M8中的“沙漏”

The Hourglass Nebula in M8, NGC 6523
AAO image reference AAT 31

Top left is NE. Image width is about 3 arc min
Image and text © Anglo-Australian Observatory, Photograph by David Malin.


At the heart of the Lagoon Nebula in Sagittarius lies the diminutive Hourglass Nebula. This extremely bright object is associated with the blue star alongside it, named Herschel 36 after its discoverer. Herschel described M8 as 'A noble nebula' and 'a fine and complicated nebula', but he was clearly intrigued by the Hourglass which he compared to the nucleus of the Andromeda nebula, M31 as 'decidedly not stellar'.

The tiny bright nebula that captures Herschel's attention is energised partly by the bright star H36 and partly by a star which, for the present, remains hidden in the pinched waist of the Hourglass. The obscured star is only visible in infrared light which can penetrate the thick clouds of dust seen over much of the Lagoon Nebula and clearly evident in a recent Hubble Space Telescope photograph. These stars are probably less than 10,000 years old, about as old as the Hourglass itself, and are evidence of recent star-formation in this very dusty and active region.