometimes includes
  a need to control others, tarnishes their
  otherwise positive and adventurous spirit. They
  need to have empathy and concern for the needs of
  others. As a lover, they are passionate, giving
  and enterprising.

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Celestial Sphere
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Seasons
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Private Universe

• http//www.learner.org/resources/series28.html

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What causes seasons?

• The tilt of the Earths axis relative to the
  ecliptic

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Seasons
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Solstices

• Summer Solstice June 21 Northern Hemisphere
  receives its most direct sunlight
• Winter Solstice December 21 Northern
  Hemisphere receives its least direct sunlight

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Equinoxes

• Sun shines equally on both hemispheres
• Spring Equinox March 21 Northern Hemisphere
  goes from slightly tipped away from the Sun to
  slightly tipped towards
• Fall Equinox September 21 - Northern Hemisphere
  goes from slightly tipped toward from the Sun to
  slightly tipped away

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• Why does the orbital difference not matter?

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Reasons

• There is only a 3 difference in the distance
  from the Earth to the Sun at its farthest and
  closest point
• The Earth is actually closer to the Sun in the
  winter than in the summer

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Long Term Changes
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Precession

• Earth precesses like a top
• Precession - phenomenon by which the axis of a
  spinning object (e.g. a part of a gyroscope)
  "wobbles" when a torque is applied to it

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Forces

• For a top, the force is gravity, which is trying
  to pull the top down
• For the Earth, the forces are due to the pull of
  the Sun and Moon, which is trying to align the
  Earths axis with the ecliptic

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Because of precession

• The position of a star that corresponds to the
  North Celestial Pole changes

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Where does the light from the Moon originate?
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Answer

• It reflects light from the Sun

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Earth-Moon System

• Earths diameter is 12,742 km
• The diameter of the Moon is 27 of the Earth
• The average distance between the Earth and Moon
  is approximately 30 times Earth's diameter.
• Orbit of the Moon is inclined 5o to the orbital
  plane of the Earth

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Eclipses

• Lunar Eclipse Moon passes through Earths
  shadow
• Solar Eclipse Moons shadow falls on Earth

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• Umbra light totally blocked
• Penumbra light partially blocked

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Lunar Eclipse
Passing through Earths shadow
Why is the Moon red? Shouldnt it be totally dark?
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Why is the Earth Red?

• Even though Earth blocks the moon from direct
  sunlight during an eclipse, some sunlight is
  refracted, or bent, by the Earth's atmosphere and
  illuminates the moon.
• Most of this refracted light is orange or red

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• Should you look directly at a Lunar Eclipse?

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YES
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Should you look directly at a Solar Eclipse?
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No!!!!!!
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Any Questions?