mercury disk observations by japanese team 1. observation of mercury transit on the solar disk
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Mercury Disk Observations by Japanese team
1. Observation of Mercury transit on the solar disk on November 9, 2007 [Dawn-Dusk Asymmetry] by Junya Ono and Ichiro Yoshikawa, University of Tokyo
2. Sodium abundance vs. Mercury’s distance from equatorial plane
[Micro meteoroid and dust distribution vs. Mercury sodium] by Shingo Kameda, ISAS/JAXA
3. Observation of Mercury disk at the time of Messenger flyby in January 2008 by Masato Kagitani and Shoichi Okano, Tohoku University
Hunten and Sprague, 1997
Schleicher et al., 2004
It is impossible to observe both dawn and dusk sides
at a time by ground-based observation.
However, based on statistics, sodium density
on the dawn side is ~ 3 times higher than
that on the dusk side
It is thought that sodium atoms are adsorbed
in the night side (low temp), while they are
released from the dayside.
Dawn-Dusk Asymmetry observed at Mercury transit on November 9, 2006 by Junya Ono and Ichiro Yoshikawa (University of Tokyo)
Dawn-Dusk Asymmetry was observed
at a time of Mercury transit on the solar disk.
Observation was made at Hida Observatory of Kyoto University on November 9, 2006 using a 60-cm vacuum solar telescope and a 10-m spectrograph (R ~ 210,000).
Conditions at a time of observation
Start time (UT)
End time (UT)
Mercury diameter
Mercury-Sun distance
True Anomaly Angle
Mercury-Sun velocity
Rotational velocity of the Sun
Wavelength
Doppler shift
g-factor
22:06
00:04
9.96 arcsec
0.315 AU
329°
5.3 → 5.2 km/s
0.9 → 1.4 km/s
589.592 nm (Na D1)
8.5 → 7.5 pm
0.18 → 0.12
Example of observed Na absorption in a single frame data
far from limb (>2.5”)
close to limb
co-added 6 data at the North polar region (improved S/N)
Column density of Na atoms along a line of sight vs. distance from the limb
Na atoms column densities at limb locations [Na atoms/cm2]
6.1 ± 1.1×1010 Morning
Evening
NorthSouth
4.1 ± 1.8×1010
5.7 ± 1.2×1010
5.4 ± 1.3×1010Morning-Evening asymmetry 1.5 ±0.71
Na temperatures derived from observed line width
Na temperature were also derived from scale height
Atmospheric seeing was determinedfrom shadow region (red lines)
Morning 1.59 arcsec
Evening
North
South
1.76 arcsec
1.73 arcsec
1.72 arcsec
Determined seeing
Temp. from line width Temp. from scale heightscale heightMorning
Evening
North
South
1750 ±500 K
2350 ±900 K
2700 ±950 K
3200 ±1150 K
152 ±30 km
124 ±40 km
128 km
134 km
1560 ±260 K
1300 ±410 K
1320 K
1380 K
Summary of Mercury transit observation on Nov. 9, 2006
1. Morning–Evening asymmetry was ~ 1.5
2. No high densities at polar regions
3. Temperatures derived from line width are different from those derived from scale height. → meaning that the Mercury atmosphere is not in the hydrostatic equilibrium.
・ source process Relation between dust distribution and
atmospheric density
Micro meteoroid and dust distribution vs. Mercury sodium
by Shingo Kameda, ISAS/JAXA #1
Tilt angle of Mercury’s orbit is 7 degrees.Assuming thatdust and micro-meteoroidsare concentrated nearecliptic plane,source rate for meteoroidvaporization will be higher (possibly).
Potter et al., 2007
TAA vsSodium density
Radiation pressure
(Potter et al., 2007)
Radiation pressure isMinimum at the TAA of0 and 180.
Micro meteoroid and dust distribution vs. Mercury sodium
by Shingo Kameda, ISAS/JAXA #2
Sprague et al., 1997
Micro meteoroid and dust distribution vs. Mercury sodium
by Shingo Kameda, ISAS/JAXA #3
TAA vsSodium density
Radiation pressure isMinimum at the TAA of0 and 180.
However,From other results,It is not definite..
Sprague et al., 1997
As a trend,Mercury is away from ecliptic plane small
density
Potter et al., 2007
Micro meteoroid and dust distribution vs. Mercury sodium
by Shingo Kameda, ISAS/JAXA #4
Potter et al., 2007
In Northern side,Heliospheric distance is small large dust density (?)
Micro meteoroid and dust distribution vs. Mercury sodium
by Shingo Kameda, ISAS/JAXA #5
As a trend,Mercury is away from ecliptic plane small
density
Problem:1. Accuracy of absolute value for each observation result2. The cause of significant increase is still unknown.
Potter et al., 2007; Sprague et al., 1997
□: Observation at Haleakala in 2006
Micro meteoroid and dust distribution vs. Mercury sodium
by Shingo Kameda, ISAS/JAXA #6
D=60cm
λ/∆λ~59,000
Platescale:0.92 ”/pix
Japan Iitate observatory
Observation of Mercury disk at the time of Messenger flyby in January 2008 by Masato Kagitani and Shoichi Okano, Tohoku University
Observation
D=60cm
λ/∆λ~59,000
Platescale:0.92 ”/pix
Slit: 2.1”x180”
Fig: Slit configuration
・Long-slit spectroscopy
・High-dispersion Echelle spectrograph
Observation
Date Time(UT)
Seeing (FWHM
)
Quality Day or Night
Jan. 15
8:13 6.9 Mid Night
Jan. 17
8:09 5.0 Mid Day
8:17 6.5 High Day
8:24 6.5 Low Night
8:30 6.9 Low Night
Jan. 19
8:04 7.0 Mid Day
date TAA Phase angle
Ang.-
Diam.
Jan. 15 98 76 5.9”
17 117 88 6.2”
19 120 90 6.4”
Data Reduction
Earth’s sodium emission
Mercury sodium tail
Mercury continuum
Spatial axis
Spe
ctra
l axi
s
Sky
back
grou
nd s
ubtr
acti
on
Sky background
Calibration
To calibrate absolute intensity, Hapke’s reflection model was used.
Hapke’s reflection model
Observed continuum
Seeing convolved Hapke’s reflection model
NaD2
NaD1MR
/nm
(co
ntin
uum
)
MR
(S
odiu
m e
mis
sion
)
Result
Date Time(UT)
Seeing (FWH
M)
Quality Disk NaD2 [MR]
Column density x1010[cm-2]
Total sodium atoms within 3RM [x1028]
Jan. 15
8:13 6.9 Mid 1.17 2.1 4.8
Jan. 17
8:09 5.0 Mid 1.67 2.9 5.2
8:17 6.5 High 1.49 2.6 5.7
8:24 6.5 Low 1.10 1.8 4.4
8:30 6.9 Low 1.18 2.1 4.6
Jan. 19
8:04 7.0 Mid 1.35 2.4 5.1
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