For generations, planet formation was only a theory. As 2018 comes to an end, here’s the evidence of what’s going on.
The theory of planet formation has been around for a long time, but lacked validation.
In principle, gas collapses to form protostars surrounded by protoplanetary disks.
As protostars grow, they heat up, while their disks race to form planets before the volatile material evaporates.
With observatories like Hubble, we’ve found and identified many disks, but couldn’t measure their internal properties.
In theory, those disks ought to display gaps where massive, early planets have begun their formation.
At the Very Large Telescope, the SPHERE instrument successfully imaged a number of protoplanetary disks directly.
Some displayed spirals due to massive outer planets, while others possessed symmetric rings caused by lower-mass worlds.
The best portraits of protoplanetary disks, however, arise from ALMA.
ALMA’s crisp images are striking.
Its Disk Substructures at High Angular Resolution Project (DSHARP) has just released their first results, revealing 20 nearby protoplanetary disks.
Most have gaps, rings, and easily-identifiable locations where candidate planets may lie.
We’ve already learned that the presence of such small-scale attributes are ubiquitous.
The most common features are the concentric emission rings and dust-depleted gaps.
Understanding planetary evolution, from nebulae to protoplanets to full-blown solar systems, is finally within reach.
Mostly Mute Monday tells the astronomical story of objects, phenomena, or observational results in images, visuals, and no more than 200 words. Talk less; smile more.Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.