The Solar System may have been more crowded than it is today, riddled with super-Earths in the inner solar system, revolving around the Sun just beyond Mercury. According to scientists, this previous generation of multiple planets were destined to destruction by Jupiter, the large gas giant that separates the inner and outer solar system. In a new study published in the Proceedings of the National Academy of Sciences, scientists have found that if Jupiter did not exist, the Solar System would have looked much like other stellar systems in the Galaxy, harboring super-size planets that would have not allowed for life on Earth to exist.
NASA’s Kepler space telescope has peered beyond the ends of the Solar System, finding over 1,000 planets that orbit their hosts stars. It allowed scientists to observe an additional 4,000 mysterious objects that are believed to be planets, though this has yet to be confirmed. The Kepler telescope uncovers these planets by watching stars that are gravitationally perturbed by something in orbit around it. As well, when a potential planet passes in front of the star, the star’s brightness decreases by a minute amount, showing a sign of a planetary system.
As astronomers discover more and more planetary systems throughout the cosmos, the more the Solar System tends to look out of place in the Universe. Most exoplanets that have been found are much larger than Earth, known as super-Earths, insofar as they are five, six, or even seven times larger in mass and volume. Astronomers state that in multi-planet systems, the orbits of stellar bodies are much closer to their host star than planets in the Solar System. For example, Kepler-11, located in the constellation Cygnus, has six planets orbiting closer to it than Venus is to the Sun.
Therefore, why is the Solar System such an oddball in the cosmos? Astrophysicists Greg Laughlin of the University of California Santa Cruz and Konstantin Batygin of Caltech have the answer. They stated Jupiter is reason why there are not more super-Earths in the Solar System, thus paving the way for the Earth to exist, giving life to carbon-based organisms.
According to both astrophysicists, the first version of the Solar System had multiple planets in what is now called the inner solar system, with the planets Mercury, Venus, Earth, and Mars, separated from the planets beyond by the asteroid belt. The initial figuration was occupied by numerous planets with masses several times that of Earth. As well, there were objects called planetesimals, which are very small masses of gas and dust that formed within the first few million years after the birth of the Sun.
Laughlin and Batygin explained the Solar System would have continued to stay like this if the initial formation of Jupiter had stayed in its original orbit, between nearly 10 astronomical units from the Sun. An astronomical unit (AU) is the distance between the Sun and the Earth, and is used to gauge the distances between planets. Currently, Jupiter is around five AU from the Sun.
Billions of years ago, Jupiter had a restless movement in its younger stages, according to a scientific model called the “Grand Tack.” In this scenario, Jupiter was perturbed by currents of gases that surrounded the infant Sun, allowing Jupiter to move closer to the center of the Solar System. The two astronomers found that the gas giant had a gravitational field large enough to grab other objects when it moved closer to the Sun. This would have caused many impacts due to planets and asteroids traveling so close to one another. As a result, “a collisional cascade that grinds down the planetesimal population to smaller sizes,” ensued, they explained. As a result, the small bits of planetary dust were carried towards the Sun, destroying the large planets orbiting close to the star.
Though, the planetesimals may not have been the only reason Earth now exists as a lush, blue-green planet teeming with life. They stated Jupiter was about as close to the Sun as Mars is today, before falling back into its current position, being pulled away by the immense gravitational pull from the newly formed Saturn. This would have ended the initial chaos in the early Solar System, allowing the Earth and the rest of the inner planets to be formed.
By Alex Lemieux
Photo by NASA, ESA, and E. Karkoschka – Flickr License