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SAT官方每日一题附答案和解析[阅读](2019年3月8日)

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Critical Reading>Select an Answer

Light from distant quasars -- early galaxies that shine with tremendous brightness -- has given researchers a new clue to the origin of vast magnetic fields studding today's galaxies: They were running strong when the universe was only a third of its present age.

Astronomers had observed that radio emissions from quasars tend to be angled, or polarized, in such a way that powerful magnetic fields must have twisted them. The greater their distance from Earth, the more polarized their light. But researchers didn't know whether the magnetic fields were part of the quasar or were present in galaxies encountered by quasar light as it made its journey to our telescopes.

So a team led by astronomers from the Swiss Federal Institute of Technology (ETH Zurich) scanned more than 70 of those quasars using the European Southern Observatory's Very Large Telescope in Chile to look for signs of galaxies hiding in front of the quasars. Specifically, they checked for a feature called the magnesium(II) absorption line, a reduction in the intensity of light of a certain wavelength, which is a commonly used indicator that gas from a star-forming galaxy has soaked up that light.

The researchers report that light from quasars showing the magnesium(II) line was more strongly polarized than light from other quasars in the sample. The interpretation: that light did indeed pass through regular galaxies and that it likely acquired its polarization in the process.

They estimated the age of the magnetic galaxies by measuring the red shift of the absorption line -- the observed reddening of light that occurs when galaxies move rapidly apart. The typical red shift of the inferred galaxies corresponded to an age of 5.2 billion years, study author Francesco Miniati says. Precision measurements of the cosmic microwave background peg today's universe at 13.7 billion years old.

Which of the following, if true, would undermine the interpretation offered by the researchers in the fourth paragraph?

A.Another team of astronomers measures the red shifts of magnesium(II) absorption lines and concludes that the galaxies formed when the universe was less than 5.2 billion years old.
B.A new study determines that quasars that are not near star-forming galaxies have high levels of polarized light.
C.A group of astronomers publishes a report that suggests the number of known quasars in the universe is higher than previously documented.
D.A massive galaxy that causes strongly polarized light is found to be situated in front of a quasar.

重点单词   查看全部解释    
vast [vɑ:st]

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adj. 巨大的,广阔的
n. 浩瀚的太

 
precision [pri'siʒən]

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n. 精确,精密度
adj. 以精准的执行而著

 
reduction [ri'dʌkʃən]

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n. 减少,缩小,(化学)还原反应,(数学)约分

 
interpretation [in.tə:pri'teiʃən]

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n. 解释,阐释,翻译,(艺术的)演绎

 
intensity [in'tensiti]

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n. 强烈,强度

 
tend [tend]

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v. 趋向,易于,照料,护理

 
certain ['sə:tn]

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adj. 确定的,必然的,特定的
pron.

 
institute ['institju:t]

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n. 学会,学院,协会
vt. 创立,开始,制

联想记忆
X
单词institute 联想记忆:
in进入,stitute站,建立-站进去;进入建立的状态-创立
 
critical ['kritikəl]

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adj. 批评的,决定性的,危险的,挑剔的
a

 
observatory [əb'zə:və.tri]

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n. 天文台,气象台,了望台

联想记忆
X
单词observatory 联想记忆:
observe观察+atory表名词,“场所,地点”→天文台
 


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