1. What is the primary observable used to infer the presence of “ultra-short-period” (USP) planets?
- A) Doppler shifts caused by stellar oscillation modes
- B) Infrared phase curves showing strong nightside cooling
- C) Rapid, shallow transits with periods <1 day
- D) Repeated stellar flares aligned with planetary longitude
Answer: ✅ :alphabet-white-c: Rapid, shallow transits with periods <1 day
USP planets are identified through extremely frequent, shallow dips in brightness repeating on cycles shorter than a day.
2. In galaxy evolution, what is “morphological quenching”?
- A) Stabilization of a gas disk by a massive bulge, preventing collapse
- B) Tidal stripping of molecular clouds in mergers
- C) Suppression of star formation by AGN-driven radiation pressure
- D) Shutdown of star formation due to removal of cold gas by the IGM
Answer: ✅ :alphabet-white-a: Stabilization of a gas disk by a massive bulge, preventing collapse
A large central bulge boosts gravitational stability, preventing gas from fragmenting—even when plenty of cold gas is present.
3. What physical mechanism drives the re-inflation of some close-in gas giants around evolved stars?
- A) Shock heating from magnetospheric reconnection events
- B) Orbital circularization releasing gravitational energy
- C) Helium rain generating latent heat in the interior
- D) Increased stellar irradiation as the host star expands off the main sequence
Answer: ✅ :alphabet-white-d: Increased stellar irradiation as the host star expands off the main sequence
As a star grows into a subgiant/giant, its rising luminosity heats nearby gas giants, causing their atmospheres to puff back up.
4. In gravitational-wave astrophysics, what defines the “chirp mass”?
- A) The mass inferred from the rate at which inspiral frequency increases
- B) The minimum mass needed for a binary black hole to emit detectable waves
- C) The mass of the merger remnant after ringdown
- D) The mass parameter controlling post-merger accretion flows
Answer: ✅ :alphabet-white-a: The mass inferred from the rate at which inspiral frequency increases
The chirp mass governs how quickly the frequency of a binary’s gravitational-wave signal accelerates before merger.
5. Why are transmission spectra of small, temperate exoplanets often featureless?
- A) Stellar spots cancel out all atmospheric spectral signatures
- B) Their orbital motion Doppler-shifts lines beyond detection
- C) Clouds or hazes obscure absorption features at observable wavelengths
- D) Their atmospheres lack elements heavier than hydrogen
Answer: ✅ :alphabet-white-c: Clouds or hazes obscure absorption features at observable wavelengths
High-altitude clouds/hazes block deeper atmospheric layers, erasing the molecular signatures that would otherwise stand out.