800年一次 罕见的圣诞星冬至能看到

罕见的圣诞之星将在今年冬至（winter solstice）出现：木星和土星对齐（align），400年才一次如此接近，800年才一次肉眼能看见。

木星和土星对齐虽然每20年有一次，但如此接近大约400年才一次。肉眼（无需设备、无需经验的老百姓）都能看到，大约800年才一次。

12月21日晚（日落之后），往西南方向的靠近水平线部位看。。。

英文原文报道：

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)