Exam 1 Flashcards
A star is 230 light-years away. The light we see tonight from that star left it
230 years ago
The point in the sky directly above your head at any given time is called the
Zenith
T OR F: The path that the Sun appears to make in the sky over the course of a year is called the celestial equator.
FALSE
The great astronomer of ancient times who summarized and improved a system of circles upon circles to explain the complicated motions of the planets (and published the system in a book now called The Almagest) is:
Ptolemy
The scientist who first devised experimental tests to demonstrate the validity of the heliocentric model of the solar system was
Galileo
The celestial sphere turns once around each day because
the planet on which we live is rotating
Which ancient Greek thinker suggested (long before Copernicus) that the Earth is moving around the Sun?
Aristarchus
T OR F: At the Earth’s equator, you would see the celestial poles on your horizon.
TRUE
How did Eratosthenes measure the size of the Earth?
by measuring the height of the Sun in the sky on the same day in two cities at different latitudes
In an ellipse, the ratio of the distance between the foci and the length of the major axis is called:
The eccentricity
Every object will continue to be in a state of rest or move at a constant speed in a straight line unless it is compelled to change by an outside force.
Newtons First Law
The change of motion of a body is proportional to an in the direction of the force acting on it.
Newtons Second Law
For every action there is an equal and opposite reaction (or: the mutual actions of two bodies upon each other are always equal and act in opposite directions)
Newtons Third Law
How do you calculate the semimajor axis given the major axis?
major / 2
The closer the eccentricity is to 1 the ellipse is more
_______
elongated
The closer the eccentricity is to 0, the ellipse is more ________
circular
T OR F: Kepler’s third law relates a planet’s orbital period to the semi-major axis of the orbit
TRUE
Is the following statement about electromagnetic radiation True? the radiation consists of tiny charged particles given off by the nuclei of atoms
YES
Which of the following has the longest wavelength? Gamma, Light, Microwave, Radio
RADIO
T OR F:
For all electromagnetic waves, the frequency multiplied by the wavelength will be the same constant number.
TRUE
Frequency of radiation is proportional to temperature
Wiens Law
total energy radiated increases rapidly with temperature
Stegans Law
The energy flux from a blackbody at temperature T is proportional to the fourth power of its absolute temperature.
Stefan Boltzmann Law
source motion changes the perceived wavelength of emitted light
The Doppler Effect
Can observe 24 hours a day
Clouds, rain, and snow don’t interfere
Observations at an entirely different frequency; get totally different information
Advantages of Radio Astronomy
Mercury, Venus, Earth, and Mars
Terrestrial Planets
Jupiter, Saturn, Uranus, and Neptune
Jovian Planets
Planetary orbits are ellipses, with the Sun at one focus.
Keplers First Law
Perihelion
the closest approach
Aphelion
the greatest approach
The imaginary line connecting Sun and planet sweeps out
Keplers Second Law
Earth is closer to the Sun in January. From this fact, Kepler’s 2nd law
tells us:
a) Earth orbits slower in January.
b) Earth orbits faster in January.
c) Earth’s orbital speed doesn’t change.
B. Earth orbits faster in January
Square of period of planet’s orbital motion is proportional
to cube of semi-major axis.
Keplers Third Law
the time it takes a
planet to travel once around
the Sun
Period
the average distance
from Earth to the Sun
AU
any circle on the surface of
a sphere whose center is at the center of the sphere.
Great circle
Great circles that pass through both the
North and South Poles are called
Meridians
