#14 - Unlike stars, planets do not generate light, but only

[jackieb]

Hey Jackieb,

The author's conclusion is that "there are celestial objects in this galaxy that generate light but are not stars", based on the fact that planets don't generate light, and there are other objects in the galaxy that aren't planets. The author sets up 3 categories of things: planets, stars, and "others" and they say that becuase the other things in the galaxy aren't planets (which don't generate light) these other things must generate light. But that's not necessarily true - there could be things in the galaxy which are not planets and which also don't generate light.

You said the author allows for some to not generate light, but they actually do not here, they assume that everything which is not a planet must also generate light - either because it is a star or because it is part of this 'other' category.

Hope that helps!

Hi Dana,

I'm sorry- I still don't understand how we know the author thinks ALL other celestial objects generate light. The conclusion says "there are celestial objects in this galaxy that generate light but are not stars." To me, the author is only saying there are some other celestial objects that generate light- not ALL of them have to. How do you know the assumption is all of them have to?

[Luke Haqq]

Hi jackieb!

To understand this one, perhaps it could be helpful to start with the conclusion and ask what's missing. The author concludes that "there are celestial objects in this galaxy that generate light but are not stars." How does the author arrive at this conclusion? We're just told that planets are unlike stars in that they do not generate light, and that there are other celestial objects that are not planets. The author's conclusion would follow if it were the case that all other celestial objects besides planets generate light.

[LSAC'sBiggestFan]

This is a pretty interesting question. The stimulus assumes, "not planets generating light," which could be repudiated easily. What annoying are the answer choices. (A), (B), and (C) all could be eliminated at first glance, but I had a tough time eliminating (D). (D) pretty much says, "Stars and planets have differences other than the fact that stars generate light." For example, let say stars = big + generating light; planets = small + not generating light. A celestial object X could be different from planets by means other than not generating light, such as X = big + not generating light. Hence, D, to some degree, does point out a flaw in the stimulus, saying, "no, objects other than planets doesn't always have to be generating light," or "planets are not the only celestial objects that do not generate light (E)." Yet, (E) is much more direct; hence it is the correct answer. I got it right, but I feel like this question could be better designed by replacing (D) with another answer choice not so conspicuous.

[Dana D]

Hey LSAC fan,

Answer choice (D) only talks about planets and stars, which is why it's not the correct answer.

A celestial object X could be different from planets by means other than not generating light, such as X = big + not generating light.

This is 100% correct, but this is not something we can deduce from answer choice (D), because it doesn't speak to celestial objects besides planets and stars at all. Answer choice (E), as you pointed out, better reflects the flaw by tying in other celestial objects.

Hope that helps!