BACKGROUND ON THE ORION STAR FORMING REGION
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One of the best known constellations in the sky is Orion, the Hunter, 
easily indentifiable by the "Orion's Belt", three bright blue stars
which cut through the middle of the constellation. Below the belt lies
one of the best known nebulae in the sky, the Orion nebula. The nebula
is a blister on the edge of a huge cloud of gas and dust known as the 
Orion Molecular Cloud. This cloud, invisible at the wavelengths which 
our eyes can percieve, contains enough raw materials to produce 200,000 
stars and is one of the most active regions of our Galaxy in which stars
are currently being born.

Infrared images of the cloud reveal an abundance of newly formed stars. 
One of the best studied portions of the cloud is the Orion BN/KL region, 
just behind the Orion Nebula. Over the past 25 years, infrared astronomers
have studied this area in detail and found that the activity in this region
is dominated by a single star in the process of forming. One of the most 
surprising aspects of star-birth is that, as a star accumulates material 
from the surrounding cloud, it also eject material at 10's of miles PER SECOND
into the surrounding gas. Typically stars eject the material in the direction 
of their North and South poles, and astronomers refer to these as "bipolar 
outflows." As the outflowing material crashes into the surrounding gas, it 
creates shock waves, supersonic disturbances which heat and compress the 
surrounding gas. These shock waves have been observed using the light given
off by molecular hydrogen (H2), the gas which makes up most of the cloud, 
and in the light given off by carbon monoxide (CO), another common molecule 
in the cloud. 

One of the predictions that astronomers have made over the past 25 years is 
that the heated gas in these shock waves will produce copius amounts of water.
There are oxygen atoms in the cloud, and when they are heated to temperatures 
around 200 Fahrenheit they should combine with the hydrogen molecules to form 
water (H2O). Despite this strong prediction, it is very difficult to observe 
water coming from these shock waves. The Earth's own atmosphere is so rich in 
water that any water emissions coming from space are easily absorbed in the 
Earth's upper atmosphere and can never reach telescopes on the ground. The 
only way to observe water vapor emissions is to take a telescope to high 
altitude (i.e. in an airplane) or into space. The observations we are 
reporting were done using an orbiting infrared telescope, the Infrared Space 
Observatory.     

The water concentration fond in Orion is consistent with the interpretation
that all of available oxygen in the cloud was converted to water by the 
shock wave. This is an important result simply because we always thought this
would be the case but could not confirm it until now. But it's important for
other reasons, as well. Water molecules are very efficient at radiating away
the heat in hot gas, and so the presence of the molecules may allow the 
gas compressed by the shock waves to remain compressed (rather than rebounding
like a squashed baloon). These dense knots of gas can then serve as the kernels
from which a subsequent generation of stars can form. So the presence of water
make make it easier to form stars. In addition, we are interested in what the
source of the water in our own solar system may be. We may be witnessing the
same process in Orion which happened when our own solar system was forming. So
the water in our solar system may have been formed in shock waves from 
another star before our our Sun was formed. In addition, the presence of that
water may have assisted in the collapse of the interstellar gas which 
ultimately formed our star/planet system.