In the early stages of our solar system, Jupiter may have swept through the initial debris destroying the first generation of inner planets before retreating into its current orbit. Had it not been for Jupiter, Earth would not exist.
UC Santa Cruz astronomy and
professor Greg Laughlin and Caltech assistant planetary sciences professor Konstantin Batygin collaborated on a recent study detailing Jupiter’s role in our solar system’s early evolution. The research was published in the Proceedings of the Natural Academy of Sciences in March.
The duo suspects Jupiter is the culprit of the mysterious missing planets around the inner orbit around the sun. The initial idea derived from findings of the Kepler NASA satellite mission that searched for extrasolar planets, Laughlin said.
The Kepler mission found more than 4,000 planets. Scientists noticed other solar systems have planets significantly larger than the ones in our solar system.
“It showed that our solar system is relatively unusual. There’s a big hole in it. We’re missing six times the mass of Earth amount of planets inside of Mercury’s orbit,” Laughlin said. “That was the question we’re trying to answer. Why is that? What happened?”
Batygin said the use of orbital periods — the time it takes a planet, in this case, to revolve around the sun once — helps them understand the peculiarity of our solar system. Mercury has an orbital period of 88 days, but most planets in other solar systems within the innermost region have orbital periods much smaller.
“If we look at Mercury’s orbit in the solar system, there is nothing there,” Batygin said. “The fact that there’s nothing in our solar system, and if you compared this to the conventional sun-like star, caused us to question what went wrong.”
As Jupiter first started to form, it collected dust that became the inner ring of the solar system. Then as asteroids started smashing through at high speeds, many individual fragments collided with other debris, creating even more fragments — this continuous pattern is called a collisional cascade. These small fragments are more prone to gas drag, meaning friction exists and Jupiter would then migrate inward.
“For a long time we couldn’t get [the study] to work,” Laughlin said. “We suspected that Jupiter was a suspect, but we couldn’t find the evidence. When we discovered the collisional cascade, that’s when everything started to fall into place. That was the critical clue we uncovered.”
Jupiter was the first planet to form in the solar system. As Jupiter migrated inward toward the sun, it corralled the inner ring of dust and asteroids to the sun, destroying them in the process. Saturn formed shortly afterward and with its massive gravitational force, “pulled” Jupiter outward.
That process is called resonant migration. However, this specific case is referred to as the “Grand Tack” theory, a reference to a maritime term meaning sailing against the wind by maneuvering in zig-zags.
Later on, the debris from the destroyed ring formed as the inner planets we have today — Mercury, Venus, Earth and Mars.
The study was mainly achieved by the use of advanced computer simulations and numerical calculations at both UCSC and Caltech to mimic the orbital evolution of our solar system. The solar system is subject to both gravitational forces and hydrodynamics, or liquids, in motion that cause planetary orbits to alter dramatically.
These numerical experiments helped scientists observe how orbits interact with the gaseous clouds around the solar system. This new discovery also provides another clue to our solar system’s evolution.
UCSC astronomy and astrophysics department manager Jenna Scarpelli said discoveries and accomplishments like these support UCSC’s status as one of the world leaders in astronomy.
“I am continually impressed by the accomplishments of the professors in my department,” Scarpelli said. “One of the great things about working at a university is the chance to work with people such as professor Greg Laughlin. The amazing research done by this faculty, while still maintaining excellence in teaching, advising and service, is a testament to this faculty’s commitment to higher education.”
She said these discoveries have a positive impact on UCSC’s reputation and make the astronomy and astrophysics department even more attractive to professors and graduate students.
Professor Batygin said he and professor Laughlin are now trying to build up from this study to figure out what material our second generation of planets were made from.
“When you look up at Jupiter in the night sky, you should really be thankful,” Batygin said. “Say, ‘Hey thanks, big guy!’”