Download Midterm Review, Greenhouse LT, Small Bodies Astronomy 1 — Elementary Astronomy

Midterm Review, Greenhouse
LT, Small Bodies
Astronomy 1 — Elementary Astronomy
LA Mission College
Spring F2015
Quotes & Cartoon of the Day
“I have just gone over my
comet computations
again, and it is
humiliating to perceive
how very little more I
know than I did seven
years ago when I first did
this kind of work.”
-- Maria Mitchell
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Announcements
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Midterm Thursday
Have you selected your observing proposal yet?
Reordering topics so as to be properly up to date on
Mars, Pluto and Enceladus!
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Last Class
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Brief Backtrack
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SS Formation
Earth in brief
LT Greenhouse Effect
Climate Change
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
This Class
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Midterm Review
Greenhouse Effect
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LT Greenhouse Effect
Climate Change
If Time:
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Meteor/oid/ite
Asteroids
Comets
Kuiper Belt
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
OLD DEAD GUYS
Greeks to Kepler
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Greek ideas
Copernican Revolution
Tycho Brahe
Kepler the dude
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Kepler’s 3 laws of Planetary Motion
1. The orbits of the planets are ellipses, with the Sun at one
focus.
2. A line from a planet to the Sun sweeps out equal areas
in equal periods of time
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Planets move fastest when physically closest to the Sun, and
slowest when farthest.
3. A planet’s orbital period squared, is proportional to it’s
farthest distance from the Sun cubed:
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P2 = a3
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Kepler to Sir Issac
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Galileo
Sir Issac
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Contributions and fields of study
Law of Universal Gravity
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Law of Universal Gravity
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Be able to explain how the force varies (larger or
smaller) with mass of either object, both objects and
distance
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Be able to work the inverse square relationship -- how
does force change if distance doubles....
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
LIGHT, OPTICS, TELESCOPES
Nature of Light
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Why this is important for Astronomy
electromagnetic radiation
waves, particles, duality
all light, from radio to gamma ray is same thing
all light travels at the same speed in vacuum
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c=3x108 m/s
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Properties of Light
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Waves
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λ = c/f
Interference
Particles
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Relationship of wavelength and frequency
Photoelectric effect
E = h f = hc/λ
h = 6.6 x 10-34 Js = 6.6 x 10-34 J/Hz
Know what these relationships mean (i.e the ranking
exercise from HW)
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Electromagnetic Spectrum
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difference between red and blue light
Basic bands of EMR (e.g. radio, visible, IR etc.)
Relationship between band, wavelength & Energy
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Telescopes and Observatories
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Refractors and Reflectors
Size (of primary) matters
Atmospheric Transmission
Multiwavelength Astronomy
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What are IR and Radio good for?
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
SOLAR SYSTEM
Solar System Properties
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Overall “bulk” properties
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Disk shape
two types of planets
Space “debris”
common age
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Solar System Properties
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“Anatomy” What and Where
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Sun
Inner SS & terrestrial planets
Asteroid Belt
Outer SS & Jovian planets
Kuiper Belt
Heliopause
Oort cloud
Size/Distance Scales
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Solar System Formation
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Raw materials -- big bang, role of supernovae
Solar Nebula Theory
Differentiation
Frost line
Planet formation -- both types
Disk clearing
Cratering & Craters
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Greenhouse Effect Recap
Astronomy 1 — Elementary Astronomy
LA Mission College
Spring F2015
Greenhouse Effect
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Glass:
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transparent to visible light
opaque to IR light
Greenhouse
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visible light enters
through glass
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warms ground & air
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Greenhouse gets warmer
than outside
ground & air give off IR
IR can’t exit through
glass
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Greenhouse Gasses
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Carbon dioxide & other gasses
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transparent to visible light
absorb IR light
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
WARMUP QUESTION
Which of the following is part of the Earth’s natural
greenhouse effect?
A. Earth’s atmosphere continually becomes thicker
with greenhouse gases.
B. Infrared light becomes permanently trapped in our
atmosphere by greenhouse gases.
C. The ozone hole causes significant increases in
surface temperature. D. Earth’s surface and atmospheric gases absorb
energy and then give off infrared light.
E. Heat is transferred in the atmosphere through the
circulation of greenhouse gases.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
LECTURE-TUTORIAL
GREENHOUSE EFFECT
Which of the following is part of the Earth’s natural
greenhouse effect?
A. Earth’s atmosphere continually becomes thicker
with greenhouse gases.
B. Infrared light becomes permanently trapped in our
atmosphere by greenhouse gases.
C. The ozone hole causes significant increases in
surface temperature. D. Earth’s surface and atmospheric gases absorb
energy and then give off infrared light.
E. Heat is transferred in the atmosphere through the
circulation of greenhouse gases.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Let’s Practice
If Earth’s atmosphere were able to completely absorb
visible light, which of the following would be true?
A. The Earth’s surface temperature would be cooler than it
is today.
B. The Earth’s surface temperature would be warmer than
it is today.
C. The Earth’s surface temperature would be the same
temperature as it is today.
D. There is not enough information to answer this question.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
HUMANS AND CLIMATE CHANGE
Greenhouse Effect
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Is a natural process
Essential to maintain Earth’s temperature
HOWEVER
Human activity has dramatically increased the level of
greenhouse gasses
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Esp. via the internal combustion engine
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Global Warming
NASA Goddard Institute for Space Studies
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Beyond any reasonable doubt, the average
temperature on Earth is increasing.
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loss of glaciers & polar ice caps
rising sea water levels
global climate change
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
ICE MELT (TIME PERMITTING)
TED Talk, Jun 2009
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Small Solar System Bodies
Astronomy 1 — Elementary Astronomy
LA Mission College
Spring F2015
Meteors
-ites, -oids
Astronomy 1 — Elementary Astronomy
LA Mission College
Spring F2015
“Meteor…”
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Meteor -- The flash of light you see in the sky when a
space rock is heated to incandescence due to
atmospheric friction.
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Meteorite -- the rock, once it lands on Earth (if it is big
enough to make it intact, through the atmosphere)
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Meteoroid -- the rock, while still in space
Meteor Shower --When lots of meteors are seen in the
sky
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80 - 100 per hour is a good showing!
Caused when the Earth, on it’s trip around the Sun, passes
through a cloud of space dust/rock.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Meteorites
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Sizes from microscopic dust to a few centimeters
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Statistically, one meteorite is expected to strike a
building somewhere on Earth every 16 months.
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Typically impact onto the atmosphere with 10 – 30 km/s
(≈ 30 times faster than a rifle bullet)
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Can come from various sources
About 2 meteorites, large enough to produce visible
impacts, strike the Earth every day.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Meteor Showers
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Earth passing through area of debris
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Let’s Practice
Which of the following could cause a meteor shower?
A. A meteoroid hits a cloud in the atmosphere and
causes a thunderstorm.
B. The Earth crosses the debris-filled orbit of a
comet.
C. Asteroids in the same orbit as the Earth.
D. A small constellation of dying stars disintegrates.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Asteroids
Astronomy 1 — Elementary Astronomy
LA Mission College
Spring F2015
Asteroids
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Small rocky bodies that orbit the Sun.
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Millions orbit the Sun between the orbits of Mars and
Jupiter -- the asteroid belt
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Most are potato shaped (not round).
Most have craters.
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Last remains of planetesimals that built the planets 4.6
billion years ago!
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Can be stony (like Earth’s crust) or iron (like Earth’s
Core).
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The largest body in the asteroid belt (Ceres) is now
classified as a dwarf planet.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Asteroid - Earth Collisions
http://www.hooked-nussu.org/images/stories/issue/armageddon.jpg
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Not a good thing
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Tunguska: June 30th
1908
Yucatan 65 million
years ago
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Asteroid - Earth Collisions
http://www.soundtrackcollector.com/catalog/soundtrackdetail.php?movieid=9365
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Not a good thing
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Tunguska: June 30th
1908
Yucatan 65 million
years ago
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Asteroid - Earth Collisions
http://astro.wsu.edu/worthey/astro/html/im-meteor/
tunguska.html
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Not a good thing
Tunguska: June
30th 1908
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Comets
Astronomy 1 — Elementary Astronomy
LA Mission College
Spring F2015
Comets
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Throughout history,
Comet McNaught in 2007
comets have been
considered as portents
of doom, even very
recently:
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Appearances of comet
Kohoutek (1973), Halley
(1986), and Hale-Bopp
(1997) caused great
concern among the
superstitious.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Comets
http://thegalaxyguide.com/galaxy/
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Objects of ice/rock/dust orbiting the Sun, with
highly elliptical orbits.
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At perihelion (closest point to the Sun), a coma
and a tail typically appear due to the increased
solar radiation
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Comets: two types of tails
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Ion tail
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Ionized gas pushed
away from the comet by
the solar wind Pointing
straight away from the
sun
Dust tail
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Dust set free from
vaporizing ice in the
comet; carried away
from the comet by the
sun’s radiation
pressure. Lagging
behind the comet along
its trajectory
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Comet Nuclei
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Comet nuclei contain
ices of water, carbon
dioxide, methane,
ammonia, etc.:
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Those compounds
sublime (transition from
solid directly to gas
phase) as comets
approach the sun..
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Short Period Comets
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orbital periods of less than 200 years
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short-period comets are thought to originate from the
centaurs and the Kuiper belt/scattered disc
more-or-less in the ecliptic plane in the same direction as
the planets
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Long Period Comets
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periods ranging from 200 years to thousands or even
millions of years.
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highly eccentric orbits
orbits take them far beyond the outer planets
plane of their orbits need not lie near the ecliptic.
Believed to come from the Oort Cloud
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Let’s Practice
The orbits of long period comets are ___.
A. identical to the orbits of short period comets
B. nearly circular
C. exactly in the same plane as the planets
D. randomly oriented with respect to the orbits of the
planets
E. more than one of the above
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
The fact that short period comets have short periods
compared to long period comets implies that shortperiod comets _____ than long-period comets.
A. originate from a place closer to the Sun
B. have a different composition
C. are less massive
D. are smaller in diameter
E. have shorter tails
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
The tail of a comet is generally directed _______.
A. toward the Sun because of its gravitational
attraction
B. away from the Sun because of radiation pressure
and the solar wind
C. opposite to the direction of motion because of
interaction with interplanetary matter
D. along the comet’s magnetic field lines
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
A distant comet at its farthest point from the Sun would
have which of the following?
A. Dust tail
B. Ion tail
C. Nucleus
D. Coma
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Kuiper Belt
Astronomy 1 — Elementary Astronomy
LA Mission College
Spring F2015
The Kuiper Belt
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~ 30 – 100 AU from the
sun.
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2nd source of small, icy
bodies in the outer
solar system
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After passing Pluto, the
New Horizons
spacecraft is planned to
fly past at least one
Kuiper Belt object.
Astronomy 1 - Elementary Astronomy
NASA
LA Mission College
Levine F2015
Oort Cloud
Astronomy 1 — Elementary Astronomy
LA Mission College
Spring F2015
Origin of Comets
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Long Period comets
are believed to
originate in the Oort
cloud
Spherical cloud of
several trillion icy
bodies, ~ 10,000 –
100,000 AU from the
sun
Astronomy 1 - Elementary Astronomy
10,000 –
100,000
AU
Oort Cloud
LA Mission College
Levine F2015
Origin of Comets
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Gravitational influence
of occasional passing
stars may perturb some
orbits and draw them
towards the inner solar
system.
10,000 –
100,000
Interactions with
planets may perturb
orbits further, capturing
comets in short-period
orbits.
Astronomy 1 - Elementary Astronomy
AU
Oort Cloud
LA Mission College
Levine F2015
Let’s Practice
Short-period comets are associated with what class of
objects?
A. Kuiper Belt objects
B. Terrestrial planets
C. The Oort Cloud
D. The giant planets
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
What property of the Oort cloud is consistent with
long-period comets having orbits that are oriented
randomly with respect to the ecliptic?
A. It is very far from the Sun
B. It contains small icy bodies
C. It may interact with other stars
D. It is spherical
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
WRAP-UP
Topic for Next Class
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Midterm
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Reading Assignment
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Read up on Mars for Tuesday
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Homework
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No new HW yet
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015