800年一次 罕見的聖誕星冬至能看到

罕見的聖誕之星將在今年冬至（winter solstice）出現：木星和土星對齊（align），400年才一次如此接近，800年才一次肉眼能看見。

木星和土星對齊雖然每20年有一次，但如此接近大約400年才一次。肉眼（無需設備、無需經驗的老百姓）都能看到，大約800年才一次。

12月21日晚（日落之後），往西南方向的靠近水平線部位看。。。

英文原文報道：

Rare ‘Christmas Star’ to be visible for first time in 800 years on Dec. 21

Jupiter, Saturn align perfectly to create rare star on winter solstice

With this year’s winter solstice comes more than just confirmation of our already-cold weather and ever-fleeting daylight: The rare “Christmas Star” will be visible for the first time in 800 years.

Each year, Earth’s northern hemisphere enters the winter solstice on Dec. 21 -- the shortest day of the year -- officially marking the start of winter. This year, bright planets Jupiter and Saturn will align perfectly on Dec. 21 to create what is commonly called the Christmas Star or the “Star of Bethlehem.”

According to NASA, Jupiter and Saturn align with one another every 20 years or so, but not as close together as they will be in 2020. The planets have not aligned this closely in about 400 years, nor has their alignment been visible (occurred at night) in about 800 years.

The timing of the occurrence couldn’t be more perfect: The winter solstice may be the shortest day of the year, but that also means it’s the longest night of the year -- so there will be plenty of opportunity to take a peak at this once-in-a-lifetime star.

Experts say the Christmas Star can be seen by the unaided eye just after sunset on Dec. 21, 2020. Just make sure you’re facing southwest.

It’s also possible that the phenomenon will be visible throughout the week.

We suggest you seize this opportunity if you can -- experts believe Jupiter and Saturn won’t be this close together again for at least another 60 years.

You can see Saturn and Jupiter nearly align on Dec. 21, forming what appears to be a Christmas star. (Credit: NASA/JPL-Caltech) (NASA/JPL-Caltech)