Why are most stars in binary systems? New Spitzer results may help explain.
Stars form from cosmic dust accumulating in sufficient quantities to generate sufficient gravity to mush the atoms with sufficient compression to cause nuclear fusion. The dust initially gathers in a large formation long thought to be more or less spherical. By the time the process is over, the star-stuff in the middle of this ‘envelope’ of dust, nuclear fusion and all, is likely to be two stars in many cases.
Most of the stars in the galaxy are binary, or twin, stars. At least some (if not most, perhaps almost all) form when this sphere of dust is condensing. Others may form subsequent to dust reaching true stardom, when two newly forming stars begin orbiting each other.
The Spitzer Space Telescope is able to see very low levels of infrared. The fact that infrared energy will be spewed out during star formation is nice, but irrelevant to seeing the cold dust in its initial spherical shape. However, since Spitzer is so freakin’ good at what it does, it can see where the dust is because it blocks the ambient background infrared.
And it turns out that when you look at the dust envelope using this approach, it isn’t so spherical. Rather, it is typically quite asymmetrical, and it is this asymmetry that is thought to contribute to the formation of two, rather than one, stars at a time.
If you want to see pictures or read more about it, NASA has a press release here: NASA Press Release