MPEWG

天文観測の観点からの
「夜間の発光」についてのレビュー
(Review on Diffuse night sky brightness )
2013/7/16 MPEWG
秋谷 祐亮
「光」を利用する観測
•
イメージング観測;「見たま
ま」の様子を記録する→対象領
域の形状や大きさを調べる
•
分光観測;波長域を選ぶこと
で、対象領域の温度や組成を調
べる
•
きっちりと分けられるものでも
なく、2つが混ざったような観測
もある。
•
どちらにしても、観測したい
「光」以外にも(場合によって
は邪魔な)いろいろな光が存在
している。
∂ni ∂ni ∂T
Di K
+
−
+
ni
∂z
∂T ∂z
Hi H
A
K(z) =
[cm2 s−1 ]
n(z)
φi = −(Di + K)
(5)
夜空には発光源がいろいろある
(6)
神は言った。
∇·B = 0
∇×E = −
∇·D = ρ
∂B
∂t
∂D
∇×H = j+
∂t
そして光があった。
•
旧約聖書の創世記1章3節はともかく、Maxwellの式から電磁波
の伝搬が導かれる。
•
大気光観測を行う際に、大気光発光以外の光を考慮する必要が
ある。また、ソースからの「光」は必ずしも可視域には限らな
い。
•
参考レビュー論文:Ch. Leinert
et
al.
The
1997
reference
1
of diffuse night sky brightness (Astronomy &
Astrophysics Supplement Series 127, 1-99 (1998))
夜空には発光源がいろいろある
•
大気光観測を行う際に、
大気光発光以外の光を考
ASTRONOMY & ASTROPHYSICS
JANUARY I 1998, PAGE 1
SUPPLEMENT SERIES
慮する必要がある。ま
た、ソースからの「光」
は必ずしも可視域には限
Astron. Astrophys. Suppl. Ser. 127, 1-99 (1998)
The 1997 reference of di↵use night sky brightness?
Ch. Leinert1 , S. Bowyer2 , L.K. Haikala3 , M.S. Hanner4 , M.G. Hauser5 , A.-Ch. Levasseur-Regourd6 ,
I. Mann7 , K. Mattila3 , W.T. Reach8 , W. Schlosser9 , H.J. Staude1 , G.N. Toller10 , J.L. Weiland11 ,
J.L. Weinberg12 , and A.N. Witt13
1
2
3
4
らない。
5
6
7
8
9
10
•
11
参考レビュー論文:Ch.
Leinert et al. The 1997
reference of diffuse
night sky
brightness (Astronomy
& Astrophysics
Supplement Series 127,
1-99 (1998))
12
13
Max–Planck–Institut f¨
ur Astronomie, K¨
onigstuhl 17, D-69117 Heidelberg, Germany
Astronomy Dept., University of California, 601 Campbell Hall, Berkeley CA 94720, U.S.A.
Observatory, P.O. Box 14, FIN-00014 University of Helsinki, Finland
Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena CA 91109, U.S.A.
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218, U.S.A.
Service d’A´eronomie, BP. 3, F-91371 Verri`eres le Buisson, France
Max–Planck–Institut f¨
ur Aeronomie, Max-Planck-Straße 2, D-37191 Katlenburg-Lindau, Germany
Institut d’Astrophysique Spatiale, Universit´e Paris XI, 91405 Orsay Cedex, France
Astronomisches Institut, Ruhr-Universit¨
at Bochum, D-44780 Bochum, Germany
General Sciences Corporation, 6100 Chevy Chase Drive, Laurel, MD 20707, U.S.A.
Hughes STX, NASA/Goddard Space Flight Center Code 685.9, Greenbelt, MD 20771, U.S.A.
MK Industries, 2137E Flintstone Drive, Tucker, Georgia 30084, U.S.A.
Ritter Astrophys. Res. Center, University of Toledo, Toledo, OH 43606, U.S.A.
Received August 7; accepted September 8, 1997
Abstract. In the following we present material in tabular and graphical form, with the aim to allow the nonspecialist to obtain a realistic estimate of the di↵use night
sky brightness over a wide range of wavelengths from the
far UV longward of Ly↵ to the far-infrared. At the same
time the data are to provide a reference for cases in which
background brightness has to be discussed, including the
planning for space observations and the issue of protection
of observatory sites. We try to give a critical presentation
of the status at the beginning of 1997.
Key words: di↵use radiation — interplanetary
medium — atmospheric e↵ects — astronomical dabases:
miscellaneous — infrared: general — ultraviolet: general
Contents
1.
2.
3.
4.
5.
6.
Overview
Brightness units
Coordinate transformations
Total sky brightness
Tropospheric scattering
Airglow
6.1 Airglow spectrum, UV to IR
6.2 Dependence on zenith distance
6.3 Variations
Send o↵print requests to: Ch. Leinert
?
Prepared by members of Commission 21 “Light of the night
sky” of the IAU, including most of the recent (vice-)presidents.
6.4 Geocorona
6.5 Interplanetary emissions
6.6 Shuttle glow
7. Light pollution
8. Zodiacal light
8.1 Overview and general remarks
8.2 Heliocentric dependence
8.3 Zodiacal light at 1 AU in the visual
8.4 Wavelength dependence and colour
8.5 Zodiacal light in the infrared
8.6 Zodiacal light in the ultraviolet
8.7 Seasonal variations
8.8 Structures in the zodiacal light
8.9 The zodiacal light seen from other places
9. Coronal brightness and polarisation
10. Integrated starlight
10.1 Model predictions based on star counts
10.2 Ultraviolet
10.3 Ground-based UBVR photometry
10.4 Pioneer 10/11 spaceborne visual photometry
10.5 Near-and mid-infrared
11. Di↵use galactic light
11.1 Overview
11.2 Visual
11.3 Near-infrared
11.4 Thermal infrared
11.5 Ultraviolet
12. Extragalactic background light
13
Ritter Astrophys. Res. Center, University of Toledo, Toledo, OH 43606, U.S.A.
夜空には発光源がいろいろある
Received August 7; accepted September 8, 1997
Abstract. In the following we present material in tabular and graphical form, with the aim to allow the nonspecialist to obtain a realistic estimate of the di↵use night
sky brightness over a wide range of wavelengths from the
far UV longward of Ly↵ to the far-infrared. At the same
time the data are to provide a reference for cases in which
background brightness has to be discussed, including the
planning for space observations and the issue of protection
of observatory sites. We try to give a critical presentation
of the status at the beginning of 1997.
Key words: di↵use radiation — interplanetary
medium — atmospheric e↵ects — astronomical dabases:
miscellaneous — infrared: general — ultraviolet: general
Contents
1.
2.
3.
4.
5.
6.
Overview
Brightness units
Coordinate transformations
Total sky brightness
Tropospheric scattering
Airglow
6.1 Airglow spectrum, UV to IR
6.2 Dependence on zenith distance
6.3 Variations
Send o↵print requests to: Ch. Leinert
?
Prepared by members of Commission 21 “Light of the night
sky” of the IAU, including most of the recent (vice-)presidents.
6.4 Geocorona
6.5 Interplanetary emissions
6.6 Shuttle glow
7. Light pollution
8. Zodiacal light
8.1 Overview and general remarks
8.2 Heliocentric dependence
8.3 Zodiacal light at 1 AU in the visual
8.4 Wavelength dependence and colour
8.5 Zodiacal light in the infrared
8.6 Zodiacal light in the ultraviolet
8.7 Seasonal variations
8.8 Structures in the zodiacal light
8.9 The zodiacal light seen from other places
9. Coronal brightness and polarisation
10. Integrated starlight
10.1 Model predictions based on star counts
10.2 Ultraviolet
10.3 Ground-based UBVR photometry
10.4 Pioneer 10/11 spaceborne visual photometry
10.5 Near-and mid-infrared
11. Di↵use galactic light
11.1 Overview
11.2 Visual
11.3 Near-infrared
11.4 Thermal infrared
11.5 Ultraviolet
12. Extragalactic background light
さまざまな発光源
C h. Leinert et al.: T he 1997 reference of di use night sk y brightness
10-4
Airglow
Lyα
OH
Brightness νlν ( W m-2 sr-1 )
10-5
Zodiacal light
OΙ
CMB (2.726K)
O2
10-6
10-7
Faint stars
10-8
Cirrus
10-9
10-10
0.1
1
10
100
Wavelength ( µm )
1000
10000
v erv iew on the brightness of the sk y outside the low er terrestrial atm osp here and at high eclip tic and galactic latitudes.
acal em ission and scat tering as w ell as the integrated light of stars are giv en for the S outh E clip tic P ole ( l = 27 ,
) . T he bright m agnitude cut- o for the stellar com p onent is V = .0 m ag for 0 .3 – 1 µm . I n the infrared, stars brighter
y betw een 1.25 and 4 .8 5 µm and brighter than 8 5 J y at 12 µm are ex cluded. N o cut- o w as ap p lied to the U V data,
µm . T he interstellar cirrus com p onent is norm aliz ed for a colum n density of 10 20 H - atom s cm 2 corresp onding to a
tinction of 0 .0 5 3 m ag. T his is close to the v alues at the darkest p atches in the sk y. S ource for the long- w av elength
1.25 µm , are CO B E D I R B E and F I R A S m easurem ents as p resented by D ´esert et al. ( 199 ) . T he I R cirrus sp ectrum
ng to the m odel of D ´esert et al. ( 1990 ) fi t ted to I R A S p hotom etry. T he short- w av elength data,  1.0 µm , are from
ing sources: z odiacal light: Leinert & G r¨u n ( 1990 ) ; integrated starlight:  0 .3 µm , G ondhalekar ( 1990 ) ,
0 .3 µm ,
198 0 ) ; cirrus: = 0 .15 µm , H aikala et al. ( 1995 ) , = 0 .3 5 0 .75 µm , M at tila & S chnur ( 1990 ) , M at tila ( 1979) . T he
al L ym an ↵( 121. nm ) and the O I ( 13 0 .4 , 13 5 . nm ) line intensities w ere as m easured w ith
6 the F aint O bj ect C am era 6
ubble S p ace Telescop e at a height of 10 km ( C aulet et al. 1994 ) . T he v arious references for the airglow em ission
6
can
in S ect.
6
view
•
夜空の明るさ=大気光+黄道光+星明かり+散乱
銀河光+銀河外からの光
6
6
• 大気による吸収や対流圏での散乱も無視できない
over all of our wavelength range.
–Extragalactic background light (IEBL ) in addition to the
輝度の単位
•
慣用的定義
•
•
S10単位;A0星基準、太陽基準
物理的定義
•
•
photons / cm2 s sr nm
•
W / m2 sr μm (流束)
Rayleigh / nm
= 106 / 4π photons cm2 s sr nm
【測光学的定義(正式):
1R = 106 / 4π photons cm2 s sr】
atm
et
sion
sen
to2.5
t
val
Ant
(K
viro
pe
tosec
a
inant
etwaa
senc
2.5
valu
Ta
(K
Fig. 9. A low resolution night sky spectrum at Palomar pen
Observatory, taken on November 28, 1972 (Turnrose 1974), sec
compared to medium band measurements on Calar Alto (CA) and
Ma
was
Ma
and Fig. 28 in Sect. 6.3). An example for the variation of
sky brightness with solar activity is given in Fig. 10.
全天の明るさ(1)
•
•
•
遠紫外域(91.2 nm - 180 nm):主
に星明かりと星間塵による散乱
•
Lyα(121.6 nm)の強い放射;中
性水素による太陽放射の散乱
•
Geocoronaの流束は3kR(夜
間)から34kR(昼間)まで10倍
近く変動する
近紫外域(180 nm - 300 nm):黄道
光、星明かり、星間塵による散乱
可視光域:大気光、黄道光、対流圏
での散乱
•
•
波長ごとに観測される強度は異な
る(右上)
太陽活動の活発さに応じて大気光
の発光強度は変動する(右下)
B
B
So
Tab
So
a
Fig. 9. A low resolution night sky spectrum at Palomar
Observatory, taken on November 28, 1972 (Turnrose 1974),
compared to medium band measurements on Calar Alto (CA)
Re
(19
Mau
5
A
Mau
B
B
Sou
4.4
Sou
a
a
Ta
240
Refe
me
(197
5 fiel
As
ser
lig
cal
全天の明るさ(2)
Ch. Leinert et al.: The 1997 reference of di↵use night sky brightness
•
•
近赤外領域
•
波長2μm以下の領域;OH大気光
(さまざまなバンド)が支配的
•
波長2μm以上の領域;大気の熱放
射が支配的
•
南極の冬は極端な低温のため波長
2μm以上の領域で様子が変わって
くる(右下)
赤外領域
•
•
•
Fig. 11. Near-infrared spectrum of the night sky brightness, meas
camera (McCaughrean 1988). Note that 104 photons m 2 s 1 200 1
1994
Ta
D
Fig. 11. Near-infrared spectrum of the night sky brightness, measured just inside the cryostat window of the U
camera (McCaughrean 1988). Note that 104 photons m 2 s 1 200 1 µm 1 correspond to 4.23 Wm 2 sr 1 µm 1 . F
1994
波長60μm以下の領域;黄道光
(熱放射)が支配的
Table 6. Minimum observed sky brightnesses
DIRBE weekly averaged sky maps
波長60μm以上の領域;星間塵の
熱放射が支配的
水素原子由来の波長21cmの電波
が宇宙空間にたくさん
(µm)
1.25
2.2
3.5
4.9
12
25
60
⌫I⌫ = I
(nW m 2 sr
393±13
150±5
63±3
192±7
2660±310
2160±330
261±22
1
)
I⌫
(MJy/sr)
0.16±0.005
0.11±0.004
0.074±0.004
0.31±0.01
10.7±1.2
18±3
5.2±0.4
R
対流圏による散乱効果
•
大気光、黄道光、恒星からの光自体も対流圏によ
る散乱の影響を受ける。黄道光は15%以上、恒星
からの光については10 - 30%近い影響がある。
•
主にRayleigh散乱とMie散乱による。天の川や黄
道光の観測を利用した観測がある[Staude, 1975]
•
一口に「対流圏の大気(あるいは空気)」と言っ
ても、反射係数が水蒸気(1.33)とエアロゾル
(1.5-0.1i)で異なるなど、単純な計算ではうまく
いかない。
Way and Zodiacal Light cone were varied independently
over the whole range occurring in practice. Some results
from this study are reported in the following.
Rayleigh散乱とMie散乱の効果
l.: The 1997 reference of di↵use night sky brightness
5.1. A uniform unpolarized source of unit brightness
S
ght sky brightThe brightness
of tropospherically scattered airglow can
scattering
(see
etermine
its unbe estimated
using the results obtained for a uniform unnd polarization.
polarized source of unit brightness (extending over the
ight come from
entire
visible sky) in the single scattering approximation,
d starlight
(ISL)
which are given in Figs. 13 and 14. They give the intensity
part determined
ces under
study
of the
scattered light and its polarization as a function of
of 10 100 S10 ,
zenith distance of the observing direction z0 , for di↵erent
Zodiacal light,
of the zenith extinction ⌧R of the Rayleigh and ⌧M
Due tovalues
the limof the Mie component.
be determined,
urements aimed
weaker compod EBL, must be
Table 7. The correction factors for multiple scattering in a
yleigh-Rayleigh
and Mie- atmosphere for di↵erent values of the zenith extincpolarization) in
tion ⌧R . See text for details
nated by a uniWay and by the
(1975) for variayleigh and Mie
ng two di↵erent
spheric aerosols
1.5 0.1i, as for
ntation of Milky
d independently
e. Some results
ing.
•
⌧R
FMS
fMS
0.05 1.12 ± 0.04 0.95 ± 0.05
Fig. 13. Intensity and polarization of the atmospheric scat0.06 atmosphere,
0.90 ± 0.05
tered0.10
light in a1.22
pure±Rayleigh
for a source of unit
0.15 and1.33
± 0.06
± 0.05
brightness
various
values of0.85
the zenith
extinction ⌧R , as a
function
0.20of zenith
1.44distance
± 0.07z 0.80 ± 0.05
Fig. 14. Same as Fig. 13 for two pure Mie atmospheres
散乱光の強度とpolarizationの大きさを、観測方向からの天
頂距離の函数として表してある。
brightness
red airglow can
r a uniform unnding over the
approximation,
ve the intensity
•
天頂角が小さいときにはMie散乱は無視できる。
Fig. 15. The intensity of the scattered integrated starlight as
a function of zenith distance, for di↵erent azimuths and zenith
17. The
intensity
thebrightness
scattered zodiacal light for pure
extincion values of the Rayleigh resp. Ch.
MieLeinert
components
of the
et al.: The
1997Fig.
reference
of di↵use
nightofsky
atmosphere. The galactic centre is assumed at the zenith, the Mie scattering with optical thickness ⌧M = 0.1, for particles
with refractive index m = 1.33. Otherwise same as for Fig. 16
galactic equator crosses the horizon at A = 90 , 270
S
[S ]
10
黄道光の散乱
S
[S ]
S 10
21
[S ]
10
Fig. 18. A typical height profile of airglow volume emission,
as measured from the satellite OGO II. The peak near 90 km
is due
Fig. 15. The intensity of the scattered integrated starlight
as to OH emission, the extended peak at higher altitudes
Fig. 16. The
intensity
of
the
scattered
zodiacal
light
for
a
pure
to [OI] emission at 630 nm. From Reed & Blamont (1967)
a function of zenith distance, for di↵erent azimuths and zenith
Rayleigh atmosphere
with
optical
thickness
⌧
=
0.1.
Position
R
extincion values of the Rayleigh resp. Mie components of the Fig. 17. The intensity of the scattered zodiacal light for pure
of the sunatmosphere.
at azimuth The
A =
90 , zenith
z at=the
105zenith,
,
galactic
centre distance
is assumed
the Mie scattering with optical thickness ⌧M = 0.1, for particles
the eclipticgalactic
is perpendicular
to
the
horizon
with refractive index m = 1.33. Otherwise same as for Fig. 16
equator crosses the horizon at A = 90 , 270
• 波長500 nmでの散乱の様子
• Polarizationは太陽の方向と直角方向としている
S
[S ]
10
大気光の発光源/高度
発光源
He+
O+
Lyβ
Lyα
O
O
O2 (Herzberg帯)
N
O
Na
O
O
Hα
擬連続光
O2
OH
•
•
波長
30.4 nm
83.4 nm
102.6 nm
121.6 nm
130.4 nm
135.6 nm
300 - 400 nm
519.9 nm
557.7 nm
589 nm
630.0 nm
636.4 nm
656.3 nm
400 - 700 nm
864.5 nm
600 - 4500 nm
発光層高度
> 1,000 km
> 1,000 km
> 1,000 km
> 1,000 km
250 - 300 km
250 - 300 km
90 km
90 km
92 km
250 - 300 km
250 - 300 km
> 1,000 km
90 km
80 km
85 km
発光強度(天頂付近)
10 R
3kR (夜) - 34kR (昼)
40 R (熱帯域)
30 R (熱帯域)
8 R / nm
3R
250 R
30 R (夏) - 100 R (冬)
60 R
20 R
4-6R
3 R / nm
1 kR
4.5 MR (OH全体で)
黄道光は大気光の2 - 3倍程度明るい(波長530nmで計測したとき)
天の川の明るさ:1 kR、満月の明るさ:1 MR
th, the
a pure
osition
105 ,
Mie scattering with optical thickness ⌧M = 0.1, for particles
with refractive index m = 1.33. Otherwise same as for Fig. 16
発光層の高度分布
HECHT ET AL.: TOMEX PHOTOMETER RESULTS
D02S05
•
左:衛星「OGO Ⅱ」による観測
Fig. 18. A typical height profile of airglow volume emission,
[Reed et al., 1967]
as measured from the satellite OGO II. The peak near 90 km
is due to OH emission, the extended peak at higher altitudes
to [OI] emission at 630 nm. From Reed & Blamont (1967)
•
•
•
高度90 km付近にOHによる発光
層、さらに高層にはOからの
630-nm発光層が見られている。
Figure 6. (top) The measured O2A VER (solid line) versus altitude compared to the four TIME-GC
predictions (see Figure 3). (middle) Same but for greenline. (bottom) Same but for OHM (9, 4). On e
plot a vertical solid line is shown offset from a vertical dashed line taken as a zero reference line. T
solid line represents the one sigma error as function of altitude in the derived VERS based on
uncertainties in the measured counting rates in Figure 5.
右:ロケットによる観測[Hecht
et al., 2004]
data and shown in Figure 7a. The agreement is quite good
above 85 km except for the dip at 93 km.
[26] Figure 9 shows a comparison between the derived
[O] profile from the O2A data and the four TIME-GCM
model predictions. Clearly the peak is lower in altitude and
実線が観測値を示している。
density is taken from TIME-GCM. Here th
shows [O] data from O2A, the dashed line sh
data from OHM using the Turnbull and Lowe
solid line are the [O] data from OHM using the
and the heavy solid line shows the [O] data
地上からの可視域観測(300 - 560 nm)
地上からの可視域観測(540 - 800 nm)
地上からの可視域観測(740 - 1000 nm)
スペースシャトルから観測すると?
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17,131
地上観測と宇宙観測とを比較すると
•
地上観測によるスペクトル図:[Broadfoot and
Kendall, 1968]
•
スペースシャトルによる観測のスペクトル図:
[Broadfoot and Bellaire, 1999]
•
輝線によっては強度が異なる:例えばO2の762 nm
輝線→地球大気による吸収が存在し、地上での観測
が難しいものもある
•
地上観測の方にHgの輝線が見える→街灯(水銀
灯)の散乱を受けたものと考えられる。いまなら
Na輝線が混じるか?
寄り道(1)∼VISIの場合
•
•
VISIは分光観測を行って
いる。特定の波長のみを
切り出してイメージング
的な観測をすることも可
能。
さまざまな輝線が観測で
きている。バンドで光る
OHの発光もより鮮明に
観測できるようになる予
定。(近日、観測テーブ
ル書き換え予定)
種子島を出発してから、
はや1年ですか…
(*_*)
400
※ いたるところにOH
Backward FOV
Forward FOV
O2
300
Intensity [R/nm]
•
O2
200
O
100
Na
O
O+
O
O
O
0
500
700
800
600
Wavelength [nm]
900
OH
a
600 nm
4.5 µm
85 km
4.5 MR(all bands)
紫外域発光の観測
after Chamberlain (1961), Roach (1964), Roach & Gordon (1973), Meier (1991); see also the references in the sections on
geocorona and ultraviolet airglow.
b
transformed to zenith, where necessary.
22
Ch. Leinert et al.: The 1997 reference of di↵use night sky brightness
•
•
˚ to 1700 A
˚ at 17 A
˚ resolution. The data were obtained from the space
Fig. 21. Left: Spectrum of the nightglow from 1250 A
宇宙機による上空での観測がほとんど
c) Near infrared
shuttle at a height of 330 km in January 1986 at minimum solar activity. The oxygen OI lines at 1304 ˚
A and 1356 ˚
A are the
From 1 µmbands
to 3 µm,
in a curve
layer around
km heightspectrum. Right:
brightest features. For the weakly visible Lyman-Birge-Hopfield
the OH
dashed
shows a90predicted
観測条件によってはnightglowとdayglowの
˚
emission.
There isona the
gap same
in the flight.
OH The solid line
Spectrum of the ultraviolet nightglow from 170 nm to dominates
310 nm atthe
29 airglow
A resolution
obtained
spectrum
2.4contribution
µm (see Fig. to
27)zodiacal
which islight.
important
shows an appropriately scaled solar spectrum and is assumed
to around
show
the
From Morrison et al.
両方が観測される
for balloon observations and also for the low background
(1992)
observations possible from Antarctica (see Sect. 4.3). Seen
上:1986年1月のスペースシャトルによる
from the ground, longward of 2.5 µ airglow is only a
small addition
to theexamples
thermal emission
tropo観測(高度330
et overview
al.,
thus enabling a “thumb-cinema” look at these spatioThese
dokm)[Morrison
not from
give the
at all
a full
on
sphere
(compare
Fig.
11
in
Sect.
4
above).
Figures
25
and
temporal variations. Quantitative examples for variation airglow
variability but just demonstrate that it is a typical
26 show the1992]
near-infrared OH spectrum at two resoluduring one night or variation with solar cycle can betions,
seenonceproperty
of this source of night sky
brightness.
with a low spectral resolution of
= 160 ˚
A,
in Figs. 8 and 10 in Sect. 4. Often a systematic decrease
and once with
a higher resolution of /
= 250 800.
左:1990年12月のスペースシャトルによる
In
the
visual
spectral
region,
correlations
between the
of airglow emission during the course of the night Wavelength
is oblists and intensities for the individual
OH
[OI]
and NaD
linesal.,
and “pseu観測(高度358
served, explained as result of the energy stored during
day canprominent
bands
be
found in
Ramsay
etkm)[Feldman
al.airglow
(1992) emission
and Olivaet
bands
at 367 nm, 440
nm, is526 nm, 558 nm,
& Origliadocontinuum”
(1992).
Obviously,
the near-infrared
airglow
in the respective atmospheric layers.
1992]
dominated634
by nm
the and
OH 670
bands.
also denmThey
have primarily
been studied
by Barbier (1956)
night
sky brightness
the J (1.2 µm)
and E.g., the corFigure 29 shows this for the OH emissions andtermine
also the
who
established
threein“covariance
groups”.
•
•
28
赤外域発光の観測
3.0
1.0
(3-1)
(4-2)
(5-3)
1.15
(6-4)
(7-5)
1.0
0.5
1.50
1.60
1.70
WAVELENGTH - MICRONS
1.80
0.5
1.10
1.20
1.30
WAVELENGTH - MICRONS
(8-6)
1.5
x106
1.40
(9-7)
1.0
0.5
0
1.90
2.00
2.10
WAVELENGTH - MICRONS
4000
3000
2000
1000
(2-0)
1.4
1.6
1.65
1.7
Wavelength in vacuum (µm)
1.5
右:マウナケアからの地上観測[Ramsay et al.,
2000
3000
1.75
1000
上:波長1.2μm以下の領域を分解能16nmで地上観
測[Harrison et al., 1973]
•
1.55
2.5μm以上の波長域では対流圏からの熱放射の割
合の方が強い。
•
1.2
1.3
Wavelength in vacuum (µm)
2.20
1.5
•
1.1
0
0
(9-6)
(8-5)
1.0
0
1.20
(7-4)
Flux (photon s-1 arcsec-2 m-2 µm-1)
1.5
x106
1.10
WAVELENGTH - MICRONS
(6-3)
0
5.0
(5-2)
1.00
6000
7.0
1.5
x106
0.90
0.95
WAVELENGTH - MICRONS
4000
(6-3)
0.85
2000
0
0.80
Flux (photon s-1 arcsec-2 m-2 µm-1)
(5-2)
(4-1)
(9-5)
1.0
DIFFERENTIAL BRIGHTNESS
(ZENITH)
RAYLEIGHS PER MICRON
9.0
x105
0.70
0.75
WAVELENGTH - MICRONS
(3-0)
(8-4)
2.0
DIFFERENTIAL BRIGHTNESS
(ZENITH)
RAYLEIGHS PER MICRON
0.65
O2(0-1) (7-3)
(6-2)
3.0
x105
Flux (photon s-1 arcsec-2 m-2 µm-1)
(9-4) (5-1)
(4-0)
2.0
1.05
DIFFERENTIAL BRIGHTNESS
(ZENITH)
RAYLEIGHS PER MICRON
(8-3)
4.0
0
DIFFERENTIAL BRIGHTNESS
(ZENITH)
RAYLEIGHS PER MICRON
(7-2)
(6-1)
DIFFERENTIAL BRIGHTNESS
(ZENITH)
RAYLEIGHS PER MICRON
6.0
x104
Ch. Leinert et al.: The 1997 reference of di↵use night sky brightness
DIFFERENTIAL BRIGHTNESS
(ZENITH)
RAYLEIGHS PER MICRON
Ch. Leinert et al.: The 1997 reference of di↵use night sky brightness
1992]
1.95
2
2.05
2.1
2.15
2.2
2.25
Wavelength in vacuum (µm)
2.3
2.35
Fig. 26. Near-infrared airglow spectrum as observed from Mauna Kea at spectral resolution /
= 250
atmospheric transmission  0.75 the flux has been arbitrarily set to zero. Longward of 2.1 µm thermal a
6
6
6
2
発光の時間変化
30
Ch. Leinert et al.: The 1997 reference of di↵use night sky brightness
•
輝度と発光の空間分布が時間的に変化する(修士のと
Fig. 29. Variation of OH airglow, observed from Mauna Kea. Left: Short term variations (minutes) caused by the passage
of wavelike structures. Right: Decrease of OH airglow during the course of a night, shown for several bands separately. From
きに似たようなでも違う話をした気が…)
Ramsay et al. (1992)
•
•
•
マウナケアからの地上観測[Ramsay et al., 1992]
左:波状構造の通過に伴う分単位の輝度変化
右:夜間の発光強度の時間変化
寄り道(2)∼「れいめい」の思い出
全データ (670nm)
2000
1500
1000
500
0
50
•
VER [photons/cc/s]
VER [photons/cc/s]
全データ (557.7nm)
40 30 20
Latitude [deg]
10
2000
1500
1000
500
0
50
40 30 20
Latitude [deg]
10
修士課程では「れいめい」による約1,200観測のデータ
を用いて、大気光発光の季節変化(春夏秋冬)および緯
度変化を調べた。
•
「れいめい」の理学観測は今年3月で終了。工学試験目
的の運用はまだ続いている(はず)。
異なる波長での発光の変化の相関
29. Variation of OH airglow, observed from Mauna Kea. Left: Short term variations (minutes) caused by the passage
avelike structures. Right: Decrease of OH airglow during the course of a night, shown for several bands separately. From
say et al. (1992)
•
Barbier et al., 1956によれ
ば、以下の輝線および波長での
発光強度にはよい相関が見られ
る:
•
•
•
•
O(557.7 nm etc. )
Na D線
擬連続光中の367 nm, 440
nm, 526 nm, 558 nm, 634
nm, 670 nm
右:467 nmの輝線の発光強度
(水平方向)と525 nmの発光
強度(鉛直方向)が極めて良い
Fig. 28. Correlation between the di↵use sky emission at 467
相関を示している。[Leinert etnm (Str¨omgren b) and at = 525 nm. The brightness variations in both bands are mainly due to airglow. From Leinert
al., 1995]
et al. (1995)
シャトルグロー
•
衛星(宇宙機)の高度と太陽活動度に
よっては、大気との作用によって赤
色∼近赤外域での発光が見られる。紫
外域での発光もある。
•
N2 Lyman-Birge-Hopfield
band(120 - 280 nm)について
•
•
太陽活動が中程度の時期に高度
250 kmで100 - 500 R/nm [Torr et al., 1985]
•
太陽活動静穏時では高度330 km
でも観測されなかった [Morrison
et al., 1992]
上:STS-062ミッション(1994年3
月)での観測
「光汚染」
32
Ch. Leinert et al.: The 1997 reference of di↵use night sky brightness
•
全天イメージャはたいてい人里離
7.
Light pollution
•
れたところに置かれる;街灯りに
Artificial
lighting at earth contributes via tropospheric
scattering to the night sky brightness over a large area
よって空が「汚染」されるから。
around
the source of light. Both a continuous component
as well as distinct emission lines are present in the light
pollution spectrum. A recent review of sky pollution is
[Walker 1970, 1977]など都市
given in McNally (1994).
の明かりによる光害の観測例がイ
タリア/カナダ/アメリカで存在
7.1.
Observations of sky pollution
する。Walkerによれば以下のも
Systematic
broad-band observations of the sky pollution
light near cities have been carried out by Bertiau et al.
のが導かれる(らしい);
(1973)
in Italy, Berry (1976) in Canada & Walker (1970,
1977) in California. Berry showed that there is a relation(1)between
人口と街の明るさの相関
ship
the population of a city and the zenith sky
brightness as observed in or near to the city. Walker inter(2) 空の明るさを都市からの距離
preted
his extensive observations by deriving the following
relationships: (1) between the population and luminosity
の函数として表す
of
a city; (2) the sky brightness as a function of distance
from the city; and (3) between the population and the
(3) 人口の増え方と都市からの光
distance
from a city for a given sky pollution light contribution. The last two relationships are shown in Figs. 31
汚染の具合の間には定量的な増加
and
32. These figures can be utilized to derive an estimate
for the sky pollution at 45 deg altitude caused by a city
関係がみられる
with
2000 4 million population and with a similar street
lighting power per head as California. Starting with the
city population Fig. 31 gives the distance at which the
Fig. 31. Variation with city population of the distance at
which the lights of a city produce an artificial increase of
the night sky brightness at 45 deg altitude toward the city
by 0.20 mag. This increase refers to an assumed natural sky
brightness of V = 21.9 mag/200 . Observations by Walker
(1977) are indicated by dots. Two models by Garstang (1986)
are shown as solid lines. K is a measure for the relative importance of aerosols for scattering light. The uppermost dot refers
to Los Angeles County, the cross below it to Los Angeles City.
From Garstang (1986)
光汚染の経験モデル
Ch. Leinert et al.: The 1997 reference of di↵use night sky brightness
•
•
[Garstang 1986, 1989a,b, 1991]のモ
デルでは以下のものが考慮されている:
•
•
•
1次と2次のレイリー散乱
•
•
光源の面分布の様子
エアロゾルによる散乱
地面による光の反射(表面の状況も含
めて)
Fig. 32. Variation with distance from the city of the sky
brightness at 45 deg altitude in the direction of the city. The
dots indicate observations in V band by Walker (1977) near
the city of Salinas. The solid curves are according to models by Garstang (1986). The brightness ratio is defined as
b(Salinas at +45 ) b(Salinas at 45 )
, where b = sky brightness.
b(sky background only at +45 )
Zenith distance +45 is towards and 45 away from the city.
The solid curves are according to models by Garstang (1986).
Curve 1: L0 = 986 lumens per head, K = 0.43, F = 11%.
Curve 2: L0 = 1000 lumens per head, K = 0.5, F = 10%. L0 is
the artificial lighting in lumens produced per head of the population. K is a measure for the relative importance of aerosols
for scattering light. F : a fraction F of the light produced by
the city is radiated directly into the sky at angles above the
horizontal plane, and the remainder (1 F ) is radiated toward
the ground. The dashed line is the relation ⇠ D 2.5 . From
Garstang (1986)
Fig. 33. Zenith distance dependence of sky pollution light according to the model calculations of Garstang (1986). Results
are for sky pollution due to Denver as seen from a distance
of 40 km in the vertical plane containing the observer and the
center of Denver. Curve 1: sky background; Curve 2: Denver
only; Curve 3: Denver and sky background. Negative zenith
Ch. Leinert et al.: The 1997 reference of di↵use night sky b
distances are away from Denver. From Garstang (1986)
天頂角依存性
街灯が「水銀灯→high pressure
sodium type→low pressure sodium
type」と変化
人工光(Hg, Na, K)のスペクトルのピーク
がだんだん長波長側に移動してきている
8. Zodiacal light
103
Levasseur-Regourd
and Dumont
Helios A and B
Pioneer 10
600
300
Ι [ S10 ]
•
33
β = 16.2°
100
β = 31.1°
60
Fig. 180
33. Zenith distanc
cording to the model ca
are for sky pollution d
of 40 km in the vertical
center of Denver. Curv
only;the
Curve 3: Denver
Fig. 34. Comparison of zodiacal light measurements along
distances are away from
30
60
90
λ - λ (°)
120
150
天文観測では
•
非常に遠くの銀河(多くは赤方偏移している)を観測
することも多く、遠くにある天体からの光量が小さい
場合も往々にしてあるので以下の「光」も問題になる
(省略しますが):
•
•
•
黄道光
•
•
散乱銀河光
太陽コロナの明るさおよびpolarization
(観測したい天体以外の)星明かり←Pioneer 10号
/11号での見積もり例もあるらしい
宇宙空間全体の背景放射(いわゆる3K波とか)
まとめ
• 地上には大気光以外にもさまざまな「光」が
降り注いでいる。それらの定量的な見積もり
によってより精度の高い観測を行うことが可
能となる。
• 地上からも光は放出されていて、それらの対
流圏での散乱の効果は無視できない。
• 大気光の発光領域は紫外域から赤外域まで広
がっている。発光源の違いによって大きく異
なる特徴を示す。
以上です。
•
•
祇園祭、宵山ですね。
本当はこれらの写真を「イメージング観測」の例として
出したかった…(出したら本題には戻って来れないだろうな)
上3点:
2013年5月から6月にかけ
ての鴨川右岸イメージング
観測。
左2点:
森田「京都・鴨川河川敷に
坐る人々の空間占有に関す
る研究」(1987)