Question 1: Define a planet according to the International Astronomical Union (IAU) criteria.

Answer: A celestial body that orbits the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and has cleared its neighboring region of planetesimals.

Question 2: Explain the main difference between terrestrial planets and gas giants.

Answer: Terrestrial planets are rocky, dense, and have solid surfaces, while gas giants are large, primarily composed of gases like hydrogen and helium, and lack a solid surface.

Question 1: Calculate the surface gravity of Mars given its mass is 6.42 × 10^23 kg and radius is 3.39 × 10^6 meters. Use the formula: g = G * M / R^2, where G = 6.674 × 10^-11 N·m^2/kg^2.

Answer: Approximately 3.72 m/s^2

Question 2: If the average distance from Earth to Jupiter is about 778 million km, and Jupiter's orbital period is approximately 11.86 years, estimate the average orbital velocity of Jupiter in km/s (use velocity = distance / time).

Answer: Approximately 13.45 km/s

Question 1: Describe a safe and effective method to observe planetary motions using a telescope. Include key safety precautions.

Answer: Students should use a telescope mounted securely on a stable surface, avoid looking directly at the Sun without proper solar filters to prevent eye damage, conduct observations in a safe, well-lit area, and handle equipment carefully to prevent damage or injury.

Question 1: A spacecraft observes that a planet has a day length of approximately 24 hours and a year length of 225 Earth days. Identify the planet and justify your answer based on these data points.

Answer: The planet is likely Venus, as it has a day length of about 243 Earth days and an orbit of about 225 Earth days, making it the slowest rotating planet.

Question 1: Discuss the significance of planetary orbits in understanding the solar system's stability. Include the role of gravitational forces and orbital resonance.

Answer: Planetary orbits are crucial for understanding the stability and structure of the solar system. Gravitational forces between the Sun and planets keep them in stable, elliptical orbits. Orbital resonance, where planets have orbital periods in simple ratios, can enhance stability or lead to orbital shifts. These dynamics help scientists predict planetary movements and understand long-term system stability.

Question 1: Describe how knowledge of planetary atmospheres contributes to advancements in climate science and satellite technology.

Answer: Understanding planetary atmospheres helps improve climate models on Earth, aids in designing better satellites with durable materials and sensors, and informs the development of remote sensing technologies for environmental monitoring.