Sol engolirá a Terra em 7,6 bi de anos, diz astrônomo

Um novo cálculo realizado por astrônomos afirma que a Terra será “engolida” pelo Sol em 7,6 bilhões de anos, segundo um estudo publicado pela revista científica Monthly Notices of the Royal Astronomical Society. A previsão quer terminar com um longo debate sobre a capacidade do nosso planeta de resistir ou não à atração gravitacional solar.

Outras teorias dizem que a Terra vai “fritar” no momento que o Sol se expandir. Mas o tempo estimado varia em bilhões de anos. “Ainda que esse problema tenha sido abordado antes, nós acreditamos que esta é a melhor abordagem sobre o assunto”, disse o astrônomo britânico Robert Smith, da Universidade de Sussex.

Ainda que 7,6 bilhões de anos pareça muito tempo, não é aconselhável deixar de lado o fato de que o clima do nosso planeta vai esquentar ainda mais, acompanhando o ritmo do Sol. “Depois de cerca de um bilhão de anos a Terra não terá atmosfera nem água, e a temperatura na superfície chegará a centenas de graus Celsius”, disse Smith.

Apesar de provavelmente não estarmos mais aqui, os cientistas estão curiosos sobre o episódio final da Terra. Estudos recentes do próprio Smith indicam que, quando o Sol envelhecer e se tornar uma gigante vermelha, ele vai perder massa e força gravitacional. Isso pode fazer com que a Terra seja capaz de se “desprender” da órbita da estrela.

Mas esse cenário não considera as forças relativas, como as exercidas pelas suas camadas externas. Os campos gravitacionais menores do Sol não são completamente insignificantes em relação à órbita da Terra – eles fazem com que o lado do Sol voltado para o nosso planeta acumule mais massa, ficando mais “inchado”.

“Ao mesmo tempo em que a Terra faz o Sol ‘inchar’, o Sol atrai a Terra, e faz com que o nosso entre vagarosamente em sua órbita”, disse Smith. “No final, vamos acabar dentro do Sol”. Além disso, o gás que a estrela expele vai arrastar a Terra à morte, sentenciou o cientista ao site Space.com.

Earth’s Final Sunset Predicted

“Some say the world will end in fire, Some say in ice,” wrote the poet Robert Frost. Astronomers, it turns out, are in the former camp.

A new calculation predicts that Earth will be swallowed up by the sun in 7.6 billion years, capping off a longstanding debate over whether the sun’s gravitational pull will have weakened enough for Earth to escape final destruction or not.

Other theorists have predicted that our planet will fry as the sun expands in its old age. But the time estimates have varied by a couple billion years.

“Although people have looked at these problems before, we would claim this is the best attempt that’s been made to date, and probably the most reliable,” said astronomer Robert Smith, emeritus reader at the U.K.’s University of Sussex, who made the new calculations with astronomer Klaus-Peter Schroeder of the University of Guanajuato in Mexico. “What we’ve done is to refine existing models and to put the best calculations we can at each point in the model.”

If 7.6 billion years doesn’t sound like an urgent death sentence, don’t relax yet. Regardless of whether Earth will ultimately be vaporized, as the sun heats up, our planet will become too hot to live on before then.

“After a billion years or so you’ve got an Earth with no atmosphere, no water and a surface temperature of hundreds of degrees, way above the boiling point of water,” Smith told SPACE.com. “The Earth will become dry basically. It will become completely impossible for life of any kind to exist. It’s a pretty gloomy forecast.”

Nonetheless, scientists are curious about the ultimate fate of our planet after we are gone (like all previous hominids and more than 99 percent of all species that have lived on Earth, humans will probably go extinct, and it will likely happen sooner than a billion years).

Smith’s earlier studies found that Earth would narrowly escape being engorged. As the sun ages and expands into a red giant star, it will shed its outer gaseous layers, thus losing mass and weakening its gravitational pull. Previous calculations found that this let-up would allow the Earth’s orbit to shift outward, enabling the planet to slip free of the smoldering sun.

But this scenario doesn’t account for tidal forces, and the drag of the sun’s outer layers. As the Earth orbits the sun, its smaller gravitational pull isn’t completely negligible — it actually causes the side of the sun closest to our planet to hoard more mass and bulge out toward us.

“Just as the Earth is pulling on the sun’s bulge, it’s pulling on the Earth, and that causes the Earth to slow in its orbit,” Smith said. “It will spiral back and finally end up inside the sun.”

In addition, the gas that the sun expels will also drag Earth inward toward its demise.

Smith’s previous calculations had ignored these effects.

“We didn’t think it mattered, but it turns out it does,” he said. “You might say our previous models had a gap.”

There may even be hope for Earth. Some scientists have proposed a scheme for down the road to use the gravity of a passing asteroid to budge Earth out of the way of the sun toward cooler territory, assuming there is life around at the time that is intelligent enough to engineer this solution.

“It sounds like science fiction, but there’s a group of people who have quite seriously suggested that it might be possible,” Smith said. “If it’s done right, that would just keep the Earth moving fast enough to keep it out of harm’s way. Maybe life could go on for as much as 7 billion years.”

Anúncios

Sobre Baldaci

A Haggai Alummi M606, An Amateur astronomer, A husband, father and a visionary baptist pastor working hard to Plant a Church in Cuiaba, Brazil and to establish the first Cyber Theater and Planetarium in my state(http://on.fb.me/hkCGff) Unique pastor and astronomer in Brazil. Working using astronomy to reach poor childrens and against drugs. http://bit.ly/eu0zgB Member of SOC-JPL-NASA (http://bit.ly/eoyow6) and Astronomer without borders (http://bit.ly/dTCOJG) Host of program “Eyes on skies” TV Assembléia Legislativa(http://on.fb.me/gmF5LE) e Ombudsman of Education State Secretary of Mato Grosso with assistance to 711 schools. About me at Haggai´s web site: http://bit.ly/hAfceX
Esse post foi publicado em Astronomy`s hot sites, Eduardobaldaci.com, observatory, Phenomena, save the planet e marcado , , , , . Guardar link permanente.

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