Until someone invents a real-life Tardis or some other time machine, there's no way for us to know the exact sequence of events in the birth of our solar system. Scientists have a good outline, but some of the details are a little fuzzy.
We can learn about the process, though, by watching infant star systems -- ones where planets may be taking shape.
An example is a system known as TW Hydrae. It's in Hydra, the sea serpent -- a long but faint constellation that slithers across the south on winter nights.
TW Hydrae belongs to a group of at least 30 infant stars. They were born only a few million years ago, from a single giant cloud of dust and gas.
TW Hydrae is a little smaller, cooler, and less massive than the Sun. But just like the Sun at that age, it's encircled by a disk of pebbles -- the possible raw materials for planets. The disk is many times wider than the realm of the planets in our own solar system.
Most of the pebbles in the disk are only about a centimeter across. Models of planet formation say that such pebbles stick together to form larger and larger bodies -- all the way up to planets. And in fact, there's a wide gap in the disk around TW Hydrae that could have been swept clean by the gravity of a planet that's already taken shape.
So keeping an eye on TW Hydrae may be the next best thing to a time machine -- a way to look at what our own solar system was like as the planets were being born.
Script by Damond Benningfield, Copyright 2008
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