Our Solar System is like a fried egg. With the Sun at the center, the planets all orbit the Sun on roughly the same plane. We call this the eclipticâitâs a line in the sky from east to west, and itâs where you can see the likes of Jupiter, Saturn and Mars after dark this week.
Sure, there are anomaliesâVenus rotates in the opposite direction to the other planets, Jupiterâs mass is more than all the others put together, and there may be a âPlanet 9â lurking in the outer fringesâbut our Solar System has relative order.
In our Solar System the eight known planets formed in a flat disk of dust and gas around a single star.
However, new research suggests thatâs not always how star systems and planets form in the Milky Way. Multiple star systems are common, which could cause âdisk tearingâ that creates planets with distant, chaotic orbits.
GW Orionis is a triple star system with a peculiar warped planet-forming disc with a misaligned … [+] ring. The left panel shows an artistic impression of the inner region of the disk.
A team of astronomers using the European Southern Observatoryâs Very Large Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA)âboth in Chileâs Atacama Desertâhave found the first direct evidence of multiple stars systems where planets exist in warped, titled and bent discs.
The researchers liken GW Orionis, a young triple-star system with a âpeculiarâ inner region similar to Tatooine in Star Wars, a fictional star system where Luke Skywalker memorably takes in a binary âsuns-setâ in the original 1977 movie.
The star system in question is GW Orionis, 1300 light-years away in the constellation of Orion and visually close to Betelgeuse, where the researchers from the UK, Belgium, Chile, France and the US spotted three stars and a deformed, broken-apart disc surrounding them.
âOur images reveal an extreme case where the disc is not flat at all, but is warped and has a misaligned ring that has broken away from the disc,â said lead author Stefan Kraus, a professor of astrophysics at the University of Exeter in the UK.
They found three separate rings in the massive planet-forming disk of GW Orionis, located about 46, 185, and 340 au from its center (an au is an astronomical unitâthe distance from the Earth to the Sun).
The inner ring was found to be massively misaligned relative to the other two rings, and to the three stars.
The researchers were able to see because the ring cast a shadow on the rest of the disc. That helped the team re-create the system in 3D.
âThe inner ring contains enough dust to build 30 Earths, which is sufficient for a planet to form in the ring,â said Kraus.
Computer simulations allowed the team to show that the misalignment in the orbits of the three stars could cause the disc around them to break into distinct ringsâsomething they observed for themselves.
The ALMA image (left) shows the discâs ringed structure, with the innermost ring separated from the … [+] rest of the disc. The SPHERE observations (right) allowed astronomers to see for the first time the shadow of this innermost ring on the rest of the disc, which made it possible for them to reconstruct its warped shape.
However, âtearingâ has deformed the disk and taken material out of the disk plane, so any planets that form in the misaligned ring will likely orbit the star, or stars, on oblique, retrograde and/or distant orbitsâmuch like our own theorised âPlanet 9.â
In fact, the outermost ring is the largest ever observed in planet-forming disks; if thereâs a planet in the gap between the inner and outer ring, it would be incredibly distant from the three stars.
This brings the prospect of future discoveries of many distant âPlanet 9â-like planets because the Milky Way is, in fact, at least 50% populated by multiple star systems.
However, there remains a mystery about the misalignment of GW Orionis. Was its disk torn apart by the gravitational pull from the three stars or by a newborn planet? âWe think that the presence of a planet between these rings is needed to explain why the disc tore apart,â says Jiaqing Bi of the University of Victoria in Canada, lead author on a study of GW Orionis published in The Astrophysical Journal Letters in May 2020.
The task now is to look for the planet, which would have a very unusual orbitâand be the first planet ever observed to orbit three stars.
I’m an experienced science, technology and travel journalist interested in space exploration, moon-gazing, exploring the night sky, solar and lunar eclipses,
I’m an experienced science, technology and travel journalist interested in space exploration, moon-gazing, exploring the night sky, solar and lunar eclipses, astro-travel, wildlife conservation and nature. I’m the editor of WhenIsTheNextEclipse.com and the author of “A Stargazing Program for Beginners: A Pocket Field Guide” (Springer, 2015), as well as many eclipse-chasing guides.
World news – GB – There Could Be Planets That Orbit 3 Stars, Say Scientists Studying Orionâs âTatooine-Styleâ Star System