The Milky Way galaxy is composed of millions of stars in a relatively flat structure containing a thin disk and a thick disk. Based on computer simulations and analysis of data on the brightness, position, and chemical composition of about 250,000 stars in the thick disk (collected from two telescopes, one in China and one orbiting in space), astrophysicists Maosheng Xiang and Hans-Walter Rix claim that the thick disk of the Milky Way formed in two distinct phases rather than a single one.

Question

Which finding, if true, would most directly support the researchers’ claim?
Choose 1 answer:
Choose 1 answer:
(Choice A) There’s an age difference of about 2 billion years between certain stars in the thick disk.
A
There’s an age difference of about 2 billion years between certain stars in the thick disk.
(Choice B) The stars in the Milky Way tend to have very similar chemical compositions.
B
The stars in the Milky Way tend to have very similar chemical compositions.
(Choice C) The thin disk contains about twice as many stars that can be seen from Earth as the thick disk does.
C
The thin disk contains about twice as many stars that can be seen from Earth as the thick disk does.
(Choice D) The telescopes used by the researchers have detected stars of similar ages in galaxies other than the Milky Way.
D
The telescopes used by the researchers have detected stars of similar ages in galaxies other than the Milky Way.

Answer 1

The finding that would most directly support the researchers’ claim that the thick disk of the Milky Way formed in two distinct phases would be:

(Choice A) There’s an age difference of about 2 billion years between certain stars in the thick disk.

This is because a significant age difference among the stars suggests that they were formed at different times, which is indicative of distinct formation phases.