This Echo is READ ONLY !   NO Un-Authorized Messages Please!
 ~~~~~~~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

European Space Agency

Press Release

ESA on the trail of the earliest stars
======================================
27 January 2003

Somewhere in the distant, old Universe, a population of stars hide
undetected. They were the first to form after the birth of the
Universe and are supposed to be far bigger in mass than any star
visible today. 

Astronomers know they must have been out there: only in this way could 
they solve the riddle of the origin and composition of stars in
today's Universe. A couple of ESA missions will help astronomers
search for this elusive population. 

When the Universe formed, there was just hydrogen and helium.
Chemical elements such as oxygen, carbon, iron and so on were forged
later, in the nuclear furnaces at the hearts of stars and then cast
into space at the end of the star's life. Astronomers call everything
that is heavier than helium a 'metal'. All stars we can observe today
contain metals. The youngest contain the most metals and astronomers
call them population I stars. The oldest contain only some metals and
astronomers call these population II stars.

Where do these metals come from? Astronomers have theorised that a
first generation of stars, which they call population III, must have
existed in the early Universe. This first generation of stars must
have formed using only hydrogen and helium, the only elements
available in the early cosmic history. After living for 'just' a
million years, they extinguished themselves, showering the metals they 
had created into space. The heavy elements lay dormant until they were 
collected into the next generation of stars and the first galaxies, 
sometime later.

The theory of population III stars suggests they are long dead in the
local Universe. How can their existence then be confirmed? In the most 
distant realms of space, where what we observe is either very old or 
even extinguished, some signs of their existence might still be 
glimpsed. One mission that will help considerably in the search is the 
James Webb Space Telescope (JWST), ESA's collaboration with NASA to 
replace the Hubble Space Telescope with a six-metre-class telescope. 
There are many questions for it to answer.

"We don't really know what the first generation of stars are like and
we don't know where exactly they formed," says Peter Jakobsen, ESA's
Study Scientist for the JWST. "One of the biggest questions is whether 
the first stars formed in clumps or as isolated individuals.  If they 
clumped, we'll be able to see them much more easily and further away 
than if they didn't." Even if JWST does not see the first stars 
directly, it will give astronomers an invaluable clue about how far 
away they are, allowing them to refine their theories.  New research 
suggests that even if the population III stars are extremely far away, 
JWST would see them exploding as supernovae, at the ends of their 
individual lives.

In addition, some astronomers suspect that some gamma-ray bursts
(GRBs) are created by the death of these earliest stars. Ironically,
we may therefore already be seeing the farewell detonation of some
population III stars. ESA's new gamma-ray observatory, Integral, is
perfectly placed to shed light on these violent events. It will
indirectly help provide clues about population III stars. "I suspect
that in the next ten years, we'll know the answers to at least some of 
our questions about what went on in the early Universe," says
Jakobsen. This includes learning more about the existence and role of
the earliest stars.


JWST
----
The James Webb Space Telescope (JWST) is a collaboration between ESA
and NASA. It is the successor to the Hubble Space Telescope and, with
a six-metre mirror, it will be almost three times the size of HST.
Engineers have designed the JWST to work best at infrared wavelengths. 
This will allow it to study the very distant Universe, looking for the 
first stars and galaxies that ever emerged. Current plans call for its 
launch in 2010.


Integral
--------
The International Gamma Ray Astrophysics Laboratory (Integral) is the
first space observatory that can simultaneously observe celestial
objects in gamma rays, X-rays, and visible light. Integral was
launched on a Russian Proton rocket in October 2002 into a highly
elliptical orbit around Earth. Its principal targets are powerful
phenomena known as supernova explosions, regions of the Universe
thought to contain black holes and violent explosions known as
gamma-ray bursts. In particular, when a gamma-ray burst goes off in
Integral's field of view, an automatic alert is sent to the world's
ground-based observatories within 30 seconds. This allows for rapid
follow-up observations that are needed to analyse these mysterious
phenomena.

For more information, please contact:

Peter Jakobsen
ESA - Study Scientist JWST
Tel: +31 (0)71 565 3614
Email: peter.jakobsen{at}esa.int

ESA - Science Programme Communication Service
Tel: +31 (0)71 565 3273
Email: irina.bruckner{at}esa.int

 - End of File -
================

---