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Post Info TOPIC: August 16, 2008 partial lunar eclipse


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The Transiting Earth 

From spectra collected during the August 2008 lunar eclipse, astronomers have been able to investigate the in-transit signature of the Earth-Sun system as would be observed from outside the solar system. They found that the refraction of sunlight as it passes through a planetary atmosphere similar to the Earth's contributes prominently to the in-transit transmission spectrum and this contribution depends on the characteristics of the atmosphere, the size of the host star, and the distance from the host star. This research has important implications for future attempts to characterise the atmospheres of Earth-like extrasolar planets, especially those in similar long-period orbits.
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Title: Glancing views of the Earth. From a lunar eclipse to an exoplanetary transit
Authors: A. García Muñoz (IAC, ULL), M. R. Zapatero Osorio (CAB, INTA-CSIC), R. Barrena (IAC, ULL), P. Montañés-Rodríguez (IAC, ULL), E. L. Martín (CAB, INTA-CSIC), E. Pallé (IAC, ULL)

It has been posited that lunar eclipse observations may help predict the in-transit signature of Earth-like extrasolar planets. However, a comparative analysis of the two phenomena addressing in detail the transport of stellar light through the planet's atmosphere has not yet been presented. Here, we proceed with the investigation of both phenomena by making use of a common formulation. Our starting point is a set of previously unpublished near-infrared spectra collected at various phases during the August 2008 lunar eclipse. We then take the formulation to the limit of an infinitely distant observer in order to investigate the in-transit signature of the Earth-Sun system as being observed from outside our Solar System. The refraction-bending of sunlight rays that pass through the Earth's atmosphere is a critical factor in the illumination of the eclipsed Moon. Likewise, refraction will have an impact on the in-transit transmission spectrum for specific planet-star systems depending on the refractive properties of the planet's atmosphere, the stellar size and the planet's orbital distance. For the Earth-Sun system, at mid-transit, refraction prevents the remote observer's access to the lower ~12-14 km of the atmosphere and, thus, also to the bulk of the spectroscopically-active atmospheric gases. We demonstrate that the effective optical radius of the Earth in transit is modulated by refraction and varies by ~12 km from mid-transit to 2nd contact. The refractive nature of atmospheres, a property which is rarely accounted for in published investigations, will pose additional challenges to the characterisation of Earth-like extrasolar planets. Refraction may have a lesser impact for Earth-like extrasolar planets within the habitable zone of some M-type stars.

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A lunar eclipse helped a group of international scientists take a snapshot of earths chemical fingerprint, which could help to identify planets most similar to earth where life may be thriving.
University of Central Florida Associate Professor Eduardo Martin was a member of the team that made the observation, which is published in the June 11 edition of Nature magazine.
The team used some of the worlds largest optical and infrared telescopes located at the Roque de los Muchachos Observatory in La Palma (Canary Islands, Spain) to observe light reflected from the moon toward the earth during a lunar eclipse on Aug. 16, 2008.


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On August 16, 2008 (and August 17 east of England) the full Moon will pass through the Earth's shadow, producing a deep partial lunar eclipse for skywatchers throughout Europe, Africa. Asia and South America. At 19:36 UT the Moon begins its entry into the innermost shadow zone. For more than an hour a circular shadow creeps across the Moon's face. At 21:10 UT maximum eclipse takes place, during which 81 percent of the Moon's diameter will be immersed in Earth's shadow. Although the Moon will not be completely hidden in the shadow, the eclipsed part of the Moon should show the eerie coppery tint that is so prominent during total lunar eclipses. The partial eclipse will end at 22:44 UT, when the Moon leaves the dark shadow.

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Start of the Penumbra

18h 23m 04s UTC

Start of the Dark Shadow

19h 35m 40s UTC

Start of Eclipse

-

Maximum of Eclipse

21h 10m 05s UTC

Finish of Eclipse

-

Exit of the Dark Shadow

22h 44m 35s UTC

Exit  of the Penumbra

23h 57m 02s UTC





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