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July 24, 1996
COMPTEL Explores The Radioactive Sky
Credit :
The COMPTEL Collaboration,
Compton Gamma Ray Observatory,
NASA
Explanation:
Diffuse gas
clouds laced with radioactive aluminum atoms
(Al26) line the plane of our Milky Way
Galaxy!
How do we see them?
Relying on
the Compton Effect,
the COMPTEL instrument onboard NASA's
immense orbiting Compton Gamma Ray Observatory
can "see" the 1.8 million electron Volt
gamma rays emitted by the
radioactive decay.
COMPTEL's first ever survey
image of the entire sky in the light
of gamma rays produced by this exotic
radioactivity is shown above.
The Galactic plane
is horizontal, passing through
the Galactic center in the middle of the picture, as indicated by
the superposed coordinate grid.
The radioactive Al26 clouds are
seen to lie in clumps near the plane, with some slightly above and
below it. The brightest feature looks like a mysterious inverted "V", just
to the left of center.
Where do they come from?
Al26 decays to magnesium (Mg26) with
a half-life
of about a million years, a very short time compared to the
age of the Galaxy -- so the clouds
must have been produced relatively "recently".
COMPTEL astronomers are exploring
several origins for the radioactive clouds including
nuclear processing (nucleosynthesis) by aging massive stars
and supernova explosions.
Because they are generally thought to be associated with short lived massive
stars, the radioactive clouds are expected to be located near sites of
recent star formation.
(Note added in press:
Don't worry - the aluminum atoms in the foil in your
kitchen are Al27
and are not radioactive!)
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry
Bonnell (USRA).
NASA Technical Rep.:
Sherri
Calvo.
Specific rights apply.
A service of:
LHEA
at
NASA/
GSFC