2.5 Stars And Planets

In which galaxy is our solar system?

The Milky Way Galaxy

How many planets make up our solar system?

Eight (plus the dwarf planets).

What do the planets in our solar system orbit around and what type of body is it?

● The planets orbit around the sun.
● The sun is a star.

What type of force pulled together the cloud of dust and gas to form the Sun?

Gravitational force of attraction.

What word is used to describe a cloud of dust and gas?

A nebula.

What type of reactions take place at the start of a star's life cycle as dust and gas is drawn together?

Fusion reactions.

What factor determines the type of lifecycle a star undergoes?

The size (and therefore mass) of the star.

Which two phases do all stars of the same or greater size than the sun undergo?

1. Protostar phase
2. Main sequence phase

What do stars like the sun become at the end of their life-cycle?

A black dwarf.

What two things can stars much bigger than the sun become at the end of their lifecycle?

1. Neutron star
2. Black hole

What two phases do stars like the sun experience between being a main sequence star and a black dwarf?

1. Red giant
2. White dwarf

What two phases do stars of greater size than the sun go through between being a main sequence star and a neutron star/black hole?

1. Red supergiant
2. Supernova

List the life cycle stages of low mass stars like the Sun.

Protostar→ Main sequence star →Red giant→ White dwarf→Black dwarf

List the life cycle stages of high mass stars.

Protostar→ Main sequence star →Red supergiant→ Supernova→ Neutron star/Black hole

Explain the life cycle of a low mass star. (QER style question)

1. Stars are formed from clouds of gas and dust.

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2. These particles are pulled together by the force of gravity, allowing the cloud to become denser.

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3. The temperature and pressure increases as the particles move closer together. When temperature and pressure is high enough, hydrogen nuclei begin to fuse together to form helium.

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4. This releases large amounts of energy in the form of heat and produces an outwards gas and radiation pressure force.

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5. When the inward force of gravity and outward force of gas and radiation pressure become balanced (equal and opposite), the star enters its stable phase; becoming a **main-sequence star.**

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6. As hydrogen begins to run out, less nuclear fusion reactions begin to take place which causes the forces to become unbalanced as the gas and radiation pressure decreases.

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7. This causes the core to shrink, becoming denser and hotter. Now, the nuclear fusion of heavier elements can take place, producing elements up to **carbon-12**.

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8. The outwards gas and radiation pressure increases, becoming greater than the inwards force of gravity. This causes the star to expand to become a **red giant.**

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9. When up to carbon-12 is produced, nuclear fusion no longer takes place, causing the outwards gas and radiation pressure to decrease. The star collapses under the pull of its own gravity, forming a **white dwarf.**

Explain the life cycle of a high mass star. (QER style question)

1. Stars are formed from clouds of gas and dust.

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2. These particles are pulled together by the force of gravity, allowing the cloud to become denser.

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3. The temperature and pressure increases as the particles move closer together. When temperature and pressure is high enough, hydrogen nuclei begin to fuse together to form helium.

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4. This releases large amounts of energy in the form of heat and produces an outwards gas and radiation pressure force.

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5. When the inward force of gravity and outward force of gas and radiation pressure become balanced (equal and opposite), the star enters its stable phase; becoming a main-sequence star.

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6. As hydrogen begins to run out, less nuclear fusion reactions begin to take place which causes the forces to become unbalanced as the gas and radiation pressure decreases.

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7. This causes the core to shrink, becoming denser and hotter. Now, the nuclear fusion of heavier elements can take place, producing elements up to **iron-56.**

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8. The outwards gas and radiation pressure increases, becoming greater than the inwards force of gravity. This causes the star to expand to become a **red super giant.**

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9. When up to iron-56 is produced, nuclear fusion no longer takes place, causing the outwards gas and radiation pressure to decrease. The star collapses under the pull of its own gravity, causing a **supernova explosion.**

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10. This will leave behind a **neutron star.** In the case of very high mass stars, a **black hole** will be formed.

What is produced during the fusion processes in a star?

Atoms of all of the naturally occurring elements.

What condition is required for fusion reactions to occur in a star?

Very high temperatures and pressures.

Where are elements heavier than iron produced?

In a supernova.

What type of nuclei fuse together to form heavier elements in a star?

Hydrogen nuclei fuse to form heavier elements.

How are elements distributed throughout the universe?

Through the explosion of a massive star (supernova).

What allows planets and satellites to maintain circular orbits?

● Gravity provides the gravitational force that acts as the object's centripetal force.

● The presence of a centripetal force allows for the object to maintain its circular orbit.

What type of satellite can a planet's moon be described as?

A natural satellite.

Give two examples of artificial satellites.

1. TV satellites
2. Satellites used for satellite imaging

What type of planet is Pluto classed as?

A dwarf planet.

What is the name given to the natural satellites that orbit planets?

Moons.

Give a basic description of a comet.

A high speed ball of ice and rock which as it melts leaves a trail of dust and gas behind it.

What term is given to the four outer planets of our solar system?

Gas giants.

What unit of measurement is used to measure distances between the sun and planets?

The Astronomical Unit (AU).

What is 1AU?

The average distance between the Earth and the Sun.

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1AU= 150 x 10^6 km

What is a light year?

The distance travelled by light in 1 year.

What is a light year a unit of?

Distance.

How do you convert light years, which measures distance, to time?

Take away light from light years.

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Light years= Distance

Years= Time

What colour stars are the hottest? Blue or red?

● Blue stars are the hottest stars.
● Red stars are the cooler stars.

What does a Hertzsprung-Russell diagram show? (Higher)

The luminosity of stars against their temperature.

Wwhat do stars on the diagonal line of a Hertzsprung-Russel diagram represent?

Main sequence stars