To understand how chaotic the early Solar System was, we need only gaze at the Moon. Its cratered surface bears the scars from multitudes of collisions. The early Solar System was like a debris field where objects smashed into each other in cascades of collisions.
The same must be true in all young solar systems, and in a new paper, researchers simulated a collision between two massive planets to see what would happen.
Some massive exoplanets’ cores could contain over 100 Earth masses of solid material. These planets likely grew so large and contained so much metal because they collided and merged with multiple smaller exoplanets’ cores, each containing about 10 Earth masses.
In new research, astronomers simulated a collision between a younger, smaller gas giant and an older, more massive gas giant to see if the impact generated long-lived seismic waves that the JWST could detect.
The research is titled “Seismic Oscillations Excited by Giant Impacts in Directly-Imaged Giant Planets.” The lead author is J.J. Zanazzi, a theoretical physicist at UC Berkeley who studies planet formation.
Two questions guide this work. One asks if a giant impact like this produces powerful and long-lived seismic waves, and the second asks if the JWST can detect them.
The JWST can’t detect seismic waves but can detect changes in light with extreme accuracy. If the seismic waves are powerful enough, the space telescope can detect them via the photometric changes in the giant planet.
“In principle, planet-scale impacts could excite seismic oscillations in directly imaged exoplanets, which could be detected by space-based missions such as JWST and Roman,” the authors write.
“Here we show that a giant impact with a young gas giant excites long-lived seismic oscillations that can be detected photometrically.”
They zero in on a specific exoplanet named Beta Pictoris b, a young super-Jupiter with about 13 Jupiter masses. Beta Pictoris b is only about 12 million to 20 million years old. The Beta Pictoris system and the exoplanet are the subject of much research.
Research shows that the planet is enriched with metals, likely due to “strong planetesimal enrichment,” a 2019 paper says. The giant exoplanet contains between 100 and 300 Earth masses of heavy metals. In astronomy, metals are anything heavier than hydrogen and helium, while heavy metals are heavier than iron.
The researchers calculated the results of a Neptune-mass planet with 17 Earth masses colliding and merging with Beta Pictoris b.
“The vast stores of heavy metals in Jupiter-mass exoplanets can be amassed from giant impacts,” the authors explain. “Impactors and the momentum they impart to a growing planet excite a spectrum of seismic modes.”
They explain that once this seismic activity is activated, it can persist over timescales similar to a young planet’s age.
The researchers found that Beta Pictoris b’s luminosity would vary in accordance with the induced seismic waves. The JWST would detect some effects if a collision occurred within the past 9 to 18 million years.
Using the JWST’s powerful photometric capabilities offers a new way of using seismic waves to probe exoplanet interiors.
“Seismology offers a direct window into giant planet interiors,” the authors write. “Because the longest-lived normal modes have frequencies comparable to the planet’s dynamical frequency…, a frequency measurement would constrain the planet’s bulk density.”
They also say that some of these observations could detect “regions of stable stratification, as has been done for Saturn.” Gravity measurements have been used to measure the internal structures of giant planets, but this method can be used on distant giant planets around other stars.
The authors explain that their method could have other uses. It could be used to detect planetary migrations.
“Impacts are not the only way to excite oscillations in giant planets,” the authors write. “Hot and warm Jupiters may form through high eccentricity migration, a process whereby tidal gravitational forces from the host star excite the lowest-frequency fundamental mode to large amplitudes.”
“The infrared light curves of highly eccentric massive planets may exhibit variations from tidally-excited 𝑓-modes,” the researchers conclude.
This article was originally published by Universe Today. Read the original article.
