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Until recently many astronomers believed that asteroids travel about

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Until recently many astronomers believed that asteroids travel about  [#permalink]

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New post Updated on: 23 Oct 2018, 17:39
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Until recently many astronomers believed that asteroids travel about the solar system unaccompanied by satellites. These astronomers assumed this because they considered asteroid-satellite systems inherently unstable. Theoreticians could have told them otherwise: even minuscule bodies in the solar system can theoretically have satellites, as long as everything is in proper scale. If a bowling ball were orbiting about the Sun in the asteroid belt, it could have a pebble orbiting it as far away as a few hundred radii (or about 50 meters) without losing the pebble to the Sun’s gravitational pull.

Observations now suggest that asteroid satellites may exists not only in theory but also in reality. Several astronomers have noticed, while watching asteroids pass briefly in front of stars, that something besides the known asteroid sometimes blocks out the star as well. Is that something a satellite? The most convincing such report concerns the asteroid Herculina, which was due to pass in front of a star in 1978. Astronomers waiting for the predicted event found not just one occultation, or eclipse, of the star, but two distinct drops in brightness. One was the predicted occultation, exactly on time. The other, lasting about five seconds, preceded the predicted event by about two minutes. The presence of a secondary body near Herculina thus seemed strongly indicated. To cause the secondary occultation, an unseen satellite would have to be about 45 kilometers in diameter, a quarter of the size of Herculina, and at a distance of 990 kilometers from the asteroid at the time. These values are within theoretical bounds, and such an asteroid-satellite pair could be stable.

With the Herculina event, apparent secondary occultations became “respectable”—and more commonly reported. In fact, so common did reports of secondary events become that they are now simply too numerous for all of them to be accurate. Even if every asteroid has as many satellites as can be fitted around it without an undue number of collisions, only one in every hundred primary occultations would be accompanied by a secondary event (one in every thousand if asteroid satellites system resembled those of the planets).
Yet even astronomers who find the case for asteroid satellites unconvincing at present say they would change their minds if a photoelectric record were made of a well-behaved secondary event. By “well-behaved” they mean that during occultation the observed brightness must drop sharply as the star winks out and must rise sharply as it reappears from behind the obstructing object, but the brightness during the secondary occultation must drop to that of the asteroid, no higher and no lower. This would make it extremely unlikely that an airplane or a glitch in the instruments was masquerading as an occulting body.

1. Which one of the following best expresses the main idea of the passage?

(A) The observation of Herculina represented the crucial event that astronomical observers and theoreticians had been waiting for to establish a convincing case for the stability of asteroid-satellite systems.
(B) Although astronomers long believed that observation supports the existence of stable asteroid-satellite systems, numerous recent reports have increased skepticism on this issue in astronomy.
(C) Theoreticians’ views on the stability of asteroid-satellite systems may be revised in the light of reports like those about Herculina.
(D) Astronomers continue to consider it respectable to doubt the stability of asteroid-satellite systems, but new theoretical developments may change their views.
(E) The Herculina event suggests that theoreticians’ views about asteroid-satellite systems may be correct, and astronomers agree about the kind of evidence needed to clearly resolve the issue.



2. Which one of the following is mentioned in the passage as providing evidence that Herculina has a satellite?

(A) the diameter of a body directly observed near Herculina
(B) the distance between Herculina and planet nearest to it
(C) the shortest possible time in which satellites of Herculina, if any, could complete a single orbit
(D) the occultation that occurred shortly before the predicted occultation by Herculina
(E) the precise extent to which observed brightness dropped during the occultation by Herculina



3. According to the passage, the attitude of astronomers toward asteroid satellites since the Herculina event can best described as

(A) open-mindedness combined with a concern for rigorous standards of proof
(B) contempt for and impatience with the position held by theoreticians
(C) bemusement at a chaotic mix of theory, inadequate or spurious data, and calls for scientific rigor
(D) hardheaded skepticism, implying rejection of all data not recorded automatically by state-of-the-art instruments
(E) admiration for the methodical process by which science progresses from initial hypothesis to incontrovertible proof



4. The author implies that which one of the following was true prior to reports of the Herculina event?
(A) Since no good theoretical model existed, all claims that reports of secondary occultations were common were disputed.
(B) Some of the reported observations of secondary occultations were actually observations of collisions of satellites with one another.
(C) If there were observations of phenomena exactly like the phenomena now labeled secondary occultations, astronomers were less likely than to have reported such observations.
(D) The prevailing standards concerning what to classify as a well-behaved secondary event were less stringent than they are now.
(E) Astronomers were eager to publish their observations of occultations of stars by satellites of asteroids.



5. The information presented in the passage implies which one of the following about the frequency of reports of secondary occultations after the Herculina event?

(A) The percentage of reports of primary occultations that also included reports of secondary occultations increased tenfold compared to the time before the Herculina event.
(B) Primary occultations by asteroids were reported to have been accompanied by secondary occultations in about one out of every thousand cases.
(C) The absolute number of reports of secondary occultations increased tenfold compared to the time before the Herculina event.
(D) Primary occultations by asteroids were reported to have been accompanied by secondary occultations in more than one out of every hundred cases.
(E) In more than one out of every hundred cases, primary occultations were reported to have been accompanied by more than one secondary occultation.



Originally posted by shard87 on 12 Jul 2018, 05:45.
Last edited by workout on 23 Oct 2018, 17:39, edited 2 times in total.
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Re: Until recently many astronomers believed that asteroids travel about  [#permalink]

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Until recently many astronomers believed that asteroids travel about  [#permalink]

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New post 24 Oct 2018, 20:49
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1. Which one of the following best expresses the main idea of the passage?

The passage states that Herculina is an important event, which helped in solidifying the Theoretician's views and the kind of evidence needed by astronomers to resolve the issue.

Options A and E mention the importance of Herculina event, but option A is extreme

Choice E is correct.

2. Which one of the following is mentioned in the passage as providing evidence that Herculina has a satellite?

Following is a except from para 2 of the passage.
Quote:
The other, lasting about five seconds, preceded the predicted event by about two minutes. The presence of a secondary body near Herculina thus seemed strongly indicated.

Based on this we can narrow it down to option D.

3. According to the passage, the attitude of astronomers toward asteroid satellites since the Herculina event can best described as

In para 3 it is mentioned that Herculina event is "respectable" and para mentions the about the possibility of photoelectric record evidence.
Using this, we can say that Choice A is correct.

4. The author implies that which one of the following was true prior to reports of the Herculina event?

Used POE for this one.

(A) Since no good theoretical model existed, all claims that reports of secondary occultations were common were disputed. -- Not mentioned
(B) Some of the reported observations of secondary occultations were actually observations of collisions of satellites with one another. -- Cant be inferred
(C) If there were observations of phenomena exactly like the phenomena now labeled secondary occultations, astronomers were less likely than to have reported such observations. -- Hold
(D) The prevailing standards concerning what to classify as a well-behaved secondary event were less stringent than they are now. -- No criteria mentioned
(E) Astronomers were eager to publish their observations of occultations of stars by satellites of asteroids. -- Never mentioned

5. The information presented in the passage implies which one of the following about the frequency of reports of secondary occultations after the Herculina event?

(D) Primary occultations by asteroids were reported to have been accompanied by secondary occultations in more than one out of every hundred cases. --Clearly Mentioned in para 3. Remaining choices are inconsistent with the info in passage.
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Until recently many astronomers believed that asteroids travel about &nbs [#permalink] 24 Oct 2018, 20:49
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