Home

949.   Sol Jovem Destruiu a Atmosfera de Marte há Bilhões de Anos










Veja o resumo do artigo :

Magnetic field and wind of Kappa Ceti: towards the planetary habitability of the young Sun when life arose on Earth

  We report magnetic field measurements for Kappa1~Cet, a proxy of the young Sun when life arose on Earth. We carry out an analysis of the magnetic properties determined from spectropolarimetric observations and reconstruct its large-scale surface magnetic field to derive the magnetic environment, stellar winds and particle flux permeating the interplanetary medium around Kappa1~Cet. Our results show a closer magnetosphere and mass-loss rate of Mdot = 9.7 x 10^{-13} Msol/yr, i.e., a factor 50 times larger than the current solar wind mass-loss rate, resulting in a larger interaction via space weather disturbances between the stellar wind and a hypothetical young-Earth analogue, potentially affecting the planet's habitability. Interaction of the wind from the young Sun with the planetary ancient magnetic field may have affected the young Earth and its life conditions

Fonte : Cornell University Library, 12/03/2016

Autor : José Dias do Nascimento Jr,...



Earth's magnetic field was crucial for giving life a kick start by protecting the planet from the harsh 'weather' of the early solar system


  Despite our best efforts at listening out for signs, life beyond our own patch of the cosmos has so far remained elusive.

  But scientists believe the 'weather' around stars plays a crucial role in making planets habitable to life, and protection from it is key to kick starting life.

  Turning to a distant star resembling a youthful version of our sun, astronomers claim Earth's magnetic field provided enough protection from the harshness of the early solar system to give life a chance to get going.

  Astronomers studied Kappa Ceti, a young star located 30 light-years away in the Cetus constellation known as the Whale.

  While the star is strikingly similar to our sun, it is calculated to be only 400 to 600 million years old, around the age the sun was when life first appeared on Earth.

  This means studying the young star can provide a window into what the conditions of the early solar system might have been like.

  'To be habitable, a planet needs warmth, water, and it needs to be sheltered from a young, violent sun,' explained José Dias do Nascimento, a researcher at the Harvard-Smithsonian Center for Astrophysics (CfA).

  Stars of this age are typically very active, with their surfaces belching out plasma into space, generating a 'wind' of ionized particles.

  But the researchers found that this stellar wind is 50 times stronger than our sun's solar wind.

  Such fierce stellar weather would make it difficult for chemical reactions to take place on nearby planets, making it extremely unlikely complex molecules needed for life would be able to form.

  That is, unless the planet had a magnetic suitable field like Earth's.

  Writing in an accompanying article in The Conversation, astronomers Jonti Horner and Stephen Marsden, from the University of Southern Queensland, explain: 'Stellar winds can be dangerous things.

  'Without protection, a star's wind can strip the atmosphere from a planet, leaving it an airless husk.

  'And a stronger wind poses more of a threat than a weaker one.'

  In extreme cases, planets lacking a protective magnetic field can have their atmospheres stripped away, which is what is believed to have happened to Mars.

  The team modeled the strong stellar wind of Kappa Ceti and its effect on a young Earth.

  They expect that early Earth's magnetic field would have been roughly as strong as it is today, or slightly weaker.

  The resulting protected region, or magnetosphere, of Earth would be about one-third to one-half as large as it is today, but this created the cover needed for life to get a foothold.

  Horner and Marsden explain: 'As it turns out, our magnetic field would have been enough, even if our sun was once as active as Kappa Ceti.

  'The Earth's shield, the magnetosphere, would have been compressed, shrunk to about one-third its current size.

  'But it would have endured, protecting Earth and allowing our planet to remain habitable.'

  The team believes models such as Kappa Ceti could help in the search for life on distant planets, where a suitable magnetic shield from their parent stars could increase the chances of life being able to start.

  Horner and Marsden conclude: 'By studying stars such as Kappa Ceti, we are building an understanding of how stars and planets interact.

  'Once those first exo-Earths are found, it will be possible to measure and characterize the winds of their host stars.

  'This will then help us determine which of those planets to target in the search for life elsewhere.'

  The research is published in Astrophysical Journal Letters.

Fonte : Daily Mail, 17/03/2016

Autor : Ryan O'Hare

Astronomers believe the 'weather' around stars plays a crucial role in whether life can gain a foothold, and protection from it was key in the struggle to life appearing on Earth billions of years ago. They studied Kappa Ceti, a star 30 light-years away that is a more youthful version of our own sun

The study modeled strong stellar winds of the sun-like star and its effect on a young Earth. They expect that early Earth's magnetic field would have been roughly as strong as it is today, or slightly weaker (pictured). They also found early Earth's magnetosphere would have been one-third as large as it is today

In extreme cases, planets lacking a protective magnetic field like Earth's (stock image) can have their atmospheres stripped away, which is what is believed to have happened to Mars

<p align="center"> <font face="tahoma" size=4> <a href="Menu_alternativo.htm" target="_top"> <font color="ff0000">Voltar para o Menu Alternativo</font> </a> </font> </p>