UCAT Question Analysis - Verbal Reasoning Question 15
TEXT
A haul of planets from NASA's Kepler telescope includes a world sharing many characteristics with Earth. Officially named Kepler-452b, this new world orbits at a very similar distance from its star as the Earth, though its radius is 60% larger than the Earth's. Astronomers tend to get excited about such worlds because they might be small and cool enough to host liquid water on their surface and might therefore be hospitable to life. NASA's science chief called the new world `Earth 2.0'.
Kepler-452b joins other so-called exoplanets, such as Kepler-186f, that are similar in many ways to Earth. However, determining which is most Earth-like depends on the properties one considers. Kepler-186f, announced in 2014, is smaller than the new planet, but orbits a red dwarf star that is sig-nificantly cooler than our own. However, Kepler-452b orbits a parent star which belongs to the same class as the Sun; it is just 4% more massive and 10% brighter. The mass of Kepler-452b cannot yet be measured and so astronomers have to rely on models to estimate a range of possible masses, with the most likely being five times that of the Earth. The new world is included in a haul of 500 new possible planets sighted by the Kepler space telescope around distant stars. Twelve of the new candi-dates are less than twice Earth's diameter, orbiting in the so-called habita-ble zone around their star. The zone refers to a range of distances at which the energy radiated by the star would permit water to exist as a liquid on the planet's surface if certain conditions are met. Around 20% of Sun-like stars, of which there are countless, have an Earth-sized planet in their hab-itable zone.
While similar in size and brightness to the Sun, Kepler-452b's host star is 1.5 billion years older than ours. Scientists therefore believe it could point to a possible future for the Earth. It is not known if Kepler-452b is a rocky planet or a small gas planet but, based on its small radius, Kepler-452b has a reasonable chance, between 49% and 62%, of being rocky. If it is a rocky planet, it may be subject to a runaway greenhouse effect similar to that seen on Venus; the increasing energy from its ageing sun might be heating the surface and evaporating any oceans. It could be experiencing now what the Earth will undergo more than a billion years from now.
Q15.1 Which of the following statements is definitely false?
A. Kepler-452b has a diameter 60% larger than the diameter of the Earth.
B. The radius of a planet can be used as an indicator of how rocky it is likely to be.
C. Earth 2.0 is smaller than Kepler-186f.
D. Venus experienced a runaway greenhouse effect.
Q15.2 Which of the following statements can reasonably be concluded from the passage?
A. The Earth's oceans will eventually disappear.
B. The Sun has a remaining lifespan of over 1.5 billion years.
C. All planets orbiting within the habitable zone of their sun contain liquid water.
D. The Sun is getting bigger and brighter as it gets older.
Q15.3 Which of the following statements is the author most likely to agree with?
A. Exoplanets are rocky.
B. Exoplanets revolve around a star similar to the Earth's Sun.
C. Exoplanets contain liquid water on their surface.
D. Exoplanets are common in the universe.
Q15.4 There is no liquid water on Venus.
❑ True
❑ False
❑ Can't tell
Answer and Explanation
Q15.1 — C: Earth 2.0 is smaller than Kepler-186f.
The text states that "Kepler-186f is smaller than the new planer (i.e. Kepler-452b/Earth 2.0). Looking at the other options:
• A: Kepler-452b has a diameter 60% larger than the diameter of the Earth. If its radius is 60% larger than Earth's radius, then so is its di-ameter (2 x radius).
• B: The radius of planet can be used as an indicator of how rocky it is likely to be. The sentence "based on its small radius, Kepler-452b has a reasonable chance, between 49% and 62%, of being rock/ indi-cates that the radius Is an indicator of how rocky it might be.
• D: Venus experienced a runaway greenhouse effect. This is made clear in the sentence' it may be subject to a runaway greenhouse effect similar to that seen on Venus".
Q15.2 — A: The Earth's oceans will eventually disappear.
In the final paragraph, the text describes how an increase in energy from an ageing sun will lead to evaporation of any oceans, making it clear also that this is a process that the Earth will undergo in a billion years' time. Looking at the other options:
• B: The Sun has a remaining lifespan of at least 1.5 billion years. The "1.5 billion years" referred to in tne text is the difference in age between the two suns. It has nothing to do with longevity.
• C: All planets orbiting within the habitable zone of their sun con-tain liquid water. All we know from the text is that the habitable zone is a zone where the levels of energy would make it possible to have liquid water "if certain conditions are met". Therefore we cannot con-clude that all planets within that zone would contain liquid water.
• D: The Sun Is getting bigger and brighter as it gets older. We know that the increasing energy from the ageing star around which Kepler-452b orbits may be evaporating the oceans and we are told that the same will happen to Earth later. So what we can surmise from that is that it is anticipated that the Sun will give out higher levels of energy; but the text is not conclusive as to whether this will Involve the Sun getting bigger and brighter.
Q15.3 — D: Exoplanets are common in the universe. Though the term "exoplanet" is not precisely defined in the text, it provides sufficient back-ground to help us conclude that an exoplanet is a planet that is similar to the Earth (see beginning of paragraph 2). We are told at the end of the penultimate paragraph that "around 20% of Sun-like stars of which there are countless, have an Earth-sized planet in their habitable zone". That would suggest that there exist a large number of planets of similar size to the Earth, which would qualify as exoplanets. This would make exoplanets common. Looking at the other options:
• A: Exoplanets are rocky. We know that Kepler-452b is an exoplanet but that it has a probability of being rocky of 49% to 62%, therefore we can't assert confidently that exoplanets are rocky (as this implies that they should all be). In fact, the text suggests that rockiness is linked to the radius.
• B: Exoplanets revolve around a star similar to the Earth's Sun. This is not the case for Kepler-186f which, we are told, 'orbits a red dwarf star that is significantly cooler than our own".
• C: Exoplanets contain liquid water on their surface. All we know from the text is that exoplanets would need to orbit within the habitable zone in order to have the potential to have surface water. It does not follow that all planets within the habitable zone will contain surface wa-ter. The habitable zone only makes it possible.
Q15.4 — CAN'T TELL.
We know from the text that Venus experienced a runaway greenhouse effect, i.e. increased energy from the Sun caused oceans to evaporate. So the statement could be true; however, it is not clear whether that process is completed or In progress. Therefore we cannot say conclusively that there is no liquid water remaining on Venus.
Drafted by Juno Wong(UCAT Prep)