Ay [T5/T6] - Observing the Solar System Flashcards
What is retrograde motion?
Orbital or rotational movement of an object in the opposite direction to the direction it usually goes
Who was Ptolemy and what was his contribution to the model of the solar system?
Suggested…
- earth was off centre
- epicycles orbited the equant
in the geocentric model
Who was Nicolas Copernicus and what was his contribution to the model of the solar system?
Re-suggested…
- heliocentric model based upon mathematical modelling
Who was Tycho Brahe and what was his contribution to the model of the solar system?
- made detailed observations of Mars using a sensitive protector
- died before they could be used
Who was Johannes Kepler and what was his contribution to the model of the solar system?
- suggested the orbits of the planets were elliptical rather than circular
Who was Galileo Galilei and what was his contribution to the model of the solar system?
- made observations of Jupiter’s moons
- observed phases of Venus
- leading to acceptance of heliocentric model
What does precession mean?
The relatively slow wobbling of the Earth’s axis, tracing a circular path in the sky.
What is the definition of the winter solstice?
The day when the sun lies directly overhead on the tropic of capricorn.
How long is one axial precession?
25,771.5 years
What tilt does the earth rotate on?
The earth rotates on a tilt of 23.5°
What is an inferior planet?
A planet closer to the Sun than Earth.
What is a superior planet?
A planet further away from the Sun than Earth.
What is the name of the path that the planets and sun take across the sky?
The zodiacal band
Why do the planets appear to sometimes move backwards in the sky?
Due to…
- retrograde motion
- the changing speeds of the planet
What does occultation mean?
A transit where one celestial body obscures and covers another and so blocks its light.
What does transit mean?
The passing of a planet in front of the sun.
What does opposition mean?
When the earth is in between the sun and a celestial object.
Typically used to describe a superior planet’s position, and is when we are able to observe it from earth the best.
What does conjunction mean?
When a planet is in front of or behind the sun as viewed from earth.
When any planet lies on the furthest side of the sun from the earth, it’s in superior conjunction.
When an inferior planet lies in between the sun and the earth, an inferior conjunction takes place.
What does elongation mean?
The angle at which we see an inferior planet - only inferior planets will have elongation
When is an inferior planet best viewed?
When it’s at a position forming a 90° angle between the sun and the earth.
What are the maximum elongation to eastern and western points called?
Greatest Eastern Elongation (GEE)
Greatest Western Elongation (GWE)
What is the definition of the summer solstice?
The day when the sun lies directly overhead on the tropic of cancer.
What and when are the two extremes of the sun’s positions in the sky?
- summer solstice (june 21st): sun reaches it’s highest point in the sky
- winter solstice (december 21st): sun reaches it’s lowest point in the sky
[Past Paper]
What is the name given to the point of zero right ascension on the celestial sphere, defined by the position of the Sun in the sky on the vernal (spring) equinox?
The first point of Aries
Why did Tycho Brahe not include Uranus and Neptune in his model?
They hadn’t been discovered yet
