More than 200 years ago, Astronomers have developed a method of mapping the eclipses which was until now authoritative. This approach considers the Moon as a smooth sphere and the Earth as a flat plane.
Therefore, the representation of the shadow of the Moonwhich we callTHE umbraconsists of an oval with smooth contours. However, the reality is quite different.. Lat NASA has developed A new method of mapping eclipses solar Who introduces an understanding realistic of the shape of theumbra.
A potato-shaped shadow
He holds account of lunar topography relying on the lunar LRO data Who reveal the rugged terrain by the differences in elevation of mountains and valleys. So, the lunar profile East-he constantly changing as the Moon's shadow passes across the Earth, lunar surface irregularities affecthasthe shape of the cast shadow.
” Traditionally, eclipse calculations assume that all observers are at sea level on Earth and that the Moon is a smooth sphere perfectly symmetrical about its center of mass. ” explains NASA. ” These calculations therefore do not take into account the different altitudes on Earth or the cratered and irregular surface of the Moon. »
Photo credit: ©NASA Reproduction of the projected images of the Sun reaching the Earth, seen from behind the Moon. The black dot in the center of the cones is the umbra. The outer edges of the images of the Sun mark the limit of the penumbra, materialized in purple.
This is what allows us to explain why theumbra looks more like a potato than a perfect oval. This very precise mapping, pixel by pixel, allownwe only to predict more accurately the duration and timing of the entirety of a solar eclipsebut also the complex interactions between light, the Moon and the Earth.
Variations in relief that can modify the duration of an eclipse
Lunar mountains shorten the shadow cast by the Moon, while valleys lengthen it slightly. These variations subtle can change the duration of the entire the eclipse of a few secondsexplains NASA.
This sheds new light on phenomena such as pearls of Bailey and the diamond ring. These events occur when sunlight passes through lunar valleys located on the visible edge of the Moon from Earthcreating bright spots just before and after totality which slightly modify the beginning and the end of the eclipse. ” Valleys on the edge of the Moon act like pinholes projecting images of the Sun onto the Earth's surface ” comments NASA.
A Better Understanding of Hybrid Eclipses
As explained Ernie Wright, expert at the Goddard Space Flight Center in NASA and lead author of the study published in Tea Astronomical Newspaperthere new mapping method revealed the existence of a third type of central eclipse, called ” broken annular eclipse ». This rare eclipse occurs when the Moon's shadow is neither completely nor “annularly” aligned with the Sun, creating a ring of sunlight interrupted by lunar peaks.
The other benefit highlighted in the scientific article is that this technique of modeling can be used to measure the sun's ray with precision by providing scientists with aelement of comparison with their actual observations.
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