Astronomy HW #1 Ch
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Mission College *
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Course
001
Subject
Astronomy
Date
Apr 3, 2024
Type
Pages
3
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Ch. 2
1.) From where on Earth could you observe all of the stars during the course of a year? What
fraction of the sky can be seen from the North Pole?
You can observe all of the stars from the equator over the course of a year. Only half the
sky can be seen from the North Pole & that half doesn’t change throughout the tear.
5.) What were four of Galileo’s discoveries that were important to Astronomy?
-
Phases of Venus: Galileo was the first astronomer to use a telescope to observe
the celestial objects. Through a telescope he observed that Venus shows the
phases just like the Moon. This provided the Heliocentric theory correct against
the then prevalent Geocentric theory.
-
Law of falling bodies: The acceleration due to gravity is independent of weight of
the objects that means two bodies of different mass will hit the ground at the
same time if dropped from the same height.
-
The uneven surface of the Moon: He observed that the surface of the Moon is
uneven and rough.
-
The discovery of the 4 Moons of Jupiter.
10.) Explain how the zodiac constellations are different from the others
They lie on the Ecliptic (apparent path of the Sun around Earth). There are a total 88
constellations in the sky out of which only 12 are considered as zodiacal constellations or Sun
signs. This is because these are the constellations which lie on the Ecliptic. Ecliptic is the
apparent path of the Sun around the Earth. In other words, it can be said that the Sun appears
to reside in 12 constellations throughout the year as the Earth revolves around it.
12.) Is the ecliptic the same thing as the celestial equator? Explain.
No, the celestial equator is an extension of the real equator, whereas the ecliptic is the path
of the Sun.
13.) What’s an asterism? Can you name an example?
An asterism is a group of stars. For example, The Big Dipper & the Little Dipper.
Ch. 3
1.) State Kepier’s three laws in your own words
a. First law states about the orbit of a planet that all planets revolve in an elliptical orbit and
having the Sun sits at one of its foci. This is a general law about planetary motion.
b. Second law states that in an orbit the radius vector ( line joining Sun and planet) covers equal
area in equal duration of time.
c. Third law states that the square of orbital period of a planet is directly proportional to the cube
of the semi-major axis of the orbit.
4.) Explain how Kepler was able to find a relationship (his third law) between the orbital periods
and distances of the planets that did not depend on the masses of the planets or the sun.
Kepler’s first and second law states about the shape of the orbit and the speed of the planet
at any point in their orbits. Kepler wanted to know why the orbits of planets are spaced and he
was looking for the pattern governing them. In 1619, he came out with a relation between the
orbits of the planet and their relative distances from the Sun.
The relation was
Here
represents the orbital period and
represents the average
distance from the Sun. The relationship is now known as Kepler’s third Law of planetary motion.
6.) Which major planet has the largest
A.) Semimajor axis? It is half the major axis and thus runs from the center, through a focus, and
to the perimeter.
B.) Average orbital speed around the sun? It is the speed at which it orbits around the
barycenter of a system, usually around a more massive body.
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