Mercury Disk Observations by Japanese team
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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

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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

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


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Dawn-Dusk Asymmetry observed at Mercury transit

on November 9, 2006

by Junya Ono and Ichiro Yoshikawa (University of Tokyo)

Hunten and Sprague, 1997

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.

Schleicher et al., 2004

Dawn-Dusk Asymmetry was observed

at a time of Mercury transit on the solar disk.


Mercury disk observations by japanese team 1 observation 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

22:06

Start time (UT)

00:04

End time (UT)

9.96 arcsec

Mercury diameter

0.315 AU

Mercury-Sun distance

329°

True Anomaly Angle

5.3 → 5.2 km/s

Mercury-Sun velocity

0.9 → 1.4 km/s

Rotational velocity of the Sun

589.592 nm (Na D1)

Wavelength

8.5 → 7.5 pm

Doppler shift

0.18 → 0.12

g-factor


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

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)


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Column density of Na atoms along a line of sight vs. distance from the limb

6.1 ± 1.1×1010

Na atoms column densities at limb locations

[Na atoms/cm2]

Morning

Evening

4.1 ± 1.8×1010

North

5.7 ± 1.2×1010

Morning-Evening asymmetry 1.5 ±0.71

South

5.4 ± 1.3×1010


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Na temperatures derived from observed line width


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Na temperature were also derived from scale height

Atmospheric seeing was determined

from shadow region (red lines)

Determined seeing

Morning

1.59 arcsec

Evening

1.76 arcsec

North

1.73 arcsec

South

1.72 arcsec

Temp. from line width

scale height

Temp. from scale height

Morning

152 ±30 km

1560 ±260 K

1750 ±500 K

Evening

2350 ±900 K

124 ±40 km

1300 ±410 K

North

2700 ±950 K

128 km

1320 K

South

3200 ±1150 K

134 km

1380 K


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

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.


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Micro meteoroid and dust distribution vs. Mercury sodium

by Shingo Kameda, ISAS/JAXA#1

・source process

Relation between dust distribution and

atmospheric density

Tilt angle of Mercury’s

orbit is 7 degrees.

Assuming that

dust and micro-meteoroids

are concentrated near

ecliptic plane,

source rate for meteoroid

vaporization will be higher

(possibly).


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Micro meteoroid and dust distribution vs. Mercury sodium

by Shingo Kameda, ISAS/JAXA#2

TAA vs

Sodium density

Radiation pressure

(Potter et al., 2007)

Radiation pressure is

Minimum at the TAA of

0 and 180.

Potter et al., 2007


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Micro meteoroid and dust distribution vs. Mercury sodium

by Shingo Kameda, ISAS/JAXA#3

TAA vs

Sodium density

Radiation pressure is

Minimum at the TAA of

0 and 180.

However,

From other results,

It is not definite..

Sprague et al., 1997


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Micro meteoroid and dust distribution vs. Mercury sodium

by Shingo Kameda, ISAS/JAXA#4

Potter et al., 2007

Sprague et al., 1997

As a trend,

Mercury is away from ecliptic plane  small density


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Micro meteoroid and dust distribution vs. Mercury sodium

by Shingo Kameda, ISAS/JAXA#5

In Northern side,

Heliospheric distance is small

 large dust density (?)

Potter et al., 2007

As a trend,

Mercury is away from ecliptic plane  small density


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Micro meteoroid and dust distribution vs. Mercury sodium

by Shingo Kameda, ISAS/JAXA#6

□: Observation at Haleakala in 2006

Potter et al., 2007; Sprague et al., 1997

Problem:

1. Accuracy of absolute value for each observation result

2. The cause of significant increase is still unknown.


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Observation of Mercury disk at the time of Messenger flyby

in January 2008

by Masato Kagitani and Shoichi Okano, Tohoku University

Japan Iitate observatory

D=60cm

λ/∆λ~59,000

Platescale:0.92 ”/pix


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Observation

・Long-slit spectroscopy

・High-dispersion Echelle spectrograph

Fig: Slit configuration

D=60cm

λ/∆λ~59,000

Platescale:0.92 ”/pix

Slit: 2.1”x180”


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Observation


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Data Reduction

Sky background

Earth’s sodium emission

Sky background subtraction

Spectral axis

Mercury sodium tail

Mercury continuum

Spatial axis


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Calibration

Hapke’s reflection model

Observed continuum

Seeing convolved Hapke’s reflection model

MR (Sodium emission)

MR/nm (continuum)

NaD2

NaD1

To calibrate absolute intensity,

Hapke’s reflection model was used.


Mercury disk observations by japanese team 1 observation of mercury transit on the solar disk

Result


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