Measuring the Solar Radius From Space During the 2003 and 2006 Mercury Transits

Emílio, M.; Kuhn, J. R.; Bush, R. I.; Scholl, Isabelle

doi:10.1088/0004-637x/750/2/135

Cited by 76 publications

(43 citation statements)

References 37 publications

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“…The data were reduced and calibrated for all the slit positions (i.e., corresponding to level 1 data). The solar diameter in that period was 31.7 (∼951.1 for the radius), the geometrical distance on the solar surface, seen under one arcsecond, was R SOHO /951.1 × 0.109 = 732.1 km (with R SOHO = 696 342 km measured by the SOHO spacecraft, Emilio et al 2012). The spatial resolution of the image is 1024 × 1024 pixels (Fig.…”

Section: Evaluation Of the Venusian Aureole With Hinodementioning

confidence: 95%

New view on exoplanet transits

Chiavassa

Pere

Faurobert

et al. 2015

A&A

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Context. An important benchmark for current observational techniques and theoretical modeling of exoplanet atmospheres is the transit of Venus (ToV). Stellar activity and, in particular, convection-related surface structures, potentially cause fluctuations that can affect the transit light curves. Surface convection simulations can help interpreting the ToV as well as other transits outside our solar system. Aims. We used the realistic three-dimensional (3D) radiative hydrodynamical (RHD) simulation of the Sun from the Stagger-grid and synthetic images computed with the radiative transfer code Optim3D to predict the transit of Venus (ToV) in 2004 that was observed by the satellite ACRIMSAT. Methods. We computed intensity maps from the RHD simulation of the Sun and produced a synthetic stellar disk image as an observer would see, accounting for the center-to-limb variations. The contribution of the solar granulation was considered during the ToV. We computed the light curve and compared it to the ACRIMSAT observations as well as to light curves obtained with solar surface representations carried out using radial profiles with different limb-darkening laws. We also applied the same spherical tile imaging method as used for RHD simulation to the observations of center-to-limb solar granulation with Hinode. Results. We explain ACRIMSAT observations of 2004 ToV and show that the granulation pattern causes fluctuations in the transit light curve. We compared different limb-darkening models to the RHD simulation and evaluated the contribution of the granulation to the ToV. We showed that the granulation pattern can partially explain the observed discrepancies between models and data. Moreover, we found that the overall agreement between real and RHD solar granulation is good, either in terms of depth or ingress/egress slopes of the transit curve. This confirms that the limb-darkening and granulation pattern simulated in 3D RHD of the Sun represent well what is imaged by Hinode. In the end, we found that the contribution of the Venusean aureole during ToV is ∼10 −6 times less intense than the solar photosphere, and thus, accurate measurements of this phenomena are extremely challenging. Conclusions. The prospects for planet detection and characterization with transiting methods are excellent with access to large a amount of data for stars. Being able to consistently explain the data of 2004 ToV is a new step forward for 3D RHD simulations, which are becoming essential for detecting and characterizing exoplanets. They show that granulation has to be considered as an intrinsic uncertainty (as a result of stellar variability) on precise measurements of exoplanet transits of, most likely, planets with small diameters. In this context, it is mandatory to obtain a comprehensive knowledge of the host star, including a detailed study of the stellar surface convection.

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Section: Evaluation Of the Venusian Aureole With Hinodementioning

confidence: 95%

New view on exoplanet transits

Chiavassa

Pere

Faurobert

et al. 2015

A&A

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“…Não devemos esquecer também do seu valor científico: recentemente os trânsitos de Mercúrio de 2003 e 2006 foram utilizados para a medição do raio do Sol com excelente exatidão (a incerteza foi de apenas 65km) [11] e posteriormente este resultado foi ainda melhorado pelo mesmo grupo com a utilização do trânsito de Vênus de 2012 (neste segundo estudo, a incerteza foi de 15km) [12]. Na próxima Seção faremos uma adaptação do método de Halley e Deslile que pode ser facilmente reproduzida em sala de aula seja no ensino médio ou superior, em cursos de introduçãoà Astronomia.…”

Section: A Importância Da Unidade Astronômicaunclassified

O antigo adapta-se ao moderno: verificação do valor da Unidade Astronômica a partir do trânsito de Vênus reproduzido com o software Stellarium

Rizzuti

Silva

2016

Rev. Bras. Ensino Fís.

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A distância Terra-Sol, conhecida como Unidade Astronômica (UA), tem papel fundamental para a Astronomia: ela fornece uma escala de distâncias dentro do nosso sistema solar e serve como base para a medida de distâncias entre o Sol e estrelas próximas. Neste trabalho, apresentamos uma das maneiras para se obter a UA a partir dos trânsitos de Vênus pelo disco solar. Esta é uma adaptação do método de Halley e foi aplicado a partir das imagens obtidas pelo software livre de Astronomia Stellarium. Encontramos o valor (1, 4±0, 3)⋅108km, em concordância de 93, 6% com o valor aceito pela literatura. A revisão do método de obtenção da Unidade Astronômica a partir do trânsito de planetas fundamenta-se por razões tanto pedagógicas quanto científicas: este trabalho pode ser facilmente reproduzido em salas de aula tanto do ensino médio quanto superior em cursos de introdução à Astronomia. Além disso, o trânsito de Vênus de 2012 foi utilizado para a determinação do raio do Sol com incerteza de apenas 15km, justificando assim o seu estudo. Por fim, este trabalho fornece um teste de autoconsistência do Stellarium, uma vez que determinamos por meios geométricos o valor da UA utilizado pelo programa.

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“…The absolute pixel calibration, orbit information, and focus step are no longer essential, but flat field, focus plane deformation, and CCD small tip-tilt can affect seriously this measure. Rolling the telescope is a fair solution for such instrumental problems (Emilio et al, 2007 and2012). To locate weighted inflexion points of the solar limb we used, as Emilio et al (2012), polar coordinates transform of limb stripes with a bilinear interpolation, while Kuhn et al (1998) decomposed the solar limb position and brightness into a linear combination of Legendre polynomials.…”

Section: Measurements Of the Solar Diametermentioning

confidence: 99%

Geometrical information on the solar shape: high precision results with SDO/HMI

Wang

Sigismondi²

2012

Proc. IAU

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Abstract. The uncertainty of measurement of solar diameter is depending on the observational time scale. Full-disc images of SDO/HMI and the images from ground observations in Huairou Solar Observing Station have been analyzed to get the values of solar diameter. The satellite observations reach a very high precision, but the absolute image scale still need to be calibrated. The solar oblateness is a more challenging measurement than the diameter, since the signal amplitude is a few milli-arcseconds. It is a relative measurement, then not affected by the pixel scale calibration required by the diameter measurement. But the results are strongly dependent on the state of instrument such as focus plane deformation and on the calculation process.

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Measuring the Solar Radius From Space During the 2003 and 2006 Mercury Transits

Cited by 76 publications

References 37 publications

New view on exoplanet transits

New view on exoplanet transits

O antigo adapta-se ao moderno: verificação do valor da Unidade Astronômica a partir do trânsito de Vênus reproduzido com o software Stellarium

Geometrical information on the solar shape: high precision results with SDO/HMI

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