All-Sky Map in Galactic Coordinates
of Radioactive Al-26
How Did the Elemental Composition
of the Universe Evolve?
- Why do we observe the types and quantities of chemical elements in
the universe revealed by astronomy? This is one of the most fundamental
questions facing astronomers. Determining how the elements were created
- the field of nucleosynthesis - draws from a range of studies,
from the Big Bang to the formation and evolution of our solar system.
- Light elements - those up to lithium on the periodic table -
were mainly created in the Big Bang. Measurement of the abundances of these
elements can give scientists important clues to the nature and evolution
of the early universe. In particular, measurement of the ratio of the normal
isotope of hydrogen to its heavier isotope known as deuterium, will provide
important insight into primordial nucleosynthesis. Missions such as Lyman
FUSE (Far Ultraviolet Spectroscopic Explorer) will provide this measurement
to far greater accuracy than previously possible.
- As galaxies formed, stars began processing this primordial matter into
heavier elements within the nuclear furnaces of their cores. In this manner,
elements up to Carbon, Nitrogen and Oxygen in the periodic table are formed.
The injection of these materials to the interstellar medium can occur through
stellar winds or in more dramatic fashion as a result of explosive events
like novae and supernovae. It is in the latter types of events that heavier
elements, up to Iron on the periodic table are formed. The production of
even heavier elements may be produced by these explosive events through
the capture of additional neutrons. Sensitive x-ray spectrometers are capable
of detecting line emission for all elements heavier than carbon. In addition,
radiation due to the radioactive decay of these nucleosynthetic products
has been measured by the COMPTEL instrument on the Compton Gamma-Ray Observatory.
The intensity of this radiation, and its distribution throughout the galaxy,
will be the focus of future missions.
- In the future, it will be important to continue to design x-ray and
gamma-ray instruments capable of providing high-resolution spectroscopy
and fine imaging capabilities to further constrain not only the intensities
and spatial resolution, but also the velocity distribution of these nucleosynthetic
byproducts. This information will reveal the clearest picture we can hope
to obtain on the chemical evolution of our own galaxy.
AXAF, CHIEFS, FUSE, HIMS, HTXS, HUBE, INTEGRAL