Astronomy Exam 1 Flashcards
(93 cards)
Stars appear to be fixed in _______ that surrounds the Earth
spherical shell (the celestial sphere)
A coordinate system that divides the celestial sphere
Equatorial system of location
The angular distance north or south of the celestial equator
Declination
The angular distance measured eastward along the celestial equator from the position of the vernal equinox
Right ascension
the time interval from one noon to the next- about 24 hours- measurement for rotation
Mean solar day
turning, or spinning, of a body on its axis
rotation
the time it takes for Earth to make one complete rotation (360°) with respect to a star other than the Sun – 23 hours, 56 minutes, 4 seconds
Sidereal day
The motion of a body, such as a planet or moon, along a path around some point in space
revolution
Earth’s orbit is _____
eliptical
Earth is closest to the Sun (perihelion) in _____
January
Earth is farthest form the Sun (aphelion) in ______
July
Direction in which Earth’s axis points continually changes- very slow Earth movement
Precession
Caused by Earth’s changing orientation to the Sunp Axis is inclined 23.5 degree and always points in the same direction
Seasons
-June 21-22- Sun’s vertical rays are located at the tropic of cancer
-the noontime Sun reaches its highest point of the year
-longest day of the year
Summer solstice
-December 21-22- Sun’s vertical rays are located at the Tropic of Capricorn
-The Sun crosses the meridian 23.5 degrees lower in alt. than the celestial equator
-sunset occurs at its farthest point south of due west for the year
-the noontime Sun casts the longest shadows
Winter Solstice
-September 22–23- Sun’s vertical rays are located at the Equator (0° latitude)
Autumnal equinox
March 21–22- Sun’s vertical rays are located at the Equator (0° latitude)
Spring (vernal) equinox
– Cycle of Moon through its phases
– 29.5 days
– Basis of first Roman calendar
– Apparent period of Moon’s revolution around Earth
Synodic Month
– True period of Moon’s revolution around Earth
– 27.3 days
sidereal month
When viewed from above the North Pole, the Moon orbits Earth in a _______ (eastward) direction
Counterclockwise
T/F The relative positions of the Sun, Earth, and Moon constantly change
True
- Moon moves in a line directly between Earth and the Sun
– Can only occur during the new-Moon phase
Solar Eclipse
– Moon moves within the shadow of Earth
– Only occurs during the full-Moon phase
Lunar Eclipse
All forms of radiation travel at
186,000 miles (300,000 kilometers) per second