Is this a giant hole in space? I show a picture similar to this as I ask this question to students and audiences that I host in my planetarium. Most people answer that it is a black hole, or dark matter, or dark energy, or something strange like that. But the amazing thing is that it is actually a thick cloud of dust that is opaque, letting no visible light from the distant stars pass through. The funny thing is that the cloud is transparent in infrared light, but in the visible spectrum it highlights something interesting about the universe:...
When the Rosetta spacecraft entered orbit around comet 67P/Churyumov-Gerasimenko, first images captured deep circular depressions among the other surface features. Now that the orbiter has taken significant observations of the comet’s surface, the science team has concluded that these depressions are actually sinkholes that form by the same processes that form sinkholes 500 Million kilometers away here on Earth. Sinkholes on Earth form when subsurface material is eroded away. Though not initially visible on the surface, the material falls deep underground leaving a circular cavern. Once enough material has eroded away, the top of the cavern collapses, leaving a large...
