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Astronomers have observed a newborn planet that formed in three million years, a relatively brief time.
天文学家观察到一颗在300万年内形成的新生行星，这个形成时间相对较短。
They say the discovery leads to questions about the current understanding of the speed of planetary formation.
他们说，这一发现让人们开始质疑现有的对行星形成速度的认知。
Space scientists estimate the planet to be around 10 to 20 times the mass of Earth.
太空科学家估计，这颗行星的质量大约是地球的10到20倍。
It is an exoplanet, meaning a planet outside our solar system. It is one of the youngest exoplanets ever discovered.
它是一颗系外行星，也就是太阳系外的行星。它是迄今为止发现的最年轻的系外行星之一。
It exists among dense gas and dust orbiting a young star. The orbiting matter is called a protoplanetary disk.
它存在于稠密的气体和尘埃中，围绕着一颗年轻的恒星运行。绕轨道运行的物质被称为原行星盘。
It provides the materials necessary for planet formation.
它为行星的形成提供了必要的物质。
The star it orbits is not as hot and is about half as bright as our sun. The star's mass is about 70 percent that of the sun.
它环绕的恒星没有太阳那么热，亮度只有太阳的一半。这颗恒星的质量大约是太阳的70%。
It is in our Milky Way galaxy, about 520 light-years from Earth. A light-year is the distance light travels in a year, 9.5 trillion kilometers.
它位于我们的银河系中，距离地球约520光年。一光年是指光在一年内传播的距离，即9.5万亿公里。
"This discovery confirms that planets can be in a cohesive form within 3 million years, which was previously unclear as Earth took 10 to 20 million years to form," said Madyson Barber, a research student at the University of North Carolina at Chapel Hill (UNC).
北卡罗来纳大学教堂山分校（UNC）的研究生麦德森·巴伯说：“这一发现证实，行星可以在300万年的时间内形成凝聚形式，以前我们并不知道这一点，因为地球需要1000万到2000万年的时间才能形成。”
Barber is the lead writer of the study published recently in Nature magazine.
巴伯是最近发表在《自然》杂志上的这项研究的主要作者。
"We don't really know how long it takes for planets to form," UNC professor and study co-writer Andrew Mann added.
“我们真的不知道行星形成需要多长时间，”北卡罗来纳大学教授、该研究的合著者安德鲁·曼恩补充说。
"We know that giant planets must form faster than their disk dissipates because they need a lot of gas from the disk.
“我们知道，巨行星的形成速度必须快于其原行星盘的消散速度，因为它们的形成需要来自原行星盘的大量气体。
But disks take 5 to 10 million years to dissipate. So do planets form in one million years? Five? Ten?"
但原行星盘需要500万到1000万年才能消散。那么行星会在一百万年内形成吗？五百万年?一千万年?”
The planet orbits its star every 8.8 days. Its mass is in between that of Earth, the largest of our solar system's rocky planets, and Neptune, the smallest of the gas planets.
这颗行星每8.8天绕其恒星运行一圈。它的质量介于地球和海王星之间，地球是太阳系中最大的岩石行星，海王星是最小的气体行星。
It is less dense than Earth and has a diameter about 11 times greater. Its chemical makeup is not known.
它的密度比地球小，直径大约是地球的11倍。其化学成分尚不清楚。
The researchers suspect that the planet formed further away from its star and then moved closer.
研究人员怀疑这颗行星形成时离它的恒星较远，后来才更靠近恒星的。
"Forming large planets close to the star is difficult because the protoplanetary disk dissipates away from closest to the star the fastest, meaning there's not enough material to form a large planet that close that quickly," Barber said.
巴伯说：“在恒星附近形成大的行星是很难的，因为原行星盘离恒星最近的地方消散得最快，这意味着没有足够的物质来形成一颗能快速靠近恒信的大行星。”
The researchers found the planet using the so-called "transit" method: observation of a drop in the star's brightness, from the perspective of an observer on Earth, when the planet passes in front of it.
研究人员使用所谓的“凌日”方法发现了这颗行星：当行星从恒星前面经过时，从地球上观察者的角度观察到恒星亮度的下降。
NASA's Transiting Exoplanet Survey Satellite, or TESS, space telescope discovered the exoplanet.
美国宇航局的凌日系外行星测量卫星（TESS）太空望远镜发现了这颗系外行星。
"This is the youngest-known transiting planet. It is on par with the youngest planets known," Barber said.
“这是已知最年轻的凌日行星。它与已知的最年轻的行星年龄差不多，”巴伯说。
Stars and planets form from clouds of interstellar gas and dust.
恒星和行星由星际气体和尘埃云形成。
"To form a star-planet system, the cloud of gas and dust will collapse and spin into a flat environment, with the star at the center and the disk surrounding it.
“想要形成恒星-行星系统，需要气体和尘埃云坍缩并旋转形成一个平坦的环境，恒星位于中心，原行星盘围绕着它。
Planets will form in that disk. The disk will then dissipate” starting from the star side, Barber said.
原行星盘上会形成行星。然后原行星盘会从恒星的一侧开始消散。”巴伯说。
"It was previously thought that we wouldn't be able to find a transiting planet this young because the disk would be in the way.
“以前人们认为，我们不可能找到这么年轻的凌日行星，因为会被原行星盘遮挡住。
But for some reason that we aren't sure of, the outer disk is warped, leaving a perfect window to the star," Barber added.
但由于某些我们不确定的原因，原行星盘外围是弯曲的，留下了一个观测恒星的完美窗口，”巴伯补充说。
I'm Caty Weaver.
我是卡蒂·韦弗。
