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Colossal dying star "saved the Earth from being a hostile ocean world"


Posted on Feb 11, 2019

Extreme ocean world

If a massive star in the Sun's birth environment, a yellow G2 dwarf star, one of a billion stars in the Milky Way, had not injected radioactive elements into the early solar system, our planet could be a hostile oceanic world covered. global ice layers. Some astronomers now think that each star similar to the Sun has at least one "Earth-like" planet in the so-called "habitable zone" around a star, the region where liquid water can exist.

When our proto-Sun was formed, a supernova occurred in the cosmic neighborhood. The radioactive elements, including the aluminum-26, were fused in this massive star and injected into our young solar system, either by excessive stellar winds or by means of the supernova ejecta after the explosion.

This great star, perhaps 30 times more massive than our Sun, exploded, destroying its outer layers, including aluminum-26, approximately one million years before the final explosion of the remaining core of the star. This initial burst would have been enough to trigger the collapse of the knot in the giant molecular cloud from which the Solar System formed. After a few million years, the star became a supernova, spilling its cosmic environment,

The explosion of the supernova must have occurred within a tenth of a light year of the formation of the Solar System, notes John Gribbin in Only in the Universe: why our planet is unique, when the sun was less than 2 million years old. No other supernova has exploded so close to the Sun; If he had, life on Earth would have been exterminated. It can not be a coincidence that this apparently unlikely event occurred where the Solar System was formed, and the natural explanation is that both the Sun and the supernova were members of a group of stars that formed together in the same gas cloud, and since then their separate ways have gone.

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"The results of our simulations suggest that there are two types of qualitatively different planetary systems," said Tim Lichtenberg of the National Center for Planet Research Competition in Switzerland. "There are those similar to our solar system, whose planets have little water, and those in which primarily oceanic worlds are created because there was not a massive star when its host system was formed."

Lichtenberg and his colleagues, including astronomer Michael Meyer of the University of Michigan, initially were intrigued by the role that the potential presence of a massive star played in the formation of a planet. Meyer said the simulations help solve some questions, while raising others.

"It's great to know that radioactive elements can help dry the wet system and have an explanation of why planets within the same system would share similar properties," Meyer said. "But radioactive heating may not be enough. How can we explain our Earth, which is very dry, in fact, compared to the planets formed in our models? Perhaps having Jupiter where it is was also important in keeping most of the ice bodies out of the inner solar system. "

Researchers say that while water covers more than two-thirds of the Earth's surface, in astronomical terms, the internal terrestrial planets of our solar system are very dry, fortunately, because many good things can do more harm than good.

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All planets have a nucleus, mantle (inner layer) and crust. If the water content of a rocky planet is significantly higher than on Earth, the mantle is covered by a deep global ocean and an impenetrable ice sheet at the bottom of the ocean. This avoids geochemical processes, such as the carbon cycle on Earth, that stabilize the climate and create surface conditions that lead to life as we know it.

The researchers developed computer models to simulate the formation of planets from their building blocks, the so-called planetesimals, icy rocky bodies of probably dozens of kilometers in size. During the birth of a planetary system, planetesimals form in a disk of dust and gas around the young star and become planetary embryos.

As these planetesimals are heated from the inside, part of the initial water ice content evaporates and escapes into space before it can be sent to the planet itself. This internal warming may have occurred shortly after the birth of our solar system 4,600 million years ago, as suggested by the primitive traces of meteorites, and may still be in progress in many places.

The researchers say that the quantitative predictions of this work will help space telescopes of the near future, dedicated to the hunting of extrasolar planets, to track possible traces and differences in planetary compositions, and refine the predicted implications of the dehydration mechanism Al-26 .

They are waiting impatiently for the launch of the next space missions with which you can see exoplanets the size of Earth outside our solar system. This will make humanity closer and closer to understanding if our planet is one of the types or if there are "an infinity of worlds of the same type as ours".

His study appears in Nature Astronomy. Other researchers include those from the Swiss Federal Institute of Technology, the University of Bayreuth and the University of Bern.

A 2012 study published by researchers at the University of Chicago challenged the idea that the force of an exploding star caused the formation of the solar system. In this study, published online last month in Earth and Planetary Science Letters, authors Haolan Tang and Nicolas Dauphas found the radioactive isotope of iron 60, the telltale sign of an exploding star, low in abundance and well mixed with the material Of the solar system. As cosmochemists, they look for remnants of stellar explosions in meteorites to help determine the conditions under which the solar system was formed. Some remnants are radioactive isotopes: unstable and energetic atoms that decompose over time. Scientists in the last decade have found high amounts of radioactive isotope 60 in the first materials of the solar system.

"If you have 60 iron in large quantities in the solar system, that's a 'smoking gun,' evidence of the presence of a supernova," said Dauphas, a professor of geophysical sciences. Iron 60 can only originate from a supernova, so scientists have tried to explain this apparent abundance by suggesting that a nearby supernova occurred, spreading the isotope through the explosion.

But Tang and Dauphas discovered that 60 iron levels were uniform and low in the initial material of the solar system. They reached these conclusions by testing meteorite samples. To measure the abundance of iron 60, they observed the same materials on which previous researchers had worked, but used a different and more precise approach that yielded very low evidence of iron.

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