# Astronomy Coursework.

Essay by lilbeats478Junior High, 9th grade January 2004

Physics Coursework

Coursework Part 1

ÃÂ· The irregular shape of Ida tells us that it may have been formed by breaking off a mother planet (possibly lying in between Mars and Jupiter). On the other hand, it may have just been some of the debris left over from the creation of the solar system, representing what it was like before planets had formed.

ÃÂ· This asteroid is covered in craters unlike the earth, which has hardly any craters. This indicates that Ida may be subject to many collisions compared to the earth. Thus, Ida may be orbiting in the asteroid belt with increased likelihood of collisions with other asteroids. Alternatively, Ida does not benefit from the "protective" affect of Jupiter compared to Earth. The earth has an atmosphere of protective gases, which causes the meteorite to "burn up" before it reaches the earth's surface, which Ida does not have. Thirdly, the fact that Ida has more craters may mean that it is considerably older than the Earth.

ÃÂ· Most craters are small but a few are much larger, indicating that it is much more likely to collide with smaller rocks rather than larger meteorites. A second explanation is that like earth, many of the larger meteorites burn up and reduce in size before they reach Ida.

ÃÂ· Ida is not very likely to support life because it does not have an atmosphere, which means you get extreme temperatures, making life very difficult for living things. In addition, the asteroid is very vulnerable to other asteroids colliding with it. The picture of Ida is very clear compared to pictures of the planets because a) Ida is nearer to Earth compared to other planets and b) There is little to no atmosphere to make the picture hazy.

Coursework Part 2

1.

a.

b. The moon takes little over 27 days to orbit the earth but a full moon occurs every 29.5 days.

c. See above diagram

d. This is called a lunar eclipse. A total lunar eclipse occurs when the moon passes completely into the umbra. If it moves directly through the centre, it is obscured for about 2 hours. If it does not pass through the centre, the period of totality is less and may last for only an instant if the moon travels through the very edge of the umbra. A partial lunar eclipse occurs when only a part of the moon enters the umbra and is obscured. The extent of a partial eclipse can range from near totality, when most of the moon is obscured, to a slight or minor eclipse, when only a small portion of the earth's shadow is seen on the passing moon. Historically, the view of the earth's circular shadow advancing across the face of the moon was the first indication of the shape of the earth.

2.

3.

a. Jupiter (142 600 km)

b. Mercury (88 days)

c. Mercury = 350ÃÂ°C

Pluto = -230ÃÂ°C

Difference = 580ÃÂ°C

d. Mars (-23ÃÂ°C) and Earth (20ÃÂ°C)

e. Seven planets have moons- Mercury and Venus do not.

f. The inner planets are made of denser, solid substances, whereas the outer planets are made of less dense gases.

4.

a. An ellipse is the name given to the shape of a comet's orbit.

b. The Asteroid Belt is in between the forth and fifth planets.

c. Man has only set foot on the earth, however machines (robots) are making expeditions to other planets.

Coursework Part 3

1. Gravity pulls the javelin back to earth.

2. The javelin can be thrown further because the faster it is thrown the further it travels.

3. Yes, I do because Isaac Newton thought and drew in his diagram that the faster the object goes, the further the object travels.

4. It falls away from the earth, as the shell is moving so fast, that the gravity pulls "to late" and the shell "misses" the earth because of its curvature.

5. The force working on the earth's surface to slow the shell down is friction/air resistance.

6. A space rocket initially climbs vertically from the earth's surface because this way gravity has less surface area to work on, and this creates less air resistance.

7. The statement is incorrect to the extent that there are still gravitational forces above the earth's atmosphere. These forces are similar to that on the earth's surface. The satellite stays in orbit because it is travelling more than 8000m/s.

8. The Earth has a gravitational field that constantly tugs at the moon; the moon has an equal but opposite force associated with its motion--pulling away from the moon. This tug-of-war of balanced forces keeps the moon in a constant orbit.

Coursework Part 4

Life Cycle of a Star

1. In a nebula, gravity is the force that pulls the hydrogen gas together.

2. As the amount of gas increases in a Protostar, three things increase. These things are: 1. Temperature

2. Pressure

3. Gravitational Force

3. Nuclear fusion begins at 10 million degrees in a protostar.

4. Hydrogen Helium + Energy

5. The steady state star is kept as a fixed size with a fine balance of nuclear explosive forces trying to blow the star apart and gravitational forces trying to pull it together.

6. A star such as the sun is expected to last about 10 million years in its steady state and we have about 5million years remaining.

7. A massive star uses its fuels up quickly because it is so big that more hydrogen is being burnt at one time.

8. At the end of its life, the Sun will start to fuse helium into heavier elements and begin to swell up, ultimately growing so large that it will swallow the Earth. After a billion years as a red giant, it will collapse into a white dwarf - the final product of a star like ours. It may take a trillion years to cool off completely.

9. A 1cm3 piece of Neutron star would weigh about one billion tonnes.

10. For a star to become a Black Hole, it must be at least approximately 30 times bigger than the sun.