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Astronomy
Astronomy
is the study of all physical objects
beyond Earth.
1. The Original Science
The seasonal movement of celestial bodies, e.g. sun,
moon and planets, has helped create our modern
day calendar.
Most calendars are made up of:
a. Year – time required for the earth to orbit the sun
b. Month – time required for the moon to orbit the earth
c. Day – time required for the earth to rotate once on it’s axis
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Earlier civilizations based their calendars on moon phases,
planet alignments and sun positions.
Julius Caesar created the Julian calendar, 365.25 days
per year; created the leap year to help realign the seasons to the
calendar
Romans had the greatest affect on our modern calendar
Later, it was discovered that the Julian calendar was wrong;
so the Gregorian calendar was created, 365.242 days per year
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Evidence from other countries that astronomy
observations was used.
a. Nabta, Egypt - the oldest known astronomical
alignment of megaliths in the world
b. Stonehenge , England – group of stones in a circle
which correlate with summer and winter solstices
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c. Babylonians
– believed in astrology, a
fuzzy science how the moon, stars and
planets affect our lives
d. Chinese – understood eclipses and
mapped hundreds of stars
e. Greeks - not so much in observation as it was in
applying logical thinking and geometry
to these observations
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f. Mayan, S. America - were quite
accomplished astronomers
g. Arabs - was for the purpose of time-keeping,
also for determination of latitude and longitude
h. Romans - created our modern day calendar, with
some revisions
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Astronomers
a.
Ptolemy
– 140 A.D. created the Ptolemaic System,
which predicted the positions of the planets based
on his earth-centered system
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b. Copernicus
– 1543 wrote Little Commentary,
Copernicus's theory of a universe with the sun at its
center.
c. Tycho Brahe– 1546 observations were made using
only a compass and an astrolabe; most accurate measurements
of the sky ever made without a telescope.
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d. Johannes Kepler – 1600’s discovering the
three laws of planetary motion
e. Galileo Galilee – 1600’s first person to
use a telescope to observe the stars
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f. Issac Newton -1600’s explained why
the planets orbited the sun:
a. centrifigal force
b. gravity
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A skater rotates around their
imaginary vertical axis
A log can rotate around its
horizontal axis
Earth rotates around on it’s imaginary axis through
the North and South poles
There is a 23.50 tilt to
the earth
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2. Mapping the Stars
Ancient civilizations linked stars into recognizable patterns;
these patterns are called constellations
Astronomers divide the regions of the sky into 88 constellations
Northern Hemisphere
Southern Hemisphere
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There are three concepts that help you describe
locations of stars
a. altitude – angle between object and horizon
b. zenith – 900 to the observer; straight up
c. horizon – sky and earth meet
The stars you see at night depend on
a. your location
b. time of year
c. time of night
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To plot positions of stars use:
a. Declination - is like latitude
north or south of equator
b. Right ascension - is like longitude; uses 24 hours as divider
east of point on equator, vernal equinox (days and nights the same)
Spring Constellations
in Northern Hemisphere
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Measuring in Space
Astronomers use the light year to measure the
distance between us and the stars or planets
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Some interesting Facts on Distance
In one second, a beam of light can travel:
Seven Times around the Earth.
From Earth to the Moon
1.25 seconds
From Earth to the Sun
8.3 minutes
From the Sun to Neptune
the furthest of the Sun's major planets 4.2 hours
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The rotation of the earth causes what we
call night and day. This occurs every 24 hours.
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Day and Night
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While the earth rotates around it’s axis, the
earth is also revolving around the sun.
One revolution or orbit around the sun takes about
365 days or one year.
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Seasons on Earth
There are four seasons on Earth;
spring,, summer, fall, winter
Why? Because of the 23.50 from vertical tilt of the earth!
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The Seasons
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Remember, the seasons are not affected
by the Earth’s distance from the sun.
Actually, during summer the Earth is furthest
away from the sun!!!!!
Let’s take a look at summer in northern hemisphere
a. north is towards the sun
b. more hours of daylight
c. winter in southern hemisphere
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Let’s take a look at winter in northern hemisphere
a. north is away from the sun
b. less hours of daylight
c. summer in southern hemisphere
Just two days a year, the noon sun is pointing north or south. This
is called solstice.
1. December 21, 23.50 south
winter in northern hemisphereWinter solstice
shortest day of the year
2. June 21, 23.50 north
summer in northern hemisphere
longest day of the year Summer solstice
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On just two days a year, the noon sun is pointing
at the equator. This is called equinox.
1. March 21,
vernal equinox
a. marks the beginning of spring
b. daytime and nighttime are the same
c. day gets longer
2. September 23,
a. marks the beginning of fall
b. daytime andautumnal
nighttimeequinox
are the same
c. days get shorter
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Motions of the Moon
Moon revolves around the earth every 27 days
Moon rotates on it’s axis every 27 days
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Phases of the Moon
The moon goes through one set of phases every
month.
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Eclipses
There are two types of eclipses
1. Solar eclipse
2. Lunar eclipse
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Solar eclipse
a. moon passes between Earth and the
sun
Two types of solar eclipse
a. total solar - shadow is centered at a point on the earth
this cone shaped shadow is called the umbra
no part of the sun can be seen
b. partial solar - shadow is outside the cone, this is
called the penumbra
part of the sun can be seen
blue – penumbra
black - umbra
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Total Solar Eclipse
Partial Solar Eclipse
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Lunar Eclipse
a. Earth passes between moon and sun, only occurs
during the full moon phase
Two types of lunar eclipse
a. total lunar – when the Earth, moon and sun are
in direct alignment; you see Earth’s shadow on the moon
b. partial lunar – when the Earth, moon and sun are not in
direct alignment
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Total lunar eclipse
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Tides
a. occurs because of differences in how
much the moon pulls on the Earth
b. actually pulls the water off of Earth
c. tides allow for animals to live in areas close
to the oceans
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image of no tides
c. Two types of tides that occur daily
low tide
high tide
high tide
low tide
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d. two types of tides that occur twice per month
1. spring tide
a. springs off the earth
b. only occurs at new moon phase
c. Earth/moon/sun in line
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2. Neap tide
a. first and last quarter moon phase
b. moon is at right angle to earth/sun
c. not much of a tide
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Earth’s moon
1. Some information about the moon
a. temperatures range from 1000 C
to -1730 C
b. 1/6th the gravity of Earth
so if a man weighs 100 lbs. on Earth,
he weighs 16 lbs on the moon
c. moon has many
craters
and
maria
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Missions to the Moon
a. July 1969 – Apollo 11, 1st landing on the moon
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b. 1994 – Clementine, photographed the moon
showed what type of minerals are on the moon
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c. 1998 – Lunar Prospector, mapped the entire moon
found there was water frozen at the poles of the moon
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Comets
chunks of ice and dust whose orbits are usually
very long ellipses
Comets are made up of two parts
1. head – made up of
a. nucleus
b. coma
2. tail – gas and dust
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Asteroids
Three main features:
1. objects revolving around the sun
2. too small to be called planets
3. between Jupiter and Mars
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Meteors
A meteoroid is a chunk of rock in space
Two things can happen
1. if burns up in Earth’s atmosphere it
is called a meteor
2. if it continues through atmosphere and hits
Earth it is called a meteorite