Observing and the Sky Astronomy 311 Professor Lee Carkner Lecture 3.
-
date post
18-Dec-2015 -
Category
Documents
-
view
220 -
download
1
Transcript of Observing and the Sky Astronomy 311 Professor Lee Carkner Lecture 3.
Observing and the Sky
Astronomy 311Professor Lee
CarknerLecture 3
Our Point of View
We are all standing on different parts of a large spinning ball moving through space Remember that everything is moving
at once
The Changing Sky North Pole of the Earth is pointed at
Polaris (the North or Pole star), which stays stationary as the other stars move around it
Sky makes one complete rotation per 24 hours (Diurnal motion)
Sky also makes one complete rotation per year (Annual motion)
Diurnal Motion
Annual Motion
The Observer’s View
Observing
Can measure distance on the sky in degrees (360 degrees = complete circle)
Horizon -- Zenith -- Meridian --
The Solar Year
The Seasons
Tilt of Earth’s axis causes seasons
Sunlight is more direct in the summer
Direct and Indirect Sunlight
Solstice and Equinox Solstice
When the Sun is highest or lowest in
the sky Equinox
When the Sun is overhead at the
equator
Times of year
Vernal Equinox -- March First day of spring
Summer Solstice -- June First day of
summer
Autumnal Equinox --September First day of
autumn
Winter Solstice -December First day of winter
Changing Day Length
Lines on a Globe Equator -- Sun is overhead at
equinox Tropic of Capricorn -- Tropic of Cancer -- Arctic and Antarctic Circles -- 23 1/2
degrees south or north of the pole, Sun never sets or rises at solstice time
Navigation
Latitude (degrees North of the Equator) Only works in Northern
hemisphere Longitude (degrees East
or West of the Prime Meridian running through Greenwich England)
The Celestial Sphere
Project the lines on a globe into space to form a coordinate system
North Celestial Pole –
Celestial Equator --
Celestial Coordinates
Right Ascension --
Declination --
The coordinates do not move or vary with location on the Earth, they are fixed to the stars
The Ecliptic
Most of the objects in the solar system have their orbits in the same plane, called the ecliptic
The ecliptic passes through 12
constellations known as the zodiac
Constellations of the Zodiac
Precession
The Earth “wobbles” as it spins, causing the Earth’s axis to point at different parts of the sky
This changes where the equinoxes
are in the sky
Astrology
The belief that the positions of heavenly bodies at the time of your birth foretells your future
Your sign is where the Sun was on the zodiac when you were born
For example: Sept 13th = Virgo, but Sun is in Leo. All star signs are about 1 month off
Science and Pseudoscience
Astronomy is a science, it tries to form a picture of the universe based on observation and reason. It is subject to proof
Next Time
Meet back in Science 102 Read Chapter 1.6