參宿四的極度昏暗被歸咎于一個塵土飛揚的噴嚏

參宿四的極度昏暗被歸咎于一個塵土飛揚的噴嚏

Between September last year and this February, red supergiant Betelgeuse experienced an unprecedented dimming period that led the supergiant to drop out of the Top 20 brightest stars in the night sky.

從去年9月到今年2月，紅巨星參宿四經歷了一段前所未有的變暗期，導致這顆超級巨星從夜空中最亮的20顆恒星中消失。

Betelgeuse's activity led to speculation it was hinting at its impending supernova. However, as a variable star, Betelgeuse experiences changes in its brightness every 420 days, and this current dimming fits with this just being an extra-strong cycle. Why it reached such an exceptionally low luminosity, dropping to around 40 percent of its usual brightness, is still curious. Now researchers have a new theory, blaming it on a release of dust from its outer layers; basically, a sneeze.

參宿四的活動導致人們猜測它是在暗示即將發(fā)生的超新星。然而，作為一顆變星，參宿四每420天經歷一次亮度的變化，而當前的調光正好與這一超強周期相吻合。為什么它的光度會降至如此低的水平，只有平常亮度的40%左右，我們仍然很好奇。現(xiàn)在研究人員有了一種新的理論，認為這是由于其外層釋放出的灰塵;基本上,一個噴嚏。

Alfredo Carpineti

A new paper, accepted in the Astrophysical Journal Letters, points out that the temperature of the star has changed marginally during this period and it is, in fact, warmer than it should be if its dimming was caused by the star's cooling surface. Instead, they think the star got rid of some of its material from its outer layers, which is blocking the light.

發(fā)表在《天體物理學雜志通訊》上的一篇新論文指出，在此期間，這顆恒星的溫度發(fā)生了微小的變化，事實上，如果它的變暗是由恒星的冷卻表面造成的，那么它的溫度就比應該的溫度要高。相反，他們認為這顆恒星擺脫了外層阻擋光線的物質。

“We see this all the time in red supergiants, and it’s a normal part of their life cycle,” lead author Professor Emily Levesque from the University of Washington said in a statement. “Red supergiants will occasionally shed material from their surfaces, which will condense around the star as dust. As it cools and dissipates, the dust grains will absorb some of the light heading toward us and block our view.”

研究報告的主要作者、華盛頓大學的埃米莉·萊維斯克教授在一份聲明中說:“我們在紅巨星身上經常看到這種現(xiàn)象，這是它們生命周期中很正常的一部分。”“紅巨星偶爾會從它們的表面脫落物質，這些物質會在恒星周圍凝結成塵埃。當它冷卻并消散時，塵埃顆粒會吸收部分射向我們的光線，從而擋住我們的視線。”

Levesque and her co-author Philip Massey were part of the team who had previously estimated the temperature of the surface of the star in 2004. They took observations on February 14 2020 to estimated how much Betelgeuse had cooled down. It turned out, not very much at all. The average surface temperature of the star is 3,325 °C ( 6,017 °F). That’s only between 50-100°C (90-180°F) cooler than the previously estimated temperature.

萊維斯克和她的合著者菲利普·梅西曾在2004年估算過這顆恒星表面的溫度。他們在2020年2月14日進行了觀測，以估計參宿四冷卻了多少。結果是，變化并不大。該恒星的平均表面溫度為3325°C(6017°F)。這只是比之前估計的溫度低了50-100°C(90-180°F)。

“A comparison with our 2004 spectrum showed immediately that the temperature hadn’t changed significantly,” said Massey. “We knew the answer had to be dust.”

Massey說:“與我們2004年的光譜相比，溫度并沒有明顯的變化。我們知道答案肯定是灰塵。”

Clouds of dust have been observed around other stars as well and the team is confident that new observations of Betelgeuse will reveal them here as well. However, this is only one reason to continue looking at this star. Betelgeuse is the nearest red supergiant to Earth and it is a perfect laboratory to work out how these celestial bodies evolve.

在其他恒星周圍也觀察到了塵埃云團，研究小組相信，對參宿四的新觀測也將在這里揭示這些云團。然而，這只是繼續(xù)觀察這顆恒星的一個原因。參宿四是離地球最近的紅色超級巨星，它是研究這些天體如何演化的完美實驗室。

“Red supergiants are very dynamic stars,” said Levesque. “The more we can learn about their normal behavior — temperature fluctuations, dust, convection cells — the better we can understand them and recognize when something truly unique, like a supernova, might happen.”

“紅巨星是非?；钴S的恒星，”萊維斯克說。“我們對它們的正常行為——溫度波動、塵埃、對流細胞——了解得越多，我們就能更好地理解它們，并更好地識別什么時候可能會發(fā)生真正獨特的事情，比如超新星爆炸。”