What we can see today that the French astronomer and discoverer Jean-Jacques d’Ortous de Mairan didn’t know: M42 and 43 are really the same star-forming nebula. As seen from Earth, there is a dark lane of dust that appears between here and there.
This illustrates the importance of recognizing the dust and gas clouds are more similar until one realizes how they are lit. A reflection nebula is visible because light from nearby stars bounces off the gas and often a wispy mix of light and dark is seen in photographs. Dark nebulas have no illuminating star, of course.
M 43 has a large, young star illuminating the nebula from within, number 37061 in the Henry Draper catalogue. A five-digit number among thousands of five-digit numbers seems like a celestial body pretty far down a listing. HD 37061 is far from ordinary. It masses almost twenty times the sun, and its energy output surpasses the sun by twenty-six thousand, almost its catalogue number.
HD 37061 isn’t the only star within this nebula. 45 trillion miles deep, this gas cloud houses a small cluster of stars. Eventually the gas will be consumed or blown off into interstellar space. That cluster will emerge into view in a few hundred thousand years, open and not quite as pretty.
Almost all the time in science fiction movies or tv, when a nebula is part of the story, it is a flashy, colorful emission nebula. When a starship wants to hide, why don’t they choose a dark nebula?
Image credit: By NASA, ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble Space Telescope Orion Treasury Project Team – Hubble space telescope, M42 image cut out., Public Domain, https://commons.wikimedia.org/w/index.php?curid=2522052
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