Further Physics Flashcards
Solar day
So today is the time taken between successive means = 24 hours
Lunar eclipse
This occurs when the Moon moves into the earth shadow. The eclipses are rare because the moon orbits the Earth at the angle about 5° to the Earth’s path around the sun
Solar eclipse
This occurs when the sun, moon and a line up so that the moon appears to block out the sun
Geocentric model
-ptolem = The earth at the centre of the solar system
Heliocentric model
- capernicus = Sun at the centre of the solar system
How do you planets move
Retrograde motion
Retrograde motion
Distant planet take longer to complete their orbits them planet is closest to the sun. Consequently, the relative position change over time
E. G. Mars
What is constellation
A named group of stars that form a pattern in the sky as seen from Earth although the stars themselves usually have no connection with each other
Why can we see more stars in the night sky in summer than winter
- The earth has moved to the other side of its orbit around the sun.
- Nights are longer in winter and there are some very bright lights on show.
- In the summer months are night skies aim towards the centre of the Galaxy
What is the Milky Way
A band of light stretching from the north-east to the south west across the sky
Celestial sphere
An imaginary sphere with the earth at the centre, on which we imagine all astronomical objects are located
Celestial equator
The midline around the celestial sphere
Ecliptic
Path taken by the sun along the celestial to be in one year
Declination
The angle of the object above or below the celestial equator
Right ascension
Angle of the object along the celestial equator with the vernal equinox (point where the elliptic crosses the celestial equator) at zero
What is one arch minute
1/60 of a degree (1’)
What is 1 arch second
1/3600 year of a degree (1”)
Parallax
This is the effect whereby the position of an object appears to change when it is viewed from a moving source
What is the equation of the parallax angle
Parallax angle = Alpha + beta/2
What does the parallax angle show
The parallax angle allows us to find out the distance to stars which are close to earth
What is the relationship between the parallax angle and parsec
When the parallax angle is one of the second the distance is 1 parsec (pc)
The simple question for parsecs (pc)
Distance (in parsecs) = 1/ parallax angle (measured in arc seconds)
What factors affect the brightness of the star
. size
. temperature/age
. distance
. chemical composition
Intensity
Intensity of a source of radiation is the number of photons which fall on a surface every second
What are the properties of intensity
- The radiation spreads out as it moves away from the source
- this means that the intensity decreases with distance. In fact, it obeys the inverse square law, which means that the intensity decreases by value which is inversely proportional to its (distance)2
Sidereal day
It’s ideal day is the time taken for the F to rotate through 360° (measured against a very distant star) = 24 hours and 56 minutes
Heber Curtis hypothesis
- Heber Curtis argued for the island universe hypothesis.
- He said that the spiral nebulae were galaxies like our own
- he believed that our galaxy was only 30,000 ly across
- that our sun was near the centre of it
Harlow Shapley hypothesis
. Harlow Shapley thought our galaxy was much bigger, 300,000 ly across, and that it formed the whole universe
. he believed that the sun was not at the centre of the galaxy
. that the spiral nebulae were just clouds of gas, relatively small and nearby
What did Edwin Hubble look at
- Edwin Hubble looked at variable stars (Cepheid Variables) in the Adronema nebula 2. the cycle of brightness (period) was long, suggesting that the stars were very bright, but they appeared very dim from Earth suggesting that they were very long way away 3. this data suggests that nebulae are other galaxies and are a very long way away
Nebulae
Extended, cloud like, objects in space, for example galaxies or gas clouds
What did Henrietta Leavitt find
She found that there was a direct correlation between the brightness of a variable star and its PERIOD
What is the period of a star
The time it takes to complete a full cycle
How do we work out how far away a a star is
We can work out how far away a star or galaxy is by looking at nearby variable stars and applying the mathematical relationship between distance and velocity
What did Hubble’s graph show
• the correlation on the graph, that is :- all the galaxies are moveing away from each other and the further apart they are, the great the speed at which they are moving (recessional velocity)
What does redshift tell us
The stretching of light to longer wavelengths caused by the expansion, space, or by the recessional velocity of a source
What is the period of a cepheid variable
Is the time taken to go through a full cycle from bright to dim
Heber Curtis hypothesis
- Heber Curtis argued for the island universe hypothesis.
- He said that the spiral nebulae were galaxies like our own
- he believed that our galaxy was only 30,000 ly across and that our sun was near the centre of it
Harlow Shapley hypothesis
- Harlow Shapley thought our galaxy was much bigger, 300,000 ly across, and that it formed the whole universe
- he believed that the sun was not at the centre of the galaxy and that the spiral nebulae were just clouds of gas, relatively small and nearby
What did Henrietta Leavitt examine
Henrietta Leavit examined variable stars in the Greater and Lesser Magellanic Clouds- this meant that she knew they were all the same distance from us
Hubble and the Great Debate
- Edwin Hubble looked at variable stars (Cepheid Variables) in the Adronema nebula
- the cycle of brightness (period) was long, suggesting that the stars were very bright, but they appeared ver dim from Earth suggesting that they were very long way away
- these data suggest that nebulae are other galaxies and are a very long way away
Nebulae
Extended, cloud like, objects in space, for example galaxies or gas clouds
What did Henrietta Leavitt find
She found that there was a direct correlation between the brightness of a variable star and its PERIOD