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Explanation: What could cause a nebula to appear square? No one is quite sure. The hot star system known as MWC 922, however, appears to be embedded in a nebula with just such a shape. The featured image combines infrared exposures from the Hale Telescope on Mt. Palomar in California, and the Keck-2 Telescope on Mauna Kea in Hawaii. A leading progenitor hypothesis for the square nebula is that the central star or stars somehow expelled cones of gas during a late developmental stage. For MWC 922, these cones happen to incorporate nearly right angles and be visible from the...

Explanation: Twenty five years ago, the brightest supernova of modern times was sighted. Over time, astronomers have watched and waited for the expanding debris from this tremendous stellar explosion to crash into previously expelled material. A clear result of such a collision is demonstrated in the above time lapse video of images recorded by the Hubble Space Telescope between 1994 and 2009. The movie depicts the collision of an outward moving blast wave with the pre-existing, light-year wide ring. The collision occurred at speeds near 60 million kilometers per hour and shock-heats the ring material causing it to glow. Astronomers...

Explanation: What's causing those odd rings in supernova 1987A? Twenty five years ago, in 1987, the brightest supernova in recent history was seen in the Large Magellanic Clouds. At the center of the above picture is an object central to the remains of the violent stellar explosion. Surrounding the center are curious outer rings appearing as a flattened figure 8. Although large telescopes including the Hubble Space Telescope monitor the curious rings every few years, their origin remains a mystery. Pictured above is a Hubble image of the SN1987A remnant taken last year. Speculation into the cause of the rings...