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Post Info TOPIC: Menzel 3
Blobrana


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RE: Menzel 3
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Title: A silicate disk in the heart of the Ant
Authors: Olivier Chesneau (LG), Foteini Lykou (LG, Universtiy Manchester), Bruce Balick (Univ. Washington), Eric Lagadec (LG, Universtiy Manchester), Mikako Matsuura (Universtiy Manchester), Nathan Smith (Univ. California), Alain Spang (LG), Sebastian Wolf (MPIA), Albert A. Zijlstra (Universtiy Manchester)

We aim at getting high spatial resolution information on the dusty core of bipolar planetary nebulae to directly constrain the shaping process. Methods: We present observations of the dusty core of the extreme bipolar planetary nebula Menzel 3 (Mz 3, Hen 2-154, the Ant) taken with the mid-infrared interferometer MIDI/VLTI and the adaptive optics NACO/VLT. The core of Mz 3 is clearly resolved with MIDI in the interferometric mode, whereas it is unresolved from the Ks to the N bands with single dish 8.2 m observations on a scale ranging from 60 to 250 mas. A striking dependence of the dust core size with the PA angle of the baselines is observed, that is highly suggestive of an edge-on disk whose major axis is perpendicular to the axis of the bipolar lobes. The MIDI spectrum and the visibilities of Mz 3 exhibit a clear signature of amorphous silicate, in contrast to the signatures of crystalline silicates detected in binary post-AGB systems, suggesting that the disk might be relatively young. We used radiative-transfer Monte Carlo simulations of a passive disk to constrain its geometrical and physical parameters. Its inclination (74 degrees ± 3 degrees) and position angle (5 degrees ± 5 degrees) are in accordance with the values derived from the study of the lobes. The inner radius is 9 ± 1 AU and the disk is relatively flat. The dust mass stored in the disk, estimated as 1 x 10-5Msun, represents only a small fraction of the dust mass found in the lobes and might be a kind of relic of an essentially polar ejection process.

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Blobrana


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The Frugal Cosmic Ant

Skinny dusty disc found in the heart of the Ant Nebula

ESO PR Photo 22/07

ESO PR Photo 42/07
A Disc in the Ant Nebula
[Preview - JPEG: 400 x 276 pix - 63k]
[Normal - JPEG: 800 x 551 pix - 148k]
[Full Res - JPEG: 2141 x 1475 pix - 590k]
[Full Res - TIFF: 2141 x 1475 pix - 9.2M]



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Blobrana


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Posts: 131433
Date:
Ant Nebula
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Using ESO's Very Large Telescope Interferometer and its unique ability to see small details, astronomers have uncovered a flat, nearly edge-on disc of silicates in the heart of the magnificent Ant Nebula. The disc seems, however, too 'skinny' to explain how the nebula got its intriguing ant-like shape.
The Ant Nebula is one of the most striking planetary nebulae known. Planetary nebulae - whose name arises because most are spherical and looked like planets when they were first discovered through older, less powerful telescopes - are glowing structures of gas cast off by solar-like stars at the ends of their lives. The morphology of the Ant Nebula - a bright core, three nested pairs of bipolar lobes and a ring-like outflow - is so unique that it was nicknamed the 'Chamber of Horrors' of planetary nebulae in the late 1950s.
But how can a spherical star produce such complex structures? The answer, many astronomers think, requires understanding of the discs surrounding the central star. By their nature, these discs bear witness to the phenomena that lead to the asymmetrical structures of planetary nebulae.

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Blobrana


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Posts: 131433
Date:
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An amorphous silicate disc in the Ant nebula, Mz 3

Authors: O. Chesneau, F. Lykou, B. Balick, E. Lagadec, M. Matsuura, N. Smith, A. Spang, S. Wolf, and A. A. Zijlstra

Aims. We aim at getting high spatial resolution information on the dusty core of bipolar planetary nebulae to directly constrain the shaping process.
Methods. We present observations of the dusty core of the extreme bipolar planetary nebula Menzel 3 (Mz 3, Hen 2-154, the Ant) taken with the mid-infrared interferometer MIDI/VLTI and the adaptive optics NACO/VLT.
Results. The core of Mz 3 is clearly resolved with MIDI in the interferometric mode, whereas it is unresolved from the Ks to the N bands with single dish 8.2 m observations on a scale ranging from 60 to 250 mas. A striking dependence of the dust core size with the PA angle of the baselines is observed, that is highly suggestive of an edge-on disk whose major axis is perpendicular to the axis of the bipolar lobes. The MIDI spectrum and the visibilities of Mz 3 exhibit a clear signature of amorphous silicate, in contrast to the signatures of crystalline silicates detected in binary post-AGB systems, suggesting that the disk might be relatively young. We used radiative-transfer Monte Carlo simulations of a passive disk to constrain its geometrical and physical parameters. Its inclination (74° ± 3°) and position angle (5° ± 5°) are in accordance with the values derived from the study of the lobes. The inner radius is 9 ± 1 AU and the disk is relatively flat. The dust mass stored in the disk, estimated as 1 x  10^-5 solar masses, represents only a small fraction of the dust mass found in the lobes and might be a kind of relic of an essentially polar ejection process.

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-- Edited by Blobrana at 12:02, 2007-09-28

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Blobrana


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Date:
Menzel 3
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This panel of composite images shows part of the unfolding drama of the last stages of the evolution of sun-like stars. Dynamic elongated clouds envelop bubbles of multimillion degree gas produced by high-velocity winds from dying stars. In these images, Chandra's X-ray data are shown in blue, while green and red are optical and infrared data from Hubble.


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Ant Nebula/ Menzel 3, 3000 light years away in the constellation Norma.
Position(2000) RA 16h 17m 12.60s | Dec -51º 59' 08.00"
Credit: X-ray: NASA/CXC/RIT/J.Kastner et al.; Optical/IR: BD +30 & Hen 3: NASA/STScI/Univ. MD/J.P.Harrington; NGC7027: NASA/STScI/Caltech/J.Westphal & W.Latter; Mz 3: NASA/STScI/Univ. Washington/B.Balick

Planetary nebulas - so called because some of them resemble a planet when viewed through a small telescope - are produced in the late stages of a sun-like star's life. After several billion years of stable existence (the sun is 4.5 billion years old and will not enter this phase for about 5 billion more years) a normal star will expand enormously to become a bloated red giant. Over a period of a few hundred thousand years, much of the star's mass is expelled at a relatively slow speed of about 50,000 miles per hour.

This mass loss creates a more or less spherical cloud around the star and eventually uncovers the star's blazing hot core. Intense ultraviolet radiation from the core heats the circumstellar gas to ten thousand degrees, and the velocity of the gas flowing away from the star jumps to about a million miles per hour.

This high speed wind appears to be concentrated into opposing supersonic funnels, and produces the elongated shapes in the early development of planetary nebulas (BD+30-3639 appears spherical, but other observations indicate that it is viewed along the pole.) Shock waves generated by the collision of the high-speed gas with the surrounding cloud create the hot bubbles observed by the Chandra space telescope. The origin of the funnel-shaped winds is not understood. It may be related to strong, twisted magnetic fields near the hot stellar core.

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