The Unknown Journey Of Jupiter Has Been Revealed

It is well known that gas giants around other stars are often situated very near their sun. As per the accepted theory, these gas planets were made far away and subsequently migrated to an orbit closer to the star.

Recently, researchers from Lund University and other institutions have utilized advanced computer simulations for learning more about Jupiter's journey through our own solar system approximately 4.5 billion years ago. At that time, Jupiter was quite newly formed, as were the other planets in the solar system. The planets were gradually made up by cosmic dust, which circled around our young sun in a disk of gas and particles. Jupiter was no larger than our own planet.

The results of the study show that Jupiter was generated four times further from the sun than its current position would reflect. Simona Pirani, doctoral student in astronomy at Lund University, and the lead author of the study, explained that this is the first time they have proof that Jupiter was generated a long way from the sun and then migrated to its current orbit. They also found evidence of the migration in the Trojan asteroids orbiting close to Jupiter. These Trojan asteroids comprise two groups of thousands of asteroids which reside at the same distance from the Sun as Jupiter, but orbiting in front of and behind Jupiter, respectively. There are approximately 50 % more Trojans in front of Jupiter than behind it. It is this asymmetry that became the key to the understanding of the researchers of Jupiter's migration.

Anders Johansen, professor of astronomy at Lund University, said that the asymmetry has always been a mystery in the solar system. Indeed, the research community had previously been not able to brief why the two asteroid groups do not comprise the same number of asteroids. However, Simona Pirani and Anders Johansen, together with other colleagues, have now analyzed the reason by recreating the course of events of Jupiter's formation and how the planet gradually reached in its Trojan asteroids.

A great thanks to extensive computer simulations, the researchers have calculated that the current asymmetry could only have happened if Jupiter was generated four times further out in the solar system and subsequently migrated to its current position. During its entire journey towards the sun, Jupiter's own gravity then drew in more Trojans in front of it than behind it. As per the calculations, the migration of Jupiter went on for around 700,000 years. This happened in a period approximately 2-3 million years after the celestial body started its life as an ice asteroid far from the sun. The journey inwards in the solar system followed a spiraling course. In this course, Jupiter continued to circle around the sun, albeit in an increasingly tight path. The reason behind the actual migration relates to gravitational forces from the surrounding gases in the solar system.

The simulations reflect that the Trojan asteroids were drawn in when Jupiter was a young planet with no gas atmosphere. This means that these asteroids most probably comprise building blocks which are similar to those which are formed on Jupiter's core. In 2021, the space probe of NASA Lucy will be launched into orbit around six of Jupiter's Trojan asteroids for studying them.

By: Preeti Narula

Content: https://www.sciencedaily.com/releases/2019/03/190322105706.htm