Download 10 Astronomy Things to Remember for 50 Years

Reminders
• Reflective Essay due Friday 4/26
– 5 points for each day late
• Final Project Thursday 5/16
• Final Exam Tuesday 5/21
• Observations No Later Than 5/23
– Any star, any constellation- big dipper, summer
triangle
– Leo (backward question mark), summer triangle
10 Astronomy Things to
Remember for 50 Years
Reason for the Seasons
• Cold winter and warm summer is not because
the earth is closer to the sun in summer.
• Seasons are caused by the tilt of the earth
relative to the sun.
• The north pole of the earth always points
toward the same position in the sky
• As the earth orbits the sun’s light falls more
directly on the northern or southern
hemisphere during different times of the year.
Draw and label this diagram or the next.
Solar System
• Terrestrial Planets (earth like rocky)
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Mercury
Venus
Earth
Mars
• Asteroid Belt
• Gas Giants
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Jupiter
Saturn
Uranus
Neptune
• Dwarf Planets
– Pluto
Star Process
• Stars emit energy produced by the fusion of light
nuclei to produce heavier nuclei energy.
• For much of their life, stars fuse hydrogen into
helium. 4 H+  He +4 + energy
• Later in life some stars are massive enough to
generate enough heat to fuse helium into carbon
or oxygen.
• Very massive stars may sustain fusion of even
heavier elements up to but not including iron.
• Elements heavier than iron are produced during
the explosion of stars not during life of stars.
Locate a constellation
• Pick a favorite constellation (asterism)
• Tell the best time of the year to see the
constellation.
• At that time of year where in the sky would
you look for the constellation.
• Sketch the asterism.
Astronomy versus astrology
• Astronomy is the branch of science
dealing with objects and phenomena
that lie beyond the Earth’s
atmosphere.
• Astrology is art or practice that seeks
to foresee and foretell future events
by the position of the stars and
planets.
Gravity
The force that ‘won” the universe.
• Common Sense versus Science
– Objects fall “down” when not supported
• Aristotle- why do things fall?
– The natural place for heavy objects is the center of the
earth
• Galileo – How not why do things fall
– Objects of different weights fall the same speed
– Falling objects move more and more quickly
– Distance fallen is proportional to the square of the
time lapsed.
Gravity
• Newton – How but not why?
– Why does the moon not fall into the earth?
– It is falling but keeps missing the earth.
– Moon and objects on the earth experience the force
of gravity (unified terrestrial and ethereal laws)
– F= G m1m2/r2
• Einstein – Why?
– Presence of matter bends spacetime causing the path
of a moving object to appear to be change by a force.
10 things to remember
1. Reason for the seasons (not Christmas season)
2. Solar System- names, order, classification
3. Star process- nuclear fusion
4. Location of a constellation
5. Difference between astronomy and astrology
6. Gravity – Newton and Einstein’s contributions
7. Light, EM spectrum, Doppler effect
8. Phases of Moon
9. Difference between Comets and Meteors
10.Light year – how to calculate
All we know about the Universe
• Everything that astronomers know about the universe
is carried on waves of electromagnetic energy (light)
• Light is produced when an electron in an atom moves
from a higher energy level to a lower energy
• When an electron in an atom absorbs a photon of
electromagnetic energy the electron moves from a
lower to a higher energy level.
• The wavelength of the photon can vary from very short
for Gamma rays to very long for radio waves depending
on the energy level jumps.
Light
• Elements can be identified by the wavelength of EM
energy emitted or absorbed. Spectral analysis
• Doppler Effect is the change in wavelength of light
energy when the source is moving toward or away
from the observer.
• The wavelength of photons produced in atoms
moving away from us are lengthened (red shift)
while photons produced by atoms moving toward
us are shortened (blue shift)
Electromagnetic Spectrum
• What we refer to as light is but the small
segment of the electromagnetic spectrum
which human eyes can detect.
• The Electromagnetic spectrum is the full
range of wavelengths and frequencies of
electromagnetic waves extending from long
radio waves to short gamma rays.
Light (continued)
• The wavelength of EM (light) emitted by a star
depends on the temperature of the star. Light
becomes the cosmic thermometer.
• The bending of light by mirrors and lenses is
used to produce telescopes which perform the
following tasks:
– Gather light - brighten (light bucket)
– magnify – resolve
Light Speed
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d=s*t
c= 186,000 miles/second = 3X105 km/s
Time in seconds
1 minute = 60 seconds
1 hour = 60 minutes
1 day = 24 hours
1 week = 7 days
1 month = 30 days
1 year = 365 days (ok 365.25)
Distance for any period
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Light hour =
Light day =
Light week =
Light month =
– Which month?
• Light fortnight =
Light Year = distance unit
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Speed of light is the cosmic speed limit
c= 3 X 108 m/s = 3 X 105 km/s = 186,000 mi/s
seconds per year
= 365 dys/yr X 24hrs/day X 60 min/hr X 60sec/min
= 3.1536 X 107 sec/year
Distance light travels in a year
= (3 X 105 km/s ) X (3.1536 X 107 sec/yr)
= 9.46 X 1012 km/yr or 5.87 X 1012 miles/year
Moon Phases
• As Moon orbits Earth the half of the moon
illuminated by sun light changes position
relative to Earth.
• This results in different amounts of illuminated
lunar surface facing Earth at different times
during the monthly orbit of the moon.
Comets and Meteors
• Comet – a small body of ice and dust in orbit
about the Sun
• Asteroid- a larger rock in space
• Meteoroid- a small rock in space
• Meteor- The streak of light seen when any
space debris vaporizes in Earth’s atmosphere
• Meteorite – A fragment of space debris which
survives passage through the atmosphere and
comes to rest on Earth.