BBC 天文奇观: 流星雨、日全食、木星土星大合的璀璨夜空,土木星最近的日期在12月21日,千载难逢。(自伽利略在世以来400年难得一见的机会)

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天文奇观: 流星雨、日全食、木星土星大合的璀璨夜空​

  • 伊娃·昂蒂维洛斯(Eva Ontiveros)
  • BBC国际部
2020年12月7日

The milky way at Durdle Door, Dorset, UK

图像来源,GETTY IMAGES
无论你身在何处,都会看到12月的精彩夜空“表演”。

不是每个人都喜欢2020年,其原因不言自明。

然而,对于观察天文现象来说,2020年则是不可多得的一年,特别是12月份将有一系列天文奇观点燃夜空,让你大饱眼福。而且,你无需购置什么昂贵的设备和望远镜,坐在家里就能看得到。

12月,人们不仅可以看到最好的流星雨、日全食,还有土星和木星大合的罕见现象。

唯一的条件是需要天空晴朗,必要时保护眼睛,并知道该朝哪里看。
依照时间顺序,本月分别有这些壮观天体现象出现:

12月13-14日:双子座流星雨,从全世界各个角落都可以看得到。​

The Geminids meteor shower during its peak, in the night sky over Tokarevsky Lighthouse on Egersheld Cape on Russky Island in the Sea of Japan, December 2017.

图像来源,GETTY IMAGES
双子座流星雨,从海参崴(如图)到达喀尔任何地方都可以看得到,只要天空晴朗就行。

你或许在过去几个月看过流星雨,但本次双子座的流星雨堪称为流星雨之王。

英国格林尼治皇家天文台的天文学家斯凯尔顿(Patricia Skelton)解释说,流星雨的形成大多数时候是因为地球穿越由彗星留下的流星群时发生的。但这次的双子座流星雨则不一样,它是由一颗叫3200的小行星(3200 Phaeton)留下的流星雨。

斯凯尔顿说,每年当地球穿过这片充满太空碎片的地带时我们都会看到丰富的夜空流星雨盛况。而从13到14日,更是达到高峰时刻。届时,每小时会有多达150颗流星出现。

A composite image of the 2017 Geminid meteor shower in Arizona.

图像来源,GETTY IMAGES
夜空越黑,观象机会越好。

斯凯尔顿表示,流星雨的速度可以达到每秒35公里,相当于每小时近13公里。

她还补充说,随着流星雨的燃烧人们还将会看到黄色,甚至偶尔绿色或蓝色的夜空。

天空越黑,观测流星雨的机会越好,即使在有轻度污染的城市地区,也可以看得到一部分流星雨现象。

这次流星雨发生之际正值新月,因此观测的时机更佳(满月时天空过亮不利于观测)。

12月14日:日全食,在南美的智利和阿根廷可以观测到​

Panoramic view of Patagonia: The recently paved road connecting El Calafate to El Chalten is renowned to be one of the most beautiful roads in the world.

图像来源,GETTY IMAGES
日全食可能让古人迷惑。

虽然你所在地看不到日全食现象,但你可以在网上欣赏人们现场上传的实况。

如果不是新冠,人们可能会跑到智利和阿根廷南部的巴塔哥尼亚去欣赏这一天文奇观。但现在,许多人选择上网观看。

但如果你有幸能亲眼看到,记住不要直视,一定要保护眼睛。

格林尼治皇家天文台的塔尼亚解释说,在月亮穿过太阳表面24分钟的时间里,仅有2分9.6秒彻底遮住太阳。虽然月亮比太阳小400倍,但由于它离地球更近所以看起来要大得多,因此能够遮蔽太阳圆盘,形成日全食现象。

这一月亮遮天蔽日的诡异现象将把南美笼罩在一片夜幕之下,而且正好是在正中午。

Low angle view of solar eclipse in sky during foggy weather.

图像来源,GETTY IMAGES
永远不要直视太阳,即使是在日全食的时候也不要这样做。

巴塔哥尼亚的土著居民马普切人对这一日全食现象特别关注 。对他们来说,太阳代表阳能,月亮则代表阴能,所以当阴阳交会时所产生的剧烈能量对他们来说是非常微妙的时刻。

在马普切人语言中还把日食现象称为“太阳之死”,他们对此感到敬畏和害怕。但塔尼亚说,日食现象在全世界已经有近5千年的历史记载。

塔尼亚表示,不难理解古代历史上把日全食看作是凶兆,这一刻太阳好像被吞吃了,白天立即变成黑夜。塔尼亚说,其实一年之内可以发生多达5次的日食现象,但日全食则大约每隔一年半左右发生一次。

而下一次日全食将发生在2021年的12月,地点在南极洲。

如果你想提前计划,请记住:2023年4月:印度尼西亚和澳大利亚;2024年4月:美国和加拿大;2026年8月:欧洲南部和格陵兰。2027年8月:北非大部分地区以及中东地区。

12月21日:木星和土星大合现象,全球都可以观测到。​

The trio of (L to R) Saturn, Mars and Jupiter in conjunction in the dawn twilight, taken from home in Alberta on March 26, 2020. This is a stack of 10 exposures.

图像来源,GETTY IMAGES
上一次木星和土星大合是近400年前,当时伽利略刚刚发明了望远镜。

格林尼治皇家天文台的另一位天文学家布卢默说,木星和土星可能是天文爱好者的最佳观测行星,因为它们明亮耀眼。

所谓土星和木星大合是指两颗星星如此接近,给人一种相互重叠,一起熠熠发光的假象。

布卢默解释说,21日两颗行星在夜空中如此接近,好像彼此重叠一样。

布卢默表示,对我们肉眼而言,土星与木星之间相距仅6.1角分(0.1度),但实际上木星距离地球有8亿多公里,木星与土星之间的距离也差不多如此。

但最近几个月,木星和土星这两颗巨大的行星似乎越走越近,直到“相会”大合。这是一个不容错过的天文现象。

布卢默说,如果你有望远镜的话,甚至可以看到木星周围的四大卫星。

Artwork of Jupiter and its largest four (Galilean) moons. From left to right the bodies are Io, Callisto, Jupiter (with the shadow of Io cast upon it), Ganymede and Europa. The bodies are all shown to the correct scale, as viewed from a distance somewhere beyond the orbit of Callisto

图像来源,GETTY IMAGES
如果用望远镜你可以看到木星的四大卫星,左边是木卫一(lo) 和木卫四(Callisto),中间是木星,右边则是木卫三( Ganymede )和木卫二(Europa)。

虽然土星和木星之合平均每19.6年发生一次,但这次的大合非常特别,因为它是自17世纪以来最接近的一次。上一次的大合发生在397年前的1623年,也就是伽利略在世的时候。

也就是说这是一次千载难逢的机会,难怪天文学家和爱好者们如此兴奋。

如果天空晴朗将很容易看得到,不过还是要做一些必要的准备,因为只有一个小时的观测窗口。

这一现象将在12月21日晚间的西南地平线方向出现,位置较低。时间是日落后半个小时。

12月21日又是北半球冬至和南半球夏至的开始。

 

lindamy

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Just in time for Christmas, Jupiter and Saturn will come closer than they have since the Middle Ages​

https://www.cnn.com/profiles/ashley-strickland-profile
By Ashley Strickland, CNN

Updated 12:03 PM ET, Thu December 3, 2020

(CNN)The two largest planets in our solar system are coming closer together than they have been since the Middle Ages, and it's happening just in time for Christmas.

So, there are some things to look forward to in the final month of 2020.

On the night of December 21, the winter solstice, Jupiter and Saturn will appear so closely aligned in our sky that they will look like a double planet. This close approach is called a conjunction.

"Alignments between these two planets are rather rare, occurring once every 20 years or so, but this conjunction is exceptionally rare because of how close the planets will appear to one another," said Rice University astronomer and professor of physics and astronomy Patrick Hartigan in a statement.

"You'd have to go all the way back to just before dawn on March 4, 1226, to see a closer alignment between these objects visible in the night sky."

If you're a stargazer, you've likely noticed Jupiter and Saturn have been getting closer together since the summer. And they're currently visible in our night sky, inching ever closer to one another.

Jupiter's moon Europa may glow in the dark
Jupiter's moon Europa may glow in the dark


But between December 16 and 25, they will become even cozier. Look for the Jupiter-Saturn conjunction low in the western sky for about an hour after sunset each evening during this time.

"On the evening of closest approach on Dec(ember) 21 they will look like a double planet, separated by only 1/5th the diameter of the full Moon," Hartigan said. "For most telescope viewers, each planet and several of their largest moons will be visible in the same field of view that evening."

While these two planets may appear close, they are still hundreds of millions of miles apart, according to NASA.

Hope for clear skies because the conjunction will be visible around the world, with the best perspective for those near the equator.

"The further north a viewer is, the less time they'll have to catch a glimpse of the conjunction before the planets sink below the horizon," Hartigan said.

Unusual molecule found in atmosphere on Saturn's moon Titan
Unusual molecule found in atmosphere on Saturn's moon Titan


The planets will be bright enough to be viewed in twilight, which may be the best time for many US viewers to observe the conjunction.

"By the time skies are fully dark in Houston, for example, the conjunction will be just 9 degrees above the horizon," Hartigan said. "Viewing that would be manageable if the weather cooperates and you have an unobstructed view to the southwest."

If you're in New York or London, or along those latitudes, try to spot the conjunction right after sunset. Waiting an hour after the sun sets will only put the planets closer to the horizon, making them more difficult to spot.

The best conditions to see this astronomical event will include a clear southwestern horizon and no low clouds in the distance, Hartigan said. Binoculars or a telescope may help you distinguish the planets. A telescope would enable a view of Saturn's rings and the brightest moons of both planets, he said.

If you miss this conjunction and want to see the planets with the same proximity, just higher in the sky, it won't happen until March 15, 2080 -- and then not again until after 2400.

Between 0 and 3000 CE, or Common Era, only seven conjunction were or will be closer than this one -- and two of those were too close to the sun to be seen without a telescope, according to Hartigan. So, yes, this is an incredibly rare event.

 
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