Question

Which characteristics are true of both planets and asteroids? a) They are approximately spherical. b) There are thousands of examples. c) They formed 1 to 2 billion years ago. d) They are present in the solar system.

Short answer

Option d: They are present in the solar system.

Step-by-step solution

Understanding the Question

We need to identify which characteristics are shared by both planets and asteroids from the given options (a, b, c, d). This involves evaluating each option to see if it applies to both types of celestial bodies.

Evaluating Option a

Option a states that both planets and asteroids are approximately spherical. Planets are generally spherical due to gravitational forces. However, most asteroids are not spherical; they tend to be irregularly shaped because they do not have enough mass for gravity to pull them into a spherical shape. Hence, this characteristic is not true for both.

Evaluating Option b

Option b asserts there are thousands of examples. While there are thousands of asteroids mainly found in the asteroid belt between Mars and Jupiter, there are not thousands of planets, especially in a typical solar system. So, this characteristic does not apply to both.

Evaluating Option c

Option c claims they formed 1 to 2 billion years ago. Both planets and asteroids in our solar system formed much earlier than 1 to 2 billion years ago, approximately 4.5 billion years ago, from the solar nebula. Therefore, this characteristic is not applicable to either.

Evaluating Option d

Option d mentions they are present in the solar system. Both planets and asteroids are indeed found in our solar system. Planets such as Earth, Mars, and Jupiter and asteroids found mainly in the asteroid belt all share this characteristic, making it applicable to both.

Selecting the Correct Answer

Based on the evaluations, option d is the only characteristic that applies to both planets and asteroids. It correctly identifies that both are present in the solar system.

Key concepts

Exploring Our Solar System

The solar system is a fascinating and complex collection of celestial bodies orbiting our Sun. At its center lies the Sun, a massive star that provides the heat and light necessary for life on Earth. Surrounding the Sun are various types of celestial objects, including planets, moons, asteroids, and comets. Each plays a unique role in the cosmic dance of the solar system.

The eight primary planets follow elliptical orbits around the Sun, a discovery attributed to the work of Johannes Kepler and Isaac Newton. Besides planets, the solar system also hosts countless smaller objects like asteroids, which primarily reside in the asteroid belt between Mars and Jupiter. This dynamic range of celestial bodies helps us understand more about the formation and evolution of the solar system.

• Planets are major bodies that orbit the Sun directly.
• Asteroids are smaller, rocky objects that can also orbit the Sun.
• The vastness of the solar system includes the Kuiper Belt and Oort Cloud, which are regions beyond Neptune containing remnants from the solar system's formation.

Understanding the solar system isn't just about knowing the Sun and its orbiting bodies. It is also about exploring how these celestial bodies interact with each other and discovering the mysteries of outer space that lie beyond our tiny corner of the Milky Way galaxy.

Understanding Planets

Planets are one of the most intriguing objects in astronomy. They are large celestial bodies that orbit a star, in our case, the Sun. There are eight recognized planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Each of these has unique characteristics and conditions that make them fascinating to study.

A planet must fulfill certain criteria:

• It must orbit a star (in our solar system, the Sun).
• It must have sufficient mass to assume a nearly round shape.
• It must have "cleared the neighborhood" around its orbit, meaning it is gravitationally dominant with no large bodies other than its moons in its path.

Planets can be grouped into two types: terrestrial and gas giants. Terrestrial planets, such as Earth and Mars, have solid, rocky surfaces, whereas gas giants like Jupiter and Saturn don't have solid surfaces and are composed largely of gas.

Additionally, planets vary in many aspects, including size, atmosphere, surface conditions, and potential for hosting life. For example, Earth is the only known planet with life, while Mars is a key focus of astrobiology studies due to signs that it may have hosted life in the past.

Demystifying Asteroids

Asteroids are rocky, airless remnants left over from the early formation of our solar system about 4.5 billion years ago. Though they revolve around the Sun like planets, they are much smaller and do not have the same set criteria to be considered planets.

Asteroids are predominantly found in the asteroid belt, a region located between the orbits of Mars and Jupiter. This belt contains millions of asteroids of varying sizes, from tiny pebbles to bodies that can reach hundreds of kilometers in diameter.

• Asteroids in the belt are leftovers from when planets formed, failing to coalesce into planet-sized objects largely due to Jupiter's massive gravitational influence.
• They have irregular shapes because they lack enough gravity to pull themselves into a spherical form.
• Occasionally, some asteroids stray from the belt due to gravitational interactions, which can potentially lead them to cross paths with Earth. These rouge paths make understanding asteroids crucial for planetary defense.

Studying asteroids gives us insights into the early solar system's conditions and processes. They are considered "time capsules" and can help scientists uncover information about the building blocks of planets and the evolution of our solar system over billions of years.