Stars form when clouds of gas and dust fragment and collapse, forming flat disks of material that feed the young stars' growth. Many times, even most times, this creates multiple stars, two or more stars orbiting each other. Models have predicted that triple stars (called trinaries) can, through the stars' gravities, carve bizarre and fantastic shapes in the disks around them.
And now, for the first time, astronomers have seen exactly that. And it's… well, bizarre and fantastic.
ALMA observations of the trinary star GW Ori (left) highlight the rings of gas and dust around it, while Very Large Telescope images (right) show the shadows in the dust that allowed astronomers to infer the 3D structure. Credit: ALMA (ESO/NAOJ/NRAO), ESO/Exeter/Kraus et al.
GW Orionis is a multiple star about 1,300 light years away in the constellation of Orion. This is a very young system, just about a million years old (the Sun is 4,500 times older, for comparison), and still surrounded by the gas and dust from which it formed.
GW Ori is a what's called a hierarchical triple: Two stars orbiting each other closely, 180 million kilometers apart (comparable to Earth's orbit around the Sun), with a third star ...