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IAS Quiz

Published: 12th January 2015 06:00 AM  |   Last Updated: 09th January 2015 12:35 AM   |  A+A-

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 been 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 exist 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 occultation’s became “responsible” – 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 occultation’s 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)  Theoreticians’ views on the stability of asteroid – satellite systems may be revised in the light of reports like those about Herculina.

(c)  Astronomers continue to consider it respectable to doubt the stability of asteroid – satellite systems, but new theoretical developments may change their views.

(d)  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 occultation that occurred shortly before the predicted occultation by Herculina.

(d)  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 be best described as:

(a)  Open–mindedness combined with a concern for rigorous standards of proof.

(b)  Bemusement at a chaotic mix of theory, inadequate or spurious data, and calls for scientific rigour.

(c)  Hardheaded skepticism, implying rejection of all data not recorded automatically by state-of-the-art instruments.

(d)  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 disrupted.

(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.

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

(a) Primary occultations by asteroids were reported to have accompanied by secondary occultations in about one out of every thousand cases.

(b) The absolute number of reports of secondary occultations increased tenfold compared to the time before the Herculina event.

(c) Primary occultations by asteroids were reported to have been accompanied by secondary occultations in more than one out of every hundred cases.

(d) In more than one out of every hundred cases, primary occultations were reported to have been accompanied by more than one secondary occultation.

6. The primary purpose of the passage is to:

(a) Describe experimental efforts by astronomers to separate theoretically believable observations of satellites of asteroids from spurious ones.

(b) Review the development of ideas among astronomers about whether or not satellites of asteroids exist.

(c) Bring a theoretician’s perspective to bear on an incomplete discussion of satellites of asteroids.

(d) Illustrate the limits of reasonable speculation concerning the occultation of stars.

7. The passage suggests that which one of the following would most help to resolve the question of whether asteroids have satellites?

(a) A review of pre – 1978 reports of secondary occultations.

(b) A photoelectric record of a well – behaved secondary occultation.

(c) A more stringent definition of what constitutes a well – behaved secondary occultation.

(d) A powerful telescope that would permit a comparison of ground – based observation with those made from airplanes.

8. Anup throws 5 standard dice at the same time. The product of the numbers on the top faces was found to be 216. The sum of these numbers cannot be

(a) 19

(b) 18

(c) 20

(d) 16

 

9. In calling out the serial numbers of some students standing in a line, 300 digits were used. How many students were there?

(a) 138

(b) 137

(c) 139

(d) 136

ANSWERS

1) D 2) C 3)  A 4) C 5) C 6) C 7) C 8) A 9) D



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