March 23, 2011
On your birthday, the Earth completed another orbit — 584 million miles traveled since your last celebration.
MWC 922: The Red Square Nebula
Birthday · March 23, 2011
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APOD published March 23, 2011. Credit: Peter Tuthill (Sydney U.) & James Lloyd (Cornell). A publication-date match, not a photo taken on your date. Independent of NASA.
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 above 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 sides. Supporting evidence for the cone hypothesis includes radial spokes in the image that might run along the cone walls. Researchers speculate that the cones viewed from another angle would appear similar to the gigantic rings of supernova 1987A, possibly indicating that a star in MWC 922 might one day itself explode in a similar supernova.
Image credit: Peter Tuthill (Sydney U.) & James Lloyd (Cornell)