space exploration beginner 10 sample questions

Exoplanets MCQ Practice Test

Planets outside our solar system and habitability

Q1. Which of the following exoplanets has a “super-Earth” mass and orbits a star with a surface temperature that is about 2,500°K, which is significantly lower than the Sun’s surface temperature?

Explanation: Gliese 1214 b is a super-Earth exoplanet that orbits a small, cool M-type star, also known as a red dwarf. The star's surface temperature is about 2,500°K, which is significantly lower than the Sun's surface temperature of about 5,500°K.

Q2. In 2020, astronomers reported a tentative and later disputed detection of phosphine gas in the atmosphere of which planet?

Explanation: Greaves et al. (Nature Astronomy, 2020) reported roughly 20 parts per billion of phosphine in Venus's cloud decks — a potential biosignature, since earthly phosphine is mainly biological in origin; later reanalyses contested the detection. The old stem's 'phosphine on LHS 1140b' was fabricated, and its formula '(πH)' is not a chemical formula.

Q3. Which exoplanet has a surface composition that is primarily silicate rocks and éclogites, with a éclogite-rich crust, and is thought to have differentiated due to a épisode of magma ocean solidification?

Explanation: 55 Cancri e is a super-Earth exoplanet that orbits a G-type star (similar to the Sun) in the constellation of Cancer. Studies suggest that 55 Cancri e has a surface composition that is primarily silicate rocks and éclogites, with a éclogite-rich crust. The planet's differentiation is thought to have occurred due to a épisode of magma ocean solidification, which is a process where a planet's surface melts and solidifies to form a crust.

Q4. What is the primary mechanism driving the atmospheric escape of hydrogen on the exoplanet K2-18b, a super-Earth with a thick atmosphere?

Explanation: K2-18b's atmospheric escape is primarily driven by thermal escape, where hydrogen atoms are heated to escape velocities by extreme ultraviolet radiation from its host star. This process is more efficient than other mechanisms such as stellar wind-induced sputtering or photochemical escape.

Q5. The 55 Cancri system is known for hosting a planetary system with multiple planets, including a super-Earth that orbits its host star within the habitable zone. Which of the following statements is true for the 55 Cancri e planet?

Explanation: The 55 Cancri e planet is a super-Earth that orbits its host star within the habitable zone, and it has a mass of approximately 8.63 times that of Earth.

Q6. Which of the following exoplanet host stars is known to have a planetary system that exhibits a significant difference in the orbital periods of its inner planets, despite being a relatively small and cool star?

Explanation: Kepler-11 is a small and cool star that hosts six confirmed planets. The inner planets of Kepler-11 have orbital periods that are significantly shorter than those of the outer planets, which is unusual for a star of its size and temperature. This is due to the fact that Kepler-11 has a relatively low mass and a small radius, resulting in a stronger gravitational pull on its inner planets.

Q7. What is the primary reason for the observed high obliquity (≥ 30°) of the exoplanet HAT-P-7b, a hot Jupiter orbiting a G-type star?

Explanation: HAT-P-7b's high obliquity is thought to be the result of gravitational interactions with a nearby stellar companion, which caused the planet's orbit to become tilted. This is supported by observations of the star's radial velocity and the planet's transit timing variations.

Q8. A planet with the same average density as Earth but a radius 60% larger would have a surface gravity about how many times Earth's?

Explanation: At fixed density, mass scales with the cube of the radius (M ∝ R³), while surface gravity g = GM/R², so g ∝ R; with R = 1.6 Earth radii the gravity is about 1.6 g. (Kepler-452b's actual mass and gravity are unmeasured; the old item wrongly claimed gravity scales with the square of the radius and keyed 1.4.)

Q9. The exoplanet KELT-9b has a surface temperature of approximately °C, which is due to the strong stellar irradiation it receives from its host star, resulting in a nearly  % of its mass being lost to space through atmospheric evaporation.

Explanation: KELT-9b is a hot Jupiter exoplanet that orbits extremely close to its host star, resulting in a surface temperature of approximately 4500°C. This extreme heat causes a significant portion of its mass to be lost to space through atmospheric evaporation, amounting to nearly 99% of its mass.

Q10. What is the primary mechanism responsible for the observed day-night temperature difference of up to 150 K on the exoplanet 55 Cancri e, a super-Earth located in the habitable zone of its star?

Explanation: 55 Cancri e is a super-Earth with a thick atmosphere, and its day-night temperature difference is primarily caused by thermal inertia, which is the resistance of the planet's interior to changes in temperature. This is due to the slow heat diffusion in the planet's interior, resulting in a significant temperature difference between the day and night sides.

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Exoplanets MCQ Practice Test | Mind Hustle