Extra Credit Quiz (F25)

Question 1:

This question was written by me, it is based on a picture from one of the pre-written slides which I noticed some issues with while presenting it. It turns out I was wrong about one of the errors (I miss-identified the constellation being used to point to Polaris as Ursa Minor instead of Ursa Major) - one of my students in their answer actually pointed out a different error I hadn’t noticed - the Earth is spinning the wrong way.

Answer(s): The direction of Earth’s rotation and the location of the North Pole on Earth’s surface.

Question 2:

This question was borrowed from the extra credit quiz written by another TA, Gibson Bowling.

Answer(s): a. $v=\sqrt{2gh}$, b. Tripling the mass has no effect, tripling the height increases the velocity by $\sqrt{3}$, c. Impact velocity has a stronger effect.

Question 3:

This question was borrowed from the extra credit quiz written by another TA, Gibson Bowling. Though, I remember getting a similar question myself on some homework a few years prior, so he may have gotten it from there.

Answer(s): a. About 7.3; larger, b. $\approx 4.38\times10^6$ light years, c. Large; smaller field of view will contain the galaxy better.

Question 4:

This question was borrowed from the extra credit quiz written by another TA, Gibson Bowling.

Answer(s): a. $\Delta E=-1.89$ eV; $\lambda=656$ nm, b. Absorption - the gas cloud absorbs light emitted by the quasar behind it, c. $\lambda_{peak}=0.0083$ nm; these are x-rays; about $6\times10^4$ times hotter than the Sun.

Question 5:

This question was borrowed from the extra credit quiz written by another TA, Gibson Bowling. The hint on part a came from me.

Answer(s): $F=\frac{L}{4\pi d^2}$, L has units of $\frac{energy}{time}$ and $d^2$ has units of area - so F has units of $\frac{energy}{area\cdot time}$; $4\pi$ is present because the light is radiating outwards in all directions - a sphere, b. Yes, c. Around 350 K cooler.

Question 6:

This question comes from A Student’s Guide to the Mathematics of Astronomy by Daniel Fleisch and Julia Kregenow, 9th printing, chapter 2, question 2.9. Everything before “How far” as well as the hint were written by me to give the students additional background information.

Answer(s): $a\approx6.76\times10^6$ meters.

Question 7:

This question was also taken from A Student’s Guide to the Mathematics of Astronomy, chapter 2, in this case question 2.11. I added everything from the equation for the force of gravity and onward. In the future, I think the point would be made better if 0.1 or 0.01 meters were used for the distance between doctor and baby in this question.

Answer(s): The difference is approximately 55 times in foavor of Jupiter.

Question 8:

This question was written by me.

Answer(s): a. The color, can tell you the temperature - bluer = hotter and redder = cooler, b. Cooler.

Question 9:

This question was written by me.

Answer(s): a. It has experienced a lot of impacts, b. Some of those impactors would have hit Earth instead, c. Earth’s tides would be much weaker (primarily controlled by the Sun instead of the Moon).

Question 10:

This question was written by me.

Answer(s): a. Transit Method: Diameter, period - Radial Velocity: Mass, period - together: density, orbital radius (with star’s information), b. No diameter (and so no density), c. Atmospheric Composition, d. The third lab is planetary atmospheres - you could then estimate the planet’s surface temperature (technically possible without the atmospheric composition, but much less accurate).
On parts a. and b., students could mention that a limitation of Radial Velocity is that it is the minimum mass of the planet rather than the actual mass due to the unknown orbital incclination - and if you see a transit then you know the incliniation is (very close to) 90° - getting this could be an additional bonus.