A Tiny Fraction of Binary Systems Belong to a Curious Subclass Whose Radiation

Reading Passage Question

A tiny fraction of binary systems belongs to a curious subclass whose radiation has a wavelength distribution so peculiar that it long defied explanation. Such systems radiate (5) strongly in the visible region of the spectrum, but some of them do so even more strongly at both shorter and longer wavelengths: in the ultraviolet region and in the infrared and radio regions.

This odd distribution of radiation is best explained by the pairing of a cool red-giant star and an intensely hot small star, known as symbiotic stars, that travel around a common center. Recently two symbiotic-star systems, the first to be detected outside our galaxy, have been observed in the Large Cloud of Magellan.

The spectra of symbiotic stars indicate that the cool red giant is surrounded by a very hot ionized gas which satellite observations finally identified as radiating from an invisible hot companion. It is possible that symbiotic stars represent a transitory phase in the evolution of certain types of binary systems in which a substantial amount of matter transfers from the larger partner to the smaller one.

The exact evolutionary course that turns a binary system into a symbiotic one is unknown. The comparative scarcity of known symbiotics in our galaxy suggests that if all binaries of modest mass pass through a symbiotic phase in their evolution, the phase must be extremely brief, perhaps as short as a million years. It is suspected that the evolutionary course of binary stars is predetermined by the initial mass and angular momentum of their gas clouds. Since red giants and Mira variables are thought to be stars with a mass of one or two suns, it seems plausible that the original cloud from which a symbiotic system is formed can consist of no more than a few solar masses of gas.

‘A tiny fraction of binary systems belong to a curious subclass’ is a GMAT reading comprehension passage with answers. Candidates need a strong knowledge of English GMAT reading comprehension.

This GMAT Reading Comprehension consists of 7 comprehension questions. The GMAT Reading Comprehension questions are designed for the purpose of testing candidates’ abilities in understanding, analyzing, and applying information or concepts. Candidates can actively prepare with the help of GMAT Reading Comprehension Practice Questions.

Solution and Explanation

1. The passage implies that symbiotic star systems differ from other binary systems in which one of the following ways?

(A) Symbiotically paired stars emit a radiation pattern different from that of most binary stars.
(B) In symbiotic star systems, one star is the center of the other's orbit.
(C) Symbiotically paired stars are the only binary stars that are capable of exchanging matter.
(D) Symbiotic star systems are more common than other binary systems.
(E) Symbiotic star systems are the only binary systems that can be detected by satellite-borne instruments.

2. The primary purpose of the passage is to

(A) argue that a great percentage of binary star systems are symbiotic
(B) criticize the theory of symbiotic stars as overly speculative
(C) describe symbiotic stars as a distinct type of binary system
(D) present evidence that binary star systems have evolved from gas clouds
(E) compare symbiotic stars to red giants and Mira variables

3. According to the passage, the radiation emitted by symbiotic stars is distinctive in that it

(A) generates standard wavelengths
(B) consists partly of visible waves
(C) is transferred from one star to its partner
(D) is strongest at the extreme ends of the spectrum
(E) emanates primarily from the larger star

4. The author suggests that

(A) the detection of radiation from an invisible hot companion star prompted scientists to investigate the peculiar ionized gas surrounding cool red giants
(B) small hot stars attach to cool red giants because red giants have a mass of one or two suns
(C) a million years is a brief period of time for the occurrence of many solar events
(D) the only symbiotic star systems to be detected outside of our galaxy are in the Large Cloud of Magellan
(E) if binary stars of modest mass passed through symbiotic phases lasting much more than a million years, it is likely that more of them would have been detected

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