Unit 8 Review & Study Guide

Hey there, space explorers! Anika, Priya, and Elijah are curious: Which of these characteristics actually qualifies the Sun a star?

• The Sun maintains a magnetic field that flows from pole to pole.

• The Sun maintains a gravitational field in which other bodies orbit.

• The Sun is composed primarily of low-temperature iron and silicon.

• The Sun is composed primarily of high-temperature hydrogen and helium.

Answer explanation

Stars like the Sun shine as a result of nuclear reactions that constantly converts the supply of hydrogen in their cores into helium.

These same reactions determine how bright a star shines – the hotter the core, the more intense the reaction and subsequently the brighter the star's surface will be. As expected, less massive stars are dimmer due to cooler centers, which produce slower reactions.

Hey there, space explorers Zoe, Luna, and Aiden! Using the table, can you figure out which description best fits the shape of the orbits of the planets in Earth's solar system?

• Circular, only

• Elliptical and circular

• Circular and triangular

• Elliptical, only

Answer explanation

Perihelion is the distance when the planet is closest to the sun in it's orbit and aphelion is the distance when the planet is furthest from the sun in it's orbit.

We know the planets follow an elliptical path because the planet-to-Sun distance is constantly changing as the planet goes around its orbit.

One clear night, Mia and Isla notice a bright object in the sky with Aria. It seems to dance across the stars, sometimes even reversing its path from previous nights. What could this mysterious object be?

• A planet, because its orbit makes it appear to move randomly.

• A star, because their movement through the sky appears random.

• A planet, because planets move in the opposite direction from Earth.

• A star, because some stars have orbital paths they follow randomly.

Answer explanation

While all the stars in the sky move east to west as our Earth rotates, planets also move within their own orbit. This causes them to appear to wander throughout the night sky when compared to other stars, which move in a fixed position each day.

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Hey Jackson, Lily, and Luna! Let's make learning fun. Complete the sentence to describe the magical motion of the planets as they gracefully orbit the Sun. Type one word into each box.

The planets __________ around the sun while they ________ on their axis.

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During a lively science club debate, Mia, Abigail, and Rohan are discussing the fascinating planets of our solar system. They examine a table showing each planet's distance from the Sun and their mean temperatures. Based on this data, they ponder: which of the following statements is correct?

• As distance from the Sun decreases, mean temperature decreases, then increases.

• As distance from the Sun increases, mean temperature increases, then decreases.

• As distance from the Sun decreases, mean temperature decreases.

• As distance from the Sun increases, mean temperature decreases.

Answer explanation

Looking at the table, you can see the correlation between distance form the sun and temperature. As the distance goes up, the average temperature goes down.

Imagine if Earth suddenly stopped pulling on the Moon! What would happen to the Moon's path? Aria thinks it might float away! What do you think?

• follow a straight path away from Earth.

• follow a spiraling path away from Earth.

• crash into the surface of Earth.

• orbit much faster around Earth.

Answer explanation

Since the moon is moving at a constant velocity, it would keep going in a straight line away from Earth at that same velocity if the force of gravity was not pulling from Earth.

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Hey space explorers! Daniel, Aiden, and Nora were discussing the quirky paths planets take around the sun. They learned that planets don't travel in perfect circles but have some wobble called eccentricity. What do you think is the main reason for this planetary eccentricity?

• Impacts from asteroids and comets

• Interference from planetary atmospheres

• Gravity from other objects in the solar system

• Magnetic fields from other objects in the solar system

Answer explanation

Earth's orbital eccentricity is due not only to our distance from the Sun but also the gravitational pull of Jupiter and Saturn.

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Imagine you're an astronaut alongside Isla and Henry, exploring the vast universe. You come across a NASA image of the Oort cloud, a mysterious sphere of objects thought to encircle Earth's solar system up to one light year from the Sun. Sophia, your mission commander, poses a question: If the Oort cloud does exist, what could explain why the objects in it have formed this spherical shape?

• They are held in orbits by the Sun's gravitational force.

• They are held in Earth's solar system by Neptune's magnetic field.

• They float freely in space because the Sun's gravitational force is too weak to hold them in orbit.

• They are held in stationary positions around Earth's solar system by other stars in space.

Answer explanation

Gravity is the governing authority for all objects and bodies in our solar system.

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Imagine you're in space with Luna and Zoe, watching planets zoom around. Ever wonder why they don't just shoot off in straight lines? Inertia wants them to keep moving straight, but something else bends their paths into cool ellipses. What's behind this cosmic dance?

• The speed of the planets combined with the Sun's gravitational pull bends their paths into curves.

• It's the gravitational bond between planets that keeps them orbiting within the solar system, according to Charlotte.

• Luna thinks it's the nuclear fusion in the Sun that bends the planets' paths with a mysterious force.

• Zoe believes distant stars exert a magnetic force that curves the planets' orbits.

Answer explanation

Planets are traveling at a constant velocity but, when combined with the Sun's gravitational pull, their paths are bent into curves.

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Imagine you're on a space adventure with Olivia, Emma, and Benjamin, observing Earth's solar system. You notice the planets moving in fascinating paths. These paths are elliptical orbits —

• largely governed by the force of gravity.

• controlled by the magnetic force at Earth's poles.

• controlled by the nuclear energy formed at the Sun's core.

• largely governed by the magnetic force of Jupiter.

Answer explanation

Elliptical orbits of planets are governed by the force of gravity, which keeps them in their paths around the Sun.

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