page_title: Shadow
hierarchical_section_title: Shadow
caption_attribution_description: English: These new NASA/ESA Hubble Space Telescope images capture a rare occurrence as three of Jupiter’s largest moons parade across the giant gas planet’s banded face. The image on the left shows the Hubble observation at the beginning of the event. On the left is the moon Callisto and on the right, Io. The shadows from Europa, which cannot be seen in the image, Callisto, and Io are strung out from left to right. The image on the right shows the end of the event, approximately 42 minutes later. Europa has entered the frame at lower left with slower moving Callisto above and to the right of it. Meanwhile Io — which orbits significantly closer to Jupiter and so appears to move much more quickly — is approaching the eastern limb of the planet. Whilst Callisto’s shadow seems hardly to have moved Io’s has set over the planet’s eastern edge and Europa’s has risen further in the west. The movement of the moons is shown in the video created from Hubble stills.
context_page_description: A shadow is a dark area on a bright surface. It is caused by something blocking a source of light. A shadow's outline, called a silhouette, will have the same shape as the object blocking the light.
  Depending on the light source, or sources, a wide range of effects can be produced. A point source of light casts only a simple shadow, called an "umbra". A "penumbra" is the region in which only a portion of the light source may be blocked. If there is more than one light source, there will be several shadows, with the overlapping parts darker, and various combinations of brightness or even colors. The more diffuse the lighting is, the softer and more indistinct the shadow outlines become, until they disappear. The lighting of an overcast sky produces few visible shadows,
  Astronomical shadows are usually sharp. This is because in space the light usually does not go through an atmosphere.
context_section_description: A shadow is a dark area on a bright surface. It is caused by something blocking a source of light. A shadow's outline, called a silhouette, will have the same shape as the object blocking the light.
  Depending on the light source, or sources, a wide range of effects can be produced. A point source of light casts only a simple shadow, called an "umbra". A "penumbra" is the region in which only a portion of the light source may be blocked. If there is more than one light source, there will be several shadows, with the overlapping parts darker, and various combinations of brightness or even colors. The more diffuse the lighting is, the softer and more indistinct the shadow outlines become, until they disappear. The lighting of an overcast sky produces few visible shadows,
  Astronomical shadows are usually sharp.  This is because in space the light usually does not go through an atmosphere.
caption: Three moons (Callisto, Europa and Io) and their shadows parade across Jupiter
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