Download Core Theme 3: The Solar System

Core Theme 3: The Solar System
—  Solar system: The Sun as part of the Solar System;
eclipses and effects on Earth; planets, dwarf
planets and other members of the Solar System
(asteroids, comets etc.). What are these? Distances,
scales, extent, history of mankind’s developing
thought on our place in the Universe.
Solar System
—  Our neighbourhood
—  Sun; 8 planets; dwarf planets; asteroids between Mars and
Jupiter; trans-Neptunian objects and Oort cloud.
—  Planets roughly spherical, orbits are usually elliptical.
Resources
—  http://www.esa.int/esa-mmg/mmg.pl?
b=b&topic=Sun&subtopic=Solar%20wind&start=3
—  http://www.bbc.co.uk/science/space/solarsystem
Relationships between Earth, Moon and Sun
—  Moon orbits the Earth and shows phases
—  Together they revolve around the Sun
—  Day and Night, Seasons and Eclipses happen, aurorae etc.
—  Eclipses:
—  Lunar Eclipse: when the full Moon moves into the shadow of
the Earth, cutting out the Moon’s normally bright, reflected
sunlight.
—  Demo and practice
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There will be some Penumbral lunar eclipses coming up, but as the Moon will not pass
through the main part of the Earth's shadow, there is not much to see, and if you didn't
know that an eclipse was taking place you would not be aware of it.
So we will have to wait for a decent lunar eclipse until the early morning of September 28,
2015. The next good lunar eclipses after that are on July 27, 2018 and January 21, 2019.
http://eclipse.gsfc.nasa.gov/eclipse.html
—  Solar Eclipse: when the whole Sun or part of the Sun is
blocked out (or occulted) by the new Moon as seen from
Earth. Can be either total, annular or partial.
—  Demo and practice
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Seasons result from the tilt in Earth’s
axis and change in angle of sunlight
falling on us during the year. DEMO
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http://en.wikipedia.org/wiki/List_of_solar_eclipses_visible_from_the_United_Kingdom_AD_1000–2090
The “Small Bodies”
—  Asteroids – small rocky, icy and metallic bodies of
the inner solar system that mainly orbit in the
asteroid belt between Mars and Jupiter.
—  Range in size from tens of metres up to 1000
kilometres. Hundreds of millions of small bodies.
—  Ceres is the largest asteroid, and like Pluto is
classified as a dwarf planet. It makes up a third of
the mass of the whole asteroid belt! Most known
asteroids are just a few kilometres across.
—  Sometimes Earth-approaching asteroids are in the
news (e.g. on 8th November 2011 an object passed
closer than the Moon, at just 0.85 lunar distances).
Usually (hopefully!) they miss the Earth.
Asteroid “Vesta” (top) and
Comet McNaught (bottom)
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Comets
—  A comet is a small dust-and-ice body (“a dirty
snowball”): a weakly bound collection of dust, ice
and small rocky particles. The central “nucleus”
can range in diameter from approximately a
kilometre (km) up to many tens of km or more.
—  Comets have been observed since ancient times
and have traditionally been considered bad omens.
—  When close enough to the Sun, comets show a
visible “head” or coma (a thin, fuzzy, temporary
atmosphere) and sometimes one or two tails.
These are much larger structures, millions of km
across or hundreds of millions of km in length.
—  They are distinguished from asteroids by presence
of a coma or a tail.
—  Comets have a wide range of orbital periods,
ranging from years up to millions of years.
—  Short-period comets (periods less than 200 years)
originate in both the Edgeworth-Kuiper belt (EKB),
a region beyond Neptune ranging up to 60 AU from
the Sun, and the Oort cloud (1,000 to 200,000 AU)
—  Long-period comets originate in the Oort cloud. It
is a nearly spherical swarm of more than 100,000
million comets with elliptical orbits extending up to
halfway to the nearest star.
—  While the asteroid belt is composed largely of rocky
or metal objects, EKB and Oort cloud objects are
mostly icy, comprising dust and frozen volatiles
such as water, methane, carbon dioxide and
ammonia (termed "ices”).
Other Solar System Facts
—  The origin and evolution of the Solar System began
approximately 4,567 million years ago (4.567 billion
years) with the gravitational collapse of a small part of a
giant molecular cloud. The Universe is roughly three times
older, i.e. approximately 13.7 billion years.
—  Most of the collapsing material collected at the centre to
form the Sun, while the rest flattened into a
protoplanetary disk from which the planets, moons,
asteroids, and other small Solar System bodies formed.
—  In roughly 5 billion years, the Sun will cool and balloon
outwards to many times its current diameter (becoming a
red giant), before casting off its outer layers as a
planetary nebula and finally leaving behind a stellar
remnant known as a white dwarf.
Meteor shower
—  A meteor shower is a celestial event in which a
number of meteors are observed to radiate from
one point in the night sky. These meteors are
caused by streams of cosmic debris called
meteoroids entering Earth's atmosphere at
extremely high speeds.
—  Most meteors are smaller than a grain of sand, so
almost all of them disintegrate and never hit the
Earth's surface. Intense or unusual meteor showers
are known as meteor outbursts and meteor storms,
which may produce greater than 1,000 meteors an
hour.
Distance, Size and Scale
—  Earth is approximately 150,000,000 km (150 million km) from Sun.
Astronomers call this standard Earth-Sun distance 1 Astronomical Unit
(AU).
—  Earth is approximately 100 times smaller than Sun in diameter; the
Moon is approximately 4 times smaller than the Earth. So 4 Moons
would just fit across the Earth, and 400 Moons would just fit across the
Sun.
—  The Moon is roughly 384,400 km from Earth. Coincidentally, this is 400
times smaller than 1 Astronomical Unit, so the Moon can just cover the
Sun as seen from Earth − making a total eclipse possible!
—  Gravity on Moon = 1/6th that on Earth, so you would be 6 times lighter
on the Moon! (Cola cans)
—  The most distant known planet, Neptune, is 30 AU from the Sun; the EKB
is 40–60 AU; and the Oort Cloud ranges from 1,000 AU to 200,000 AU .
—  Let’s build a scale model of the solar system together; see
worksheet
A practical activity spaced over 100m in the playground
Huge Distances
—  For greater distances we use the speed of light to
measure the immense distances in space.
—  Light travels through empty space at nearly
300,000 km per second. Therefore in one year it
can travel nearly 10 million, million km. We call
this distance 1 light year (LY): the distance light
travels in one year.
—  Our Milky Way galaxy is roughly 100,000 LY across!
—  The next nearest galaxy is more than 2 million LY
away.
Our Place in the Universe
—  Galaxy: Milky Way: contains approximately 200,000 million
stars, in a flattened disc-like structure 100,000 light years
across. Our Solar System orbits the Galactic Centre every
250 million years: a “Galactic year”.
—  Another galaxy: Andromeda nebula (picture, beautiful and
inspiring). Can be seen with naked eye, 2.5 million LY away.
We may be able to spot it tonight – in which constellation?
—  Hubble Deep Field: image showing lots of other galaxies
billions of LY away. Astronomers estimate that there are
hundreds of billions of galaxies in the known Universe.
Putting all our previous information together now!!
Galilean moons
Activity to spot them
Kepler’s Laws on the HO
History of mankind’s developing thought on
our place in the Universe
—  Since early times, man has been fascinated with
discovering the origins of the cosmos. Similarly, man has
often been influenced by his creationist ideas: that some
divine power created the universe and everything in it.
—  For example, the Ancient Greeks developed some of the
earliest recorded theories of the origin of the universe.
Unfortunately, many of these Greek philosophers and
astronomers placed the Earth in the center of their
models of the universe. They thought, if the heavens are
divine, and the gods created man, well then certainly the
universe must be geocentric, meaning the Earth is the
center of the universe.
—  Ancient societies were obsessed with the idea that
God must have placed humans at the center of the
cosmos (a way of referring to the universe). An
astronomer named Eudoxus created the first model
of a geocentric universe around 380 B.C. Eudoxus
designed his model of the universe as a series of
cosmic spheres containing the stars, the sun, and
the moon all built around the Earth at its center.
—  Unfortunately, as the Greeks continued to explore
the motion of the sun, the moon, and the other
planets, it became increasingly apparent that their
geocentric models could not accurately nor easily
predict the motion of the other planets.
—  After Aristotle developed a more intricate geocentric model (which was later
refined by Ptolemy), general cosmology clung to these misconstrued ideas for the
next 2,000 years. Even when Nicholas Copernicus introduced the notion of a
heliocentric universe, many contemporary societies greatly influenced by religious
beliefs refused to accept it. Today we consider this a ridiculous question; we can
directly observe that the Earth and the other planets in our solar system orbit
around the sun. It is obvious that the technological advancements of the 20th
century have allowed us to look out to the farthest corners of the visible universe,
but our past history of erroneous assumptions should make us cautious.
—  As we discover more and more about the origins of our early universe, we should
realize that our present theories must be continually tested and modified because
new theories frequently arise as we learn more through our observations. That is
why most physicists and astronomers today are so inclined to accept the Big
Bang Theory as the most plausible explanation for the origin of the universe. It
puts together so many of the pieces of how the universe came into being, and
seems to correct so many of the flaws found in previous theories.
—  Until the 1920s, cosmology was still dominated by the theory of a
Steady State Universe, or the idea that the universe was homogeneous (has the
same general make-up throughout), infinite (that the universe just extends
forever), and static (the universe is not expanding, it just is). If you just study the
night sky, it seems easy just to think that this is the way the universe has always
looked and will always look. In the 20th century, however, observations of the
universe did not seem to add up with Steady State theory