VOA科学技术2024--'Mini Moon' Object Moves Away from Earth's Orbit

An asteroid¹ that moved closer to Earth's orbit in recent months is now moving away from our planet as gravity pulls it back toward the sun.

The asteroid is small - about 10 meters long - and never presented any threat to Earth. But the object, known as 2024 PT5, was recently pulled closer to our planet by Earth's gravitational forces.

Scientists sometimes call such objects "mini-moons." This is because they behave similarly to the permanent moon orbiting Earth when they are captured by gravity. But they are much smaller and stay only temporarily in Earth's orbit.

The American space agency NASA said it does not consider 2024 PT5 a mini-moon because it was never expected to be fully² captured by Earth's gravity. But NASA has described the small asteroid as "an interesting object" that is worthy³ of study. Such asteroids⁴ are considered near-Earth objects.

The space agency noted⁵ that similarities between the asteroid's motion and that of Earth suggest the object could be a large piece of rock that broke off from the moon's surface after an asteroid strike in the distant past.

The object was first observed on August 7 by two astronomer⁶ brothers from Spain's Complutense University of Madrid - Carlos de la Fuente Marcos and Raúl de la Fuente Marcos. They identified the asteroid through observations made by a telescope in South Africa.

The Spanish astronomers⁷ said it appeared 2024 PT5 is part of a group of near-Earth objects within the Arjuna asteroid belt. They wrote that asteroids in this belt are believed to be "surrounding the path followed by the Earth-moon system."

The Associated Press reported the astronomers had used telescopes in the Spanish Canary Islands, off the coast of northwestern Africa, to make hundreds of observations. The object is currently more than 3.5 million kilometers from Earth. Only powerful telescopes can see the asteroid because of its small size and low brightness.

The astronomers say 2024 PT5 should head back to Earth in the coming weeks. It is expected to pass as close as 1.8 million kilometers from Earth in January. The moon stays at a distance of about 384,000 kilometers from our planet, NASA explains.

The asteroid will then move farther into the solar system while orbiting the sun. Scientists say the next time the object is expected to make another close move toward Earth is in 2055.

Raul de la Fuente Marcos told the AP that 2024 PT5 was first identified in August and began its move toward Earth in late September. He said the object's path was similar to the shape of a horseshoe.

De la Fuente Marcos noted that by the time the asteroid returns in January, it will be moving at more than double the speed from September. Current data suggests that during its 2055 visit, it will again make a temporary and partial circle around Earth.

NASA said teams at its Center for Near Earth Object Studies had continually followed the movements of 2024 PT5. It is normal for NASA and its international partners to continuously search the skies for near-Earth objects. Such objects include asteroids and comets that come within 50 million kilometers of Earth's orbit.

The search system, called ATLAS⁸, involves four different telescopes. Two of them are based in Hawaii. Another operates in Chile and the other sits in South Africa. NASA explains that ATLAS is designed to search the whole sky several times each night looking for moving objects.

The space agency says it will use its large Goldstone Solar System Radar⁹ observer - which sits in Barstow, California - to follow 2024 PT5 when it again is pulled toward Earth's orbit in 2025.

I'm Bryan Lynn.

The Associated Press reported this story. Bryan Lynn adapted the report for VOA Learning English.

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Words in This Story

asteroid - n. a rocky object that goes around the sun like a planet

comet - n. an object in space that leaves a bright line behind it in the sky

1 asteroid   

n.小行星；海盘车(动物)

参考例句：

• Astronomers have yet to witness an asteroid impact with another planet.天文学家还没有目击过小行星撞击其它行星。
• It's very unlikely that an asteroid will crash into Earth but the danger exists.小行星撞地球的可能性很小，但这样的危险还是存在的。

2 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

3 worthy   

adj.(of)值得的，配得上的；有价值的

参考例句：

• I did not esteem him to be worthy of trust.我认为他不值得信赖。
• There occurred nothing that was worthy to be mentioned.没有值得一提的事发生。

4 asteroids   

n.小行星( asteroid的名词复数 )；海盘车，海星

参考例句：

• Asteroids,also known as "minor planets",are numerous in the outer space. 小行星，亦称为“小型行星”，在外太空中不计其数。
• Most stars probably have their quota of planets, meteorids, comets, and asteroids. 多数恒星也许还拥有若干行星、流星、彗星和小行星。

5 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。

6 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。

7 astronomers   

n.天文学者，天文学家( astronomer的名词复数 )

参考例句：

• Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
• Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪，为什么只有土星有光环。 来自《简明英汉词典》

8 atlas   

n.地图册，图表集

参考例句：

• He reached down the atlas from the top shelf.他从书架顶层取下地图集。
• The atlas contains forty maps,including three of Great Britain.这本地图集有40幅地图，其中包括3幅英国地图。

9 radar   

n.雷达，无线电探测器

参考例句：

• They are following the flight of an aircraft by radar.他们正在用雷达追踪一架飞机的飞行。
• Enemy ships were detected on the radar.敌舰的影像已显现在雷达上。