Earth’s atmosphere’s lowest layers probed during a lunar eclipse

Kawauchi, Kiyoe; Narita, Norio; Sato, Bun’ei; Hirano, Teruyuki; Kawashima, Yui; Nakamoto, Taishi; Yamashita, Takuya; Tamura, Motohide

doi:10.1093/pasj/psy079

Cited by 18 publications

(15 citation statements)

References 33 publications

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“…The remaining red light undergoes refraction by the Earth's atmosphere and focusses onto the Moon like in a spyglass (that's why the eclipsed Moon appears bloody red). The selective absorption must be rather inhomogeneously distributed around the atmospheric circumference because our atmosphere is structured differently above sea and land, and poles and equator as well as with height above ground (see Kawauchi et al 2018). The rotation of the Earth causes some of these absorption lines appear red shifted, some blue shifted, and some not shifted at all, depending where in the Earth's atmosphere the sunlight had been absorbed.…”

Section: Identifying the Spectrum Componentsmentioning

confidence: 99%

“…Another approach to observe the spectral signature of Earth is during lunar eclipses (Pallé et al 2009, Vidal-Madjar et al 2010, García Munoz et al 2012, Ugolnikov et al 2013, Arnold et al 2014, Yan et al 2015, Kawauchi et al 2018. The major difference to Earthshine observations is that in this case the radiation is dominated by selective absorption and scattering processes of sunlight transmitting the Earth atmosphere rather than by its reflection off the Earth's atmosphere, its clouds and the ground.…”

Section: Introductionmentioning

confidence: 99%

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High-resolution spectroscopy and spectropolarimetry of the total lunar eclipse January 2019

Strassmeier

Ilyin

Keles

et al. 2020

A&A

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Context. Observations of the Earthshine off the Moon allow for the unique opportunity to measure the large-scale Earth atmosphere. Another opportunity is realized during a total lunar eclipse which, if seen from the Moon, is like a transit of the Earth in front of the Sun. Aims. We thus aim at transmission spectroscopy of an Earth transit by tracing the solar spectrum during the total lunar eclipse of January 21, 2019. Methods. Time series spectra of the Tycho crater were taken with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in its polarimetric mode in Stokes IQUV at a spectral resolution of 130 000 (0.06 Å). In particular, the spectra cover the red parts of the optical spectrum between 7419-9067 Å. The spectrograph's exposure meter was used to obtain a light curve of the lunar eclipse.Results. The brightness of the Moon dimmed by 10. m 75 during umbral eclipse. We found both branches of the O 2 A-band almost completely saturated as well as a strong increase of H 2 O absorption during totality. A pseudo O 2 emission feature remained at a wavelength of 7618 Å, but it is actually only a residual from different P-branch and R-branch absorptions. It nevertheless traces the eclipse. The deep penumbral spectra show significant excess absorption from the Na i 5890-Å doublet, the Ca ii infrared triplet around 8600 Å, and the K i line at 7699 Å in addition to several hyper-fine-structure lines of Mn i and even from Ba ii. The detections of the latter two elements are likely due to an untypical solar center-to-limb effect rather than Earth's atmosphere. The absorption in Ca ii and K i remained visible throughout umbral eclipse. Our radial velocities trace a wavelength dependent Rossiter-McLaughlin effect of the Earth eclipsing the Sun as seen from the Tycho crater and thereby confirm earlier observations. A small continuum polarization of the O 2 A-band of 0.12 % during umbral eclipse was detected at 6.3σ. No line polarization of the O 2 A-band, or any other spectral-line feature, is detected outside nor inside eclipse. It places an upper limit of ≈0.2% on the degree of line polarization during transmission through Earth's atmosphere and magnetosphere.

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Section: Identifying the Spectrum Componentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

High-resolution spectroscopy and spectropolarimetry of the total lunar eclipse January 2019

Strassmeier

Ilyin

Keles

et al. 2020

A&A

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“…It is difficult to rigorously assess the significance or cause of the effective height differences, because of the large uncertainties in our determination of each of relevant parameters in converting to effective height as well as the average eclipse angle and CLV correction corresponding to our data. However, these figures highlight that the rapidly evolving geometry during a transit results in probing different altitudes as a function of time as has been discussed in García Muñoz & ), Arnold et al (2014), and Kawauchi et al (2018.…”

Section: Discussionmentioning

confidence: 73%

“…Many lunar eclipse observations aimed at studying Earth as an exoplanet have been conducted at visible and infrared wavelengths (Pallé et al 2009;Vidal-Madjar et al 2010;Ugolnikov et al 2013;Arnold et al 2014;Yan et al 2015a,c;Kawauchi et al 2018), revealing the spectral signatures of many gaseous species as well as aerosols. Observations can be obtained in two different phases of an eclipse, the penumbral and umbral phases.…”

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confidence: 99%

The Hubble Space Telescope's near-UV and optical transmission spectrum of Earth as an exoplanet

Youngblood,

Arney,

Muñoz

et al. 2020

Preprint

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We observed the 2019 January total lunar eclipse with the Hubble Space Telescope's STIS spectrograph to obtain the first near-UV (1700-3200 Å) observation of Earth as a transiting exoplanet. The observatories and instruments that will be able to perform transmission spectroscopy of exo-Earths are beginning to be planned, and characterizing the transmission spectrum of Earth is vital to ensuring that key spectral features (e.g., ozone, or O 3 ) are appropriately captured in mission concept studies. O 3 is photochemically produced from O 2 , a product of the dominant metabolism on Earth today, and it will be sought in future observations as critical evidence for life on exoplanets. Ground-based observations of lunar eclipses have provided the Earth's transmission spectrum at optical and near-IR wavelengths, but the strongest O 3 signatures are in the near-UV. We describe the observations and methods used to extract a transmission spectrum from Hubble lunar eclipse spectra, and identify spectral features of O 3 and Rayleigh scattering in the 3000-5500 Å region in Earth's transmission spectrum by comparing to Earth models that include refraction effects in the terrestrial atmosphere during a lunar eclipse. Our near-UV spectra are featureless, a consequence of missing the narrow time span during the eclipse when near-UV sunlight is not completely attenuated through Earth's atmosphere due to extremely strong O 3 absorption and when sunlight is transmitted to the lunar surface at altitudes where it passes through the O 3 layer rather than above it. INTRODUCTIONAs we approach the era of directly characterizing the atmospheres of Earth-sized exoplanets, considerable preparation is underway to determine how we would recognize signatures of habitability or life from many parsecs away using techniques like transit spectroscopy and direct imaging. A major component of these preparations is the evaluation of biosignatures, the remotely observable features

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“…There are three main methods for removing these telluric absorption lines. One uses the spectra of a rapidly rotating star (a rapid rotator) (e.g., Winn et al 2004;Kawauchi et al 2018), one uses the telluric lines in out-of-transit spectra (e.g., Astudillo-Defru & Rojo 2013;Wyttenbach et al 2015), and one uses "molecfit" program (Smette et al 2015;Kausch et al 2015) which combines model spectra of Earth's atmosphere with the local weather profile (e.g., Hoeijmakers et al 2020;Seidel et al 2020b).…”

Section: Telluric Correctionmentioning

confidence: 99%

Investigation of the upper atmosphere in ultra-hot Jupiter WASP-76 b with high-resolution spectroscopy

Kawauchi,

Narita,

Sato

et al. 2021

Preprint

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Alkali metal lines are one of the most important key opacity sources for understanding exoplanetary atmospheres because the Na I resonance doublets are thought to be the cause of low albedo, as the alkali metal's wide line wings absorb almost all of the incoming stellar irradiation. High-resolution transmission spectroscopy of Na absorption lines can be used to investigate the temperature of the thermosphere of hot Jupiters, which is increased by stellar X-ray and EUV irradiation. We applied high-resolution transmission spectroscopy to the ultrahot Jupiter WASP-76 b with the High Dispersion Spectrograph (HDS) on the Subaru 8.2 m telescope. We report the detection of strong Na D excess absorption with line contrasts of 0.42 ± 0.03 % (D1 at 5895.92 Å) and 0.38 ± 0.04 % (D2 at 5889.95 Å), FWHMs of 1.63 ± 0.13 Å (D1) and 1.87 ± 0.22 Å (D2), and EWs of (7.29 ± 1.43) × 10 −3 Å (D1) and (7.56 ± 2.38) × 10 −3 Å (D2). These results show that the Na D absorption lines are shallower and broader than those in previous work, whereas the absorption signals over the same passband are consistent with those in previous work. We derive the best-fitted isothermal temperature of 3700 K (without rotation) and 4200 K (with rotation). These results suggest the possibility of the existence of a thermosphere because the derived atmospheric temperature is higher than the equilibrium temperature (∼ 2160 K).

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Earth’s atmosphere’s lowest layers probed during a lunar eclipse

Cited by 18 publications

References 33 publications

High-resolution spectroscopy and spectropolarimetry of the total lunar eclipse January 2019

High-resolution spectroscopy and spectropolarimetry of the total lunar eclipse January 2019

The Hubble Space Telescope's near-UV and optical transmission spectrum of Earth as an exoplanet

Investigation of the upper atmosphere in ultra-hot Jupiter WASP-76 b with high-resolution spectroscopy

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