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(IAAC) Fwd: Hubble Reveals Previously Unseen Shocks



Very marginally topical, as I suspect this object is well outside the
visual range of (any) amateur telescopes. On the other hand, sketching
and logging such features in *brighter* protoplanetaries is a favorite
pastime of many of us! Clear skies,
Lew Gramer <owner-netastrocatalog@atmob.org>
------- Forwarded Message
X-Listname: Astronomy List <ASTRO-L@uwwvax.uww.edu>
From: Ron Baalke <baalke@zagami.jpl.nasa.gov>
Subject: Hubble Reveals Previously Unseen Shocks
To: astro-l@uwwvax.uww.edu (Astronomy List)
Date: Fri, 24 Aug 2001 12:50:50 -0700 (PDT)
ESA Science News
http://sci.esa.int
Contacts:
Lars Lindberg Christensen
Hubble European Space Agency Information Centre, Garching, Germany
Phone: +49-(0)89-3200-6306
Cellular (24 hr): +49-(0)173-38-72-621
E-mail:lars@eso.org
Valentin Bujarrabal
Observatorio Astronomico Nacional, Spain
Phone: +34-91-8855060
E-mail: bujarrabal@oan.es
24 Aug 2001
Hubble reveals previously unseen shocks
A new, detailed Hubble image of a planetary nebula in the making shows for
the first time the complex gas structures predicted by theory. Astronomers
are thrilled by observations showing the violent gas collisions that give
rise to supersonic shock fronts. 
Stars like our Sun will eventually expel most of their material out into a
planetary nebula. This is in the process of happening to an object called
OH231.8+4.2 -- a proto-planetary nebula surrounding a cool and dying star.
The system is better known as the Calabash Nebula because of its peculiar
shape. Another nickname for this object -- the Rotten Egg Nebula -- is
derived from the large amount of sulphur compounds present, which would
certainly produce an unpleasant smell if one could smell in space. 
The nebula is composed of gas ejected by the central star and subsequently
accelerated in opposite directions. The gas (coloured yellow in the image)
has reached tremendous velocities of up to one and a half million kilometres
per hour. The ejection process is so efficient that most of the stellar mass
is now contained in these bipolar gas structures. 
A team of Spanish and American astronomers has used the NASA/ESA Hubble
Space Telescope to study how the gas stream rams into the surrounding
material (shown in blue). Such interactions are believed to dominate the
formation process in planetary nebulae. Due to the high speed of the gas,
shock-fronts are formed on impact and these heat the surrounding gas.
Although computer calculations have predicted the existence and structure
of such shocks for some time, the observational evidence has so far been
poor. 
This new Hubble image reveals the shocks in impressive detail. Using filters
that only let through light from ionised hydrogen and nitrogen atoms,
astronomers have been able to distinguish the warmest parts of the gas heated
by the violent shocks and have found that they form a complex double-bubble
shape. The bright yellow-orange colours in the picture show how the high- 
speed gas is flowing from the star -- like two supersonic speeding bullets
ripping through a medium in opposite directions. The central star itself is
hidden in the dusty band at the centre. "This is the first time that these
shock components have been seen clearly in such a nebula," says Valentin
Bujarrabal from the Observatorio Astronomico Nacional in Spain. "The deep,
high-resolution images show the complex structure of the shocks in great
detail, which we can now compare with predictions from computer models." 
"In the image we can see how the shocks have broken through the surrounding
gas. We believe we can see both of the shock components we expect -- the
forward and the backward shockwaves," states Valentin Bujarrabal. 
Much of the gas flow observed today seems to stem from a sudden acceleration
that took place only about 800 years ago. The astronomers believe that in
yet another 1000 years from now the Calabash Nebula will evolve into a fully
developed planetary nebula -- like a butterfly emerging from its cocoon. 
The Calabash Nebula is 1.4 light-years along its longest extent and located
in an open stellar cluster some 5000 light-years away in the constellation
Puppis. 
The Hubble image was taken shortly before Christmas 2000 with the WFPC2
instrument (Wide Field and Planetary Camera 2) in four different filters.
Here, light from 791 nm is displayed in red (exposure time 900 s), 675 nm
in green (900 s), while combined light from hydrogen (656 nm) and ionised
nitrogen atoms (658 nm) are shown as blue (14,700 s). 
Credit: ESA & Valentin Bujarrabal (Observatorio Astronomico Nacional, Spain) 
Notes for editors:
The Hubble Space Telescope is a project of international co-operation between
ESA and NASA. 
Members of the group of scientists involved in these observations are:
Valentin Bujarrabal, Javier Alcolea (Observatorio Astronomico Nacional,
Spain), Carmen Sanchez Contreras and Raghvendra Sahai (Jet Propulsion
Laboratory, Pasadena, USA). 
USEFUL LINKS FOR THIS STORY
* News release textfile
  http://sci2.esa.int/hubble/docs/heic0111.txt
* News release PDF
  http://sci2.esa.int/hubble/docs/heic0111.pdf
* More on planetary nebulae (from Vincent Icke)
  http://www.strw.leidenuniv.nl/~icke/html/VincentPN.html
* Earlier ESA/NASA News release about infrared observations of the Rotten Egg
  http://hubble.esa.int/hubble/news/index.cfm?aid=31&cid=630&oid=12601
* Hydrodynamical Simulation (simulated images of planetary nebulae)
  http://www.msi.umn.edu/Projects/twj/jetcol.html
IMAGE CAPTION:
[http://sci.esa.int/hubble/gallery/new_searchresult.cfm?ooid=28164&imgid=12318]
This new, detailed, Hubble image shows a planetary nebula in the making -- a
proto-planetary nebula. A dying star (hidden behind dust and gas in the centre
of the nebula) has ejected massive amounts of gas. Parts of the gas have
reached tremendous velocities of up to one-and-a-half million kilometres per
hour. 
Shown in blue is light from hydrogen and ionised nitrogen arising from
supersonic shocks where the gas stream rams into the surrounding material.
The image shows for the first time these complex gas structures which are
predicted by theory. 
The Hubble image was taken shortly before Christmas 2000 with the WFPC2
instrument (Wide Field and Planetary Camera 2) in four different filters.
Here, light from 791 nm is displayed in red (exposure time 900 s), 675 nm
in green (900 s), while combined light from hydrogen (656 nm) and ionised
nitrogen atoms (658 nm) are shown as blue (14,700 s).
Credits: ESA & Valentin Bujarrabal (Observatorio Astronomico Nacional, Spain)
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