火山

2020 March 14 Moonrise and Mountain Shadow Image Credit & Copyright: Daniel Lopez (El Cielo de Canarias) Explanation: What phase of the Moon is 3.14 radians from the Sun? The Full Moon, of course. Even though the Moon might look full for several days, the Moon is truly at its full phase when it is 3.14 radians (aka 180 degrees) from the Sun in ecliptic longitude. That’s opposite the Sun in planet Earth’s sky. Rising as the Sun set on March 9, only an hour or so after the moment of its full phase, this orange tinted and slightly flattened Moon still looked full. It was photographed opposite the setting Sun from Teide National Park on the Canary Island of Tenerife. Also opposite the setting…

2020 January 14 Evidence of an Active Volcano on Venus Image Credit: NASA, JPL-Caltech, ESA, Venus Express: VIRTIS, USRA, LPI Explanation: Are volcanoes still active on Venus? More volcanoes are known on Venus than Earth, but when Venusian volcanoes last erupted is not directly known. Evidence bolstering very recent volcanism on Venus has recently been uncovered, though, right here on Earth. Lab results showed that images of surface lava would become dim in the infrared in only months in the dense Venusian atmosphere, a dimming not seen in ESA’s Venus Express images. Venus Express entered orbit around Venus in 2006 and remained in contact with Earth until 2014. Therefore, the infrared glow (shown in false-color red) recorded by Venus Express for Idunn Mons and featured…

2019 June 9 大型火山的三角形阴影 图片来源及版权：Juan Carlos Casado (TWAN) 说明：这座火山的影子，怎么看起来是三角形的？泰德火山实际的形状，和它三角形影子所暗示的有别，并非是完美的金字塔形。此外，三角形的影子不是泰德火山所特有，而是站立于巨峰或火山峰顶时，会经常见到的景象。关键的因素之一，是日落（或日出）时，观测者是顺着向地平线伸展的长长影子远眺。即使巨大的火山是个完美的立方体，影子也会是长方形的，而且影子向远方的地平线伸展时，会逐渐缩减成锥形，就如同平行的火车铁轨会聚在远处一样。这张壮丽的主题影像，前景有西班牙．加那利群岛．特内里费岛的Pico Viejo火山口。接近满相的月亮，则是摄于月全食过后不久。 A Triangular Shadow of a Large Volcano Image Credit & Copyright: Copyright: Juan Carlos Casado (TWAN) Explanation: Why does the shadow of this volcano look like a triangle? The Mount Teide volcano itself does not have the strictly pyramidal shape that its geometric shadow might suggest. The triangle shadow phenomena is not unique to the Mt. Teide, though, and is commonly seen from the tops of other large mountains and volcanoes. A key reason for the strange dark shape is that the observer is looking down the long corridor of a sunset (or sunrise) shadow that extends to the horizon. Even if the huge volcano were a perfect cube and the resulting shadow were a…