千年等一回—日环食归来

Ring of fire' solar eclipse to occur Sunday, May 20

日环食将于5月20日出现

A partial solar eclipse photographed by the joint Japanese-American Hinode satellite. (Hinode/XRT)

被日美联合卫星“日之出”所拍摄到的一颗日偏食

(Space.com) Skywatchers in East Asia and the western United States should circle Sunday (May 20) on their calendars. That's when a solar eclipse will block out most of the sun, leaving a spectacular "ring of fire" shining in the sky for observers located along the eclipse's path.

东亚和美国西部的观测者应该在日历上圈上周日(五月20日)这天。这一天日食会遮住太阳的大部分，只留下一个壮观的“火环”在天空闪烁，位于日食运行轨迹上的观测者都有机会观测到这一景象。

The event is what's known as an annular solar eclipse -- from the Latin "annulus," meaning "little ring" -- and its full glory should be visible from much of Asia, the Pacific region and some of western North America, weather permitting. At its peak, the eclipse will block about 94 percent of the sun's light.

这一景象就是我们所说的日环食，拉丁语“annulus”意思为“小环”。如果天气条件允许，位于亚洲，太平洋地区及西北美一些地区的观测者将有幸目睹这一壮观景象。日食最大时会遮住94%的太阳光。

Other parts of the United States and Canada will still see a partial solar eclipse, without being treated to the ring of fire effect, though the East Coast will miss the event since the sun will have set before it begins. The eclipse will occur in the late afternoon or early evening of May 20 throughout North America, and May 21 for observers in Asia.

虽然东海岸的观测者会因为太阳在日食开始前就日落而错过这次日食，但美国和加拿大其他地区的观测者仍然可以看到日偏食，只不过不是火环状。日食将在北美5月20日的傍晚时分或晚上出现。

Solar eclipses occur when the moon comes between Earth and the sun, casting a shadow on our planet. When the moon lines up perfectly with the sun and blots out all of its light, the result is a total eclipse. Partial eclipses cover only part of the sun's face.

当月亮运行到地球和太阳之间时，日食就会出现，并在地球上投下月影。当月亮和太阳完全成一条直线并遮住太阳时，就形成了日全食。日偏食即月亮只遮住了部分太阳。

Annular eclipses are similar to total eclipses in that the moon lines up with the sun dead-on. But in this case, the moon is close to apogee -- the farthest point from Earth in its elliptical orbit around our planet -- so it's a smidge too small in the sky to cover the solar disk completely. As a result, a ring of bright sunlight will still blaze around the moon's circumference.

日环食与日全食的形成是相似的，即在月亮与太阳完全成一条直线时才会发生。但在这种情况下，月亮接近最高点——位于它椭圆轨道上的最远点。而这时它的表面积太小不足以完全遮住太阳表面，就形成了一个在月亮周围发光的日光环。

Like other types of solar eclipses, annular eclipses are spectacular but potentially dangerous skywatching events. Care must be taken to observe them properly, or serious and permanent eye damage -- including blindness -- could result.

和其他种类的日食一样，日环食是很壮观的景象，但同时对观测者来说却也存在潜在危险。观测者要十分注意以正确的方式进行观测，否则眼睛会被严重灼伤或导致永久失明。

Warning: Never look directly at the sun, either with telescopes or binoculars without the proper filters.

提醒：不要直接用眼睛观看，要使用望远镜或者无过滤片双筒镜。

To safely observe the May 20 annular eclipse, you can buy special solar filters to fit over your equipment, or No. 14 welder's glass to wear over your eyes. Do NOT use standard sunglasses or any kind of homemade sun-shading contraption.

安全起见，为观测5月20日出现的日环食，你可以购买特殊的太阳滤镜并将其安装在观测设备上或者佩戴No. 14 welder's眼镜。不要使用普通太阳镜或者任何自制的遮阳装置。

The safest and simplest technique is perhaps to watch the eclipse indirectly with the solar projection method. Use your telescope, or one side of your binoculars, to project a magnified image of the sun's disk onto a shaded white piece of cardboard.

最安全和最简单的方法可能就是通过太阳投影来观测日食。用你的望远镜或者双筒镜的一面在一块白色的纸板上投影一个放大的太阳图像。

The image on the cardboard will be safe to view and photograph. Be sure to cover the telescope's finder scope or the unused half of the binoculars, however, and don't let anybody look through them.

观察和拍摄纸板上的图像是安全的。确保要遮住望远镜的可视范围部分或者双筒镜不使用的一面，不要让任何人通过望远镜和双筒镜来观察。