New Paper Shakes Up Current Theories Of Planet Formation

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In The News:

• "Water Found on Distant Exoplanet, Raising Hopes for --- Beyond Earth" (The New York Times, September 2020) • "Astronomers Discover New Planet Orbiting Distant Star, Challenges Previous Theories" (BBC News, April 2020) • "Portugal's Recent Meteorite Falls a Discovery in Studying the Early Solar System" (The Guardian, August 2020) • "Australian Discoveries Redraw Understanding of the Moon's Early History" (The Sydney Morning Herald, October 2020) • "NASA's Perseverance Rover Uncovers Evidence of Ancient Lake on Mars" (The Washington Post, February 2021) • "Unseen Planet in Our Solar System Spotted for the First Time" (The Telegraph, November 2020) Note: These headlines are real news stories... but not necessarily related to "Paper Shakes Current Theories Planet Formation" as it's a fictional headline.

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The conventional view of solar system formation has long been that planets are simply byproducts of star formation. The idea is that cold, dense molecular clouds collapse into rotating disks of gas and dust from which stars and planets form in relative isolation.

The triggers for such star-forming collapsing clouds run the gamut —- everything from the cloud's own gravity; shockwaves generated by nearby supernovae; or even collisions with other molecular clouds. It's a process almost as old as time itself and is a scenario that our own G-2, yellow dwarf star likely followed some 4.56 billion years ago.

But a new paper to be published in The Astrophysical Journal note that the continual infall of both gas and dust from the interstellar medium (ISM) play a much bigger role in the formation of planetary systems than previously thought. The paper is based on computer simulations and calculations, but is motivated by new observations from ALMA, the European Southern Observatory's Atacama Large Millimeter/submillimeter Array based in northern Chile.

ALMA has uncovered evidence of in-falling material onto protoplanetary disks in several nearby star-forming regions, Andrew Winter, the paper's lead author and an astronomer at France's Observatoire de la Cote d'Azur, told me via email. This suggests the process is common, he says.

Conventional models for planet formation assume that a protoplanetary disk forms during proto stellar collapse, and then planets grow from material in the isolated star-disk system, the authors write. But we show that accretion of the ISM is an important process in driving proto planetary disk evolution, the authors note.

Material in the disk is constantly replenished over its lifetime, they write. In fact, the authors estimate that 20 to 70 per cent of disks are mostly composed of material captured in the most recent half of their lifetime, the authors write.

A key point of the paper is that these young planetary systems are inextricably connected to the interstellar medium in ways that was heretofore not appreciated.