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23 October, 2000

Inside the hourglass: a young massive star reveals its hatchlings

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Inside the hourglass: a young massive star reveals its hatchlings

Credit: Image courtesy of W. Brandner
University of Hawaii, IfA, Honolulu, HI. USA

(collaborators: Laird Close (ESO, U of. Arizona) and Dan Potter, Claude Roddier, Franç ois Roddier, Buzz Graves, Malcolm Northcott (UofH, IfA)

MWC 1080 is a young star with about 8 times the mass of our Sun and about 10,000 times the luminosity of the Sun. It has an age of less than 1 Million years and is located in constellation Cassiopeia at a distance of 6,000 lightyears. MWC 1080 is embedded in a dark cloud and illuminates a bright nebulosity. Previous studies reported a handful of young low-mass stars associated with MWC 1080. For the first time MWC 1080 has now been observed with high-spatial resolution from the ground using a technique called adaptive optics.

The new adaptive optics observations reveal that the nebulosity is quite symmetric and is shaped like an hourglass viewed from its side. The color gradients (blue to red) visible in the adaptive optics image are typical signatures of scattered light and indicate that the hourglass is actually a hollow structure illuminated from within by MWC 1080. Fast bipolar outflows have removed cloud material along the axis of the hourglass and cleared the view to less massive stars associated with MWC 1080.

The new observations suggest that up to 100 faint, young low-mass objects cluster around MWC 1080, i.e. ten times as many stars as had previously been assumed. The young star cluster has a diameter of 3 lightyears. Its stellar density is several 100 times higher than the stellar density near the Sun (3 lightyears corresponds to slightly less than the distance from the Sun to its nearest neighbor). Still, astronomers expect the cluster to gradually dissolve over the next 10 to 20 Million years. The cluster members will then become ``free-floating'' field stars.

Technical description:

The observations were obtained in October 1996 with an experimental 13 element curvature sensing adaptive optics system and the infrared camera QUIRC. Both the camera and the adaptive optics system have been developed at the University of Hawaii. Curvature sensing is a novel adaptive optics technique, which was conceived by Prof. Francois Roddier and his group in 1991. The image presented above is a composite color image of near infrared J, H, and K band observations. The pixel scale is 0.035"/pixel and the field of view 44" times 35". The spatial resolution in the K-band is about 0.15 arcsec, i.e. 320 Astronomical Units or 4 times the size of the solar system. Individual 60s exposures (3 times 3 dither positions) were coadded to produce the final image with an effective exposure time of 9min in each band. The faintest objects detected in all three bands have J=20mag.

next week: To be announced shortly

editors: François Ménard, Jean-Charles Cuillandre & Catherine Dougados
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