How to detect a supernova - Samantha Kuula

譯者: Songzhe Gao 審譯者: 瑞文Eleven 林Lim

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

就在剛剛 一顆恆星在宇宙某處爆炸

There goes another one.

接著又一顆

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

在可觀測的宇宙中 幾乎每一秒都有超新星爆炸

and there is one on average every 25 to 50 years

而且平均每 25 到 50 年 就會出現一顆

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

跟銀河系一樣大 一樣古老的超新星

但我們從未完整觀測過

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

一顆超新星爆炸的激烈過程

from its first violent moments.

Of course, how would we?

要怎麼觀測呢？

有數千億顆恆星的距離近到

There are hundreds of billions of stars close enough

that we could watch the supernova explosion

可以直接看到超新星爆炸

break through the surface of the star.

突破恆星表面

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

但是必須在正確的時間點 動用最好的望遠鏡

at precisely the right time to get meaningful data.

觀測該顆恆星 才能得到有意義的數據

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

簡單地說

能夠準確觀測的機率非常低

能不能在爆炸的光線 傳過來之前先觀測到？

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

That may seem impossible.

聽起來不太可能

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

畢竟沒有東西比光速快，對吧？

As far as we know, yes.

就目前所知，沒錯

但是你如果在一場比賽中蛇行前進

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

while someone else beelines it for the finish line.

其他人則是直線奔跑 速度快便不是重點了

For exactly that reason,

換句話說

最先到地球的不是蛇行的光子

photons don't win the supernova race to Earth.

Neutrinos do.

中微子才是贏家

Here's why.

原因在於超新星有兩種：

There are two types of supernova.

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

第一種，當恆星從鄰近恆星 累積過多物質時

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

意外突發的核反應 引燃了恆星產生爆炸

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

第二種，當恆星耗盡了核燃料

so the gravitational forces pulling in

重力把它向內吸的強度

overwhelm the quantum mechanical forces pushing out,

大於量子力學向外的推力

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

恆星內核因為自身的重量 在百分之一秒內塌

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

而恆星的表面不受內核坍塌的影響

the inner edges accelerate through the void,

恆星內部的空隙瞬間增加

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

撞向內核後反彈引發爆炸

In both of these scenarios,

恆星在這兩種形況下 會散發無可比擬的能量

the star expels an unparalleled amount of energy,

as well as a great deal of matter.

和大量的物質

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

事實上，所有比鎳重的原子

包括金和銀

only form in supernova reactions.

皆在超新星爆炸中產生

In type 2 supernovae,

第二種超新星爆炸裡

about 1% of the energy consists of photons,

有大約百分之一的能量是光子

which we know of as light,

就是所謂的光

while 99% radiates out as neutrinos,

其餘百分之九十九的能量 是輻射出去的中微子

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

這種基本粒子 幾乎不會與其它物質反應

Starting from the center of the star,

從恆星的中心開始

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

爆炸產生的物質 需要數十分鐘、數小時

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

有些甚至數日 才會突破恆星的表面

但是多虧中微子不反應的特性

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

take a much more direct route.

會採用更筆直的路線

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

當恆星表面出現可測的變化時

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

中微子會比光子提前幾小時到達

That's why astronomers and physicists

所以天文學家和物理學家

have been able to set up a project called SNEWS,

制定了 SNEWS 計劃

the Supernova Early Warning System.

全名為「超新星早期預警系統」

When detectors around the world pick up bursts of neutrinos,

當全世界的探測器一接收到中微子

they send messages to a central computer in New York.

它們會傳送信號到紐約的中央電腦

If multiple detectors receive similar signals within ten seconds,

如果多個探測器在十秒內 接收到相同的信號

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

SNEWS 便發出 超新星即將爆炸的警報

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

根據中微子的訊息分析距離和方向

the amateur astronomers and scientists alike

狂熱的天文學家和科學家

will scan the skies and share information

會快速掃描天空並分享訊息

to quickly identify the new galactic supernova

辨認出新的超新星

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

並把世界主要的天文望遠鏡轉向那裡

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

上一次地球接收到 超新星中微子的時間是 1987 年

由大麥哲倫星系旁的 蜘蛛星雲散發出來

on the edge of the Tarantula Nebula

in the large Magellanic Cloud, a nearby galaxy.

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

它的中微子比可見光 早約三小時到達地球

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

我們隨時都有可能接收到微中子

當那天來臨

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

SNEWS 將讓我們第一次目擊

that no human has ever seen before.

人類史上從未見過的現象