三星凌木及交食

2021年8月21日

Triple Transit and Mutual Events
Image Credit & Copyright: Christopher Go

Explanation: These three panels feature the Solar System’s ruling gas giant Jupiter on August 15 as seen from Cebu City, Philippines, planet Earth. On that date the well-timed telescopic views detail some remarkable performances, transits and mutual events, by Jupiter’s Galilean moons. In the top panel, Io is just disappearing into Jupiter’s shadow at the far right, but the three other large Jovian moons appear against the planet’s banded disk. Brighter Europa and darker Ganymede are at the far left, also casting their two shadows on the gas giant’s cloud tops. Callisto is below and right near the planet’s edge, the three moons in a triple transit across the face of Jupiter. Moving to the middle panel, shadows of Europa and Ganymede are still visible near center but Ganymede has occulted or passed in front of Europa. The bottom panel captures a rare view of Jovian moons in eclipse while transiting Jupiter, Ganymede’s shadow falling on Europa itself. From planet Earth’s perspective, similar mutual events, when Galilean moons occult and eclipse each other, can be seen every six years or so when Jupiter is near its own equinox.

Tomorrow’s picture: RS Ophiuchi

三星凌木及交食
影像提供与版权: Christopher Go

说明: 这幅三格影像，呈现8月15日从地球菲律宾宿雾市看出去，所见的太阳系最大气态巨行星——木星之景观。这些摄于那天精准计时的望远镜影像，呈现由木星的伽利略卫星担纲演出的精采凌越及交食事件。在最上端的影板里，右缘附近的木卫一即将进入木星的影子里，不过其他3颗伽利略卫星还悬浮在木星的带纹盘面上方。其中，较亮的木卫二与较暗的木卫三在左侧，并在这颗气态巨行星的云顶投下2团暗影，而木卫四则在木星盘的右下缘附近，形成三星凌木的景观。在中间的影板里，中心处的木卫二及木卫三暗影依然可见，但木卫三掩食通过木卫二前方。最下端的影板，则记录了罕见的木卫彼此交食、木卫三的暗影落在木卫二并同步凌越木星的景象。从地球看出去，类似的木卫掩食及交食的事件，每隔6年当木星在它的春分或秋分时就会发生。

明日的图片: RS Ophiuchi