银河系和仙女座星系可能注定不会相撞

一项新的研究表明，这种命运并不一定是写在星星上的。

The Milky Way and Andromeda galaxies are hurtling towards each other at a speed of about 110 kilometers (68 miles) per second. That might sound pretty fast, but don’t panic just yet – the galaxy is still about 2.5 million light-years from Earth, so it’s expected to take a few billion years to get here.

银河系和仙女座星系正以每秒约 110 公里（68 英里）的速度相互冲撞。这听起来可能相当快，但先别惊慌——银河系距地球仍约 250 万光年，因此预计需要数十亿年才能到达这里。

Previous studies have been fairly confident that a collision is all but inevitable, but a deeper analysis of our galactic neighborhood by researchers from the University of Helsinki and Durham University in England puts the odds closer to 50/50 of a collision occurring within the next 10 billion years.

之前的研究相当确信碰撞几乎是不可避免的，但赫尔辛基大学和英国达勒姆大学的研究人员对我们银河系附近的更深入分析表明，未来 10 年内发生碰撞的可能性接近 50/50亿年。

Using the newest, most accurate motion and mass data from the Gaia and Hubble space telescopes, the team simulated the movements of not just the Milky Way and Andromeda, but two other major players in our Local Group – the Large Magellanic Cloud (LMC) and the Triangulum Galaxy.

使用来自盖亚和哈勃太空望远镜的最新、最准确的运动和质量数据，该团队不仅模拟了银河系和仙女座星系的运动，还模拟了我们本地群中的其他两个主要参与者——大麦哲伦星云（LMC）和三角星系。

When the Milky Way and Andromeda were considered in isolation, a collision within the next 10 billion years occurred in just under half of the simulations, the team says.

研究小组表示，当单独考虑银河系和仙女座星系时，不到一半的模拟会在未来 100 亿年内发生碰撞。

Adding Triangulum to the mix boosted the probability to two-thirds, while simulations with the Milky Way, Andromeda and the LMC dropped the chances to just one-third. Combining all four galaxies in one simulation resulted in a Milky Way-Andromeda merger just over 50 percent of the time.

添加三角座星系将概率提高到三分之二，而对银河系、仙女座星系和大麦哲伦星系进行模拟则将概率降低到只有三分之一。在一次模拟中合并所有四个星系，导致银河系与仙女座星系合并的概率略高于 50%。

In cases where collisions do occur, it seems we have more time than previously thought. The study found a median merger time of more than 7.6 billion years in the future, far longer than the previous estimate of 4 to 5 billion years.

如果确实发生碰撞，我们的时间似乎比之前想象的要多。研究发现，未来合并时间中位数超过76亿年，远长于之前估计的4至50亿年。

“Even using the latest and most precise available observational data, the future evolution of the Local Group is uncertain,” the team concluded. “Intriguingly, we find an almost equal probability for the widely publicized merger scenario (albeit with a later median time to merger) and one where the [Milky Way and Andromeda] survive unscathed.”

“即使使用最新、最精确的观测数据，本地群的未来演变仍不确定，”该团队总结道。 “有趣的是，我们发现广泛宣传的合并场景（尽管合并的中位时间较晚）与[银河系和仙女座]毫发无损的概率几乎相同。”

Galaxies smashing into each other sounds like an apocalypse of epic proportions, but it’s not really anything to worry about. The first point, of course, is the time frame – the Sun is only expected to live another 5 billion years or so, meaning life on Earth will experience several local, devastating Armageddons long before a galactic merger.

星系相互碰撞听起来像是一场史诗般的灾难，但其实没什么好担心的。当然，第一点是时间框架——太阳预计只能再活 50 亿年左右，这意味着地球上的生命早在银河合并之前就将经历几次局部的、毁灭性的世界末日。

Even if other lifeforms find themselves in the crossfire, it’s unlikely they’d really notice the cosmic pileup happening around them. Galaxies look pretty dense from a distance, but up close they’re mostly empty space. There’s plenty of room for stars to slot in around each other, so it’s extremely unlikely that any two stars would actually collide.

即使其他生命形式发现自己处于交火之中，他们也不太可能真正注意到周围发生的宇宙连环爆炸。从远处看，星系看起来非常密集，但近距离观察时，它们大多是空旷的空间。有足够的空间让恒星彼此围绕，因此任何两颗恒星实际上不太可能发生碰撞。

Their gravitational interactions would, however, jostle each other into new orbits: For example it’s thought that our Sun, probably in its red giant phase by then, would be bounced farther into the outskirts of the galaxy.

然而，它们的引力相互作用会将彼此推入新的轨道：例如，人们认为我们的太阳，那时可能处于红巨星阶段，会被弹到更远的星系边缘。

In its place, new stars would form more rapidly, as compressed hydrogen triggers an increase in star formation. Both galaxies would lose their current spiral shapes, forming one giant elliptical galaxy instead. Astronomers have already taken to nicknaming the end result “Milkomeda.”

取而代之的是，新恒星的形成速度会更快，因为压缩的氢会引发恒星形成的增加。两个星系都将失去当前的螺旋形状，而形成一个巨大的椭圆星系。天文学家已经给最终结果起了个绰号“米尔科墨达”。

Or of course, the Milky Way and Andromeda might swing past each other and continue to evolve as individual galaxies for eons to come. The point is we just don’t know for certain what their timelines look like, and while other studies were confident enough to claim a collision as a near certainty, the new work puts it down to a coin toss.

或者当然，银河系和仙女座星系可能会相互掠过，并在未来的亿万年里继续作为单独的星系演化。关键是我们只是不确定它们的时间表是什么样的，虽然其他研究有足够的信心声称碰撞几乎是确定的，但新研究将其归结为抛硬币。

More research, including upcoming Gaia data releases, could help paint a clearer picture.

更多的研究，包括即将发布的盖亚数据，可以帮助描绘出更清晰的图景。

“As it stands, proclamations of the impending demise of our galaxy appear greatly exaggerated,” the paper concluded.

该论文总结道：“就目前情况而言，关于我们银河系即将灭亡的声明似乎被严重夸大了。”

The research has been posted as a preprint on ArXiv.

该研究已作为预印本发布在 ArXiv 上。