A5 - Solar System observation Flashcards
How would you observe the Sun safely? Why is this a safe method?
pinhole projection
-make a small hole in a piece of card
-project onto a screen behind the hole
-reduces excess radiation from the Sun entering the eye
Describe the apparent motion of the Sun:
follows the ecliptic in prograde motion over the course of a year
What is prograde motion? Describe it using equatorial coordinates:
movement from West to East relative to the stars (increasing RA)
The Sun and Moon always exhibit prograde motion
What is retrograde motion? Describe why it happens:
-movement from East to West relative to the stars (a “backwards” motion happening over several months)
-Earth “overtakes” the planet in its orbit and the other planet appears to move backwards
This motion can happen for both inferior and superior planets
Describe and explain the apparent orbital paths of planets:
Don’t refer to their motion
-confined to the zodiacal band
-their orbital paths are slightly inclined to the plane of the Solar System so it is not perfectly on the ecliptic
What is the First Point of Aries?
-a point on the ecliptic that crosses the celestial equator, where the Sun lies at the Spring/Vernal Equinox
-where Right Ascension is measured from (0hrs)
It now lies in Pisces, axial precession changed its location
What is the First Point of Libra?
-another point on the ecliptic that crosses the celestial equator where the Sun lies at the Autumnal Equinox
-12hrs RA
It now lies in Virgo, axial precession changed its location
What is the ecliptic? Describe 2 main points on the ecliptic:
-the apparent path the Sun takes over the course of a year, inclined at 23.5° to the Celestial Equator
-crosses the CE twice - once as the First Point of Aries, and then at the First Point of Libra
What causes a meteor shower?
Earth passes through a comet’s dust trail which is full of meteoroids orbiting the Sun
Why might a meteor come from a different direction than the radiant of a meteor shower at that time?
-it is a sporadic meteor
-not part of the current meteor shower
What is the difference between a superior and inferior conjunction?
-superior conjunction is when a planet is furthest from us as it is opposite the Sun
-inferior conjunction is when an inferior planet is between Earth and the Sun, and if it crosses the solar disk it is called a transit
What is opposition?
when a superior planet is closest to Earth (directly opposite the Sun), and is when it appears biggest and brightest
What is meant by greatest elongation?
when an inferior planet has the greatest elongation (angular separation) from the Sun
In general, elongation is defined as the angular separation between the Sun and another planet, using Earth as a reference point
