Topic 2 Flashcards
(22 cards)
what is the shape of the moon
oblate spheroid
where is sea of tranquility on moon
beside sea of crisis (not below it.)
define maria
a mare is a dark area on the moon (latin for sea)
darker as they contain more irob-ruch elements
what % of the moon’s surface can we see from earth
59% due to libration
define terrae
highlands of the moon, terra (latin for earth)
brught areas that are higher on moon’s surface
what is the period of time called where the moon underwent a time a frequent and violent impacts
the ‘Heavy Bombardment’ period
how were maria created
millions of years after heavy bombardment period, moon underwent time of volcanic activity, forcing lava to the surface. this later turned to basalt and flooded lower aeas (not highlands)
define valleys
long depressions of lunar surface
define synchronous rotation
where orbital and rotational period of the moon are the same
how long are sidereal and synodic months
sidereal- 27.3 days
synodic- 29.5 days
what will happen when moon achieves synchronous orbit
moon is moving away from us at 4cm a year
tidal forces slows down moons rotation as it provides a braking force to moon’s rotation.
This tidal friction slows down eatg’s rotation
in billions of years, an earth day will be 55 (present) days and so will moon’s
the moon will appear to hang in same position in the sky
reasons for libration:
1.elliptical orbit of moon around earth
2.planes of moon’s orbit
3.our own obseving position
4.moon has a precession effect so wobbles slightly
libration in longitude
from varying speed in moon’s orbit around earth (elliptical)
can see more of eastern or western limbs
libration in latitude
as equator of moon is titled from orbital plane (5.1 degrees) to the ecliptic
can see over northern and southern polar regions
how many degrees is moon tilted
1.5
diurnal libration
rotation of earth allows us to see more of eastern limb at moonrise and western limb at moonset
due to position on earth (helped by earth’s rotation)
list 3 effects of lunar libration
-can see nearly 59% of moon’s surface
-reveals different features at lunar limbs
-helps astronomers map and study surface of moon in greater detail
name an appropriate time period for measuring linar libration
weeks
give another term for synchronous rotation
being tidally locked
at what position in moon’s orbit will we see a supermoon
when moon is at perigee
what is the moon’s position and phase from night to night a result of
its revolution around the earth
where is the best place to observe moon’s features on moon
along the terminator
-moving line between the illuminated and dark side of moon where features are more pronounced due to long shadows cast by the sun
