Space (Chapter 16)

Question 1

What are the main objects in our solar system?

Answer 1

• Sun
• (8) planets
• dwarf planets
• moons
• asteroid (belt)
• comets

Question 2

What kind of object is the sun?

Answer 2

Star

Question 3

Which galaxy is our Solar System in?

Answer 3

The milky way

Question 4

What do all stars start of as?

Answer 4

huge cloud of gas and dust called a nebula

Question 5

Which force is responsible for forming a protostar from a nebula?

Answer 5

gravity

Question 6

What kind of reaction causes the expansion of a star?

Answer 6

nuclear fusion

Question 7

How does a main sequence star remain stable?

Answer 7

fusion reactions produce outwards forces which balance the gravitational forces pulling it inwards

Question 8

What determines the life cycle of a star?

Answer 8

mass

Question 9

What is the life cycle of a star with about the same mass as the Sun?

Answer 9

protostar→main sequence star→red giant→white dwarf→black dwarf

Question 10

What is the life cycle of a star with much more mass than the Sun?

Answer 10

protostar→main sequence star→red supergiant→supernova→neutron star or black hole (if mass big enough)

Question 11

How are naturally occurring elements formed?

Answer 11

From nuclear fusion during the life cycle of stars

Question 12

What element are only produced in a supernova?

Answer 12

elements heavier than iron

Question 13

How are the elements distributed throughout the universe?

Answer 13

supernovas scatter them

Question 14

How does the force of gravity make objects in orbit change their velocity but not their speed?

Answer 14

gravity provides a centripetal force which keeps orbiting objects moving in a circle - they are constantly changing direction

Question 15

to change the speed of an object in a stable orbit what factor must change

Answer 15

radius of the orbit

Question 16

what is red shift

Answer 16

wavelengths of light get longer if the light source is moving away from the observer

Question 17

what evidence suggests that the universe is expanding

Answer 17

light from more distant galaxies is more red-shifted so more galaxies are moving away faster

Question 18

what is the big bang theory

Answer 18

the scientific theory that the universe started of as an extremely small, hot, and dense region

Question 19

what are the eight planets in order

Answer 19

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune (NOT Pluto)

Question 20

How was our Sun formed?

Answer 20

• The Sun formed about 4.5 billion years ago when a cloud of gas and dust (a nebula) was pulled together by gravitational attraction.
• The particles in the cloud got faster and collided more.
• The gas warmed up and eventually became hot enough to glow. This was a protostar.
• As the protostar gets more dense, more collisions take place and it gets hotter. Eventually the cloud gets hot enough for hydrogen atoms to fuse, forming helium. We call a star in this state a main sequence star.

Question 21

Why does the Sun remain in the main sequence stage?

Answer 21

In the main sequence stage, the gravitational attraction still pulling on the gas (actually a plasma) is balanced by the outward force of the radiation from the nuclear fusion in the core. We say the forces are in equilibrium

Question 22

Why do we have uranium

Answer 22

Uranium and other such heavy elements naturally present on Earth can only be formed in a supernova explosion so the Sun must have formed from the remnants of a supernova.

Question 23

What is going to happen to our Sun
eventually?

Answer 23

• When a star starts to run out of hydrogen to fuse, its core collapses and the outer layers swell, cool down and the star will become a red giant.
• Here, helium and other light elements in the core fuse to form heavier elements.
• When there are no more light elements in the core, fusion stops and no more radiation is released. The star collapses, and as it does it turns from red to yellow to white becoming a white dwarf (much smaller than it was before). Such stars eventually fade out becoming black dwarfs.

Question 24

What would happen eventually if our
Sun was much bigger?

Answer 24

• Stars much bigger than ours become red supergiants then they collapse. Because there is more mass the collapse is more violent and a supernova explosion occurs. This is where elements heavier than iron can form from fusion.
• The explosion compresses the core into a neutron star, an extremely dense object made only of neutrons.
• If the original star was massive enough, it becomes a black hole instead of a neutron star. The gravitational field of a black hole is so strong nothing can escape from it, not even light.

Question 25

What is a planet

Answer 25

A planet orbits a star, enough gravity to make it spherical and sweeps out its own orbital path of other smaller objects.

Question 26

what is a moon

Answer 26

A moon orbits a planet.

Question 27

what is a satillite

Answer 27

A satellite is something that orbits something else. The Moon is a natural satellite. There are many artificial (man-made) satellites.

Question 28

What provides the force that allows planets and satellites (natural and artificial) to maintain their circular orbit?

Answer 28

Gravity. It is an example of a centripetal force because it is acting towards the centre of a circle.

Question 29

Describe a circular orbit.

Answer 29

An object orbits another at a constant speed. Its direction is constantly changing so its velocity is changing (speed in a given direction). Therefore we say the object is accelerating towards the centre of the circle. The acceleration is a change of velocity per second.

Question 30

What happens to the orbit of an object if its speed changes?

Answer 30

* If an object in orbit slows down, it will fall into a lower orbit (closer to the Earth). If it gets too slow, it will crash to the surface. * If an object in orbit speeds up, it will move to a higher orbit (further from the Earth). If it gets sufficiently fast it will escape the gravitational pull of the object it is orbiting and fly off into space. * At the correct speed an object will orbit at a constant height and speed.

Question 31

What evidence is there for the Big Bang theory?

Answer 31

(Red-shift and) In 1965 scientists discovered microwaves coming from every direction in space. This microwave radiation had been red-shifted suggesting that 13.5 (ish) billion years ago there must have been a massively energetic event in one place to still have evidence of it today. This radiation was called the Cosmic Microwave Background Radiation (CMBR).

Question 32

Were there any other theories (not the big ban) for the origin of the universe?

Answer 32

* The Steady State theory suggested that the universe was expanding, but it had always been there and matter was created into the spaces that the universe expanded into. * More evidence was present for the Big Bang theory so that is why it is widely accepted today as being the most probable origin story for the universe.

Question 33

What will happen to our universe?

Answer 33

Depending on the total mass of matter in the universe (unknown because we still have not observed dark matter, a strange substance that is needed for galaxies to maintain their shape) the universe could: 1. [If the universe is less dense than a certain amount] Expand forever, the stars will gradually die out and the universe will cool (Big Yawn) 2. [If the universe is more dense than a certain amount] Stop expanding and collapse (Big Crunch) - Some scientists currently think the universe has gone through cycles of this.