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ASTA01H3 Study Guide - Quiz Guide: Orbital Node, Deferent And Epicycle, Semi-Major And Semi-Minor Axes


Department
Astronomy
Course Code
ASTA01H3
Professor
Parandis Tajbakhsh
Study Guide
Quiz

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Given its orbital period of 76 years, the average distance of Comet Halley from the Sun is
18 AU .
Using p^2 (yr) = a^3 (AU); a = 76^(2/3) = 17.94 18
P^2=4π^2r^3/(GM) is the equation relating the variable physical quantities Orbit period,
orbit radius, and mass of central body.
All three are variables. (Newton’s version of Kepler’s third law)
The book “De Revolutionibus Orbium Coelestiumlays out the Copernican theory for
the first time.
It (On the Revolutions of the Heavenly Spheres by Nicolaus Copernicus)
offered an alternative model, a Heliocentric universe, to Ptolemy's geocentric system in
1543.
Nicolaus Copernicus accounted for the retrograde motion of the planets by Inner planets
orbit the Sun faster and pass outer planets as they orbit around the Sun.
Earth was not at the centre.
If you went to the Moon, your weight would change but mass would not.
The weight of an object is the force of gravity felt by that object but the mass
of an object is the amount of matter the object has.
The phases of Venus observed by Galileo support the model of the universe presented by
Nicolaus Copernicus.
At both first quarter Moon and third quarter Moon are tides at their lowest.
Tycho Brahe’s greatest contribution to astronomy was his 20 years of careful
observations of the planets.

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astronauts are not weightless in space; they are in perpetual free-fall toward the
Earth, but traveling fast enough in their orbit to continuously "miss the Earth”.
They still have mass and are affected by Earth's gravity.
The Copernican system was no more accurate than the Ptolemaic system in predicting the
positions of the planets because it used uniform circular motion which was unchanged
from the Ptolemaic system.
You are observing the night sky from Mars. Retrograde motion is observable for planets
more distant from the Sun than Mars.
The orbit of the planet Mars is an ellipse with the Sun at one focus. Nothing is located at
the other focus.
Hypothesis is the term for a single conjecture that can be tested.
Regard to the centre of the orbit of a two-object system, both objects orbit the centre of
mass of the system, with the more massive object having a smaller orbit.
Retrograde motion is the term for the apparent westward motion of a planet in the sky
compared to the background stars (as viewed from the Earth) when observed on
successive nights.
If you lived on Mars, planets (include Saturn, Uranus, Neptune, and jupiter) would
exhibit retrograde motion.
Suppose that Planet Q exists such that it is an identical planet to Earth yet orbits the Sun
at a distance of 5 AU. The amount of gravitational force exerted on Planet Q by the Sun is
1/25 the force on Earth.
Fg=GMm/r^2, Fg1/r^2 (the inverse square rule applies)
If your mass is 65 kg on the earth, your mass would be 65 kg on Jupiter.
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We call an orbit that has the same period as the rotation period of the Earth a
geosynchronous orbit.
The basis for Isaac Newton’s conclusion that a force from the Earth must be acting on the
Moon was a force is needed to accelerate the Moon toward the Earth, away from
straight-line motion.
Galileo made several important telescopic discoveries. Galileo's telescopic discovery that
Venus went through the same cycle of phases as the Moon contradict Ptolemaic theory as
it was possible in Copernican theory, but not Ptolemaic theory.
Copernicus's theory allowed all the phases for Venus.
The "centre of mass" of a system is meant by a point that is closer to the more massive
of two objects by how many more times massive it is than the less massive object.
The "centre of mass" of the Earth-Moon system is at a point about 80 times closer to
the centre of the Earth than the centre of the Moon; actually inside the Earth.
Galileo’s observations of moons orbiting Jupiter conflict with the geocentric model of the
universe of his time because the moons did not appear to orbit the Earth.
It’s true that many classical Greek astronomers believed the Earth could not move
because they detected no parallax.
The circular velocity in m/s of an Earth satellite 3.42 x 10^7 m from Earth's center is 3415
m/s. (Hints: The circular orbital speed is equal to [GM/(orbital radius)], Earth's mass is
5.98 x 10^24 kg and G = 6.67 x 10^(-11) in mks units)
[GM/(orbital radius)] = [(6.67x10^(-11)x5.98x10^24)/(3.42x10^7)]^(1/2) = 3415.077 3415
The statement “The larger the orbit, the longer its orbital period” best describes
Kepler’s third law of planetary motion.
The Ptolemaic model of the universe was not heliocentric.
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