New stars shed light on the past (Forwarded)

ESA News
http://www.esa.int

8 Jan 2007

New stars shed light on the past

A new image from the Hubble Space Telescope shows N90, one of the
star-forming regions in the Small Magellanic Cloud. The rich populations
of infant stars found here enable astronomers to examine star forming
processes in an environment that is very different from that in our own
Milky Way.

This new image taken with the Advanced Camera for Surveys onboard the
NASA/ESA Hubble Space Telescope depicts bright blue newly formed stars
that are blowing a cavity in the centre of a fascinating star-forming
region known as N90.

N90 is located in the wing of the Small Magellanic Cloud, in the
constellation of Tucana, approximately 200,000 light-years away from the
Earth. Its proximity makes it an exceptional laboratory to perform
in-depth studies of star formation processes and their evolution in an
environment close to that in the early Universe. Dwarf galaxies such as
the Small Magellanic Cloud, with small numbers of stars compared to our
own Milky Way, are considered to be the primitive building blocks of
larger galaxies. The study of star formation within this dwarf galaxy is
particularly interesting to astronomers because its primitive nature means
that it lacks a large percentage of the heavier elements that are forged
in successive generations of stars through nuclear fusion.

The high energy radiation blazing out from the hot young stars in N90 is
eroding the outer portions of the nebula from the inside, as the diffuse
outer reaches of the nebula prevent the energetic outflows from streaming
away from the cluster directly. Because N90 is located far from the
central body of the Small Magellanic Cloud, numerous background galaxies
in this picture can be seen, delivering a grand backdrop for the stellar
newcomers. The dust in the region gives these distant galaxies a
reddish-brown tint.

Hubble has often been used to observe star birth regions, but they are
rarely as stunning and fascinating as N90. At the heart of N90 lies NGC
602, a relatively isolated star cluster whose environment is a close
analogue to what existed in the early Universe. The existence of dark
clouds of dense dust and the cluster being rich in ionized gas suggest the
presence of ongoing star formation processes.

Ridges of dust and gaseous filaments are seen towards north-west (in the
upper left part of the image) and towards south-east (in the lower right
hand corner). Magnificent elephant trunk-like dust pillars point towards
the hot blue stars and are tell-tale signs of their eroding effect.

An international team of astronomers, led by Antonella Nota of the
European Space Agency and the Space Telescope Science Institute in the US,
has discovered a population of small newborn stars scattered across the
picture. Observable around the bright blue stars at the centre of the
image, these stars have caught astronomers' attention because they are
still forming from gravitationally collapsing gas clouds. Furthermore,
they have not yet contracted to the point where their cores are hot enough
to begin converting hydrogen into helium.

In this region it is possible with Hubble to trace how the star formation
started at the centre of the cluster and propagated outwards, with the
youngest stars still forming today along the dust ridges.

This image was presented by Lynn Redding Carlson, Johns Hopkins
University, at the 2007 January meeting of the American Astronomical
Society in Seattle.

Notes for editors:

The Hubble Space Telescope is a project of international cooperation
between ESA and NASA.

The other science team members a L. Carlson (JHU), M. Sirianni
(STScI/ESA), E. Sabbi (STScI), M. Tosi (INAF - Bologna Observatory), J.S.
Gallagher (Univ. of Wisconsin), M. Meixner (STScI), M. Clampin (GSFC), S.
Oey (Univ. of Michigan), A. Pasquali (MPIAE), L. Smith (STScI/Univ.
College London), and R. Walterbos (New Mexico State Univ.).

Image credit: NASA, ESA, and the Hubble Heritage Team
(STScI/AURA)-ESA/Hubble Collaboration

Acknowledgement: A. Nota (ESA/STScI) and L. Carlson (JHU)

Links:

* NASA's photo release
http://hubblesite.org/newscenter/arc...leases/2007/04

Contacts:

Antonella Nota
ESA/Space Telescope Science Institute, Baltimore, USA
Tel: +1-410-338-4520
E-mail:

Lynn Redding Carlson
Johns Hopkins University, Baltimore, USA
Tel: +1-410-338-3014
E-mail:

Lars Lindberg Christensen
Hubble/ESA, Garching, Germany
Tel: +49-(0)89-3200-6306
Cellular: +49-(0)173-3872-621
E-mail:

Ray Villard
Space Telescope Science Institute, Baltimore, USA
Tel: +1-410-338-4514