1. The discovery of exoplanet 51 Pegasi b in 1995 was groundbreaking because it was the first:
- A) Earth-sized planet orbiting a Sun-like star
- B) Exoplanet detected using the transit method
- C) Jupiter-mass planet found orbiting a Sun-like star
- D) Planet discovered through direct imaging
Answer: ✅ :alphabet-white-c: Jupiter-mass planet found orbiting a Sun-like star
51 Pegasi b was the first confirmed exoplanet around a main-sequence star, discovered via the radial velocity method. Its existence proved that gas giants could form—and survive—in close, short-period orbits.
2. What phenomenon explains why rotating black holes can transfer energy to their surroundings?
- A) The Penrose process
- B) The Unruh effect
- C) Frame dragging in neutron stars
- D) The Hawking radiation cascade
Answer: ✅ :alphabet-white-a: The Penrose process
In the Penrose process, particles entering a rotating black hole’s ergosphere can gain energy by splitting—one falls in, while the other escapes with more energy than it entered, effectively extracting rotational energy from the black hole.
3. Which atmospheric molecule is considered a potential biosignature when detected alongside oxygen on an exoplanet?
- A) Carbon dioxide
- B) Methane
- C) Nitrogen
- D) Ozone
Answer: ✅ :alphabet-white-b: Methane
Methane (CH₄) coexisting with oxygen (O₂) or ozone (O₃) is a strong biosignature candidate, since these gases naturally destroy each other chemically. Their simultaneous presence implies continuous replenishment—potentially from biological activity.
4. What does the “main sequence turnoff point” in a star cluster’s Hertzsprung–Russell diagram reveal?
- A) The metallicity of the cluster
- B) The distance to the cluster
- C) The age of the cluster
- D) The mass distribution of its stars
Answer: ✅ :alphabet-white-c: The age of the cluster
The point where stars leave the main sequence corresponds to the most massive stars that have exhausted hydrogen in their cores. Comparing this point with stellar models gives an accurate measure of the cluster’s age.
5. Why do astronomers use spectrographs with very high resolving power for exoplanet searches?
- A) To isolate thermal noise in the detector array
- B) To measure extremely small Doppler shifts in stellar absorption lines
- C) To prevent contamination from interstellar dust
- D) To detect the planet’s reflected light directly
Answer: ✅ :alphabet-white-b: To measure extremely small Doppler shifts in stellar absorption lines
High-resolution spectroscopy allows detection of minute shifts in a star’s spectral lines caused by orbiting planets. These tiny radial velocity changes—often less than a few m/s—require ultra-precise wavelength measurements.