Bad Answers by Astronomy Students

These answers were written by actual astronomy students on homeworks, labs, or exams graded by me or my fellow teaching assistants during my time at Boston University. I have included the questions the students were answering, and I've preserved the original spelling and grammar wherever possible.

Q: What planets might you expect to exhibit differential rotation?

A1: Those made of a crust of ice. The melting and refreezing with the dirt/dust on the planet would change any evident spots.

A2: ...planets with a highly elliptical orbit probably exhibit differential rotation.

Q: Now that you are an apprentice astrophysicist, discuss the two components of the binary star. Which one is the hotter one? Which one is probably the larger one?

A: The star that isn't blinking is the larger one, since the other one orbits around it.

Solar Rotation Lab Report:

Purpose: To completely baffle ourselves with unintelligible data and archaic graphing techniques with the help of a solar telescope and some differential rotation of the sun.


Conclusion: The data sucks. I've been messing around with it for days and it doesn't work. I have achieved nothing with these calculations and they're driving me crazy. It's a day late and I have other things I need to do. So I give up. The error involved with this lab can be calculated as such: galaxy < error < globular super cluster complex. The so called results do not match theoretical predictions. Does the sun rotate differentially? Probably. But you wouldn't know it from reading this report.

Q: What is a "blue moon"? What is so unusual about the January - March 1999 period?

A: A "blue moon" is an expression which says that when things happen, it is very rare. It is very rare that you will get a "blue moon". You might get a "red moon", but you hardly see a blue one. Eclipses are rare to [sic] because they don't happen every day. During the January-March period, Earth will see 2 eclipses. Since eclipses are rare, astronomers can study them when they are occuring.

Q: Why are most stars in an HR diagram located on the main sequence?

A: Most stars are found in the main sequence because they only spend a small fraction of their lives in the transitional regions outside the main sequence, like cars in garages.

Q: One reason why radio and infrared radiation is more useful than visible light in studying molecular clouds is that the clouds are more transparent at those wavelengths. What is another reason why the longer wavelengths are more useful?

A: They are not as dangerous.

"Kepler's laws were more like rules in his time because they could not be fully explained but they proved many unexplainable theories at the time."

Q: Consider two regions of the ISM that are in pressure equilibrium with one another. One of the regions has a temperature of 10K and the other is at 1000K. What is the ratio of their densities?

A: The density of the cooler region is greater then [sic] the hotter region. It's like if you put a rock in a pot of boiling water, but not really, because it would be hard to achieve pressure equilibrium in this way, but kind of. The only was [sic] rock can withstand the pressure is if it were dense, according to pv=nRT.

Q: What is the most common molecule in interstellar space? What is the most heavily observed molecule?

A: The most common molecule is H2, but it is difficult to observe, so the most heavily observed molecule is Titanium oxyllar [sic] because the emission lines are easier to observe.

Q: The surface of a lake is an equipotential while the surface of a river is not. Why is that difference important?

A: A lake that is in equipotential has come to a constant elevation whereas a river flows either from high elevation to low elevation or vice versa. [!!]

[Student is to write a report on Pleiades. It begins with normal information about star names and descriptions. Then the following is written.] "...Alcyone [sic] is the central sun of the Pleiades. An interesting theory known as the Photon Belt story concerns this particular star. Our solar system makes one complete orbit around Alcyone everyone [sic] 25,000 to 26,000 years. In 1961, a group of scientists discovered a belt a [sic] photon light particles encircling the star cluster. Every 12,500 years, our sun reaches the midpoint of this belt. It takes 2000 years to travel through the midpoint and another 10,500 before the solar system enters it again. A null zone is located at the edge of the belt in which the earth will experience three days of absolute darkness. During these three days, no electrical device will be able to operate. The main part of the belt is where earth will experience 24 hours of daylight. Because of this entrance into the belt, some believe that people will develop psychic abilities like telepathy and telekinesis. Before entering the belt, however, a Supreme Creator Force will rescue the solar system by thrusting the [sic] it through the fifth dimension in an interdimensional rescue bubble. Supposedly, the solar system will find a new location only three light years from the Sirius star system. The solar system will reach the bubble around 2013. The period from 1996-2013 marks the end of 24 hours of daylight and brings back days consisting of 12 hours of sunlight and 12 hours of darkness."

Q: Describe the evidence that quasars are only a few parsecs or smaller in size.

A: Quasars are only a few parsecs or smaller in size because of their extreme distance.

[Quote from a Changing Seasons lab report, which was unpopular because its conclusions were so obvious.] "...In conclusion, it is now apparent that the change in position of the sun causes the temperature changes associated with the seasons. This came as quite a shocker to me; I had always figured the earth became more massive (and thus gravity became stronger) in the wintertime, which caused two things to happen. First, the cold air from the upper atmosphere would get pulled in closer to the surface, making it colder; second, the increase in gravity pulled all the leaves off the trees. But after careful consideration of the data that was collection [sic], I now know that the seasons change because the sun appears to change elevation in the sky, which occurs because the earth is tilted. Go figure."

[Actual situation that occurred in Prof. Spence's AS101 final exam, 9-11am]

Student, approaching Professor at 9:30am: "Here's my test. I'll be back at 11:15 to finish it." Walks out. Professor was speechless.
At 11:15am in Professor's office, student returns.
Student: "I'm back to finish my test."
Professor: "Why did you leave?"
Student: "I had to go see my English professor."
Professor: "Right now? You couldn't schedule it for after the exam?"
Student: "Well, um, he'll be gone, and I really had to pick up my term paper."
Professor: "You left to pick up a term paper?"
Student: "Well, no. Actually I had to go study for another exam."
Professor: "Do you really think I'm going to let you finish the exam now?"
Student: "No, I guess not!" Leaves.
Q: In the space below...present one of the major theories or ideas which aims to account for the spiral structure of galaxies.

A: Galaxy collision is one theory, huge pieces of mass collided (supposedly in the "big bang"), creating many planets which all were gravitationally attracted to one another thus forming this spherical orbitting [sic] system which we now know to be our galaxy.

Q: List two observations which support the Big Bang model of the universe. Indicate what aspect of the model each supports.

A: different galaxies -- supports collision theory and gravitational manner craterings of Earth -- suggests earth was ripped off or smashed with other huge masses

Q: Which planets(s) could never be seen from Earth at midnight?


Q: Suppose a tenth planet, beyond Pluto, was discovered... Explain how you would figure out...its average temperature.

A: The temperature will probably be cold, because it is far in space. Maybe use big termomiter [sic].

Q: The Sun's corona shows weak emission lines. Why?

A: According to fraunhofer [sic] lines the Sun has the most extensive set of observed absorption lines. Also, the sun has low density but the emission spectrum does not have any density.

Q: Why do we see the sky? At night we see through the sky to view the stars. Why don't we see through the sky during the daytime?

A: Due to all the life that takes place on earth it makes its way up to the sky and thereby creating a visible atmosphere. It is too bright out during the daytime to view stars.

Q: Why does the sky appear blue during the day? Especially, why is it bluer than the Sun?

A: The sky appears blue during the day b/c there is a lot of Hydrogen in the air. The sky has more emmission [sic] spectrum and the Sun is full of absorption spectrum. The Sun wants to gain energy but the sky wants to get rid of the energy by ejecting a photon.

Q: Towards which direction would you launch [the space shuttle]? Explain.

A1: You would want to launch East so as to go with the flow of gravity which moves counter-clockwise.

A2: You would launch it going south because it takes less energy to move something down than it does to move that same object up/to the side. Then, once the object is in motion, it will stay in motion until another force stops/slows it.

Q: Suppose you want to set up a spaceport to launch space shuttle [sic]. Based only on energy requirement [sic], what would be the best place for the launch complex?

A: The best place for the launch complex would be wherever it would be closest to the horizon so it could escape into the horizon as quickly as possible. Also a flat plane so that the rocket aims straight into the horizon.

"If the distance b/w two objects were tripled, then the gravitational force between them would drop by a factor of 16. This is b/c gravity is an inverse square law. Double the distance, four times weaker; triple distance, sixteen times weeker, etc..."

Q: [Student Survey for AS202] Comment on the night labs. Are they interesting and relevant? What could be done to improve them?

A: Too cold. Ask God to turn on the heater.

Q: Metabolizing a candy bar releases about 10^6 J. How fast must the candy bar travel to have the same 10^6 J in the form of kinetic energy? (Assume the candy bar's mass is 0.2 kg.) Is your answer faster or slower than you expected?

A: [math calculations] v=3162m/s. This is a much faster speed than I would have expected for a candy bar, especially considering that candy bars have no self propelled movement. The only time a candy bar should be moving is when I'm bringing it toward my mouth.

Q: The diffraction-limited resolution of a 5-meter telescope is about 0.01 arcsecond for visible light. Would you expect the angular resolution of a 5-meter radio telescope to be better than, equal to, or worse than 0.01 arcsecond?

A: I would expect the angular resolution of a 5-meter radio telescope to be better than 0.01 arcsecond because a radio telescope has to deal with light and spectrums. [sic]

Q: Suppose that two atmosphere-less planets with identical densities have the same surface temperature. If the larger planet is 8 times more massive than the smaller one, which one will cool faster? How much faster?

A1: The larger one will cool faster because it will cool slower because the inner temp will escape in less time as it works its way through the surface.

A2: Since larger is 8 times more massive and density is equal, the larger is 8 times as voluptuous. Since the cooling varies directly with surface area/volume ratio, which is 3/r, the smaller one will cool 8 times faster.

A3: The planet with more density would cool faster.

Q: Explain how we could observe from far away if a planet has a magnetic field.

A: Magnetic field would create gravity thus, planet would influence motion of other planets or capture asteroids or get moons.

Q: When would Venus be best observed? When would Jupiter be best observed?

A: Venus would be best observed when it in [sic] opposition with the sun. Meanwhile Jupiter would be best observed while in conjunction.

Q: If the Earth had no atmosphere, name one thing of astronomical significance that would be different and explain why.

A: If the Earth didn't have an atmosphere then it probably wouldn't have much gravity. This is astronomically significant because we would probably not have a moon.

Q: What are the main internal energy sources of the following objects and how do they work? (The Sun, Jupiter)

A1: Radioactive decay causes the release of energy in the sun's core which then travels outward towards the surface.

A2: [For the Sun] The energy source for the sun is its mantle. [For Jupiter] The energy source of Jupiter may be its methane. This burns up in the mantle and thus gives off pressure that forms volcanoes.

Q: Explain what convection is. Then name two places it can be found in the solar system: what object and where in the object convection is found.

A: When 2 planets or objects align with the Sun on the same side of the Solar System and form a right angle. a) When the earth, aligns with Mars and the Sun to form a right angle. b) When the Venus [sic] and Mercury align in such a way as to form a right angle.

Q: Before the invention of telescopes, how did we know there were planets, different from stars?

A: Because some of them were more visible, but more importantly because they moved horizontally, from W to E, and not vertically like the stars.

Q: Choose one planet or large moon other than the Earth and describe what we know about its interior.

A: We know that Jupiter has many different layers of compressed gasses like metalic [sic] hydrogen, some silicates, and a metal core that is a little larger than earth because the Russians sent a wearther [sic] balloon through its atmosphere.

Q: What phase must the Moon be in for a solar eclipse to occur? At approximately what time of day would the Moon rise when it is in this phase?

A: The phase must be full moon. The moon will rise at sunset, probably around 6AM.

Q: If you could take a sample of the material of any object in the solar system in order to find the age of the solar system, what object would you choose and why?

A: If it were possible, I would choose air bubbles because no matter how many times they have been recycled through different stages, they would be the best indicator. On earth, air bubbles give evidence of a longer history than rocks do because rocks get sucked into the earth sometimes through plate tect.

Q: Explain the conditions necessary for the Earth to generate a magnetic field. What is different about how Jupiter's magnetic field is created?

A: For the Earth to have a magnetic field, it is essential for it to have its core emitting waves and to receive the Electro Magnetic [sic] waves from the Sun to interact with its own atmosphere. Of course, it also needs the gravity to maintain this atmosphere. Jupiter generates its atmosphere and m. field through its rapid rotation which heats up the core.

Q: Are there any abberations similar to those seen through the refracting telescope?

A: No, the image is very lucid.

Q: You and the Earth attract each other gravitationally, so you should also be subject to a tidal force resulting from the difference between the gravitational attraction felt by your feet and that felt by your head. Explain why you can't feel this tidal force.

A: Because the air and atmosphere interfere.

Q: [Explain why statement is sensible or not sensible.] If you put an ice cube outside the Space Station, it would take a very long time to melt, even though the temperature in Earth orbit is several thousand degrees (Celsius).

A: It would still be held together because there is no gravity and the atoms wouldn't separate.

Q: Why does a 100-kg satellite orbiting Jupiter have more gravitational potential energy than a 100-kg satellite orbiting the Earth, assuming both satellites orbit at the same distance from the planet centers?

A: A 100-kg satellite orbiting Jupiter has more gravitational potential energy than a 100-kg satellite orbiting the Earth, assuming both satellites orbit at the same distance from the planet centers, because there is more gravity on Earth, and Earth is more solid -- it could keep falling through Jupiter.

Q: The Sun's corona shows emission lines. Why?

A: [Student has English as a second language. This is a partial answer.] The corona is at a very high temperature location, so hydrogen and helium do not have their erections.

Q: The nearest star has a parallax of 0.75 arc-seconds. What is its distance?

A: 0.8660254 meters [no work shown]

Q: What is the total mass (in solar masses) of a visual binary system in which the average separation of its components is 10AU and the period is 10 years?

A: [Student uses Kepler's law correctly, but puts units on at end] 10 grams = total mass

[The following is a student essay. Spelling and typos reproduced.]

The Two Faces of the Moon

I am going to write about the two faces of the moon. The light face of the moon formed when crystals of mineral "feldspar" went to the top of "magma ocean". But there is something else about the two faces.

The center of the moon's mass is not at the center of the moon because the gravity is stronger on the far side of the moon. This causes the light face of the moon to face us. The dark side of the moon has heavier magma made of "basalt rock". This is how the dark side of the moon is so dark.

The dark side of the moon does not face use ever because the gravity is heavier and the moon is asymmetrical. Its development is different from the light side of the moon. The lava of the moon could not make through the dense material that was on the dark side of the moon. The lava was trapped to form hard magma.

On the light side of the moon the lava was able to burst through. On the light side of the moon lava is hotter and thats why its lighter. On the Dark side lava is cooler. Thats why dark side is heavier than the light side. We can only see the light side. Also the moons gravity tilts the dark side so we can't see it.

[Student has a picture of the near side of the Moon labeled "The Dark side of the Moon" and a picture of the far side labeled "The light side of the moon".]

Q: If two white dwarf stars have different masses but the same surface temperature, which star will be more luminous?

A: The one with the smaller mass will be less luminous than the one with the larger mass because the one with larger mass will secrete more energy per second than the one with the smaller mass.

Q: When the Sun becomes a red giant, it will swell to perhaps 100 times its present size. How will its average density then compare with the density of water (which is 1000 kg/m^3)?

A: It's [sic] average density will be much less than the density of water due to the fact that all of the central energy and emission would red-shift with the growth, thus leaving it not as dense as it was earlier and definitely less than water.

Q: A spectral type B main-sequence star has a luminosity 10,000 times that of the Sun, and a mass of 10 solar masses. Compare the lifetime of this star with that of the Sun.

A: The Sun will have a shorter lifetime then [sic] that star because the Sun does not have as much matter to ignite in its core to maintain the stars [sic] shells from not collapsing in. The material in the star will be consumed more quickly then [sic] that of the Suns [sic], but the Sun will most likely seize to exist before the other star.

Q: What do you call an atom missing an electron?

A: Dangerous.

Q: Detroit, MI, has coordinates of about 84 deg W and 42 deg N, so it must be 84 deg west of Greenwich, England, and 42 deg north of _____.

Some answers: Miami, FL; Texas; Boston; Detroit; Greenwich; Mexico; Ecuador; South America; Australia.

Q: State Newton's Third Law.

A: In a vaccuum[sic], objects accelerate at 8 m/s/s.

Q: A planets orbits in an ellipse around the Sun, with the Sun at one focus. What is at the other focus?

A1: The Sun.

A2: The North Star.

A2: The peripheal [I don't know what this is].

Q: Why do we send satellites into orbit around the Earth to observe ultraviolet and x-ray light?

A: Because there needs some power to accelerate against gravity.

Q: State Kepler's Three Laws of Planetary Motion.

A: [1st and 3rd laws correct] 2. The orbit of a planet will scoop out an equilarium.

Q: Which color of star corresponds to cooler stars, and which to hotter ones? Explain your reasoning.

A1: Blue would be cooler and red hotter because red is fire and blue is water.

A2: Blue corresponds to cooler stars and red corresponds to hotter ones. According to humans, red is the universal symbol for hot and blue is the universal symbol for cold.

Q: In what way did, or would, the presence of the Moon affect your observations?

A: The Moon increases the amount of light that reaches Earth, therefore, decreasing the disparity between the void of space and the light of the stars.

Q: Explain how the greehouse effect works to cause the surface of Venus to be so hot.

A: The Venus's atmosphere, mostly covers with surfuric [sic] acid. When Sun's radioactive ray heats the Venus's cruster [sic], it converted to CO2 and worth the surface.

Q: Why are impact craters circular?

A: Impact craters are circular because when they travel near the sun, the sun creates tails or gas and dust on the craters. The sun smooths out the shape and the craters remain circular.

Q: We are confident that the present meteor rate has been fairly constant for the last 3.8 billion years. Parts of the Moon's highlands appear to be older than the universe based on the number of craters. How do we resolve this?

A1: The moon may have been hit by craters perhaps not of this universe, or the universe may be older than we actually believe it to be.

A2: The highlands have more craters b/c They're [sic] higher up in elevation so more bolides can hit That [sic] area because They're [sic] closer.

A3: That part had craters on it when it was still part of the Earth.

Q: [difficult math problem]

A: No idea. Honestly, if I tried it would just look like a monkey had attempted it. About the same math skills, anyway.

Q: What is a lunar rille?

A: Canyons in moons [sic] surface where lava may have once flown.

Q: What caused the solar nebula disk to develop two zones? [terrestrial and jovian]

A: The asteroids got in between them.

Q: Which planets might you expect to exhibit differential rotation? Explain your line of reasoning.

A: Mercury, Venus. Because they are the only planets that come between us and the sun and therefore exhibit differential rotation.

Q: Describe the electromagnetic spectrum in terms of frequency, wavelength, and energy. Distinguish among radio, infrared, visible light, ultraviolet, x-rays and gamma rays.

A: The electro magnetic [sic] spectrum is an electrical magnetic field that covers the earth[sic]. These electric and magnetic fields vibrate. This electro magnetic [sic] field (light) is made up of small particles called "photons". [Student writes correctly about visible light and infrared.] Radio waves are even more further right then infrared waves. Radio waves are the longest and detected as vibrations in the human ear (which allows us to hear).

Q: List three observations Galileo made and indicate how they supported the Copernican view of the solar system.

A1: [partial answer] Rings of Saturn -- showed that the Earth moved due to the existance[sic] of these + gravity.

A2: Objects in the sky, such as birds and clouds, move with the earth[sic]. This supported the Copernican view that the planets orbit the Sun.

Q: How does Pluto fit into the terrestrial and jovian planets?

A: Pluto is a bit different than the rest. It is small like a terrestrial planet but is comprised of low densit ice and is rather cold considering its distance from the Sun. It is possible that Pluto is an object roaming the outer portions of our solar system.

"Even though the moon isn't a planet, it fits all the symptoms of the terrestrial planets."

Q: In what way did the presence or absence of the Moon affect your observations?

A: The moon[sic] acted as to light up the sky. This helped us see more stars than we would be able to without that light.

Q: Which planets might you expect to exhibit differential rotation? Explain your line of reasoning.

A1: All except Uranus. On all the planets except Uranuse [sic], regions near the equator have to rotate faster in order to make the same rotation as regions on the poles. Because Uranus is tilted on its side and rotates vertically, spots on its 90 degree longitude will rotate faster than on 0 degree or 180 degree, but the principle is the same for all planets.

A2: Ones affected by other planets/moons/objects. Magnetism & gravity slightly speeding up or slowing down the rotation period.

Q: How do we think Jupiter generates its internal heat? How do the other Jovian planets generate internal heat?

A: Even though the Jovian planets are far away from the Sun, they still have a lot of greenhouse gasses which trap the heat from the Sun. The planets also create their own internal heat which the gas then traps inside. As a result, all the planets are very hot.

"Uranus doesn't admit much excess internal heat."

Q: Why do objects observed at the zenith appear sharper than objects located at lower altitudes?

A1: The objects at lower altitudes may have a direction further away. The zenith is 90 degrees altitude but has no direction since it is straight overhead.

A2: Below the zenith, the light, coming from the object of observation, has to travel the least distance and has the best angular resolution.

A3: They are closer therefore sharper + the Earth's shape is more oblong than spherical.

Q: Imagine that the Earth had evolved without any Moon. Write down one example of a difference in the evolution of the Earth that would be expected in the following areas:
  1. the Earth's geologic activity
  2. the length of a day on the Earth
  3. the evolution of Earth's atmosphere.
  1. I think the geologic activity would be less than what it is now. Because if there was not any moon then there would always be light. Which means that things would start to dry up EX. (ariculture [sic])
  2. I think the length of the day will be the same but there just would not be any nights.
  3. I don't think Earth's atmosphere would have evolved because if the sun [sic] was always out, the Sun would actually kill all the crops, animals would go thirsty because H2O would vaporized [sic] so I think it will not evolve for that reason.

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