Astronomy Test 1 Objectives
No description yet. This curated deck is ready for daily study.
Card preview (24)
Name the five north circumpolar constellations and tell what each represents.
Ursa Major - the Great Bear, the Big Dipper Ursa Minor - the Little Bear, the Little Dipper Cassiopeia - the Queen Cepheus - the King Draco - the Dragon
On an unlabeled star chart, draw in the connecting lines to identify the five north circumpolar constellations. On the diagram, label the positions of Polaris, Thuban, and Mizar.
/
Describe the geocentric theory of the universe held by many early Greeks.
Earth is motionless at the center of the universe. The stars are attached to a celestial sphere that rotates daily around the Earth. There are 7 objects (Greek: “planet” = wanderer) (Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn) that moves in front of the celestial sphere.
Name the 7 objects that can be seen with the eye to move against the background stars. With which day of the week is each identified?
Sun - Sunday Moon - Monday Mars - Tuesday Mercury - Wednesday Jupiter - Thursday Venus - Friday Saturn - Saturday
List the astronomical contributions of the ancient Greek philosophers Aristotle, Eratosthenes, Hipparchus, and Ptolemy.
Aristotle - concluded that Earth was round because always cast round shadow when it eclipses the moon geocentric Earth motion requires a continued push or pull Eratosthenes - determined diameter of the Earth Hipparchus - catalogued the location of about 850 stars divided brightness of stars into 6 groups measured the length of the year to within minutes of today’s value developed a method to predict lunar eclipses Ptolemy - wrote the Almagest, a summary of astronomy developed a geocentric model that explained retrograde motion
Describe the Ptolemaic model of the universe. What is the retrograde motion?
planets move in perfect circular orbits around a motionless Earth planets orbit on small circles (epicycles) and revolve on large circles (deferents)
Describe the contributions to modern astronomy of Nicolaus Copernicus, Tycho Brahe, Johannes Kepler, Galileo Galilei, and Isaac Newton.
Copernicus - 1. Stars are stationary, therefor Earth rotates 2. Heliocentric model 3. Planets move in perfect circles at constant speeds Brahe - made careful observations that were good to within 1-2 min of arc (could not detect parallax) Kepler - Kepler’s (3) Laws of Planetary Motion Galileo Galilei - “Father of Modern Science”; discovered inertia (no force necessary to keep Earth/planets in motion); made first astronomical telescope and with it discovered: Jupiter’s moons; planets are disks; moon has mountains, craters, darker areas; Milky Way made up of stars; Sun has dark spots that move; Venus shows a full range of phases Isaac Newton - invented calculus; invented reflecting telescope; established celestial mechanics; Three Laws of Motion; Law of Universal Gravitation
List and describe the three main obections to the heliocentric model of the universe at the time of Copernicus.
• from theologians - Earth is not at the center (mankind is supposed to be pinnacle of creation) • counter to “common sense” -no effects of motion could be observed 3, no parallax effect observed -stars should move in small closed loops
“Modern” science is often dated from Galileo. Why? List some of Galileo’s significant discoveries.
overthrew authority of Aristotle through observation and experimentation discovered inertia advocated the Copernican model because of its simplicity and logic made first astronomical telescope -Jupiter’s moons -planets are disks,not points of light like the stars -Moon has mountains, craters, darker areas - Maria - Milky Way is made up of many stars - Sun has dark spots that move around the Sun -Venus shows a full range of phases and appears to vary in size -expected in Copernican (heliocentric) model
Describe Kepler’s three laws of planetary motion. What is meant by the eccentricity of a planet’s orbit? Given the distance to a planet in AU, calculate the period of its orbit.
• The planets orbit the Sun in ellipses, with the Sun at one focus. • A line joining the Sun and a planet sweeps out equal areas in equal times. • The square of the period of revolution (P) is proportional to the cube of the average distance (R) of the planet from the Sun. Eccentricity is the ratio of the distance between the foci of the orbit to the length of the major axis.
Describe/apply Newton’s three laws of motion. • Distinguish between mass and weight. • Describe why a light object falls at the same rate as a heavy object, neglecting the effects of air resistance.
• Every object at rest remains at rest or every object in motion remains in uniform motion in a straight line unless acted upon by some outside force. • The acceleration given to an object is equal to the net force applied to it divided by its mass. • For every action there is an equal and opposite reaction. Mass is a measure of the inertia of an object and is the same everywhere. Weight is a measure of the gravitational force of attraction on an object and depends on where it is measured. Because F/m=a, and 10F/10m=a.
Describe/apply Newton’s Law of Universal Gravitation.
Every object in the universe attracts every other object with a force that is directly proportional to their masses and inversely proportional to the square of the distance between them. F=G((m1m2)/rsquared) double mass doubles weight double mass, leave r the same, double weight
Describe the difference between rotation and revolution. What time periods do each of these produce for the Earth?
rotation: spinning on its axis; revolution: orbiting, i.e. Earth’s movement around the Sun day and night; seasons
What is a solar day and a sidereal day, and describe why one is different than the other.
avg time from noon to noon; avg. ~ 24 hours Sidereal day is the rotation of the Earth with respect to a star other than our Sun. 23 hrs 56 min 4 sec
Describe some characteristics of the Earth’s orbit around the Sun (e.g., elliptical shape, perihelion, aphelion, avg. distance from the Sun, etc.).
elliptical shape - two foci as opposed to a circle’s one perihelion - nearest to sun, 91.5 mil miles, Jan. 3 apheliond - furthest from sun, 94.5 mil miles, July 4 avg. distance from Sun 93 mil miles
Describe what precession means and what effect it produces.
a slow motion of Earth’s axis that traces out a cone over a period of 25,800 years; the “wobble” of the Earth’s axis
Name and describe some characteristics of the Moon and its orbit around the Earth.
More elliptical around the Earth than the Earth’s orbit around the Sun (e=.055 vs. .017) perigee - point of closest approach of the Moon to the Earth apogee - point where Moon is farthest away from Earth avg. distance from Earth to Moon - 238,00 miles
Distinguish between a lunar sidereal and synodic month and explain why there is a difference between them.
sidereal: revolution of moon wrt a star - 27 1/3 days synodic: revolution of moon wrt the Sun - 29 1/2 days because moon revolves around earth while earth-moon system also orbits Sun. after moon completes revolution, still not reached starting position wrt Sun which is directly between directly between Sun and Earth (new moon). This takes an additional 2 days.
Given a diagram of the Earth, Moon, and Sun with the Moon at different positions in its orbit about the Earth, name and identify the positions of the eight phases of the Moon. Tell when each phase will rise, be overhead, and set as viewed from Earth.
see chart
Describe the relation between rotation and revolution for the Moon.
the time period is the same - 27 1/3 days
Describe the difference between the umbra and penumbra of a shadow.
umbra- the central, completely dark part of a shadow produced during an eclipse penumbra- the portion of a shadow from which only part of the light source is blocked by an opaque body
Describe how eclipses and tides are produced. • partial, total, and annular solar eclipses • spring tides and neap tides • partial and total lunar eclipses
Sun, Moon, and Earth must be exactly lined up. partial solar eclipse: when the penumbra of the moon’s shadow hits the Earth total solar eclipse: when the umbra of the Moon’s shadow hits the Eart annular solar eclipse: when the Moon is at apogee at the time of a solar eclipse causing the tip of the umbra to not quite reach the Earth; Sun appears as a bright ring around the Moon partial lunar eclipse: when penumbra of Earth’s shadow hits moon total lunar eclipse: when umbra of Earth’s shadow hits moon Tides created by gravitational pull of the Moon (and the Sun but to a lesser extent). There are two “bulges” on opposite sides of the Earth. spring tides: new moon and full moon; the effects of the Moon and the Sun combine to create a larger tidal range neap tides: first and third quarter phases; moon’s effect minus sun’s effect creates smaller tidal range
Describe and/or identify the lunar highlands, maria, craters, rayed craters.
highlands: densely cratered, brighter areas; 4.5 bil yrs old maria: darker areas, relatively flat, large impact basins flooded with lave, circular in shape; 3.2-3.8 bil yrs old craters: produced by impact of meteoroids, floors may be flooded with lava, may have central peak, ejecta rayed craters: a ray system comprises radial streaks of fine ejecta thrown out during the formation of an impact crater, looking somewhat like many thin spokes coming from the hub of a wheel.
How do the lunar highlands compare in age to the maria basins?
Highlands are older.