Transcript Document 7713422

Spectral analysis of Saturn
Keio Senior High School
Earth Science Club
Shun Shinozaki Yutaro Ao Ryosuke Nyui Atsushi Takei
Objectives
1.To investigate the atmospheric element of
Saturn.
2.To calculate the relative velocity between
Saturn’s ring and the main body.
The spectral image of Saturn
Image source
http://www.astroarts.co.jp/news/2004/
03/02cassini/index-j.shtml
the slit
We dispersed the middle of
the Saturn as the upper chart.
Green・・・the spectrum of the main body
Purple・・・the spectrum of Saturn’s ring
Date:2006/11/24 Telescope: Takahashi 30cm reflector
Place: Gunma astronomical observatory
Why did we need the
spectrum of the Saturn’s ring?
The ring is mainly composed of ice.
→Sunlight is either reflected or passes through
the ice
→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.
How to investigate
1. 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.
2. By using BeSpec, we converted the data to obtain
spectral intensity, and then processed it through Excel.
3. 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.
Result
reflection
rate(%)
140
120
100
80
6200Å
60
c
7250Å
40
7900Å
20
0
5500
6000
6500
7000
7500
w avelength(Å)
Absolution by methane
8000
8500
Conclusion ①
As the result of the analysis , we found
the absorption line of methane.
Therefore…
We can conclude that there must be
methane in Saturn’s atmosphere.
How to calculate relative velocity ①
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.
We compared Hα wavelength at
body with same one at Ring to
investigate gaps between them by
using “makali’i”.
How to calculate relative velocity ②
We determined the center of absolution by Hα.
We found out that Body’s minimal value was 870 pixels.
How to calculate relative velocity ③
Minimum
of absorption line (upper Ring’s)
吸収線ピーク位置の推定（上）
formula of the Doppler Effect
⊿λ/λ=v/c(“c”means the speed of
light )
The wavelength of Hα is 6562.81Å
⇒(3.19･0.51)/6562.81=v/300000
∴v≒
74km/s
輝度
pixels
y = 36.838x2 - 64056x + 3E+07
1950
1900
1850
1800
1750
1700
1650
元データ date
original
多項式 (元データ)
polynomial
expression
866
868
870
872
874
X‐coordinate
Ｘ座標
869.43Å
Minimum of absorption line (lower Ring’s)
吸収線ピーク位置の推定（下）
pixels
輝度
We drew approximate
curves, calculated the local
minimum and its
coordinates.
The gap of minimal value is...
upper Ring:0.57 pixels
lower Ring:0.44 pixels
average: about 0.51 pixels
※one pixel 3.19 Å wide
3.19×0.51≒1.63
y = 31.85x2 - 55447x + 2E+07
1750
1700
1650
1600
1550
1500
1450
original date
元データ
polynomial
多項式
(元データ)
expression
866
868
870
872
X‐coordinate
Ｘ座標
874
870.44Å
Conclusion ②
calculated relative velocity in this investigation
→ about 74 km/s
A big error in calculation
the referred date→ about 18 km/s
Why?
Because the observation equipment was low
dispersion, so we couldn’t observe the Doppler
Effect very well.
References
Jupiter Spectra Project
NASA JPL Spectrum Date Base
http://spec.jpl.nasa.gov/
http://astro.ysc.go.jp/saturn-ring-opening-sunearth.jpg
http://www.shokabo.co.jp/sp_e/optical/solar/sa
turn/saturn.htm
Published by Hamashima book store
“New Stage Graphical book of Earth Science”
Acknowledgment
Toshihiko Hamane
(Gunma astronomical observatory)
Thank you very much for your great help !