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MEISSA

One of the fainter stars to carry a proper name, Meissa is the Lambda star of Orion. At faint third magnitude, Meissa is not important in star-lore for its brightness, but for its position, as (with a pair of other stars) it marks the head of the ancient Hunter. Its name, apparently something of a mistake, seems to have been taken from an older (no longer much used) name for Alhena in Gemini (Gamma Geminorum), showing how confused star names can be. More confusing, the significance of the name is rather mysterious, possibly meaning (from Arabic) "the Proudly Marching One." Who that might be is not known. The star may not immediately overwhelm the eye, but it certainly does its surroundings. Meissa is a double that consists of a hot (35,000 Kelvin!) fourth magnitude class O star four seconds of arc away from a still-pretty-warm sixth magnitude B star ("only" 27,000 Kelvin). Though both stars (easily seen in a small telescope) are white, various observers have seen lovely colors, showing how the eye can be fooled. From its distance of 1000 light years, we find the hot, bright component to radiate 65,000 times more energy than our Sun (including its ultraviolet radiation), while the other one radiates about 5500 times the solar light. Meissa is also the luminary of a small cluster. But it is most- famed for a huge surrounding ring of gas an amazing 150 light years across that is illuminated (ionized) by the star, showing the immense power of these (fortunately very rare) hot class O stars. This structure is set within an even larger ring of interstellar dust and molecules. The rings may be leftover material from which Meissa formed, compressed by the action of the O star. It is also possible that the rings were created from the blast of another star that exploded in the neighborhood of Meissa a few million years ago. No one really knows. With an immense mass nearly 25 times that of the Sun, explosion is almost certain to be the fate of Meissa's brighter component. The fainter one, however, is right at the edge of those that explode and those that turn into heavy white dwarfs, condensed stars about the size of the Earth. The explosion of the more-massive star, however, will outdo even that, as its stellar remnant will collapse to the size of a small town and perhaps appear to future astronomers as a rapidly spinning neutron star, or pulsar. (Thanks to Monica Shaw, who helped research this star.)