A new interpretation of light emissions from stars has led scientists to the conclusion that there may be vast numbers of earthlike planets in the universe.

Norman Murray of the University of Toronto claims that the presence of iron in the starlight of more than half the stars in a sample of our galaxy indicates that they may have rocky planets in orbit around them.

Professor Murray says, “if there are bodies in orbit around these stars, at least the probability that there is life–similar to what we consider to be life–has to be more likely than it would have been before we discovered this evidence.”

All of the 55 extrasolar planets so far discovered have been gas giants, some of them as large as small stars. Due to their small size, earthlike planets, if they are there, cannot be detected using direct methods.

However, some of the small, rocky planets in our solar system, such as Earth and Mars, contain a high proportion of iron. Some of this iron will end up in the atmosphere of the stars the planets orbit, in the form of dust and debris, and would be detectable in light shining from the star.

Professor Murray found that 466 of the 640 stars he studied had at least half a planet’s worth of iron in their atmospheres. Given that the Milky Way galaxy contains a hundred billion stars, and the known universe a hundred billion galaxies, the overall number of earthlike planets could be well into the billions or even higher, with hundreds of millions of them in our galaxy alone.

Even so, this does not argue for a profusion of intelligent species, or even higher life-forms. This is because planets harboring complex life need heavy atmospheres, and such atmospheres will move at high speeds due to the rotation of the planets, unless the planets have large moons to slow them down.

For a planet to have a viable atmosphere, with variable weather instead of continuously roaring rotational winds, it must have a moon large enough for its gravity to brake the flow of the wind on the planet. The moon must also be situated at the right distance from the planet.

The odds of a given earthlike planet also possessing a moon that would damp the speed of its atmosphere’s rotation winds are unknown.

In addition, the earthlike planet must be just the right distance from its star for the atmosphere to be neither too warm nor too cold, and the star–unlike most that have been observed–must not be in the habit of sterilizing its surroundings with frequent massive flares and other energy bursts.

So the probability of us finding intelligent life on another planet remains vanishingly small, but if Professor Murray is right, the odds are that such planets, although extremely rare, probably do exist.

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