Download TY Course Day 2 Friday 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/esammg/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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http://en.wikipedia.org/wiki/List_of_solar_eclipses_visible_from_the_United_Kingdom_AD_1000–2090
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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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
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!!
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.