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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

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Mercury Disk Observations by Japanese team 1. Observation of Mercury transit on the solar disk

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  1. 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

  2. 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.

  3. 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

  4. 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)

  5. 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

  6. Na temperatures derived from observed line width

  7. 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

  8. 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.

  9. 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).

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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.

  15. 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

  16. 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”

  17. Observation

  18. Data Reduction Sky background Earth’s sodium emission Sky background subtraction Spectral axis Mercury sodium tail Mercury continuum Spatial axis

  19. 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.

  20. Result

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