【自然科学-天文】
7 Earth-Size Planets Orbit Dwarf Star, NASA and European Astronomers Say
（403字 精读 必做篇）
Not just one, but seven Earth-size planets that could potentially harbor life have been identified orbiting a tiny star not too far away, offering the first realistic opportunity to search for signs of alien life outside of the solar system.
The planets orbit a dwarf star named Trappist-1, about 40 light years, or 235 trillion miles, from Earth. That is quite close in cosmic terms, and the orientation of the orbits of the seven planets allows them to be studied in great detail.
One or more of the exoplanets in this new system could be at the right temperature to be awash in oceans of water, astronomers said, based on the distance of the planets from the dwarf star.
“This is the first time so many planets of this kind are found around the same star,” Michael Gillon, an astronomer at the University of Liege in Belgium and the leader of an international team that has been observing Trappist-1, said during a telephone news conference organized by the journal Nature, which published the findings on Wednesday.
Scientists could even discover compelling evidence of aliens.
“I think that we have made a crucial step toward finding if there is life out there,” said Amaury H.M.J. Triaud, an astronomer at the University of Cambridge in England and another member of the research team. “Here, if life managed to thrive and releases gases similar to that we have on Earth, then we will know.”
Telescopes on the ground now and the Hubble Space Telescope in orbit will be able to discern some of the molecules in the planetary atmospheres. The James Webb Telescope, scheduled to launch next year, will peer at the infrared wavelengths of light, ideal for studying Trappist-1.
“The Trappist-1 planets make the search for life in the galaxy imminent,” said Sara Seager, an astronomer at the Massachusetts Institute of Technology who was not a member of the research team. “For the first time ever, we don’t have to speculate. We just have to wait and then make very careful observations and see what is in the atmospheres of the Trappist planets.”
While the Trappist planets are about the size of Earth, the star is very different from our sun.
Trappist-1 is what astronomers call an “ultracool dwarf,” with only one-twelfth the mass of the sun and a surface temperature of 4,150 degrees Fahrenheit, much cooler than the 10,000 degrees radiating from the sun.
Source: The New York Times
【自然科学-天文】
You Live In a Strange Solar System
（275字 1分53秒 精听 必做篇）
先做精听再核对原文哦~
The more astronomers study the heavens, the more they realize: our solar system is weird.
"There are a few things that make the solar system kind of strange.”Lauren Weiss, an astrophysicist at the University of Montreal. "One of which is we have a giant planet. Only about 10 percent of sunlike stars have a giant planet. And there are probably even fewer that have two giant planets."
In addition to giant Jupiter and lesser giant Saturn, we have tiny Mercury—just a bit bigger than Earth’s moon.
So if we’re weird, what does a typical solar system look like? Weiss and her team trained their telescopes on 355 star systems known to host a handful of small exoplanets. And they found that most of the planets within individual star systems tended to be similar in size.
"So if I'm a planet, and I'm, say, two times the size of Earth, my neighbor, the next planet over, is also likely to be two times the size of Earth, give or take a little bit."
And they were strung out at similar distances from each other too…like peas in a pod, she says. Compared to that orderly array, our system looks more like, "Uh let's see, if I stick with food…I don't know…like a whole Thanksgiving dinner or something?"
The results are in The Astronomical Journal.
As for hunting for habitable worlds: "If we're trying to find an Earth-sized planet in the habitable zone”—not too close to the star but not too far away either—“and we find an Earth-sized planet closer in, it might be worthwhile to continue searching for planets around that star."
Because there might just be a few more peas in the pod.
Source: Scientific American
【自然科学-天文】
Strange Object May Be Remains of a Planet Torn Apart
（430字 4分5秒 精听 选做篇）
先做精听再核对原文哦~
A long, thin object moving through our solar system may be the remains of a planet that was pulled apart, scientists say.
Researchers say the planet was likely destroyed long ago when it moved either too far from or too close to the star it once orbited.
The object is called ‘Oumuamua, which means “messenger from afar” in the native Hawaiian language. A report on the recent findings appears in the journal Nature Astronomy.
Scientists have been trying to understand more about ‘Oumuamua since its discovery in 2017. Some have even proposed it may be an alien spacecraft. In the recently published research, astronomers Yun Zhang and Douglas Lin said computer predictions suggest the object was a piece of a planet or planetary building block. The planet might have been torn apart by its star’s “tidal forces.”
‘Oumuamua is the first object from another star system found passing through our solar system. It is about 400 meters long. Its shape, strange way of moving and lack of dust and gases suggest it is not a normal comet or asteroid.
When a smaller body passes near a much bigger one, tidal forces created by the larger body can destroy the smaller one. That is what happened when comet Shoemaker–Levy 9 came too close to the planet Jupiter in 1992.
Zhang told the Reuters news agency that most planetary bodies are made of groups of rocks joined under the influence of gravity. In a way, they are similar to the sandcastles that children make at the beach, except that they are floating through space, Zhang said.
“Their structure can be disrupted when the force acting on the individual ‘sand particle’ is larger than their mutual gravity,” he added.
Zhang noted that ocean tides on Earth are affected in this way. Tides result from the gravitational pulls of the sun and moon. In space, a planetary body that comes close enough to a star falls victim to its strong gravitational pull.
Lin is an astrophysicist at the University of California, Santa Cruz. He said the star that destroyed ‘Oumuamua’s home world probably was one-tenth to eight-tenths of the mass of our sun. Or it might have been a rare kind of cool and dense star called a white dwarf, Lin added.
The study suggests the existence of many objects formed this way.
“We show the possibility of panspermia carried by these objects,” Zhang said. Panspermia is the hypothesized spread of microorganisms or chemicals that support life on objects moving through space.
‘Oumuamua is continuing on its path out of our solar system.
Source: VOA
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精读笔记格式要求：
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3.摘抄印象深刻或者觉得优美的句子
4.总结文章中的生词
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2.对照原文修改听写稿，标记出错原因
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4.总结精听过程中的生词
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这里也给大家两点学习小建议哦~
精读：如遇到读不懂的复杂句，建议找出句子主干，分析句子成分，也可以尝试翻译句子来帮助理解~
精听：建议每句不要反复纠结听，如果听 5 遍都没听出来，那就跳过，等完成后再回听总结原因，时间宝贵，不要过于执着哦~
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发表于 2020-5-15 22:30:54
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