Scientists are celebrating the thousandth scientific publication from ESA’s
Infrared Space Observatory. ISO is fast becoming one of the world’s most
productive space missions, even though its operational life ended in 1998.

ISO was the first space observatory able to see the sky in infrared light. Using
its eyes, we have discovered many new phenomena that have radically changed our
view of the Universe.

Everybody knows that when something is heated it glows. However, things also
glow with a light our eyes cannot detect at room temperature: infrared light.
Infrared telescopes do not work well on the Earth’s surface because such light
is absorbed by the atmosphere.

ISO looked at the cold parts of the universe, usually the ‘cold and dusty’
parts. It peered into clouds of dust and gas where stars were being born,
observing for the first time the earliest stages of star formation. It
discovered, for example, that stars begin to form at temperatures as low as -250
C or less. Scientists were able to follow the evolution of dust from where it is
produced (that is, old stars — the massive ‘dust factories’) to the regions
where it forms new planetary systems. ISO found that most young stars are
surrounded by discs of dust that could harbour planets. The observatory also
analysed the chemical composition of cosmic dust, thereby opening up a new field
of research, ‘astromineralogy’.

With ISO we have been able to discover the presence of water in many different
regions in space. Another new discipline, ‘astrochemistry’, was boosted when ISO
discovered that the water molecule is common in the Universe, even in distant
galaxies, and complex organic molecules like benzene readily form in the
surroundings of some stars.

"ISO results are impacting most fields of astronomical research, almost
literally from comets to cosmology," explains Alberto Salama, ISO Project
Scientist. "Some results answer questions. Others open new fields. Some are
already being followed up by existing telescopes; others have to await future
facilities."

When ISO’s operational life ended, in 1998, its observations became freely
available to the world scientific community via ISO’s data archive. In May 2003
the ‘milestone number’ of 1000 scientific papers was reached. Even now ISO’s
data archive remains a valuable source of new results. For example, some of the
latest papers describe the detection of water in ‘protostars’, which are stars
in the process of being born, and studies of numerous nearby galaxies.

"Of course we were confident ISO was going to do very well, but its actual
productivity has been far beyond our expectations. The publication rate does not
even seem to have peaked yet! We expect many more results," Salama says.

Note for editors

ISO’s data archive contains scientific data from about 30,000 observations.
Astronomers from all over the world have downloaded almost eight times the
equivalent of the entire scientific archive. As much as 35% of all ISO
observations have already been published at least once in prestigious scientific
journals.

ESA is now preparing to continue its infrared investigation of the Universe. The
next generation of infrared space observatories is already in the pipeline. ISO
is to be followed by the NASA SIRTF observatory to be launched later this year.
Then, in 2007, ESA will follow up the pioneering work of ISO with the Herschel
Space Observatory, which will become the largest imaging telescope ever put into
space.

ISO

The Infrared Space Observatory (ISO) was launched in 1995 and operated from
November that year to May 1998, when it ran out of the coolant needed to keep
its detectors working. At the time it was the most sensitive infrared satellite
ever launched and made particularly important studies of the dusty regions of
the Universe, where visible light telescopes can see nothing. ESA will reopen
its examination of the infrared Universe when Herschel is launched in 2007.

Herschel

Herschel will be the largest space telescope when, in 2007, it is launched on an
Ariane-5 rocket, together with ESA’s cosmology mission, Planck. Herschel’s
3.5-metre diameter mirror will collect longwave infrared radiation from some of
the coolest and most distant objects in the Universe. These include forming
stars and galaxies.

For more information, contact:

ESA Communication Department
Media Relations Office
Paris, France
Tel: +33 (0)15369 7155
Fax: +33 (0)15369 7690

Dr Alberto Salama, ESA ñ ISO Project Scientist
VILSPA – Villafranca, Spain
Tel : + 34 91 8131374

For more information about ISO and the ESA Science Programme, visit:
http://www.esa.int/science

For more information about ESA, visit:
http://www.esa.int

Further information:

ESA Media Relations Service
Tel: +33.(0)1.5369.7155
Fax: +33.(0)1.5369.7690

Related articles

* New study reveals twice as many asteroids as previously believed
http://www.esa.int/esaCP/ESAASPF18ZC_index_0.html
* A game reserve for brown-dwarf hunters — ISO finds 30 ‘failed
stars’ in nearby stellar nursery
http://www.esa.int/esaCP/ESARMQZK0TC_index_0.html
* Cold comfort for newborn stars
http://www.esa.int/esaCP/ESAPHA2VMOC_FeatureWeek_0.html

Related links

* ESA Science website
http://www.esa.int/science
* ISO
http://www.esa.int/science/iso

IMAGE CAPTIONS:

[Image 1:
http://www.esa.int/export/esaCP/SEMLSTXO4HD_index_1.html]
ISO finds steamy cloud in interstellar space.

Credits: ESA

[Image 2:
http://www.esa.int/export/esaCP/SEMLSTXO4HD_index_1.html#subhead1]
This is such an unusual view of the impressive M16 nebula, also known as ‘The
Eagle’, that even the most devoted sky-lovers will be surprised. It shows
exactly what in the best known pictures of this famous nebula remains invisible:
huge amounts of the cold dust that enshrouds newborn stars.

Credits: ESA/ISOGAL team

[Image 3:
http://www.esa.int/export/esaCP/SEMLSTXO4HD_index_1.html#subhead2]
Three of the most massive young stars in this stellar nursery are easy to find
in this image: one in the centre of the right-hand-side border; a second one in
the middle of a comet-shaped nebula in the lower-right of the image; and
finally, one in the middle of the small nebula close to the centre-right. Other
point-like sources are also young stars and ‘protostars’ — stars that are still
‘growing’ by ‘sucking in’ gas from the cloud. In the dust surrounding the
newborn stars there are plenty of small carbonaceous grains. The exact nature of
these grains is still a matter of debate. The young stars heat these grains and
make them radiate infrared light (seen in the image as extended halos). This
image was taken by Alain Abergel (Institut d’Astrophysique Spatiale, Paris) with
the infrared camera, ISOCAM, on board ISO. The colour image was constructed from
a 7.7 micron infrared exposure (shown as blue), and a 14.5 micron infrared
exposure (shown as red). The green colour is a combination of the blue and red
exposures.

Credits: ESA ISO/ISOCAM/Alain Abergel (Abergel et al.(1996) A&A 315, L329)