📍W2 L2 - Looking at the sky - Cycles and phases Flashcards
What season did the dinosaur destroying asteroid hit the Earth?
Northern hemisphere spring, Southern hemisphere autumn
What is the single eponymous term used for the 3 periodic motion changes in Earth’s orbit?
Milankovitch cycles
What is the Earth’s spinning top motion called?
Precession
How long does it take for Earth to complete one precession cycle?
26,000 years
What is the change in Earth’s axial tilt called?
Change in obliquity
How much does the Earth’s axial tilt range between?
22.1’ and 24.5’
How long does the obliquity cycle take to complete?
41,000 years
What is the change in eccentricity of the Earth’s orbit called?
Elliptical eccentricity
Why does the zero point for right ascension change over time?
Earth’s precession
What coordinate system do we use at present for alt/azimuth?
J2000
What are 2 names for the phenomenon called where the same part of the moon faces Earth?
Tidal locking or synchronous rotation
In one sentence, and in relation to the moon, define a sidereal month
One full revolution of the moon relative to background stars
How long is a sidereal month
27.3 days
Define a lunar month
One full revolution with respect to the Sun to return to the same phase
How long is a lunar month?
29.5 days
What angle is the moon offset to the ecliptic/
5.2 degrees
What is the name for the point in the moon’s orbit where it crosses the ecliptic?
The line of nodes - where lunar orbit crosses ecliptic
What is special about the moon sun relationship at the line of nodes
Eclipses can happen
What is the name for the period in its orbit when the moon is rising above the ecliptic plane?
Ascending node
During eclipse, what is the darkest part on Earth that the eclipse shadow falls on called?
The umbra
What is the partial shadow area falling on the Earth during a solar eclipse known as?
The penumbra
Is the moon’s orbit circular or elliptical?
Elliptical
When viewed from the Earth, what type of eclipse occurs when the moon is far from the Earth?
An annular eclipse
the edge of the sun remains visible around the moon
What type of eclipse occurs when the moon is close to the Earth (and between the Earth and the Sun)?
Total solar eclipse
What type of eclipse occurs when the Earth is between the moon and Sun?
Lunar eclipse
What colour is the moon when it’s eclipsed by the Earth and in its umbra?
Red
What duration is the moon’s precession?
18.6 years
