Stars and Planets

Question 1

1 Astronomical unit is….

Answer 1

150 million km

Question 2

Order the life cycle of a Large Star

Answer 2

Nebula → Protostar → Main Sequence Star → Red Super giant → Supernova →Neutron Star → Black hole

Question 3

Order the life cycle of a small star

Answer 3

Nebula → Protostar → Main Sequence Star → Red giant → White Dwarf

Question 4

How does a star become a white dwarf?

Answer 4

The helium fuel begins to run out and the reaction will slow. The gas and radiation pressure will decrease. The star will shrink and become a White dwarf.

Question 5

When will a main sequence star turn into a red giant/supergiant

Answer 5

The hydrogen fuel begins to run out and the star will begin to fuse helium into larger elements (e.g. iron). This increases the gas and radiation pressure. The star will expand

Question 6

How do stars obtain their energy?

Answer 6

By fusing light nuclei into heavier nuclei

Question 7

How do elements of a giant star end up in space at the end of it’s life?

Answer 7

During it’s supernova phase, when the star produces iron, fusion stops and the core contracts. The centre of the star heats up so much that it explodes and ejects all it’s materials into space.

Question 8

How did our solar system start?

Answer 8

• The Solar System formed from a cloud of gas, mainly hydrogen and helium, and dust ejected from a supernova. Gravitational forces caused this cloud to collapse and the particles to collect together.
• As the cloud collapsed it began to spin, this made it turn into a disk.
• The centre of the disk became the Sun and the rest collected together to form the planets.

Question 9

What gets ejected in a supernova?

Answer 9

Elements heavier than iron such as uranium

Question 10

What is the cycle from nebula to protostar to main sequence star?

Answer 10

1. Stars are formed from clouds of gas, hydrogen and helium, and dust.
2. Protostars form when gravity collects this cloud together and as it is compressed it heats up.
3. In main sequence stars, hydrogen fuses to form helium. This creates enough radiation and gas pressure to balance the gravitational forces

Question 11

How does a supernova change to a neutron star or black hole?

Answer 11

The remaining matter will collapse due to the gravitational force as the gas and radiation pressure will be small and shrink to form a Neutron star or a Black hole

Question 12

Why are some planets rocky?

Answer 12

When the solar system formed, rocks tended to gather closer to the Sun, and these materials combined together to form the inner planets.

Question 13

Why are there gas giants?

Answer 13

When the solar system formed, gaseous substances gathered together further away from the Sun and formed the gas giants.