Exercises: The Solar System

List the components of the Solar System and explain in one sentence what each type of body is.

The diagram shows the Solar System on a qualitative scale (the orbits and sizes are not realistic). Name the planets labelled with numbers from 1 to 8, from closest to furthest from the Sun.

Explain the difference between a rocky planet and a gas planet, and classify the eight planets of the Solar System into one of these two groups.

Earth is currently the only planet with known life. Explain three characteristics of Earth that make it suitable for life, such as its distance from the Sun, the presence of liquid water or its atmosphere.

In 2006, Pluto came to be considered a dwarf planet. Explain which requirement of the definition of a planet it does not meet and name another dwarf planet in the Solar System.

What are the asteroid belt and the Kuiper belt? State where each one is located and what type of bodies it contains.

You are going to design a scale model of the Solar System in the hallway of your school, which is $50\ \text{m}$ long. You decide to represent the Sun with a basketball of $24\ \text{cm}$ in diameter (the actual diameter of the Sun is approximately $1\,390\,000\ \text{km}$).

1. a) At that same scale, calculate what diameter the Earth should have (actual diameter: $12\,742\ \text{km}$) and compare it with a small everyday object (such as a pinhead or a grain of sand).
2. b) Knowing that the average Earth-Sun distance is $1.5 \times 10^8\ \text{km}$ and Neptune's distance to the Sun is about $4.5 \times 10^9\ \text{km}$, calculate at what distance from the ball you would have to place both planets.
3. c) Based on the results, justify whether the complete model fits in the hallway while simultaneously maintaining the scale of sizes and the scale of distances, and explain why Solar System diagrams in textbooks are often misleading.

A robotic probe is exploring Neptune, at $30\ \text{AU}$ from the Sun ($1\ \text{AU} = 150\ \text{million km}$). At a time when Earth and Neptune are aligned on the same side relative to the Sun (minimum distance of $29\ \text{AU}$), the probe detects a rock on a collision course that will strike it in $6\ \text{hours}$.

1. a) Calculate the minimum time (in hours) it would take for an alarm signal to travel from the probe to Earth and for the corrective command to return to Neptune, knowing that radio signals travel at $300\,000\ \text{km/s}$.
2. b) Based on your calculation, predict whether the probe would survive if it depended on a command sent from ground control and justify why spacecraft in the outer Solar System must operate with real-time autonomous navigation systems.

A space telescope has detected three rocky exoplanets orbiting a red dwarf star that is cooler and smaller than the Sun, whose habitable zone lies between $0.15\ \text{AU}$ and $0.30\ \text{AU}$:

• Planet A: Distance to the star: $0.06\ \text{AU}$. Mass: $1.1$ Earth masses. Dense atmosphere rich in water vapor.

• Planet B: Distance to the star: $0.22\ \text{AU}$. Mass: $0.9$ Earth masses. Detectable magnetic field and atmosphere with $N_2$, $CO_2$, and water vapor.

• Planet C: Distance to the star: $0.25\ \text{AU}$. Mass: $0.02$ Earth masses (similar to the Moon). No noticeable atmosphere.

1. a) Analyze with reasoning which of them is the ideal candidate to harbor liquid water and life, justifying why you rule out the other two.
2. b) Explain why being located within the "habitable zone" is a necessary but not sufficient condition for a planet to be habitable.