奥陌陌真的是外星飞船吗？科学家提出了新答案｜科学60秒

2023-04-14 19:04

奇怪天体奥陌陌

奥陌陌实在太小了，即使在最大的望远镜中，也只能显示为一个光点。但我们知道它一定是一个高度拉长的物体，因为它的亮度在每七到八小时的时间段内变化很大｜图片来源：NASA/JPL-Caltech

今天我们将讨论行为“怪异”的奥陌陌（'Oumuamua），它是第一个已知的来自太阳系外的星际访客，于2017年10月经过地球，绕过太阳。《科学美国人》（Scientific American）的新闻记者梅根·巴特尔斯（Meghan Bartels）不久前写了一篇关于这个神秘天体的新文章，她采访了其中一位研究人员。

奥陌陌在五年多以前顺路拜访了我们所有人，但它没有逗留，以弹弓般的轨迹绕过太阳后，它就回到了星际空间。天文学家几乎没什么机会对它进行研究，它早已飞远，我们为什么还在谈论它？

因为奥陌陌真的太奇怪了。天文学家不确定它究竟是一颗小行星还是一颗彗星，它形状奇特，又长又细，像雪茄一样，同时又有点像扁而薄的煎饼。在离开时，它似乎以一种科学家难以解释的方式加速了。

这里奇怪的加速指的是在它离开太阳、从太阳引力作用下滑离时，速度比预期的要快。就像汽车司机在上坡时踩了油门一样。科学家称之为“非引力加速度”（non-gravitational acceleration）。

非引力加速度本身其实并不奇怪，当彗星靠近太阳时，这种情况经常发生，太阳光会让它们温度上升，彗星的冰会变成气体并从表面喷出，有点类似火箭。但通常，我们能观察到相应的气体或尘埃轨迹，但在奥陌陌身上却没有发现任何类似的东西。

这就解释了为什么科学家会提出各种各样的猜想来解释奥陌陌加速的原因：也许它是由静电力攒起来的巨大尘埃球，就像沙发下一团团灰尘的超大版；也许它是由固态氢构成的巨大冰山；又或者是一艘废弃的外星飞船。（须要明确的是，目前我们还从未见过上述这些东西，我们……[查看全文]

Science Has New Ideas about 'Oumuamua's Weirdness

Lee Billings: Hey there and welcome to Cosmos, Quickly, this is Lee Billings. Today we’re talking about the curious case of ‘Oumuamua, which became the first known interstellar visitor to our solar system when it swooped by Earth and around the Sun back in October of 2017.

I’m joined by our news reporter Meghan Bartels who just wrote a story on a fresh study about this mysterious object and talked to one of the researchers behind it.

Hi, Meghan!

Meghan Bartels: Hi Lee. Happy to be here!

Billings: So, ‘Oumuamua dropped in on all of us more than five years ago, and it didn’t hang around – after slingshotting around the Sun it soared back on a trajectory to interstellar space. Astronomers barely got a chance to study it. It’s long gone. Why are we still talking about it?

Bartels: Well, ‘Oumuamua was really weird. Astronomers weren’t sure if it was an asteroid or a comet, and it was strangely shaped–long and thin like a cigar (or maybe flat and thin like a pancake?). And it seemed to speed up on its outbound journey in a way scientists struggled to explain.

Billings: Speed up?

Bartels: Well, as it traveled away from the Sun and slipped away from our star’s gravitational grip, its departing velocity was faster than expected. Almost like a driver of a car hitting the gas while coasting up a hill. Scientists call that “non-gravitational acceleration.”

Billings: Non-gravitational acceleration. Got it. And that’s weird because?

Bartels: It’s not that weird, actually–comets do it all the time when they come close to the Sun. Sunlight warms their ice which turns to gas and jets off the surface, a bit like a rocket.

Billings: But usually, you can see that gas or the dust trail, and we didn’t see any of that with ‘Oumuamua, right?

Bartels: Yeah, that’s right.

Billings: That explains why scientists keep offering these wacky out-of-leftfield ideas about what caused the acceleration.

Maybe it was a big dustball held together by electrostatic forces–like a supersized version of the dust bunnies under your couch. Maybe it was a huge iceberg made of solid hydrogen. Or maybe it was a derelict alien starship.

(Some folks say all these things. To be clear–these are all things we have never ever seen before, as far as we know. We don’t...[full transcript]

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论文信息

Bergner, J.B., Seligman, D.Z. Acceleration of 1I/‘Oumuamua from radiolytically produced H2 in H2O ice. Nature 615, 610–613 (2023).

DOI: 10.1038/s41586-022-05687-w

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