Planet-forming Lifeline Discovered in a Binary Star System

http://www.eso.org/public/news/eso1434/

For the first time, researchers using ALMA have detected a streamer of gas flowing from a massive outer disc toward the inner reaches of a binary star system. This never-before-seen feature may be responsible for sustaining a second, smaller disc of planet-forming material that otherwise would have disappeared long ago. Half of Sun-like stars are born in binary systems, meaning that these findings will have major consequences for the hunt for exoplanets. The results are published in the journal Nature on 30 October 2014

Since GG Tau Ab is itself a binary star (GG Tau Ab1, Ab2), that's a circumtriple disc, in a quintuple system (GG Tau B is a low-mass binary with Bb being substellar)

Phuong et al. (2020) "Planet-induced spirals in the circumbinary disk of GG Tau A"
https://doi.org/10.1051/0004-6361/202037682

They propose that the main spiral in the disc can be explained by a roughly Neptune-mass planet "GG Tau Ac" in the disc hotspot at a projected separation of 290 AU. Additional weaker spirals might be explained by additional planets "GG Tau Ad" at 450 AU (which would be close to a 2:1 resonance with "Ac") and "GG Tau Ae" at 600 AU (close to a 3:1 resonance with "Ac").

Not sure what the prospects are for building a multi-resonant system at such large distances in ~1.5 Myr, but if they exist these would be the first circumtriple (circumtrinary?) planets.