P7.1 Flashcards
- In what direction do the sun, moon and stars appear to travel over what time period?
Sun: from East to west- 24 hours
Moon: from East to west- 25 hours
Star: from East to west- 23 hours 56 minutes
- What is a sidereal day?
- The time taken for a star to return to the same position in the sky
- 23 hours 56 minutes
- the time it takes for the Earth to spin on its axis 360⁰
- What is a solar day?
- the time taken for the Sun to appear the same position in the sky.
- 24 hours
- What is the difference between a sidereal and a solar day?
-a solar day takes 4 minutes longer as the Earth rotates on its axis in the same direction that we orbit the sun, so it takes an extra degree of rotation for the sun to appear the same position in the sky
- What planets can be seen with the naked-eye?
-Mercury, Venus, Mars, Jupiter and Saturn
- What does ‘naked-eye’ mean?
-without a telescope
- What do all planets seem to move with?
-the stars
- Planets can change their position relative to what?
-fixed stars
- What is a total eclipse?
- sunlight is totally blocked
- lunar/solar
- What is a partially eclipse?
-part of sunlight is blocked
- What is a solar eclipse?
- moon blocks the sun
- at right position/angle
- What is a lunar eclipse?
-moon in earth’s shadow
- What is the frequency of total eclipses?
-low frequency
- Why are eclipses rare?
-partial eclipses more likely
-have to be at right angle
(the relative tilt of the orbits of the Moon about the Earth and the Earth about the Sun)
- Where can total eclipses be seen from?
-small regions of the earth
- Why are different stars seen in the night sky at different times of the year, in terms of the movement of the Earth round the Sun?
-earth moves round sun= direction we face changes each day
=we see different patch of stars each night
- How often will you see the same patch of stars?
-same day each year, as an earth year is
- What is an Earth year?
- the time it takes the Earth to orbit the sun once
- What are the two angles that the positions of astronomical objects are described in terms of?
- right ascension
- declination
- What is right ascension?
- celestial longitude (how much across)
- measured in degrees or time
- What is declination?
- celestial latitude (how much up)
- measured in degrees
- How are the positions of stars measured by?
-angles seen from earth
- What are the two fixed positions astronomers measure from when describing the positions of astronomical objects (and describe)?
- pole star: almost directly above north pole so doesn’t seem to move (on spin axis)
- the celestial equator: imaginary plane extending out from earths equator
- What does right ascension do as you go further east?
-increases
- How is it possible to have an angle as time?
-earth turns 360⁰ every 24 hours
- What is a full moon?
-when the lit up half of the moon faces us
- What is a new moon?
-when the dark side of the moon faces us
- What are naked eye planets?
-planets you can see without a telescope
- What are examples of naked eye planets?
-Mercenary, Venus, mars, Jupiter, Saturn
- What is the orbit of planets in our solar system like?
- all orbit in same direction
- different speeds (closer to sun= quicker
- What planets show retrograde motion?
- outer planets
- Mars, Neptune
- What causes retrograde motion?
- because the planets and further planets orbit the sun in the same direction at different speeds
- we see the motion relative to earth
- Where does retrograde motion happen?
-against a background of fixed stars
