This artist’s impression of the Solar System shows the sizes, but not the distances, of the planets to scale. Image credit: The International Astronomical Union/Martin Kornmesser.

The science of how solar systems begin

From a speculative story to solid science!

“The new ALMA images show the disk in unprecedented detail, revealing a series of concentric dusty bright rings and dark gaps, including intriguing features that suggest a planet with an Earth-like orbit is forming there.” 
Sean Andrews

The question of “where do solar systems come from” has now been scientifically answered and verified.

The very young protostar M17-SO1, as imaged with the Subaru telescope. Image credit: Subaru / NAOJ.

Deep inside star-forming nebulae, dense regions of gas collapse to become hot and dense at their centers.

30 protoplanetary disks, or proplyds, as imaged by Hubble in the Orion Nebula. Image credit: NASA/ESA and L. Ricci (ESO).

These central regions first glow in infrared light, while the material surrounding the center “pancakes” into a disk shape.

The young star 2MASS J16281370–2431391 is surrounded by a disc of gas and dust seen nearly edge-on: a protoplanetary disk. Image credit: Digitized Sky Survey 2/NASA/ESA.

The disk rotates, and tiny densities imperfections form within it. In the densest regions, mass begins to clump together, creating the first protoplanets.

Protoplanetary disks can be seen in archival Hubble data, and come in a variety of geometries around young stars and protostars. Image credit: NASA/ESA, R. Soummer, Ann Feild (STScI).

As more time passes, these infant planets accrue more and more matter, clearing their orbits and creating large “gaps” in the protoplanetary disk.

Gaps, clumps, spiral shapes and other asymmetries show evidence of planet formation in the protoplanetary disk around Elias 2–27. Image credit: L. Pérez / B. Saxton / MPIfR / NRAO / AUI / NSF / ALMA / ESO / NAOJ / NASA / JPL Caltech / WISE Team.

Meanwhile, gravitational collapse causes the central protostar to heat up.

The evolving protoplanetary disk, with large gaps, around the young star HL Tauri. ALMA image on the left, VLA image on the right. Image credit: Carrasco-Gonzalez, et al.; Bill Saxton, NRAO/AUI/NSF.

Once a critical threshold is reached, nuclear fusion begins in the stellar core, and the protostar becomes a full-fledged star.

When nuclear fusion ignites, ultraviolet radiation works to blast any remaining protoplanetary material away. Image credit: NASA/ESA, J. Bally (University of Colorado, Boulder, CO), H. Throop (Southwest Research Institute, Boulder, CO), C.R. O’Dell (Vanderbilt University, Nashville, TN).

It’s then a race for the protoplanets to grow as quickly as possible and hang onto the material they’ve accrued, while the central star’s radiation works to burn it all off and eject it.

The distance from the young, central star determines the type of material that’s present. Heat and energy flux changes everything in these systems. Image credit: K. Zhang in G. A. Blake’s research group, from Geoffrey A. Blake & Edwin A. Bergin, Nature 520, 161–162 (09 April 2015).

Meanwhile, gravitational interactions cause ejections or mergers, leaving only a few planets.

By time the present day arrives, all we can see are the solar system’s survivors.

Both Kepler 62 and sol’s inner planetary systems were likely richer in the past. All we can see today are the survivors. Image credit: NASA Ames/JPL-Caltech.

Mostly Mute Monday tells the story of a single astronomical phenomenon or object in mostly visuals, limited to no more than 200 words.

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