Spectral analysis of Saturn
Keio Senior High School Earth Science Club
Shun SHINOZAKI*1, Yutaro AO*2, Ryousuke NYUI*3, Atsushi TAKEI*４
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1. Introduction
Our investigation is about the spectral analysis of Saturn. We had two objectives. First, to investigate the atmospheric element of Saturn. Second, to calculate the relative velocity between Saturn’s ring and the main body.
2. Why did we need the spectrum of the Saturn’s ring?
As the ring is mainly composed of ice, sunlight is either reflected or passes through the ice. Therefore, we hypothesized that the spectrum of the ring would be the same as that of the sun. Consequently, if we compare the spectrum of the main body with that of the ring, we can find the atmospheric element proper to Saturn.
3. How to investigate
First, by using makali’i PC software, we digitized the spectrum image of both the main body and the ring in order to measure their respective brightness. Second, by using BeSpec, we converted the data to obtain spectral intensity, and then processed it through Excel. Third, we calculated the spectral intensity of the main body as well as the ring to fit both spectrums. Then we divided the body’s spectral intensity by the ring’s spectral intensity to get the reflection rate.
4. Result①
We found the absorption lines of methane in 6200Å 7250Å and 7900Å. Therefore, we can conclude that there must be methane in Saturn’s atmosphere.
5. How to calculate relative velocity
We compared Body’s spectrum with Ring’s to investigate the gaps between them. Then we calculated relative velocity by using formula of the Doppler Effect. Then, we determined the center of absolution by using Hα line. We found out that Body’s minimal value was 870 pixels. Secondly, we drew approximate curve, calculated the local minimum and its coordinate. As a result that the gap of minimum value between upper ring’s and Body’s was 0.57pixels and that between lower’s and Body’s was 0.44pixels so the average was 0.51pixels. We substituted 0.51pixels and 3.19Å. 3.19Å means the width of one pixel. After that we substituted the wavelength of Hα. It is 6562.81Å. “c” means the speed of light. Therefore v is equal to about 74km/s.
5. Result②
Calculated relative velocity in this investigation is about 74km/s, and on the other, the referred data is about 17.6km/s. There is a big error in calculation between them. Why? From our point of view, this is because the observation equipment was low dispersion, so we couldn’t observe the Doppler Effect very well.
6. Conclusion
l As the result of the spectral analysis, we can conclude that there must be methane in Saturn’s atmosphere.
l Calculated relative velocity is about 74km/s, but, the referred data is about 17.6km/s. From our point of view, this difference is because the observation equipment was low dispersion, so we couldn’t observe the Doppler Effect very well.
References
[1]Jupiter Spectra Project
[2]NASA JPL Spectrum Date Base
http://spec.jpl.nasa.gov/
[3]http://astro.ysc.go.jp/saturn-ring-opening-sun- earth.jpg
[4]Cosmic Spectral Museum-Optical-
http://www.shokabo.co.jp/sp_e/optical/solar/saturn/saturn.htm
[5]Published by Hamashima book store
“New Stage Graphical book of Earth Science
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