PTE阅读练习:夜空中最神秘的星

随着PTE考生对PTE口语和PTE听力的重视,大家口语和听力的分数得到极大提高,但是PTE阅读渐渐成为考生们新的难题。墨尔本悉尼文波PTE特别为PTE考生们挑选了适合练习PTE阅读的文章,主题,内容,长度都与PTE阅读题中的文章相似。激活学过的词汇,更新新的词汇,提高阅读速度,全面提升自己的阅读能力。

Astronomers understand big flaming balls of gases very well, and there is very high confidence that lone F3 main-sequence stars cannot have variations of more than 0.01 percent on any time scale shorter than millions of years. (Well, except for superflares, which these are not.) Further, the light curve dips are not modulated by the known stellar rotation. So the dips aren’t from the underlying star.

This forces us into thinking that they could only be due to something passing across the line of sight, blocking the background starlight (the technical term is “occulting”). After all, the PlanetHunters were explicitly looking for exactly this case, where some orbiting planet occults the star as it passes in front (the term for that is “transits”). But planet transits are always very small in amplitude (less than about one percent or so) and periodic. Whatever it is that is randomly passing in front of Tabby’s Star is not a planet.

The deepest dip dims the star by 21 percent, so whatever was covering up the starlight must have been covering at least 21 percent of the star’s area. This implies that the body, or cloud, or structure must have just under half the radius of the star—which makes it 70 percent the size of our Sun. Whatever it is, it might be solid (like a planet), gaseous (like a star or a gas cloud), or something like a cloud of dust.

The trouble is that any such idea requires that all of these things should be emitting large amounts of infrared light. It should be bright enough to be readily seen above the normal expected infrared light from the primary star. In astro-jargon, Tabby’s Star does not have any excess of infrared light.

superflares 超耀斑

modulated 调节

occult 掩蔽

amplitude 振幅;

radius 半径

gaseous 气态的,气体的

infrared 红外线的

 

 

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