The Sky, The Moon and Astronomy Flashcards
How long is a sidereal day?
23 hours and 56 minutes
What is a sidereal day?
The time taken for a star to return to the same position in the sky.
Which way do stars appear to cross the sky?
East to west
What is a solar day?
Time taken for the sun to appear at the same position in the sky
How long is a solar day
24 hours
Why are solar and side real days different?
Because the earth orbits the sun as well as spinning on its axis, so it has to go an extra four minutes
Why does the moon go more slowly than the sun?
Because the moon orbits the earth in the same direction as the earth is rotating (it takes 25 hours)
What is an earth year?
Time it takes the earth to orbit the sun once
Does the direction we face change each year?
Yes, it means each night we see different stars
Does the moon glow???
No it reflects light from the sun, only the half facing the sun is lit up, leaving the other half in shadow
What are the two extremes of the phases of the moon?
Full moon - the whole of the lit up surface of the moon is facing the sun
New moon - when the dark surface is facing the moon
What are the two main types of eclipses called
Lunar eclipse
Solar eclipse
Explain a total lunar eclipse
As the moon orbits the earth, it sometimes passes into the earths shadow. The earth blocks sunlight from the moon, so almost no light is reflected from the moon, so the moon seems to DISAPPEAR
Explain a partial lunar eclipse
More often, the moon isn’t fully in the earths shadow so only part of it appears dark
Explain a total solar eclipse
The moon by chance is just the right side and distance away that when it passes between the sun and the earth, it can block it out. SO WE CAN’T SEE THE SUN
Explain a partial eclipse
When only part of the sun is blocked out, this is more likely
Why don’t eclipses happen very often
The moon orbits the sun at an angle to earths orbit around the sun. So most of the time the sun, moon and earth don’t line up to cause an eclipse
Why do partial eclipses happen more often?
Moon, earth and sun do not have to line up perfectly.
How are positions of stars measured?
By angles seen by earth
What is the pole star?
A star that doesn’t seem to move because its almost directly above the North Pole and the spin axis of earth
What is the celestial equator
An imaginary plane running across the sky, extending out from the earths equator
What are the two angles used to measure portions in the sky?
Declination
Right ascension
What is declination?
Celestial latitude measured in degrees
What is right ascension?
Celestial longitude (how much across angle) measured in degrees or time
How does the distance of planets from the sun affect their speed?
The closer to the sun, the quicker the planet
In what direction do planets seem to travel ?
From west to east
What is retrograde motion?
When a planet seems to change direction, making a loop or squiggle in its track before carrying on as normal.
Which planets does retrograde motion happen to?
Only the outer planets
Why does retrograde motion happen?
Because both the planet and earth are moving around the sun. We see the motion of the planet relative to the earth
Do planets further in or out change frequency more often
Planets further out change direction less frequently
