Last night's flight didn't last very long since a crucial piece of the telescope,
called the chopping secondary, did not work. Observing in the infrared (light with
wavelengths between about 1 and 1000 micrometers, and far redder than the reddest light
we see with our eyes) is difficult since everything at room temperature glows brightly at
these wavelengths. It is similar to trying to observe stars with you eyes during the day.
To accomplish this difficult task, we use a mirror which rocks back and forth ,
alternately putting the object we want to observe and blank sky on our detectors. The
mirror moves back and forth 7 times per second, and we have programmed our computers to
read the light intensity in our spectrometer* at the same rate. This technique enables us
to measure signals that are 10,000 to 100,000 times weaker than the general glow of our
surroundings. The moving mirror is called a chopper, and it was this part of the
telescope that was not working.
The KAO staff will most likely be able to fix the chopper so we can have a good flight
on Monday to do the observations planned for last night. If the chopper had worked, we
would have observed a few more bright infrared stars in icy regions, similar to t hose on
the first flight on May 5. We also had a group of objects on the list which are
completely different. Instead of showing the chemical nature of the material surrounding
the star by absorbing light from the star, we can tell what is around the stars by the
light that the gas emits, having been excited by ultraviolet (bluer than our eyes can see)
light from the stars. We have evidence that this material is similar to the soot that
comes out of car exhaust and leaves the black marks you see on the road. They are called
polycyclic arom atic hydrocarbons (PAHs) and are very large molecules, especially by
astronomical standards, composed entirely of carbon and hydrogen. The observations we had
planned would test this idea by searching for emission features which others at NASA Ames
have found in laboratory spectra of PAHs. Finding these new features in the spectra of
the objects we will look at with the KAO telescope will confirm that these molecules are
indeed PAHs. We will then be able to use spectra of PAH molecules to determine the kinds
of environments in which the molecules can exist. It may be that when the earth was
formed, PAHs were included and became the building blocks for more complex organic
molecules which eventually led to life on our planet.
* (Note by Edna DeVore) The spectroscope is the instrument attached to the KAO
telescope which allows astronomers to spread out the infrared radiation like a prism or
diffraction grating spreads out visible light into a band of colors cal led the spectrum.
When the infrared radiation is spread out, astronomers can look at a small piece of the
spectrum, and see bright (emission) or dark (absorption) lines. These strength of the
lines (the "signal strength") is stored as numbers in a computer for later analysis and
comparison with the spectra of dust and ice viewed by spectroscopes in the laboratories
at NASA Ames. By comparing the spectra of astronomical objects with the spectra of dust
and gas that is of known composition, the astronomers are able to identify the
composition of the dust and gas in space.
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