Looking at our own Galaxy with different telescopes and in different
energies,
we can see why multiwavelength astronomy is important. Each of the images to
the right shows our Milky Way Galaxy, but each gives a different perspective
on it.
The infrared image taken by the Infrared
Astronomical Satellite (IRAS),
shows the center region of our Galaxy. The hazy, horizontal S-shaped
feature
that crosses the image is faint heat emitted by dust in the plane of the
solar system.
The
optical picture is one we may be most familiar with. It shows something
similar to what you would see if you drove out into the country in the
summer and looked towards the center of our Galaxy. Large optical
telescopes
can show us fine detail that our eyes are unable to resolve.
The X-ray image is from the ROSAT
All-Sky Survey. It shows
X-rays at energies of .75 keV. This image is dominated by the radiation
from the north polar spur and from the large-scale central region
of our Galaxy, which contains hot interstellar matter and tens of thousands of
unresolved point sources. Near the equator in the left half of the image, the
Cygnus superbubble becomes visible as a broken yellow and red ring.
The Vela supernova remnant is an
isolated red spot towards the right side of the image.
The
gamma-ray image includes all photons with energies greater than 100 MeV.
At these extreme energies, most of the celestial gamma-rays originate in
collisions of cosmic rays with hydrogen nuclei in interstellar clouds.
Confused by the different units used for measuring the different energies of
light? Click here
for a handy chart that explains this!
What specific information do observations in different energies give us?
Well, let's examine the Crab Nebula in four different energies of light and
see how different the information from each observation is.
The
radio
image of our Galaxy, taken at a frequency of 408 MHz, is a mosaic of
data taken
by the Jodrell Bank, Effelsberg and Parkes radio telescopes. Near this
frequency, cosmic radio waves are generated by high energy electrons
spiraling along magnetic fields. This false color image shows the
Galactic
plane running horizontally through the center, however, you will find that
no stars are visible. Instead, many of the bright sources near the plane are
distant pulsars, star forming regions, and supernova remnants, while the
grand looping structures are pieces of bubbles blown by local stellar
activity. External galaxies like Centaurus A, located above the plane to the
right of center, and the Large Magellanic Cloud (LMC) (below and right)
also shine in the radio sky.
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