A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Astronomy and Astrophysics » Astronomy Misc
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Revealing the Beast Within: Deeply Embedded Massive Stellar ClustersDiscovered in Milky Way Powerhouse (Forwarded)



 
 
Thread Tools Display Modes
  #1  
Old July 22nd 03, 04:56 PM
Andrew Yee
external usenet poster
 
Posts: n/a
Default Revealing the Beast Within: Deeply Embedded Massive Stellar ClustersDiscovered in Milky Way Powerhouse (Forwarded)

ESO Education and Public Relations Dept.

Contacts:

Nicole Homeier
ESO-Garching
Germany
Phone: +49 89 3200 6418
email:

Joao Alves
ESO-Garching
Germany
Phone: +49 89 3200 6503
email:


Joao Alves will be at the IAU General assembly in Sydney
(Australia) during the week of July 21 to 25, 2003 and may
be reached via the IAU Press Office.

----------------------------------------------------------------------------
The full text of this Press Release, with two photos (ESO PR
Photos 21a-b/03) and all related links, is available at:

http://www.eso.org/outreach/press-re.../pr-20-03.html
----------------------------------------------------------------------------

For immediate release: 21 July 2003

ESO Press Release 20/03

Revealing the Beast Within

Deeply Embedded Massive Stellar Clusters Discovered in Milky Way
Powerhouse

Peering into a giant molecular cloud in the Milky Way galaxy --
known as W49 -- astronomers from the European Southern Observatory
(ESO) have discovered a whole new population of very massive
newborn stars. This research is being presented today at the
International Astronomical Union's 25th General Assembly held in
Sydney, Australia, by ESO-scientist Joao Alves.

With the help of infrared images obtained during a period of
excellent observing conditions with the ESO 3.5-m New Technology
Telescope (NTT) at the La Silla Observatory (Chile), the
astronomers looked deep into this molecular cloud and discovered
four massive stellar clusters, with hot and energetic stars as
massive as 120 solar masses. The exceedingly strong radiation
from the stars in the largest of these clusters is "powering" a
20 light-year diameter region of mostly ionized hydrogen gas (a
"giant HII region").

W49 is one of the most energetic regions of star formation in
the Milky Way. With the present discovery, the true sources of
the enormous energy have now been revealed for the first time,
finally bringing to an end some decades of astronomical
speculations and hypotheses.

Giant molecular clouds

Stars form predominantly inside Giant Molecular Clouds which
populate our Galaxy, the Milky Way. One of the most prominent
of these is W49, which has a mass of a million solar masses.
It is located some 37,000 light-years away and is the most
luminous star-forming region known in our home galaxy: its
luminosity is several million times the luminosity of our
Sun. A smaller region within this cloud is denoted W49A --
this is one of the strongest radio-emitting areas known in
the Galaxy.

Massive stars are excessive in all ways. Compared to their
smaller and ligther brethren, they form at an Olympic speed
and have a frantic and relatively short life. Formation sites
of massive stars are quite rare and, accordingly, most are
many thousands of light-years away. For that reason alone,
it is in general much more difficult to observe details of
massive-star formation.

Moreover, as massive stars are generally formed in the main
plane of the Galaxy, in the disc where a lot of dust is present,
the first stages of such stars are normally hidden behind very
thick curtains. In the case of W49A, less than one millionth of
the visible light emitted by a star in this region will find
its way through the heavy intervening layers of galactic dust
and reach the telescopes on Earth.

And finally, because massive stars just formed are still very
deeply embedded in their natal clouds, they are anyway not
detectable at optical wavelengths. Observations of this early
phase of the lives of heavy stars must therefore be done at
longer wavelengths (where the dust is more transparent), but
even so, such natal dusty clouds still absorb a large
proportion of the light emitted by the young stars.

Infrared observations of W49

Because of this observational obstacle, nobody had ever looked
deep enough into the central most dense regions of the W49A
molecular cloud -- and nobody really knew what was in there.
That is, until Joao Alves and his colleague, Nicole Homeier
decided to obtain "deep" and penetrating observations of this
mysterious area with the SofI near-infrared camera on the
3.5-m New Technology Telescope (NTT) at the ESO La Silla
Observatory (Chile).

A series of infrared images was secured during a spell of good
weather and very good atmospheric conditions (seeing about
0.5 arcsec). They clearly show the presence of a cluster of
stars at the centre of a region of ionized hydrogen gas (an
"HII-region") measuring 20 light-years across. In addition,
three other smaller clusters of stars were detected in the
image.

Altogether, the ESO astronomers were able to identify more than
one hundred heavy-weight stars inside W49A, with masses greater
than 15 to 20 times the mass of our Sun. Among these, about
thirty are located within the 20 light-year central region and
about ten in each of the three other clusters.

The discovery of these hot and massive stars solves a
long-standing problem concerning W49A: the exceptional
brightness (in astronomical terminology: "luminosity") of the
entire region requires the energetic output from about one
hundred massive stars, and nobody had ever seen them. But
here they are on the deep and sharp SofI images!

Formation scenarios

The presence of such a large number of very massive stars
spread over the entire region suggests that star formation
in the various regions of W49A must have happened rather
simultaneously from different seeds and not, as some theories
propose, by a "domino-type" chain effect where stellar winds
of fast particles and the emitted radiation of newly formed
massive stars trigger another burst of star formation in the
immediate neighbourhood.

The present research results also imply that star formation
in W49A began earlier and extends over a larger area than
previously thought.

Joao Alves is sure that this news will be received with
interest by his colleagues: "W49A has long been known to
radio astronomers as one of the most powerful star-forming
region in the Galaxy with 30 or so massive baby-stars of the
O-type, very deeply embedded in their parental cloud. What
we have found is in fact quite amazing: this stellar maternity
ward is much bigger than we first thought and it has not
stopped forming stars yet. We now have evidence for no less
than more than one hundred such stars in this region, way
beyond the few dozen known until now".

Nicole Homeier adds: "Above all, we uncovered four massive
clusters in there, with stars as massive as 120 times the
mass of our Sun -- real 'beasts' that bombard their
surroundings with incredibly intense stellar winds and strong
ultraviolet light. This is not a nice place to live -- and
imagine, this is all inside our so-called 'quiet Galaxy'!"

More information

The research described in this press release is presented in
a research article in the professional research journal
Astrophysical Journal ("Uncovering the Beast: Discovery of
Embedded Massive Stellar Clusters in W49A" by Joao Alves
and Nicole Homeier, Volume 589, pp. L45-L49). It is also
one of the topics addressed by Joao Alves during his talk
given at the General Assembly of the International
Astronomical Union in Sydney on Tuesday, July 22, 2003.

----------------------------------------------------------------------------
ESO Press Information is available on Receive email notification
the WWW at about important news from ESO -
http://www.eso.org/outreach/press-rel/. subscribe to the
----------------------------------------------------------------------------
(c) ESO Education & Public Relations Department
Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
----------------------------------------------------------------------------

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Electric Gravity&Instantaneous Light ralph sansbury Astronomy Misc 8 August 31st 03 02:53 AM


All times are GMT +1. The time now is 05:41 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.