VOA科学技术2023--Study: One-third of Milky Way Planets May Hold Conditions to Support Life

Study: One-third of Milky¹ Way Planets May Hold Conditions to Support Life

A new study suggests about one-third of planets orbiting our galaxy²'s most common stars may hold conditions to support life.

The study was based on data collected by two telescopes. Researchers involved in the study centered their examinations on stars in our Milky Way galaxy known as red dwarfs⁴.

The American space agency NASA notes that red dwarfs are generally much smaller than our sun. They are also the coolest stars and appear more orange than red. Red dwarfs are also known as M dwarfs. NASA estimates that they make up about 75 percent of all stars in the Milky Way. Experts believe billions of planets orbit red dwarf³ stars.

The study found that a third of planets orbiting red dwarf stars could be in what scientists call the "habitable zone." Being in a star's habitable zone means a planet has temperatures that could permit liquid water to exist on the surface.

Since water is necessary for life as we know it, the presence of liquid means a planet could possibly support life.

The planets examined in the study are called exoplanets. These are planets that orbit a star other than our sun.

Sara Ballard, an astronomer⁵ at the University of Florida, carried out the research. Doctoral student Sheila Sagear helped Ballard on the project. Their findings were recently published in Proceedings⁶ of the National Academy of Sciences.

Sagear said in a statement that red dwarfs "are excellent targets to look for small planets in an orbit where it's conceivable that water might be liquid and therefore the planet might be habitable."

Sagear added that the new findings will be "really important" for additional exoplanet research in the coming years.

The researchers said that because dwarf stars are cooler, the exoplanets would have to be very near their star to be warm enough to keep liquid water. But the researchers also noted⁷ that being so close means the planets would also be affected⁸ by "extreme tidal forces caused by the star's gravitational effect on the planets."

The researchers said the remaining two-thirds of planets around red dwarf stars have likely been subjected to gravitational forces that cause the planets to heat up. This process is known as tidal heating. It can result in planets being "sterilized," with no chance for holding liquid water.

Sagear and Ballard said they measured the "eccentricity¹⁰" of more than 150 exoplanets orbiting red dwarf stars. They described eccentricity as the shape of the planet's orbit around the star.

The data came from NASA's Kepler telescope and the European Space Agency's Gaia telescope. Instruments helped the team collect data on how often the planets move in front of their stars. They also helped the team measure distances between red dwarfs.

Sagear said the distance measurements were a very important part of the research. Past studies had not included such measurements. The team noted that stars with several planets were "most likely to have the kind of circular orbits" that permit them to keep holding liquid water. On the other hand, stars with only one planet were most likely to see tidal extremes that could sterilize⁹ the surface.

The researchers said their results mean that the Milky Way may have hundreds of millions of planets that could be studied for possible signs of life.

Words in This Story

galaxy – n. a very large group of stars held together in the universe

habitable – adj. able to support conditions to support life

conceivable – adj. possible to imagine or believe

tidal – adj. relating to the regular rising and falling of the sea

sterilize – v. to make an area unsuitable to support life

1 milky   

adj.牛奶的，多奶的；乳白色的

参考例句：

• Alexander always has milky coffee at lunchtime.亚历山大总是在午餐时喝掺奶的咖啡。
• I like a hot milky drink at bedtime.我喜欢睡前喝杯热奶饮料。

2 galaxy   

n.星系；银河系；一群(杰出或著名的人物)

参考例句：

• The earth is one of the planets in the Galaxy.地球是银河系中的星球之一。
• The company has a galaxy of talent.该公司拥有一批优秀的人才。

3 dwarf   

n.矮子，侏儒，矮小的动植物；vt.使…矮小

参考例句：

• The dwarf's long arms were not proportional to his height.那侏儒的长臂与他的身高不成比例。
• The dwarf shrugged his shoulders and shook his head. 矮子耸耸肩膀，摇摇头。

4 dwarfs   

n.侏儒，矮子（dwarf的复数形式）vt.（使）显得矮小（dwarf的第三人称单数形式）

参考例句：

• Shakespeare dwarfs other dramatists. 莎士比亚使其他剧作家相形见绌。 来自《简明英汉词典》
• The new building dwarfs all the other buildings in the town. 新大楼使城里所有其他建筑物都显得矮小了。 来自辞典例句

5 astronomer   

n.天文学家

参考例句：

• A new star attracted the notice of the astronomer.新发现的一颗星引起了那位天文学家的注意。
• He is reputed to have been a good astronomer.他以一个优秀的天文学者闻名于世。

6 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼

7 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

8 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

9 sterilize   

vt.使不结果实；使绝育；使无效；杀菌，消毒

参考例句：

• Antiseptic is used to sterilize the skin before giving an injection.杀菌剂被用于在注射前给皮肤消毒。
• He pricks the blister on his heel with a sterilize needle.他用一根消过毒的针扎破他脚后跟上的水泡。

10 eccentricity   

n.古怪，反常，怪癖

参考例句：

• I can't understand the eccentricity of Henry's behavior.我不理解亨利的古怪举止。
• His eccentricity had become legendary long before he died.在他去世之前他的古怪脾气就早已闻名遐尔了。