Astrophysicists observing a freshly formed solar system nearly 300 light-years away from our home planet had the fortuitous chance to uncover planetary evolution in its ending stages.
The insight came from studying a large new planet, very similar to Jupiter but 11 times more massive and discovered just three years ago by American, Dutch, and Italian scientists.
Known as HD 106906b, the planet is extremely young by celestial standards: barely 13 million years old, as opposed to 4.6 billion years, the age of our solar system.
"We have a snapshot of a baby star that just formed its planetary system - a rare peek at the final stage of planet formation," said study co-author Smadar Naoz, a physics and astronomy assistant professor at the University of California, Los Angeles.
The researchers, who published their findings in the Astrophysical Journal Letters, pointed out that the study of this planet offers incredible insight into how solar systems develop and expand. This knowledge can't be otherwise acquired by simply observing our own solar system, which has already undergone billions of years of evolution.
"We're seeing this young system revealed to us before it has had a chance to dynamically mature," explained Michael Fitzgerald, the study's other co-author and an associate professor at UCLA.
A Strange And Curious Planet
The young planet, HD 106906b, proved to be equally fascinating and bizarre. One of its peculiarities, the most evident of all, is its position in reference to the planet's star.
Until now, scientists were convinced that most planets outside of our solar system inhabit a vast disk of dust and debris in the proximity of their solar system's center. Nevertheless, HD 106906b exists far beyond this disk, at a distance so vast it takes it 1,500 years to complete a full orbit.
Measurements placed the new planet approximately 650 times farther from its star than the Earth is from the sun, highly unusual according to astronomers' previous theories, which didn't consider the possibility of planets forming outside the debris disk.
Closer studies revealed that, unlike previously assumed, HD 106906b took shape outside the disk, where it can be seen today, and wasn't in fact exiled beyond it by gravity of exterior cosmic events.
According to Naoz, this also accounts for the mysterious shape of its debris disk, another eccentric characteristic of this young planet. HD 106906b orbits its sun-like star in an elliptical trajectory, approaching it more closely on one side than the other.
Its gravitational pull has influenced the shape of the disk as well - which is also elliptical and passes closer to the star on one side, where the dust is consequentially warmer and more radiant.
Planetary Birth
Astronomers were able to study the planet's debris disk, captured on camera in 2016, with the help of software designed by lead author Erika Nesvold, a postdoctoral fellow at the Carnegie Institution for Science.
Her program - called Superparticle-Method Algorithm for Collisions in Kuiper belts and debris disks, or SMACK - enabled the team to recreate the planet's orbit. This simulation was an essential step in the study, since HD 106906b moves so slowly it is barely visible.
Research showed the disk is similar to the Kuiper belt in our solar system, a gigantic cluster of celestial bodies found beyond Neptune. Whether there are other planets located within the disk is currently unknown.
Debris disks play a crucial part in planetary formation. Typically representing an accumulation of gas, dust and ice, they give rise to new planets when a gas cloud disintegrates under its own gravity, producing a disk and a star.
After the gas disperses in time, dust and debris revolve around in space and crash into each other around the star until gravity thrusts them further away, shaping a structure such as the Kuiper belt.
