How to detect a supernova - Samantha Kuula

翻译人员: Haochen Wang 校对人员: Gabriella Hu

Just now, somewhere in the universe, a star exploded.

刚刚，在宇宙的某一处，就有一颗恒星爆炸了。

There goes another one.

接着，又有一颗爆炸了。

In fact, a supernova occurs every second or so in the observable universe,

事实上，每秒种都有超新星。

and there is one on average every 25 to 50 years

在巨大的宇宙里，每25至50年就会产生

in a galaxy the size and age of the Milky Way.

似银河系大小和年龄的星系。

Yet we've never actually been able to watch one happen

然而，我们从没机会目睹

from its first violent moments.

爆炸的瞬间。

Of course, how would we?

当然，这怎么可能呢？

There are hundreds of billions of stars close enough

有上千亿颗恒星

that we could watch the supernova explosion

在我们可观察到的范围内

break through the surface of the star.

演变超新星爆炸。

But we'd have to have our best telescopes focused on the right one

但真正去取得有力的数据 首先需要一台先进望远镜

at precisely the right time to get meaningful data.

以及它精准的对焦与时间的拿捏。

Suffice it to say, the odds of that happening are astronomically low.

不用多说，这个实践是很困难的。

But what if we could anticipate a supernova before its light reached us?

或许，我们可以尝试在光线传达到地球前 预测超新星的发生？

That may seem impossible.

这听起来不可能。

After all, nothing travels faster than the speed of light, right?

毕竟，没有力量可以超越光速，不是吗？

As far as we know, yes.

据我们所知，确实没有。

But in a race, fast doesn't matter if you take a detour

不过，在竞赛中，速度不代表一切。

while someone else beelines it for the finish line.

相比绕路，走直径才能胜出。

For exactly that reason,

同样的道理

photons don't win the supernova race to Earth.

最早往地球传达超新星的不是光子

Neutrinos do.

而是中微子。

Here's why.

这就是原因：

There are two types of supernova.

超新星分为两类。

Type 1 is when a star accumulates so much matter from a neighboring star,

第一类是当一颗恒星从周围累积足够的物质后

that a runaway nuclear reaction ignites and causes it to explode.

失控核反应启动并致其爆炸。

In type 2, the star runs out of nuclear fuel,

在第二类中，恒星耗尽核燃料

so the gravitational forces pulling in

因此引力的作用

overwhelm the quantum mechanical forces pushing out,

压倒量子力

and the stellar core collapses under its own weight in a hundredth of a second.

使恒星的内核因自身重量的压力在百分之一秒内崩塌。

While the outer reaches of the star are unaffected by the collapsed core,

虽然星系的外围不受内部的影响

the inner edges accelerate through the void,

内缘在孔隙巨洞不断加速

smash into the core, and rebound to launch the explosion.

直到核心受到重击，而以此爆炸。

In both of these scenarios,

在这两类情况下

the star expels an unparalleled amount of energy,

恒星将排出前所未有的能量

as well as a great deal of matter.

以及大量物质。

In fact, all atoms heavier than nickel, including elements like gold and silver,

实际上，所有比镍重的原子，包括金和银

only form in supernova reactions.

只能在超新星爆炸中诞生。

In type 2 supernovae,

在第二类超新星中，

about 1% of the energy consists of photons,

大约1% 的能量是由光子组成的

which we know of as light,

也就是我们所说的光。

while 99% radiates out as neutrinos,

而其中的99%以中微子放射

the elementary particles that are known for rarely interacting with anything.

它们的基本粒子很少交涉。

Starting from the center of the star,

从恒星的中央

the exploding matter takes tens of minutes, or even hours,

爆炸物需要数分钟，或数小时

or in rare cases, several days, to reach and break through the surface of the star.

甚至有些时候花几天时间来抵达和突破恒星的表层。

However, the neutrinos, thanks to their non-interactivity,

相比之下，中微子的非交互性质

take a much more direct route.

促使它们选择更快的直径线路。

By the time there is any visible change in the star's suface,

在恒星表面发生明显变化前

the neutrinos typically have a several hour head start over the photons.

中微子就比光子占有时间上的优势。

That's why astronomers and physicists

这就是为什么天文学家与物理学家

have been able to set up a project called SNEWS,

建立了SNEWS项目，全称

the Supernova Early Warning System.

超新星早期预警系统。

When detectors around the world pick up bursts of neutrinos,

当探测器检测到微中子的存在时

they send messages to a central computer in New York.

这些信息将被传输到位于纽约的中央计算机。

If multiple detectors receive similar signals within ten seconds,

如果多个探测器在十秒内同时检测到信号

SNEWS will trigger an alert warning that a supernova is imminent.

SNEWS会启动超新星爆炸警报。

Aided by some distance and direction information from the neutrino detectors,

从微中子探测器提供的距离、方向等信息里

the amateur astronomers and scientists alike

业余的天文学家以及科学家

will scan the skies and share information

可通过扫描天空以及分享资料

to quickly identify the new galactic supernova

从而识别新的超新星

and turn the world's major telescopes in that direction.

并且将世界最高级的望远镜转到那个方向。

The last supernova that sent detectable neutrinos to Earth was in 1987

在1987年最新探测到往地球 发送中微子的超新星处于在

on the edge of the Tarantula Nebula

蜘蛛星云边缘

in the large Magellanic Cloud, a nearby galaxy.

位于临近的大麦哲伦星系中。

Its neutrinos reached Earth about three hours ahead of the visible light.

这些中微子比可见光提前三小时抵达地球。

We're due for another one any day now, and when that happens,

现在，随时都有可能发生超新星爆炸

SNEWS should give you the opportunity to be among the first to witness something

而当它发生的时候，SNEWS将给你一个千载难逢的机遇

that no human has ever seen before.

来见证人类从未见过的场景。