参宿四已经停止变暗，并再次变亮

参宿四已经停止变暗，并再次变亮

After months of progressive dimming, Betelgeuse has started brightening again. The pronounced dimming event that this peculiar red giant star experienced was the most severe in recorded history, but it appears to have come to an end.

经过几个月的逐渐变暗，参宿四再次开始变亮。这颗奇特的红巨星所经历的明显的变暗事件是有记录以来最严重的，但它似乎已经结束了。

Observations during February showed that the rate of dimming was slowing down following the dramatic drop in brightness late last year. Now astronomers have seen signs of rebrightening, discussing the increase in luminosity in an Astronomer’s Telegram as well as partially solving the mystery of the dimming event.

2月份的观测表明，随着去年年底亮度的急剧下降，调暗的速度正在放缓。现在天文学家们已经看到了重新变亮的迹象，他们在一位天文学家的电报中讨论了亮度的增加，并部分地解决了变暗事件的谜团。

Alfredo Carpineti

It is well known that Betelgeuse is a semiregular variable star. This means that there is some periodicity to its brightness changes, but how much it varies and the precise length of these periods are not set in stone. The lowest point of the dip that has just concluded took place about 424 days after the last measured minimum, matching up with the star's primary period, which takes place every 420-430 days.

众所周知，参宿四是一颗半规则的变星。这意味着它的亮度变化有一定的周期性，但它变化的程度和这些周期的精确长度并不是固定不变的。刚刚得出结论的倾角最低点发生在最后一次测量最小值后的424天，与恒星的主周期相匹配，主周期每420-430天发生一次。

What remains to be understood is why the reduction in brightness was so significant this time around. Since last September, Betelgeuse has got more than 2.5 times dimmer, dropping out of the top 20 brightest stars in the night sky. And for this reason, astronomers want more telescopes on this peculiar object.

目前尚不清楚的是，为什么这一次亮度的降低如此显著。自去年9月以来，参宿四的亮度已经下降了2.5倍以上，在夜空中最亮的20颗星星中，参宿四被排除在外。由于这个原因，天文学家想要更多的望远镜来观测这个奇特的物体。

“Observations of all kinds continue to be needed to understand the nature of this unprecedented dimming episode and what this surprising star will do next,” the researchers wrote in the latest Astronomer’s Telegram.

研究人员在最新一期的《天文学家电报》中写道:“我们仍需要通过各种各样的观察来了解这次前所未有的暗化事件的本质，以及这颗令人惊讶的恒星接下来会发生什么。”

Some of these observations are already coming in with another Astronomer’s Telegram, which details brand new infrared observations of the star. The infrared photometry measured in February does not differ from previous measurements, even those from decades ago, and these values are a good proxy for the total luminosity of the star. Since they have not varied much, the researchers behind these observations suggest that the changes in brightness are to do exclusively with the outer layers of Betelgeuse.

其中一些观测结果已经和另一位天文学家的电报一起寄来了，电报中详细介绍了对这颗恒星的全新的红外观测结果。今年2月进行的红外光度测定法与以往的测量方法没有什么不同，甚至与几十年前的测量方法也没有什么不同，这些数值可以很好地反映出这颗恒星的总光度。由于它们的亮度变化不大，这些观测背后的研究人员认为，亮度的变化只与参宿四的外层有关。

Betelgeuse is a red supergiant star with an estimated mass almost 12 times that of our Sun, but much much larger in size. If it switched place with the Sun, it would extend past the orbit of Jupiter. The star has a low density and its outer layers are strongly affected by even small changes. It might be surprising to know that the star is not spherical, instead, its shape changes as a result of the many forces acting on it.

参宿四是一颗红色的超巨星，据估计其质量几乎是太阳的12倍，但体积要大得多。如果它与太阳交换位置，它将会越过木星的轨道。这颗恒星的密度很低，即使是很小的变化也会强烈地影响它的外层。知道这颗恒星不是球形可能会让人惊讶，相反，它的形状会因为作用在它上面的许多力而改变。