UNIT 4 - STARS AND PLANETS

Question 1

DESCRIBE HOW ALL STARS ARE FORMED

Answer 1

• Stars are formed from in clouds of hydrogen and helium (Nebulae)
• Protostars form when gravity collects the cloud together. It heats up as it’s compressed.

Question 2

DESCRIBE THE LIFE CYCLE OF A LOW MASS STAR

Answer 2

• In the main sequence stars, hydrogen fuses to form helium
• This creates gas and radiation pressure equal to gravitational force
• When hydrogen fuel runs out, the star begins to fuse helium into larger elements (up to Carbon), this increases the gas & radiation pressure causing it to expand into a RED GIANT.
• When helium fuel runs out the reaction slows. Gas & radiation pressure decreases causing the red giant to shrink into a WHITE DWARF.

Question 3

DESCRIBE THE LIFE CYCLE OF A HIGH MASS STAR

Answer 3

• When hydrogen fuel runs out high mass stars begin to fuses helium into larger elements (up to iron).
• The gas and radiation pressure increases causing it to expand
• When fuel runs out the star becomes unstable and explodes into a SUPERNOVA throwing out gas and dust
• The high temperature will cause the heaviest elements to fuse.
• The remaining matter will collapse due to gravitational force and shrink to form a NEUTRON STAR
• If there is enough mass it could form a black hole.

Question 4

WHAT IS A MOON ?

Answer 4

A body that orbits a planet (Natural Satellite)

Question 5

WHAT IS AN ASTEROID ?

Answer 5

A small rocky object that orbits the sun, most asteroids in our solar system are found in the belt between Mars and Jupiter

Question 6

WHAT IS A COMET ?

Answer 6

A lump of frozen gas, rock and dust that orbits the sun.
Its tail always points away from the sun due to radiation pressure

Question 7

NAME THE PLANETS IN ORDER

Answer 7

MERCURY
VENUS
EARTH
MARS
JUPITER
SATURN
URANUS
NEPTUNE

Question 8

WHICH IS THE WARMEST PLANET ?

Answer 8

VENUS ( DENSE ATMOSPHERE)

Question 9

WHICH IS THE COLDEST PLANET ?

Answer 9

Neptune (Furthest from the sun)

Question 10

WHAT IS A PLANETARY SYSTEM ?

Answer 10

Comprises of a star and all the objects that orbit it. Our solar system is a planetary system

Question 11

WHAT IS A GALAXY ?

Answer 11

A galaxy is a collection of billions of stars and their solar systems -
Our galaxy is the milky way

Question 12

WHAT IS ONE ASTRONOMICAL UNIT ?

Answer 12

The distance from the earth to the sun

Question 13

WHAT IS A LIGHT YEAR ?

Answer 13

The distance light travels in one year. 3x10 8 M/S

Question 14

WHAT IS NUCLEAR FUSION ?

Answer 14

When smaller nuclei fuse together to form a heavier nuclei
Apart from hydrogen all elements in stars are produced through fusion
In the main sequence, hydrogen nuclei fuse to make helium. This process releases gas and radiation pressure which balances the inward gravitational force.

Question 15

WHAT HAPPENS IN A SUPERNOVA ?

Answer 15

In a supernova elements heavier than iron are formed. This material is expelled into space and used to make stars and planets

Question 16

HOW WAS THE SOLAR SYSTEM FORMED ?

Answer 16

The solar system formed approx 4.6 BILLION years ago from a cloud of gas and dust and elements ejected from supernovae.
The cloud began to spin, the core of the cloud became hot and dense under the influence of gravity.
The cloud formed a disc which heated to the point where fusion began. This created the sun.
During the formation of the sun radiation pressure flung materials away. Lighter gasses went further out in the solar system and heavier elements remained closer to the sun.
Heavy metals near the sun where brought together by gravity and eventually formed the rocky planets
Cold temperatures caused gas to condense forming the gas giants

Question 17

WHAT DOES A H-R DIAGRAM DISPLAY ?

Answer 17

It displays the properties of stars and their evolutionary paths