P7: Naked Eye Astronomy

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What can observations of the Sun, Moon, nearby planets and stars tell us?
A lot about the nature and movement of objects in the solar system and beyond.
Which are the nearest planets that can be seen with the naked eye?
Mercury, Venus, Mars, Saturn and Jupiter.
What do the planets sometimes appear to move with?
Retrograde Motion
What is retrograde motion?
The real of apparent movement of an astronomical object across the sky in the opposite direction to the rotation of the sun.
How do the stars appear to move across the sky?
From east to west in slightly less than 24 hours.
How long does it seem to take the moon to move from east to west across the sky?
Slightly longer than 24 hours.
Why will different stars will be visible from a position on Earth at different times of the year?
Because the earth orbits the sun.
What is the lunar cycle?
The Moon's appearance changing during its 28-day orbit of the Earth.
What is a new moon?
When the Sun is effectively behind the Moon, the side of the Moon that faces the Earth is in shadow.
What is a full moon?
When the side of the Moon that faces the Earth is fully illuminated by the Sun.
When does a solar eclipse happen?
When the Moon passes directly between the Sun and the Earth - on the same line - casting a shadow of the Moon on the surface of the Earth.
At what phase of the moon's orbit would a solar eclipse occur on?
New moon
What is a total eclipse?
If the moon completely obscures the sun.
What is a partial eclipse?
If the moon partially obscures the sun.
Why is viewing solar eclipses with the naked eye dangerous?
It can burn your retina and lead to permanent damage to your eye.
What is a safe way of viewing solar eclipses?
using a pinhole viewer
What is a Lunar eclipse?
When the Earth passes directly between the Sun and the Moon, casting a shadow of the Earth on the surface of the Moon.
Which of the moon's phases would a lunar eclipse occur under?
Full moon
How can the position of an astronomical object can be plotted?
With 2 angles, relative to a point on the Earth.
What does the angle of declination refer to?
Whether the object is above or below the line of the equator. A positive angle of declination means that the object will be seen more clearly from a position in the Northern hemisphere.
What is the angle of right ascension and what is it measured in?
The measurement of the angle east from the vernal equinox point. Measured in degrees and minutes.
What is the vernal equinox point?
The day in the springtime when the duration of the day is the same as the duration of the night.
What is a solar day?
The time taken for the Sun to move from its highest point in the sky back to its highest point the following day. This is exactly 24 hours.
What is a sidereal day?
The time it takes for the Earth to actually rotate once on its axis. A sidereal day is four minutes shorter than a solar day.
Why is the sidereal day shorter than the solar day?
as well as rotating on its axis, the Earth also orbits the Sun.
What is the ecliptic?
The path that the Sun traces across the sky.
What is the ecliptic plane?
The plane in which the Earth orbits the Sun
How frequently do solar and total eclipses ocur?
Solar- 2-5 somewhere on earth every year
Total- approximately once every 18 months.
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