Scientists have identified an area in space called the Orion Nebula where tiny specks of dust are growing into infant planets. Conditions there favor the development of Earth- and Mars-sized planets, which have the potential for developing life, rather than gas giants like Jupiter and Saturn.

?We?ve never seen dust in astrophysics that behaves like this,? says Henry Throop at Southwest Research Institute. ?It?s not direct visual evidence of planets, but it?s very direct evidence for large grains, which means these things are sticking together and growing on their way to becoming planetesimals and planets.?

Astronomers have found some 50 planets orbiting stars beyond our solar system in the past 5 years, most of them gas giants inhospitable to life as we know it. None of them are in the Orion Nebula. The potential for solar systems with Earth-sized planets is exciting for those who hope to find extraterrestrial life.

The challenge for these baby planets is the intense ultra-violet radiation emitted by nearby bright stars, which can destroy the tiny dust grains before they form into planets. If they lose the battle against radiation, the dust specks will fail to grow into the slightly larger grains (still 20 times thinner than a human hair) that are needed to begin the formation of planets. ?If they are one millimeter size, then these are huge particles and planets are just around the corner,? says Throop.

There are 3 kinds of objects in our solar system, besides stars (suns). There are rocky terrestrial planets, like Earth and Mars, gas giants, like Jupiter and Saturn, and icy comets. Scientists are hoping that smaller, rocky terrestrial planets are abundant and typical, rather than the exception, because this type of planet could harbor life.

?The search for extrasolar planets must continue,? says Alan Boss, a Carnegie Institution astrophysicist. ?We still do not know what the census results will be for our neighborhood of the galaxy, how many gas giants live here, how many ice giants and especially, how many Earth-like planets.?

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