PrepTest 146, Section 2, Question 18
The consensus among astronomers, based upon observations of(84 more words not shown)
The statement that the core(21 more words not shown)
- AIt helps explain(18 more words not shown)
- BIt forms part(15 more words not shown)
- CIt helps explain(12 more words not shown)
- DIt presents a(12 more words not shown)
- EIt points out(17 more words not shown)
Reading the argument
Seeing neutrons on the outside doesn't necessarily tell us what's inside.
That's the alternative the author is developing. Astronomers infer a ball of neutrons from the surface observations, but a quark-filled interior could still fit what they see. We don't need outside physics knowledge to follow the proposed explanation: a positively charged core would attract a layer of negatively charged particles, and that layer could support a neutron crust.
What we’re looking for
The question points to the positive charge. What is that doing for the argument? It supplies a step in the explanation of how the alternative interior could produce the observed surface. I'd expect an answer that describes support for the quark possibility, not a claim that we've proved what is inside every pulsar.
Working the answers
- ACorrect
The positive charge starts the proposed chain: it attracts negatively charged particles, which could support neutrons at the surface. So a neutron surface could exist even when the entire pulsar isn't made of neutrons. That is how the statement helps the author explain the alternative.
- B
This has the direction backward. The statement helps show how a quark-filled pulsar could fit the observations. It doesn't challenge the possibility that some pulsars contain quarks; it helps defend that possibility.
- C
Nobody is struggling to recognize the objects as pulsars. The disagreement concerns what the pulsars contain. An astronomer could correctly identify a pulsar while remaining unsure whether its interior contains neutrons or quarks.
- D
The statement describes what a quark-filled core would be like; it doesn't report the discovery of an actual quark-filled core. That distinction matters. A proposed mechanism can show that the observations fit an alternative without establishing that the alternative has been found. D turns that conditional explanation into a new finding.
- E
The author doesn't dispute the stated mass. The alternative concerns the pulsar's composition, not whether its mass is roughly equal to the sun's. We can accept that mass while asking what the interior is made of.
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