| In the programme of photon
dominated regions (PDRs) the submillimeter satellite ODIN
will observe the best studied dense interface regions of
ionized HII regions, reflection nebulae, low-density UV
PDRs, as well as X-ray PDRs, in order to get a better
understanding of the physical and chemical effects of the
incident radiation flux on PDRs. The ODIN stallite will
also probe which role H2O and O2 have in the overall oxygen
abundance and ion chemistry. |
| Orion is a key target for the
submillimeter satellite ODIN. The Orion Nebula marks the
location of one of the highest concentrations of young
stars in the sky. It is the best studied star-forming
region in the sky, and continues to yield new insights as
more technically advanced telescopes equipped with new
frequency ranges are focused on it. |
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The bright nebula M16 (or Eagle nebula) is
located 7000 light years from Earth (some 3 degrees away
from the bright star Altair). Massive young stars
illuminate and pump out huge amounts of UV radiation, which
heats the nebula through the photoelectric effect. Three
darker pillars in the center of the nebula are
concentrations of dust and gas and have been eroded by the
UV radiation. Only the densest parts of the cloud, which
are well shielded from UV through dust particles have
survived. Hubble Space telescope has zoomed on these dust
pillars (see the enlargement below). The left pillar is
three light years long. The turquoise background is
artificially colored in order to better show the bright
rims of the pillars. |
| The ODIN research team of photodominated
regions will observe many bright interaction zones between
UV radiation and dense cloud material. Especially we will
search for thermal water vapor, which is an efficient
coolant of warm gas and which should be enhanced in warm
photodominated regions like the ones shown in these
Figures. |
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