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Astronomy
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Chapter 7
Universe Cycle - Solar System
14.04. 2013 Exam
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Meteorology / (Chapter 6 )
Chapter 6
Universe Cycle - Solar System
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Meteorology
Gosmolgy: the branch of astronomy that deals with the general structure and
evolution of the universe.
The Milky Way is the galaxy that contains the Earth.
Galaxy: A system of millions or billions of stars, together with gas and dust,
held together by gravitational attraction
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Chapter 6
Universe Cycle - Solar System
• The universe is commonly defined as the totality of everything
that exists, including all physical matter and energy, the
planets, stars, galaxies, and the contents of intergalactic
space.
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Contents
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•
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The Solar System
Stars
Solar Systems, Galaxies & the Universe
Comets, asteroids and meteoroids
History of the Universe
Future of the Universe
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The Solar System
What is the Solar System?
In the Universe,
the Solar System is our homeland,
and the Earth is our hometown.
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The Solar System
The Solar System consists of
• the sun in its centre
• nine planets,
circling around the sun
• moons
• asteroids
• and comets.
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The Solar System
How did the Solar System evolve?
• Scientists are quite sure, that in the beginning of our
Solar System there was a huge disc of dirt, rocks,
gas, ice etc.
• In the middle of this disc, the Sun formed itself and
began to glow.
• In some distances from the centre, the planets
emerged from these rings of dirt, rocks and gas.
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The Solar System
How large is our Solar System?
• The orbit on which Pluto (the farthest planet)
circles the sun, has an average diameter of
5.910.000.000 km (Pluto‘s orbit is rather noncircular).
• The sun itself, the largest object in our Solar
System has a diameter of 1.392.520 km.
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The Solar System
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Planets
• Rocky planets
􀁹 Formed below the frost line (≈ 3 AU)
􀁹 Rich in metal and silicates. Small sizes
􀁹 Unable to retain H2 or He. Thin atmospheres
• Gaseous planets
􀁹 Formed beyond the frost line
􀁹 Condensation of volatiles. Large sizes
􀁹 Large atmospheres of H2 and He
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The Planets
Mercury is the planet that is closest to our Sun.
Pluto is the farthest. Remember the order of
the planets like this:
My Very Educated Mother Just Showed Us Nine
Planets
which means
Mercury Venus Earth Mars Jupiter Saturn
Uranus Neptun Pluto
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Stars
• Stars are burning balls of gas e.g. our Sun
• Stars give out light
• This light reflects off planets so we can see them
• Planets are much smaller than stars
… but they seem much bigger as they are much closer
• The 9 planets orbit the sun, Earth orbits the Sun once a year
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Solar Systems, Galaxies & the Universe
Our Sun is one of
millions of stars that
orbit the centre of the
Universe
The Milky Way is one of
more than a billion
galaxies in the Universe
The Universe is expanding
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Solar Systems, Galaxies & the Universe
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Small Bodies
There are other smaller object that orbit the Sun, including asteroids,
comets, meteoroids and dwarf planets.
•Asteroids (also called minor planets) are rocky or metallic objects, most of
which orbit the Sun in the asteroid belt between Mars and Jupiter.
•Comets are small, icy bodies that orbit the sun. They have very long tails.
•Meteoroids are small bodies that travel through space. They are stony
and/or metallic and are smaller than asteroids. Most are very tiny.
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Comets
• Comets appear every few years
• Comets have highly elliptical orbits around the Sun
Tail is pushed away from sun by solar pressure
Tail is made of ice and rock
• Comets are visible when they are close to the Sun
• A comet’s orbit is fastest near the Sun due to the Sun’s gravity. It
slows as it moves further away from the Sun
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History of the Universe
Big Bang Theory
• Universe was compressed and exploded – Big Bang
• Occurred 15 billion years ago
• Estimated by current rate of expansion
• Expansion is slowing due to gravity
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Summary
• Solar system – 9 planets & 1 star
• Stars emit light, planets reflect this light
• Solar systems are in galaxies which are in the Universe
• Comets (rock and ice) have long elliptical orbits around Sun
• Life cycle of stars – differs for massive & small stars
• History of the Universe – Big Bang
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The terminating of
part 1
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Planets
• Rocky planets
􀁹 Formed below the frost line (≈ 3 AU)
􀁹 Rich in metal and silicates. Small sizes
􀁹 Unable to retain H2 or He. Thin atmospheres
• Gaseous planets
􀁹 Formed beyond the frost line
􀁹 Condensation of volatiles. Large sizes
􀁹 Large atmospheres of H2 and He
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The Planets
Mercury is the planet that is closest to our Sun.
Pluto is the farthest. Remember the order of
the planets like this:
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Mercury
What are Mercury‘s features?
•
•
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second smallest planet
nearest to the sun
one Mercury-year is a quarter Earth-year
Mercury is very difficult to be spotted with the naked
eye
• Mercury has no moons
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Venus
What are Venus‘ features?
• it is a medium sized planet, 2.5 times as large as
Mercury
• second nearest to the sun
• Venus is very well visible to the naked eye, always
close to the sun before sunrise or after sunset
• Venus has no moons
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Earth
What are Earth‘s features?
• it is a medium sized planet, a bit larger than Venus
• (probably) the only planet with liquid water in our
Solar System
• the Earth has one moon
• (probably) the only planet with intelligent life in our
Solar System
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Mars
What are Mars‘ features?
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•
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it is a small sized planet, half as large as Earth
Mars is well visible to the naked eye
Mars has two moons: Phobos and Deimos
Mars has been visited by robotic vehicles:
Pathfinder, Spirit and Opportunity
• the question for (former) life on Mars is still unsolved
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Jupiter
What are Jupiter‘s features?
• it is the largest planet of the Solar System,
more than 1.300 Earths could fit inside
• Jupiter is well visible to the naked eye
• The Great Red Spot on its surface is a giant storm as
wide as three Earths
• Jupiter has 63 moons! (the largest are Io, Callisto,
Ganymede and Europa)
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Saturn
What are Saturn‘s features?
• it is the second-largest planet of the Solar System,
only a bit smaller than Jupiter
• Saturn is well visible to the naked eye
• the famous rings can be seen with small telescopes
• Saturn has at least 34 moons! (recently a probe
landed on Jupiter‘s moon Titan)
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Uranus
What are Uranus‘ features?
• it is medium sized planet of the Solar System
• it is quite far away but still can be spotted with small
telescopes
• like Saturn, Uranus has a system of rings
• Saturn has at least 27 moons
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Neptune
What are Neptune‘s features?
• it is medium sized planet of the Solar System, only a
little bit smaller than Uranus
• it is quite far away but still can be spotted with small
telescopes
• Neptune has four rings and at least 13 moons
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Pluto
What are Pluto‘s features?
• it is the smallest planet of our Solar System
• Since Pluto is far away and so small, you need a
medium-sized professional telescope or a good
amateur telescope to spot it.
• Noone knows what Pluto looks like – it‘s too far away
and too small. The picture in the background is an
artist‘s rendition.
• Pluto has one moon: Charon
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Moons
What are moons?
• Moons are like little planets that encircle the real
planets.
• Usually, they are much smaller than planets.
• Planets can have no moons (like Mercury and Venus),
one moon (like Earth) or up to a very large number of
moons (e.g. 63 for Jupiter).
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Moons
Phobos and Deimos
• Phobos and Deimos are Mars‘ companions. Phobos
means “fear“, Deimos means “panic“. Mars itself has
been named for the Roman God of War.
• They are quite small (<15km) and look rather like
potatoes than like moons.
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Moons
Io, Callisto, Ganymed and Europa
• These four moons are the biggest moons of
Jupiter. They can be seen with small
telescopes or even with binoculars.
Io
Europa
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Planets of other stars
Are there more planets in the Universe (except for the
ones in the Solar System)?
• Yes, there are other planets, so-called extra-solar
planets.
But it is very difficult to spot them, since they are far
far away.
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Planets of other stars
How can planets of other stars be spotted?
There are two main ways that astronomers search for these
planets:
• If you observe a star very accurately with special instruments,
you may be able to measure a slight “wobble“. This can
indicate a planet.
• If you can observe many stars after night, you may sometimes
see one get slightly fainter for a little while. This happens if a
planet passes between us and the star – like a mini-eclipse.
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More Information
SkyWatch links:
• Views of the Solar System
• The Nine Planets
• StarChild
Celestia Exploration Activity:
http://learn.arc.nasa.gov/planets/
Solar System Exploration:
http://solarsystem.nasa.gov/planets/
Welcome to the Planets:
http://pds.jpl.nasa.gov/planets/
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The terminating of part 2
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Discovering the atmosphere on different planets
An atmosphere is the layer of gases that envelop a planet. On the Earth, it is this envelope
that allows organisms to live. Atmospheric ozone protects us from ultraviolet radiation. CO2
and other gases trap heat and keep the surface warm enough for life to thrive. Oxygen has
allowed life to evolve.
Each of the planets has a different atmosphere, although there are clear similarities between
the atmospheres of the four terrestrial planets and the four gas giant planets. The terrestrial
planets are rich in heavier gases and gaseous compounds, such as carbon dioxide, nitrogen,
oxygen, ozone, and argon. In contrast, the gas giant atmospheres are composed mostly of
hydrogen and helium.
The atmospheres of at least the inner planets have evolved since they formed. This is
clearest for the Earth. The Earth’s original atmosphere was probably similar to Venus in
composition, consisting of carbon dioxide and nitrogen. The evolution of photosynthesis
converted carbon dioxide in the Earth’s atmosphere to oxygen, increasing the amount of O2
in it from an initial 0.01% to its current 22% level.
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Astronomical unit
1 AU = 149,597,870.691 kilometers
Definition: An Astronomical Unit is approximately the mean
distance between the Earth and the Sun. It is a derived constant and
used to indicate distances within the solar system
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NASA
• The
(National
Aeronautics
and
Space
Administration) is an Executive Branch agency of
the United States government, responsible for the
nation's civilian space program and aeronautics and
aerospace research. Since February 2006, NASA's
self-described mission statement is to "pioneer the
future in space exploration, scientific discovery and
aeronautics research."
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Atmospheres of the rocky planets
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Atmospheres of Uranus and Neptune
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Homework
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