Source: Official Guide Revised GRE 2nd Ed. Part 9; Section 3; #20


Which of the following, if true, most

Which of the following, if true, most helps to resolve the status of the orbiting body without casting doubt on the two standard theories mentioned? Astronomers found a large body orbiting close to the star Upsilon Andromedae. The standard theory of planet formation holds that no planet that large could be formed so close to a star, leading to the suggestion that the body is a companion star. A subsequent discovery puts that suggestion in doubt: two other large bodies were found orbiting close to Upsilon Andromedae, and the standard theory of companion stars allows for at most one companion star. The smaller a planet orbiting a star is, and the farther away it is from the star, the less likely it is to be discovered., If a planet’s orbit is disturbed, the planet can be drawn by gravity toward the star it is orbiting., The largest of the bodies orbiting Upsilon Andromedae is the farthest away from the star, and the smallest is the nearest., It is likely that there are many stars, in addition to Upsilon Andromedae and the Sun, that are orbited by more than one smaller body., In most cases of companion stars, the smaller companion is much fainter than the larger star.

3 Explanations


Sanjoy Saha

How B is perfect? I don't understand the explanation

Apr 5, 2018 • Comment

Cydney Seigerman, Magoosh Tutor

Hi Sanjoy :)

Happy to help! First, it's useful to identify the two conflicting theories:
1. Planet theory: No planet that large could be formed so close to a star.
2. Companion star theory: at most one companion star.

The conflict is that there are two bodies orbiting the star Upsilon Andromedae.

Remember that the planet theory says that a planet as large as the observed bodies cannot form very close to the star. But what if that planet formed farther away from the star and, after being formed, began to orbit the star? This situation is allowed by the planet theory (the planet did not form so close to the star), while also holding up the companion star theory (only 1 of the 2 bodies is a star).

Choice B explains how it would be possible for a planet formed farther away to orbit closer to the star: the planet's original orbit may be changed somehow so that the planet is drawn closer by gravity to the star. This explains how we can have a planet so close to the star and also explains how two different bodies (a companion star and a planet) may be in orbit.

I hope this better explains how B successfully resolves the conflict in the passage :)

if, as it asserts, it is possible for a planet to be formed relatively far from a star and later move closer to it, then the observed large bodies found close to Upsilon Andromedae can be planets without casting doubt on the standard theory of planet formation. This explanation also leaves the standard theory of companion stars intact.

Apr 5, 2018 • Reply


cheyenne manafi

what kind of question is that? paradox ?

May 13, 2017 • Comment

Cydney Seigerman, Magoosh Tutor

Hi Cheyenne :) Excellent question! Yes, you're correct that we would consider this a paradox (or discrepancy) question. These questions ask you to find the answer choice that best explains the discrepancy in the argument. In this case, that paradox is between the two standard theories presented in the passage :)

May 15, 2017 • Reply


Gravatar Chris Lele, Magoosh Tutor

Dec 2, 2012 • Comment

Romeharsh Gupta

bonne explication mais une très belle question

Nov 8, 2017 • Reply

Add Your Explanation

You must have a Magoosh account in order to leave an explanation.

Learn More About Magoosh