PHYS1160 prelim results

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School

University of New South Wales *

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Course

1160

Subject

Astronomy

Date

Dec 6, 2023

Type

docx

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Uploaded by PrivateKnowledgeMule17

PHYS1160 – Preliminary results: Understanding the Solar System 1a) What is the shape of the orbit of the planet? The shape of the orbit is elliptical, meaning it is slightly oval in shape. The planet orbiting begins exactly 2 grids away from the sun's centre but halfway through the orbit we see that it exceeds the 2 grid measurement meaning that the orbit is not a perfect circle and therefore must be an ellipse. 1b) How many earth days does it take to complete one orbit? 365 Earth days 1c) Which planet in our solar system does this represent? Earth 2a) Take a screen capture of the orbit? 4a) What happens to its orbit? Remains the same, still elliptical. 4b) How is the orbit different to the first case? No difference is noticed. 4c) If it is different, why is it different? No difference is noticed at this scale because Earth’s mass is still much more insignificant in comparison to the Sun’s mass and because of this, the gravitational force of the sun still dictates Earth’s orbit (the shape of the orbit/Earth’s course around the sun). Therefore no difference is noticed at this scale. 4d) Take a screen capture of the orbit.

5a) Take a screen capture of the orbit (shortened velocity arm) 5b) What is the new orbital period of the planet? 228 Earth days 5c) How did the shape of the orbit change? The decrease in velocity caused the orbit to become more elliptical in shape (oval). The orbit is further elongated and lengthened compared to the initial orbit which was more circular 5d) Why did it change? The change in orbit shape occurred due to the decrease in velocity. It is understood through celestial mechanics that the initial velocity of an object in orbit is what determines the course/shape of the orbit. In this experiment where the velocity of Earth is decreased, the gravitational relationship between the Sun and Earth is also altered, the Sun’s gravitational pull is weakened and not forceful enough to secure/maintain a more circular orbit due to the decrease in velocity and therefore causing a more elliptical (oval) orbit. 5e) How did the length of the velocity arrow change throughout a full orbit? What does this mean? The velocity arrow grew and shrunk throughout the full orbit, this occurs due to the understood notion that when Earth orbits the Sun its distance also varies. When reaching and leaving perihelion (an object's closest distance to the sun when in orbit) Earth will move faster due to a stronger gravitational pull from the Sun which is why the velocity arrow would elongate as it is travelling at an increased speed. In comparison when moving towards, reaching and leaving aphelion (an object's furthest distance to the sun when in orbit) the gravitational pull is much weaker from the sun causing Earth to move at a slower pace and therefore the arrow would decrease in length. The change in length of the velocity arrow is representative of the speed at which Earth is orbiting the Sun. 5f) Which of Kepler’s laws explains this? Kepler’s second law of equal areas explains the changes in the length of the velocity arrow. Kepler’s second law states that the imaginary line connecting a planet to the sun sweeps equal areas in equal amounts of time. In relation to the experiment, this means that in the process of Earth reaching perihelion the gravitational pull of the Sun will be much stronger and will cause Earth to orbit that period much faster and conversely in the process of Earth reaching aphelion the gravitational pull of the Sun will be much weaker and will cause Earth to orbit that period much slower. Kepler’s second law also discusses the conservation of angular momentum in a gravitational system which also relates to the change in orbit shape as a result of a decrease in initial velocity.

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