A Summer of Supermoons presented by Science@NASA
由 Science@NASA 帶來的「超級月亮之夏」
In June of last year, a full moon made headlines. The news media called it a "supermoon" because it was 14% bigger and 30% brighter than other full moons of 2013. Around the world, people went outside to marvel at its luminosity. If you thought one supermoon was bright, how about three? The full moons of summer 2014─July 12, August 10, and September 9─will all be supermoons.
去年六月，一次滿月佔據各大頭條。新聞媒體稱之「超級月亮」，因為它較 2013 年其他次滿月還大百分之十四、亮度多百分之三十。在世界各地，人們到外頭驚嘆超級月亮的亮度。如果你以為一次超級月亮已經夠亮了，那來個三次呢？2014 年夏日的滿月－－在七月十二日、八月十日和九月九日－－都將是超級月亮。
The scientific term for the phenomenon is "perigee moon." Full moons vary in size because of the oval shape of the moon's orbit. The moon follows an elliptical path around Earth with one side, perigee, about 50,000 kilometers closer than the other, apogee. Full moons that occur on the perigee side of the moon's orbit seem extra big and bright. This coincidence happens 3 times in 2014. On July 12 and September 9, the moon becomes full on the same day as perigee. On August 10 it becomes full during the same hour as perigee, arguably making it an extra supermoon.
此現象的科學專有名詞為「近地點滿月」。因為月球運行軌道的那橢圓形狀，滿月在尺寸方面有所變化。月球遵循橢圓路線繞行地球，其中一端，「近日點」，大約比另外一端，「遠地點」距離地球更近五萬公里。在月球運行軌道上近地點那端發生的滿月似乎特別龐大、明亮。這種巧合於 2014 年會發生三次。在七月十二日和九月九日，月亮在抵達近地點的同一天變滿月。八月十日時月亮在抵達近地點的同一小時變圓，更可說是使它變成特大超級月亮。
It might seem that such a sequence must be rare. "Not so," says Geoff Chester of the U.S. Naval Observatory. "Generally speaking, full moons occur near perigee every 13 months and 18 days, so it's not all that unusual," he says. "In fact, just last year there were three perigee moons in a row, but only one was widely reported. In practice, it's not always easy to tell the difference between a supermoon and an ordinary full moon. A 30% difference in brightness can easily be masked by clouds and haze. Also, there are no rulers floating in the sky to measure lunar diameters. Hanging high overhead with no reference points to provide a sense of scale, one full moon looks about the same size as any other." Chester expects most reports of giant moons this summer to be illusory.
看來這樣的一連串事件肯定非比尋常。「並不見然」美國海軍天文臺的 Geoff Chester 表示。「一般來說，滿月每十三個月又十八天會在近地點附近發生，所以這一切並不那麼不尋常。」他說。「事實上，光去年就相繼有三次近地點滿月，但只有一次被大幅報導。實際上，要分辨超級月亮及一個平常的滿月並不總是簡單的。百分之三十的亮度差異可能輕易被雲和霧矇蔽。此外，也沒有漂浮在半空測量月球直徑的尺。高掛在上頭沒有參考點以提供比例感，一次滿月看起來大概和任何其他的一般大。」Chester 認為今夏大部分有關巨大月亮的報導都是虛構。
''The moon illusion is probably what will make people remember this coming set of full moons more than the actual view of the moon itself," he says. The illusion occurs when the moon is near the horizon. For reasons not fully understood by astronomers or psychologists, low-hanging moons look unnaturally large when they beam through trees, buildings, and other foreground objects. When the moon illusion amplifies a perigee moon, the swollen orb rising in the east at sunset can seem super indeed.
"I guarantee that some folks will think it's the biggest moon they've ever seen if they catch it rising over a distant horizon, because the media will have told them to pay attention to this particular one," says Chester. "There's a part of me that wishes that this supermoon moniker would just dry up and blow away, like the Blood Moon that accompanied the most recent lunar eclipse, because it tends to promulgate a lot of misinformation," admits Chester.
「我保證有些人會認為這是他們見過最大的月亮，如果他們撞見它從遠方地平線升起，因為媒體將會已經告訴人們要特別去留意這一個。」Chester 說。「有部分的我希望這個超級月亮的綽號就這樣消失然後消散，像是伴隨最近一次月蝕的血月，因為這樣容易散布大量錯誤資訊」Chester 承認道。
"However, if it gets people out and looking at the night sky, and maybe hooks them into astronomy, then it's a good thing." Indeed it is. Mark your calendar─July 12, August 10, and September 9─and enjoy the super-moonlight. For more news about big bright things in the night sky, visit science.nasa.gov.
- 「一般而言」- Generally Speaking
"Generally speaking, full moons occur near perigee every 13 months and 18 days, so it's not all that unusual," he says.
- 「一連串，連續」- In A Row
"In fact, just last year there were three perigee moons in a row, but only one was widely reported."