1\10 Hubble Discovers Powerful Laser Beamed From Chaotic Star

FOR RELEASE: January 10, 1995

CONTACT:  Ray Villard
          Space Telescope Science Institute, Baltimore, MD
          (Phone: 410-338-4514)

          Sveneric Johansson
          University of Lund, Sweden
          (Phone: 46-4612-6097)

          Kris Davidson
          University of Michigan, Minneapolis
          (Phone: 612-624-5711)

PRESS RELEASE NO.: STScI-PR96-06


HUBBLE DISCOVERS POWERFUL LASER BEAMED FROM CHAOTIC STAR

Darth Vader take heart.  Astronomers have discovered a powerful
ultraviolet laser beam, several times brighter than our Sun, shooting
toward Earth from a super-hot "death star."

The observations, made with NASA's Hubble Space Telescope have
identified a gas cloud that acts as a natural ultraviolet laser, near
the huge, unstable star called Eta Carinae -- one of most massive and
energetic stars in our Milky Way Galaxy.  The interstellar laser may
result from Eta Carinae's violently chaotic eruptions, in which it
blasts parts of itself out into space, like an interstellar geyser.

Sveneric Johansson, a specialist in atomic spectroscopy at the
University of Lund in Sweden, has been analyzing Hubble Space
Telescope observations of Eta Carinae, made with the Goddard
High-Resolution Spectrograph (GHRS).  Johansson reports that his
interpretation is not yet proven, but that it appears to be the most
plausible explanation of the data.

A laser, (which is an acronym for Light Amplification by Stimulated
Emission of Radiation) creates an intense coherent beam of light when
atoms or molecules in a gas, liquid or solid medium, force an incoming
mix of wavelengths (or colors) of light to work in phase, or, at the
same wavelength.  Laser light is analogous to a loud, single-pitch
note, while normal white light is analogous to audio static on a
radio.

The  ultraviolet laser in Eta Carinae shines by the same physics that
led to the invention of artificial optical lasers in 1960 and similar,
microwave devices called masers, in 1954.  Natural masers have been
seen in space since  the mid-1960s, and an infrared laser was
discovered around the hot young star MWC 349, earlier this year.

"Each ultraviolet light particle (photon) generated in the Eta Carinae
laser has almost 700 times the energy of a photon in MWC 349, and so
the total energy output is far greater," said Kris Davidson of the
University of Minnesota. "Natural infrared lasers are very rare in
space; this ultraviolet laser is even more difficult for nature to
arrange, and nothing like it has been seen before."

Eta Carinae is several million times brighter than the Sun, and one
hundred times as massive.  The superstar, located 8,000 light-years
away underwent a colossal outburst 150 years ago.  Radio and X-ray
astronomers have recently detected smaller outbursts in gas around the
star.  Previous HST observations found that the gas from the earlier
giant explosion now forms a bizarre double-lobed nebula pinched in the
center by a ragged equatorial disk.

In a Hubble Space Telescope investigation led by Davidson, including
nine other collaborators in the U.S., Germany, and Sweden, ultraviolet
light from the same gas is being closely studied. (This ultraviolet
emission is in the wavelength range that is absorbed by the Earth's
ozone layer, and hence must be studied from space).

Team member Johansson was particularly interested in emission by iron
ions that seemed unnaturally bright in the new data.  He has found the
only plausible explanation of the relative brightness of the iron
emission lines is a natural laser emitting at energetic ultraviolet
light.  "The spectrum of singly-ionized iron (an iron atom with one
electron removed) has almost a thousand known energy states and some
of these are apparently well-suited to making a laser effect," said
Davidson.

The gas was ejected along the equatorial  plane of Eta Carinae about
100 years ago.  Moving outward at about 100 thousand miles per hour,
the gas is now about  60 billion miles, (100 billion kilometers), or
700 times the distance between Earth and the Sun.

The discovery could provide scientists with a new tool for studying
gas recently shot out of unstable stars, interactions of radiation
with atoms in space, and atomic structure in cosmic gas clouds.

The researchers are planing to use Hubble's Faint Object Spectrograph
to observe the same gas, covering a wider range of wavelengths than
the GHRS data.  This will hopefully lead to a better understanding of
how the monster laser actually works.

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