Undernews is the online report of the Progressive Review, edited by Sam Smith, who covered Washington during all or part of one quarter of America's presidencies and edited alternative journals since 1964. The Review has been on the web since 1995. See main page for full contents

August 11, 2009


Space Fellowship - One of the hottest topics at this year's XXVIIth General Assembly of the International Astronomical Union in Rio de Janeiro, Brazil involves the study of the astrophysical conditions favorable for the development and survival of primordial life. New research shows that compared to middle-aged stars like the Sun, newly formed stars spin faster generating strong magnetic fields that result in emission of more intense levels of X-rays, ultraviolet rays and charged particles -- all of which could wreak havoc on budding atmospheres and have a dramatic effect on the development of emerging life forms. . .

The Sun is awe-inspiring and fearsome -- a superheated ball about 300,000 times as heavy as the Earth, radiating immense amounts of energy and hurling great globs of hot plasma millions of kilometers out into space. The intense radiation from this giant powerhouse would be fatal close to the Sun, but for a planet like Earth, orbiting at a safe distance from these violent outbursts, and bathed by a gentler radiation, the Sun can provide the steady energy supply needed to sustain life. Now sedate and middle-aged, at around 4.5 billion years old, the Sun's wild youth is behind it.

Edward Guinan, a professor of astronomy and astrophysics at Villanova University, and his "Sun-in-Time" project team have studied stars that are analogues of the Sun at both early and late stages of its lifecycle. These "solar proxies" enable scientists to look through a window in time to see the harsh conditions prevailing in the early or future solar system, as well as in planetary systems around other stars. . . . This work has revealed that the Sun rotated more than ten times faster in its youth (over four billion years ago) than today. The faster a star rotates, the harder the magnetic dynamo at its core works, generating a stronger magnetic field, so the young Sun emitted X-rays and ultraviolet radiation up to several hundred times stronger than the Sun today. . .

Guinan explains a surprising realisation that emerged from their work: "The Sun does not seem like the perfect star for a system where life might arise. Although it is hard to argue with the Sun's success as it so far is the only star known to host a planet with life, our studies indicate that the ideal stars to support planets suitable for life for tens of billions of years may be a smaller slower burning 'orange dwarf' with a longer lifetime than the Sun -- about 20-40 billion years. These stars, also called K stars, are stable stars with a habitable zone that remains in the same place for tens of billions of years. They are 10 times more numerous than the Sun, and may provide the best potential habitat for life in the long run". He continues: "On the more speculative side we have also found indications that planets like Earth are also not necessarily the best suited for life to thrive. Planets two to three times more massive than the Earth, with a higher gravity, can retain the atmosphere better. They may have a larger liquid iron core giving a stronger magnetic field that protects against the early onslaught of cosmic rays. Furthermore, a larger planet cools more slowly and maintains its magnetic protection. This kind of planet may be more likely to harbor life. I would not trade though -- you can't argue with success".. . .

The scientists agree that we do yet know how ubiquitous or how fragile life is, but as Guinan concludes: "The Earth's period of habitability is nearly over -- on a cosmological timescale. In a half to one billion years the Sun will start to be too luminous and warm for water to exist in liquid form on Earth, leading to a runaway greenhouse effect in less than 2 billion years".


Anonymous robbie said...

For an excellent depiction of this, read Carl Sagan's "Cosmos"

August 11, 2009 9:02 PM  
Anonymous Mairead said...

A half-billion years might be enough time for Earth to become habitable again and a new dominant lifeform to arise after the evil mix of Capitalism and Big Religion flush all high-order life down the toilet into the fossil record.

August 12, 2009 5:09 AM  

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