Space Infrared Telescope Facility (SIRTF): The Herschel Experiment. Dr. Michelle Thaller [email protected] SIRTF Science Center California Institute of Technology sirtf.caltech.edu. Dr. Denise Smith Dan McCallister Origins Education Forum Space Telescope Science Institute.
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Where did we come from?Are we alone?
Space Infrared Telescope Facility
A Fortunate Accident
In 1800, while placing thermometers in each color of the solar spectrum, Herschel places his “control” thermometer just outside the red end of the spectrum.
Result: the thermometer outside the visible spectrum registered the highest temperature!
The first detection of invisible light, which Herschel called infrared (“beneath red”) light.
Objective: To perform a version of the experiment of 1800, in which a form of radiation other than visible light was discovered by the famous astronomer Sir Frederick William Herschel.
Target Audience: Grades 7-9, easily extended to higher grades (10-12)
Do not look directly at the Sun.
The thermometers will register differences almost immediately.
After approx. 10 minutes, the thermometers show a 10 degree difference:
The highest temperature is found outside the visible spectrum, where infrared light is falling on the thermometers.
The Herschel Experiment can be done in groups of 2 to 4. Team members can be assigned the following roles:
Useful discussion questions for the workshop (and classroom) setting:
For best results, do experiment in direct sunshine, when the Sun is high (noon). Putting the prism in the cut notch provides stability and easy rotation.
Glass prisms work much better than plastic ones (this is Herschel’s original prism).
Blacken the bulbs of the thermometers with black paint. Flat black spray paint works best, but even a black magic marker will yield results.
The experiment WILL NOT WORK without the paint (Herschel soot-blackened his thermometers in the original experiment).
Every object with a temperature above absolute zero radiates in the infrared.
Finding “brown dwarfs” helps us measure the mass of the universe.
Debris disks– signs of other solar systems?
Dust absorbs visible light and re-emits it in the infrared.
Some galaxies emit most of their light in the infrared.
Just as the pitch of a train whistle changes as it passes an observer, the observed wavelength of light emitted by a moving object also shifts.
Visible light from very distant objects is shifted to the infrared.
Infrared light is mostly absorbed by our atmosphere.
SIRTF Science Center,
California Institute of Technology
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Origins Education Forum
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