Habitability of Exoplanets — MCQs

1. The habitable zone is the region around a star where:
(A) Planets can form rings
(B) Liquid water can exist on a planet’s surface
(C) All planets have moons
(D) Atmospheres always form

2. The habitable zone of a star mainly depends on:
(A) Star’s mass and luminosity
(B) Size of planets
(C) Rotation of planets
(D) Age of the galaxy

3. Earth is considered habitable because:
(A) It has rings like Saturn
(B) It is in the Sun’s habitable zone and has atmosphere and water
(C) It is closest to the Sun
(D) It rotates faster than Venus

4. Which element is most essential for life as we know it?
(A) Helium
(B) Carbon
(C) Sodium
(D) Sulfur

5. A tidally locked exoplanet may struggle with habitability because:
(A) It moves too slowly in orbit
(B) One side is too hot and the other too cold
(C) It lacks solid surface
(D) It has too many moons

6. Which type of stars generally provide the longest-lived habitable zones?
(A) O-type
(B) B-type
(C) G-type
(D) M-type

7. Which factor protects Earth’s atmosphere from solar wind?
(A) Magnetic field
(B) Large oceans
(C) Moon’s gravity
(D) Plate tectonics

8. Planets around M-dwarfs face challenges for habitability due to:
(A) Weak gravity
(B) Strong stellar flares
(C) Absence of iron
(D) Smaller size

9. Which molecule is considered a strong indicator of possible habitability?
(A) Oxygen
(B) Nitrogen
(C) Water vapor
(D) Helium

10. Which detection method is best for analyzing exoplanet atmospheres?
(A) Transit method
(B) Radial velocity
(C) Direct imaging
(D) Microlensing

11. Venus is in the Sun’s habitable zone but not habitable due to:
(A) Lack of volcanoes
(B) Runaway greenhouse effect
(C) Small size
(D) No moons

12. What is the “Goldilocks zone”?
(A) Region with extreme heat
(B) Region not too hot, not too cold for water
(C) Region where gas giants form
(D) Region only for icy planets

13. What is the main reason Mars is less habitable today?
(A) Too close to the Sun
(B) Thin atmosphere and loss of magnetic field
(C) Too many moons
(D) Large volcanoes

14. Which of the following is a “super-Earth”?
(A) A gas giant larger than Jupiter
(B) A rocky planet larger than Earth but smaller than Neptune
(C) A planet with rings like Saturn
(D) A frozen planet beyond Pluto

15. Which greenhouse gas is most important for maintaining habitability?
(A) Carbon dioxide
(B) Oxygen
(C) Nitrogen
(D) Argon

16. Why is liquid water so important for habitability?
(A) Helps maintain orbit
(B) Acts as a universal solvent for life processes
(C) Generates magnetic fields
(D) Produces light

17. Which planetary feature stabilizes Earth’s climate over long timescales?
(A) Mountains
(B) Plate tectonics and carbon cycle
(C) Large deserts
(D) Earth’s tilt

18. Which type of planets are more likely habitable?
(A) Gas giants
(B) Rocky terrestrial planets
(C) Ice giants
(D) Ringed planets

19. Why are exomoons also considered possible habitable worlds?
(A) They always contain oceans
(B) They may have water and atmosphere despite orbiting giant planets
(C) They are smaller than planets
(D) They reflect starlight

20. Which planetary size range is often considered best for habitability?
(A) Smaller than Mercury
(B) About Earth-size or slightly larger
(C) Larger than Jupiter
(D) Same as Pluto

21. The habitable zone around massive stars is:
(A) Wide but short-lived
(B) Narrow and long-lived
(C) Absent
(D) Same for all stars

22. Which factor prevents small planets from being habitable?
(A) Low gravity cannot retain thick atmosphere
(B) They rotate too fast
(C) They have no magnetic field
(D) They have too many craters

23. Europa, a moon of Jupiter, is considered potentially habitable because:
(A) It has a thick atmosphere
(B) It has an underground liquid water ocean
(C) It orbits in the Sun’s habitable zone
(D) It is larger than Earth

24. Which is a key limitation of the radial velocity method for habitability studies?
(A) Cannot detect atmospheres directly
(B) Cannot detect small stars
(C) Cannot measure distance
(D) Cannot find large planets

25. Why are M-dwarf stars considered both promising and risky for habitability?
(A) They live long but emit strong stellar flares
(B) They are very large stars
(C) They form only gas giants
(D) They lack gravity

26. Which condition is necessary for plate tectonics to support habitability?
(A) Thin crust
(B) Presence of internal heat and water
(C) No volcanoes
(D) Absence of gravity

27. Which gas in Earth’s atmosphere mainly supports photosynthesis-based life?
(A) Carbon dioxide
(B) Methane
(C) Oxygen
(D) Nitrogen

28. Why does the presence of ozone (O₃) in an atmosphere suggest habitability?
(A) Indicates strong magnetic field
(B) Protects life from harmful UV radiation
(C) Reflects sunlight
(D) Maintains temperature

29. What is the main role of an atmosphere in planetary habitability?
(A) Creates strong winds
(B) Regulates temperature and protects from radiation
(C) Increases planet’s size
(D) Generates water

30. A “runaway greenhouse effect” makes a planet uninhabitable because:
(A) Atmosphere is blown away
(B) Temperatures rise uncontrollably
(C) Orbit becomes unstable
(D) Planet shrinks in size

31. Which planet in our solar system is a good model for studying habitable exoplanets?
(A) Mercury
(B) Earth
(C) Neptune
(D) Pluto

32. The Drake Equation is used to:
(A) Calculate habitable zone size
(B) Estimate the number of advanced civilizations in the galaxy
(C) Measure orbital distance
(D) Detect magnetic fields

33. Which property of water makes it vital for life?
(A) Expands when frozen
(B) High heat capacity and solvent abilities
(C) Absorbs light strongly
(D) Reflects starlight

34. Why is the concept of “habitability” broader than just temperature range?
(A) It includes atmosphere, chemistry, and radiation environment
(B) It refers only to liquid water
(C) It ignores stellar activity
(D) It only applies to Earth-like planets

35. Which factor may allow planets outside habitable zones to still host life?
(A) Internal heating from tidal forces
(B) Large craters
(C) Slow rotation
(D) Small size

36. Exoplanet Kepler-452b is called “Earth’s cousin” because:
(A) It is the same size as Jupiter
(B) It lies in its star’s habitable zone and is Earth-like in size
(C) It has rings and moons
(D) It is the nearest planet

37. Which stellar property shortens habitability lifespan?
(A) Small mass
(B) High mass and rapid fuel consumption
(C) Strong magnetic field
(D) Low metallicity

38. The outer edge of the habitable zone is limited by:
(A) Too much CO₂ freezing out
(B) Too much starlight
(C) Lack of magnetic field
(D) Planetary rotation speed

39. Which type of radiation from stars can harm habitability most?
(A) Radio waves
(B) Ultraviolet and X-rays
(C) Infrared
(D) Visible light

40. Which planetary factor helps avoid global freezing?
(A) Thick greenhouse atmosphere
(B) Fast rotation
(C) Large number of moons
(D) Strong albedo

41. Which is the most important requirement for complex life forms?
(A) Stable environment over long timescales
(B) Frequent asteroid impacts
(C) Lack of atmosphere
(D) Constant volcanic eruptions

42. What is an “exo-Earth”?
(A) A gas giant with moons
(B) A rocky exoplanet similar to Earth in size and orbit
(C) A frozen exoplanet far from its star
(D) A star-like object

43. Why do scientists search for biosignature gases?
(A) To detect star’s rotation
(B) To find chemical signs of life in exoplanet atmospheres
(C) To measure distance
(D) To calculate surface gravity

44. Which is a potential biosignature?
(A) Methane with oxygen
(B) Helium
(C) Argon
(D) Neon

45. What is meant by “planetary habitability index”?
(A) Score measuring economic resources of a planet
(B) Numerical estimate of likelihood for life-supporting conditions
(C) A measure of distance
(D) A test of atmosphere thickness

46. What is the main reason gas giants are unlikely habitable?
(A) Too much gravity
(B) No solid surface for liquid water
(C) Too small
(D) Too close to stars

47. Why are binary star systems challenging for habitability studies?
(A) Planets cannot form
(B) Complex gravitational effects on orbits
(C) Too little light
(D) Too cold environments

48. Why is surface temperature not enough to confirm habitability?
(A) Atmosphere, radiation, and chemistry also matter
(B) All planets are the same size
(C) Stars do not emit light equally
(D) Temperature cannot be measured

49. Which mission has been most famous for discovering thousands of exoplanets?
(A) Hubble
(B) Kepler
(C) Voyager
(D) Chandra

50. The study of habitability of exoplanets is important because:
(A) It helps in designing telescopes
(B) It improves understanding of where life may exist beyond Earth
(C) It reduces the need for astronomy
(D) It only explains Earth’s history