Problems
1. Semi-amplitude sanity check 15 points
51 Pegasi b has e≈0. Using the mass-function equation, show algebraically that in the limit e→0 and Mp<<M*, K ∝ Mp sin(i) P^(-1/3) M*^(-2/3). Using this scaling relation (not the full numerical solve), estimate by what factor K would change if 51 Pegasi b's period were instead 8.46 days (double the real value) with all other parameters fixed.
2. Minimum mass from a hypothetical measurement 15 points
A newly discovered planet orbiting a 1.11 Msun star (51 Pegasi's real mass) shows K=25.0 m/s and P=10.0 days with e≈0. Compute this planet's minimum mass in Jupiter masses.
3. HD 209458 b transit depth from scratch 15 points
Using only HD 209458 b's real published mass (0.682 MJup) and mean density (compute it from mass and radius, 1.359 RJup) together with the host star's radius (1.20 Rsun), compute the transit depth two independent ways: (a) directly from Rp and Rstar, and (b) by first computing Rp from the mass and density and then applying the same formula. Confirm both methods agree.
4. Transit-duration scaling 15 points
Using T ∝ P^(1/3) (from a ∝ P^(2/3) via Kepler's third law, holding Rstar fixed), estimate the transit duration a planet identical to HD 209458 b would have if its period were instead 1.0 day (roughly a quarter of the real value), and state whether this makes such a planet's transit easier or harder to schedule follow-up observations for.
5. Combining methods to get bulk density 15 points
Using HD 209458 b's real transit-derived radius and radial-velocity-derived true mass (both given in this problem set's reading), compute its bulk density in kg/m^3 and in g/cm^3, and state which solar-system body (if any) it is closest to in density among Mercury, Venus, Earth, Mars, Jupiter (see materials/ASTR350/data/).
OpenStax Companion Reading
OpenStax Astronomy 2e (local extracted reference copy: references/openstax-astronomy-2e-extracted.txt) introduces exoplanet detection methods in the "Exoplanets" section of Chapter 7 (Other Worlds: An Introduction to the Solar System) and astrobiology topics (habitable zone, biosignatures, the Drake equation) in Chapter 30 (Life in the Universe); these citations follow the ASTR320/330 precedent of using native OpenStax chapter numbering, extrapolated by analogy rather than independently cross-checked against embedded figure/table numbering this session -- flagged for human spot-check in reference-log.md. Nearly every quantitative derivation in this course (the radial-velocity semi-amplitude equation, transit depth/duration, the mass-radius interior degeneracy, the radiative-equilibrium habitable-zone boundary, and the Drake equation as a structured estimation framework) goes well beyond OpenStax Astronomy 2e’s introductory, descriptive treatment; each lecture states explicitly where this course extends beyond the assigned reading.