Where did these gigantic space bubbles come from? - Ashkbiz Danehkar

譯者: 穎君 紀 審譯者: Helen Chang

In November 2010, NASA announced the discovery of a strange,

2010 年 11 月，美國 太空總署宣布他們發現一個

前所未見的奇怪天文物體：

never-before-seen galactic object:

two gigantic gaseous bubbles,

兩個巨大的氣體泡泡，

each emanating an impressive 25,000 light years

各朝我們家園的所在地—銀河系—的中心

from the center of our home galaxy, the Milky Way.

上下兩個方向擴散整整兩萬五千光年。

Inside the structures, named the Fermi Bubbles,

在這些被稱為費米泡泡的結構內，

streams of high energy particles traveling faster than the surrounding medium,

高能粒子流動得比周圍介質還快，

collide with dust, gas, and light,

與灰塵、氣體和光相撞

to create gamma rays, the most energetic form of light.

產生伽瑪射線，也就是 最高能量形式的光。

Astronomers were perplexed.

天文學家感到困惑。

While gamma rays are not uncommon in space,

雖然伽瑪射線在太空中很常見，

radiation of this magnitude had only been observed in distant galaxies.

但這種規模的輻射 只在遙遠的星系才觀察得到，

And they are typically produced by large-scale powerful events,

且通常由大規模、高能量的事件產生，

like explosions of supernova.

例如超新星爆發。

Yet, compared to our galactic neighbors,

然而，與我們附近的星系相比，

the center of the Milky Way and the supermassive black hole

銀河系的中心和其中的超大質量黑洞，

that resides within it,

was always thought to have been relatively calm.

長久以來被科學家認為是相對穩定的。

So, what was the powerful event that created these massive structures?

那，創造這些巨大結構的 重大事件是什麼？

And is the center of our galaxy not so sleepy after all?

銀河系的中心究竟穩不穩定？

A clue to answering these questions came in December 2020,

解答這些問題的線索 在 2020 年 12 月出現—

when astronomers announced the discovery

天文學家宣布發現另一組輻射球體，

of yet another set of radiating spheres.

Entitled the eROSITA bubbles, these structures are even wider,

被稱為 eROSITA 氣泡，它更巨大，

extending nearly half the distance of the entire Milky Way in both directions,

向上下延伸近整個銀河系的距離，

and fully encapsulating the Fermi Bubbles.

並完整包覆住費米泡泡。

They emit soft X-rays, which have frequencies lower than gamma rays,

它們輻射柔和的 X 射線 ， 頻率低於伽瑪射線，

but are still highly energetic forms of light.

但仍然是高能量的光。

Astronomers quickly surmised that the overlapping bubbles

天文學家立刻推測，重疊的氣泡

most likely share a single origin.

可能是從同個地方冒出來的，

And the event that formed them must have generated a massive amount of energy—

且創造出這些泡泡的事件 一定產生了大量能量—

approximately 1 million times that which the Sun will produce

約是太陽活動期間產生的 能量總量的一百萬倍。

during its entire lifetime.

Based on the speed of the jets of energetic electrons within the bubbles,

根據泡泡內高能電子們前進的速度，

they calculated the event most likely took place

他們計算出不到三百萬年前， 很可能發生了某件事。

less than 3 million years ago.

This is relatively recent compared to the galaxy’s 13-billion-year lifespan,

與銀河系的十三億年壽命相比， 這件事發生的時間點相對近期，

and means our early ancestors might have even witnessed the powerful event,

也就是說，我們的祖先 可能有目擊到這項重大事件：

as a gigantic ball of heated mass illuminating the night sky.

一顆大火球點亮夜晚的天空。

But what exactly was the powerful event?

那，重大的事件到底是什麼？

Two theories quickly emerged about what could have created the bubbles

關於泡泡和其中的高能粒子如何產生，

and the high energy particle jets within.

兩個理論很快就被提出，

And both are still debated today.

至今仍沒有定論。

The first theory is that the bubbles

第一個理論是，這些泡泡

stem from a recent massive burst of star formation

來自最近一場恆星形成事件， 其爆炸發生在銀河中心。

toward the center of our galaxy.

Newly forming stars produce a vast outflowing of hot gas,

新形成的恆星會產生大量的熱氣，

called stellar winds.

稱為星風。

Meanwhile, young massive stars die quickly,

同時，年輕的巨型恆星迅速死去，

causing energetic supernova explosions.

造成高能量的超新星爆發。

Stellar winds combined with these explosions

星風與超新星爆發同時發生的話

can lead to the formation of large-scale galactic winds.

會形成大規模星系風。

These galactic winds can push away the surrounding material,

星系風能推走周圍的物質，

creating gigantic bubbles.

形成巨大的氣泡。

The second theory is that the structures are the result of a powerful outburst

第二個理論是，這些泡泡是銀河系中心

from the supermassive black hole at the center of our galaxy.

超大質量黑洞發生強大爆發的產物。

Named Sagittarius A*,

這個黑洞叫人馬座 A 星 ，

this black hole lives up to its title of supermassive,

它超質量的稱號可不是浪得虛名，

as it’s approximately 4 million times the mass of the Sun.

因為它的質量大約是太陽的 4 萬倍。

And scientists have documented similar jets of energy

科學家在別處的活躍星系裡也觀察到

emanating from similar black holes in other distant active galaxies.

與其相似的黑洞 發生類似的能量噴發活動。

These jets are found in active galactic nuclei known as quasars,

這些能量噴發活動發生在一種 稱為「類星體」的活躍星系核裡，

and they're created as dust and gases rapidly fall into the feeding black hole.

因灰塵、氣體迅速落入 成長中的黑洞裡而出現。

This gathers hot ionized gas around the vicinity,

離子化的氣體開始聚集在 成長中的黑洞周圍，

which is then ejected from the center at ultra-fast velocities.

並以超快的速度從中心射出。

This theory suggests that Sagittarius A*, which is thought to be relatively quiet,

這個理論指出，被認為 相對穩定的人馬座 A 星

may have been active relatively recently.

最近可能比較活躍。

And it begs the question: will it wake up again?

這帶出一個問題： 它會再次活躍起來嗎？

Scientists use supercomputers

科學家使用超級電腦

to run what is known as hydrodynamic numerical simulations,

進行名叫「水動力數值模擬」的運算，

where different physical conditions that may have led to bubble formation

探討這些泡泡形成的各項物理條件。

are explored.

While several results suggest that extreme outbursts from Sagittarius A*

一些結果表明，來自 人馬座 A 星的大規模爆發

likely contributed to the creation of the bubbles,

可能參與泡泡的形成，

it remains to be seen whether past star formations may have also played a role.

過去恆星形成的活動是否參與 泡泡形成則還需進一步驗證。

Other simulations show evidence of other contributing factors,

其他模擬實驗證實 別項形成因素的參與，

like the influence of circumgalactic medium winds from outside our galaxy,

例如星系外的星系周介質風，

which may explain some of the bubbles’ unique features.

這可能解釋了兩組泡泡的一些特性。

These computational simulations will only get more precise

發射到太空的望遠鏡更靈敏、先進，

as we continue to launch more sensitive and dynamic telescopes into space.

我們的電腦模擬就會越來越精確。

But whatever answers we unlock will undoubtedly lead to more surprises

但無論我們找到什麼樣的答案， 它們都毫無疑問地會為我們

about our mysterious, and perhaps not so calm, galaxy.

神秘且或許不那麼平靜的 銀河系帶來更多驚喜。