Newsletter

Title : THE WATERY BIRTH OF STARS
Author : Weizmann Institute of Science
Date :

THE WATERY BIRTH OF STARS

Weizmann Institute of Science - http://www.weizmann.ac.il/

Logically, stars should not exist. They are born when clouds of
interstellar gas collapse inwardly under their own weight, growing denser
and hotter until nuclear fusion causes them to emit energy in the form of
light. However, since heat forces matter to expand, this hot contracting
gas could be expected to immediately move outward again, preventing star
formation from ever reaching completion.

To resolve this paradox, scientists have postulated the existence of a
water-based "cooling system" that regulates the temperature of
interstellar clouds, enabling the contraction to continue. Now a Weizmann
Institute study reported in Physical Review Letters provides experimental
evidence that the billions of stars that populate our firmament indeed
had a watery birth.

Researchers have theorized that water molecules in interstellar clouds
exert a cooling effect by colliding with the gas particles and absorbing
their energy that is later released in the form of radiation. But
attempts to observe water in the stars using Earth-bound telescopes have
always been thwarted by the presence of water particles in our planet's
atmosphere.

Scientists have, however, detected a similar substance that could be an
intermediary product in water formation: hydronium, or H3O+, which
contains three hydrogen atoms (as compared with water's two), along with
one oxygen atom.

Drs. Daniel Zajfman and Oded Heber of the Weizmann Institute's Particle
Physics Department have now completed an experiment demonstrating that
water is indeed formed in interstellar clouds in a reaction involving
hydronium. The experiment was carried out at an advanced installation
called an ion storage ring at the University of Aarhus, Denmark, in
collaboration with Aarhus researchers Dr. Lars Andersen, Dr. Dror Kella
and Lisa Vejby- Christensen. The scientists simulated the physical and
chemical conditions in interstellar clouds and showed that water is
formed there in a reaction between a charged hydronium molecule and a
single electron. They also found that a permanent ratio between water and
hydronium molecules is maintained in these clouds.

Special equipment aboard the U.S. research satellite SWAS, to be launched
later this year, will be used to further explore the new findings without
the interference of the Earth's atmosphere, in particular by directly
measuring the quantity of water in the forming stars.

Dr. Zajfman holds the Martha S. Sagon Career Development Chair at the
Weizmann Institute. Funding for the study was provided by the Israel
Science Foundation and the Danish National Research Foundation.

The Weizmann Institute of Science is a major center of scientific
research and graduate study located in Rehovot, Israel.