Q13 - When astronomers observed the comet

[geverett]

I can see how C would be the correct answer. I chose D. Would love to hear thoughts on this question.

[maryadkins]

This is an Explain a Result question. We are asked to resolve the apparent discrepancy in the statements. First we need to identify what the conflict is--what was expected and why that was violated.

The two conflicting facts are:

1) Astronomers saw a comet get brighter in September and accurately predicted it was breaking up because when comets break up, the gas and dust they emit make them look brighter.

2) Astronomers didn't actually see the comet breaking into pieces until two months later, in November.

What might explain the two month gap? Maybe the dust and gas precede the actual breaking into pieces. That would explain the time lapse between the brightening and the actual breaking. (C) offers this possibility.

(A) is the opposite of what we want.

(B) is irrelevant--we've been told the gas and dust cause the brightening, we don't care how.

(D) offers a reason why the comet might have gotten brighter and brighter between Sept. and Nov., but that's not what we're interested in. We want to know why it was brighter in Sept. but wasn't actually observed breaking until Nov. (D) doesn't provide this link.

(E) is irrelevant. It doesn't matter why it broke apart.

Hopefully that's helpful!

[racerfan123]

I understand and agree with everything said above but am still unclear about one thing... in the stimulus it says "when comets, break up, they emit LARGE AMOUNTS of gas and dust." after reading C "gas and dust can be released by CRACKS" this answer seems weak because a a crack (my assumption obviously being that a crack does not equal large) would not emit a large amount of gas.

i took the parts in the stimulus "the increased brightness was a result of..." and that the commet did not actually break into pieces to mean that the commet was started to break up when it was first observed and continued to do so until it finally stopped in november. can someone please clear this up for me?

[kfitz]

A late reply to a question, but hopefully this will help others who look upon this thread...

You cannot assume anything about the size of the crack given that no adjectives are used with crack. Even if the crack were relatively 'small', a 'small' crack on an extremely large comet would be emitting a large amount of gas & dust.

Racerfan123's pre-phrase that the comet started to break up and continued to do so until November is directly matched by (C). (C) gives the explanation of cracks, gas, dust & brightness preceding the comet breaking "all the way through".

To add on to why (D) is incorrect -- maryadkins alluded to the only thing we can infer from (D): increased brightness. We cannot infer that the comet was slowly breaking up. Why? Because we only know that Breaking Up --> Gas & Dust --> Brightness. We cannot assume that increased gas & dust implies the comet was slowly breaking up. There could have been another explanation for the steady increase of gas & dust in option (D) which has nothing to do with resolving our conflict.