The great nebula in Orion

The great nebula in Orion

Fig. 16.5 . This nebulosity, the brightest in the sky and designated M 42 or NGC 1976, forms the middle star of Orionís sword. It is 1,500 light years away, a relatively short distance compared with the 100,000 light-year width of our Milky Way Galaxy. Gravity has already pulled some of the interstellar gas into dense concentrations, igniting the celestial fires of newborn stars. The massive stars in the center of the nebula have blown out most of the gas and dust in which they formed, providing a clearer view of other young stars, some of them still embedded in protoplanetary disks in which future planetary systems can form. Hot, massive stars also ionize the nearby interstellar gas, causing this debris of other long-dead stars to fluoresce with red light. More than 3,000 stars of various sizes appear in this crisp, detailed image that was taken from the Hubble Space Telescope in 2005. (Courtesy of NASA/ESA/Massimo Robberto, STScI and the Hubble Space Telescope Orion Treasury Project Team.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University