Understanding how planets grow from 'seeds'
Image credit: NASA/JPL-Caltech
Jill Tarter: We often make statements like, “a planet forms in the following way,” and I liken that to a wonderful cartoon that has a scientist standing up at a blackboard with this very long equation, and somewhere down at the beginning of the equation there’s an arrow and it says, “and here, a miracle occurs.”
That’s astronomer Jill Tarter, director of The Center for the Search for Extraterrestrial Intelligence Research. And she’s talking about the seeds around which entire planets form. They’re called ‘planetesimals.’
Jill Tarter: Where do those planetesimals come from? Well, ultimately they come from small grains of dust that coalesce. And what we don’t yet have is good observational data that will allow us to build a convincing model for how the dust grains grow through collisional accretion into that kilometer-size planetesimal. So that’s where our miracle is, at the moment, in our theory of planet formation.
A new radio telescope, called ALMA, is set for completion in the year 2012 in the Atacama desert of Chile. Tarter said that ALMA might be able to answer questions about dust grains and planetesimals.
Jill Tarter: That will be working at millimeter wavelengths, which is again, just the scale of those dust grains as they begin to grow. And so this will be an optimal instrument for helping us to better understand the physical processes.
And that might, Tarter added, help explain the miracle of how grains of dust form into planets.
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