GCSE A* REVISION NOTES


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Planetary Systems

Size of the Solar System

Planets

Dwarf Planets

Asteroids

Comets

Centaur

TNO (Trans-Neptunian Objects)

Kuiper Belt

Oort cloud

Orbits

The earth orbits the sun on the elliptical plane. The orbits of the other planets are slightly inclined to the ecliptic. Mercury is the greatest with +7 degrees.

This means that the planets appear to move across the sky in the zodiac band.

Sometimes the planets appear to move backwards. This is called retrograde motion.

Ecliptic – The path the sun takes through the celestial sphere in a year

Zodiac Band - An area eight degrees either side of the ecliptic which contains the constellations of the zodiac and the planets.

Perihelion - When an object is closest to its focus

Aphelion - When an object is furthest from its focus

Greatest Elongation - When an inferior planet is at a position forming a right angle between the earth and the sun. This is the best time for viewing the planet as it is from our perspective furthest from the sun

Conjunction - When a superior planet is on the opposite side of the sun or when an inferior planet is in front of the sun

Opposition – When a superior planet is on the opposite side of the earth to the sun. This is when it is best to view the planet.

Transit – When a smaller body passes in front of a larger one

Occultation – When a body is hidden by another

Characteristics of the planets

Planet

Orbital Period

(years)

Average Temperature

Diameter (1000 km)

Rotation Period (days)

Distance from Sun (AU)

Mercury

0.24

170

4.0

59

0.38

Venus

0.62

470*

12.1

243 (retrograde)

0.72

Earth

1.0

15

12.8

1.0

1.0

Mars

1.9

-50

6.8

1.0

1.5

Jupiter

11.9

-150

143

0.41

5.2

Saturn

29.5

-180

121

0.43

9.5

Uranus

84

-210

51

0.72

19.1

Neptune

165

-220

50

0.67

30.0

*Venus is an exception to this trend because its dense atmosphere full of greenhouse gasses insulate it. This is a good demonstration of the greenhouse effect and what global warming could turn earth into

Space Probes

Manned Disadvantages

Space adaptation Syndrome – The lack of gravity causes disorientation, headaches, poor concentration and vomiting

Physical Problems – Lack of gravity causes the muscles to deteriorate and bones become weaker

Communication Delays – On longer missions the astronauts would take a long time to communicate with control

Radiation Issues – Without the Earth’s protective shielding the prolonged exposure to solar radiation could cause cancer

Psychological Problems – Living and working with the same people in a confined environment could cause fatigue, irritability and low motivation

Time Factor – Most missions take too long for humans

Life Support – Humans need a lot more room and resources than a probe such as oxygen and water which you have to take – extra weight

Unmanned Disadvantages

Adaptation – Probes cannot improvise and perform new experiments

Independence – They are reliant on control to get them out of trouble

Case Studies

Moons

Mars

Neptune

Triton (largest)

Dark Proteus

Nereid

Origins

Ring Systems

Origins

Comets

Meteors

Meteoroid – In space

Meteor – In atmosphere

Meteorite – On ground

Micrometeorite – Really small meteorite

PHOs

Near Earth Objects – bodies those trajectory may bring them closer to the earth than 0.3 AU

Potentially Hazardous Objects – bodies that have objects that bring them closer than 0.05 AU to the earth

Evidence

Discoveries

Heliocentric Solar System

Tycho

Galileo

Kepler’s Laws

Ceres

Uranus

Neptune

Pluto

Gravity

Exoplanets

Methods of discovery

Astrometry

Transit Method

Radial Velocity Method

Goldilocks Zone

Water

Extra-terrestrial life

 


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