ASP MCQ 5 — Questions and Answers
Question 1: What is dark matter?
- Interstellar dust that absorbs visible light
- Matter composed of undetected, non-luminous particles that interacts gravitationally (Correct answer)
- Black holes distributed throughout galaxies
- Cold molecular hydrogen clouds in galactic halos
Correct answer: Matter composed of undetected, non-luminous particles that interacts gravitationally
Dark matter is an undetected form of matter inferred from gravitational effects (galaxy rotation curves, lensing) that does not emit or absorb electromagnetic radiation.
Question 2: What is the defining characteristic of a Type Ia supernova that makes it useful as a standard candle?
- It always occurs in spiral galaxies
- It results from a white dwarf reaching the Chandrasekhar limit, giving uniform peak luminosity (Correct answer)
- It is caused by the collapse of a massive star's iron core
- It produces a pulsar remnant with predictable spin
Correct answer: It results from a white dwarf reaching the Chandrasekhar limit, giving uniform peak luminosity
Type Ia supernovae occur when a white dwarf reaches ~1.4 solar masses and explodes; their consistent peak luminosity allows astronomers to measure cosmic distances.
Question 3: What is the angular resolution of a telescope primarily limited by?
- The focal length of the eyepiece
- Diffraction due to the finite aperture of the telescope (Correct answer)
- The magnification used during observation
- Atmospheric absorption of radio waves
Correct answer: Diffraction due to the finite aperture of the telescope
Diffraction sets the theoretical minimum angular separation a telescope can resolve, with larger apertures producing sharper images (smaller Airy disks).
Question 4: Which phenomenon provides evidence that the universe is expanding at an accelerating rate?
- The rotation curves of spiral galaxies
- Observations of distant Type Ia supernovae appearing fainter than expected (Correct answer)
- The anisotropy of the cosmic microwave background
- The abundance of light elements from Big Bang nucleosynthesis
Correct answer: Observations of distant Type Ia supernovae appearing fainter than expected
In 1998, studies of distant Type Ia supernovae found them dimmer (farther) than expected, revealing that cosmic expansion is accelerating — attributed to dark energy.
Question 5: What is the Roche limit?
- The maximum orbital radius at which a moon remains tidally locked
- The minimum distance at which tidal forces from a planet will disrupt a satellite held together by gravity alone (Correct answer)
- The orbital distance at which retrograde orbits become stable
- The radius at which a gas giant captures a passing body
Correct answer: The minimum distance at which tidal forces from a planet will disrupt a satellite held together by gravity alone
The Roche limit is the critical distance from a massive body inside which tidal forces overcome the self-gravity of an orbiting fluid or loosely bound satellite, tearing it apart.
Question 6: What is the primary method used to detect exoplanets in the transit method?
- Measuring the Doppler shift of stellar spectral lines
- Detecting the dimming of a star as a planet passes in front of it (Correct answer)
- Directly imaging the planet in infrared light
- Observing the gravitational microlensing of background stars
Correct answer: Detecting the dimming of a star as a planet passes in front of it
The transit method detects periodic dips in a star's brightness caused by a planet crossing (transiting) the star's disk, blocking a fraction of its light.
Question 7: What is the Local Group in astronomy?
- The cluster of stars within 100 light-years of the Sun
- The collection of galaxies including the Milky Way, Andromeda, and about 80 smaller galaxies (Correct answer)
- The group of star-forming nebulae in the Orion Arm
- A supercluster containing thousands of galaxy groups
Correct answer: The collection of galaxies including the Milky Way, Andromeda, and about 80 smaller galaxies
The Local Group is the gravitationally bound collection of ~80 galaxies dominated by the Milky Way and Andromeda (M31), spanning roughly 10 million light-years.
