Jupiter Twin Found Orbiting Sun-like Star

The hunt for planetary systems similar to our own Solar System has understandably focused on a rather obvious method so far: looking for Earth-like planets.

   But a team of researchers has instead found a potential Solar System 2.0 not by looking for Earths, but instead through finding a Jupiter twin similar to our own gas giant in an almost identical orbit. The discovery was made using the HARPS instrument on the European Southern Observatory's (ESO) 3.6-meter telescope at the La Silla Observatory in Chile.

“The quest for an Earth 2.0, and for a complete Solar System 2.0, is one of the most exciting endeavors in astronomy,” said Jorge Melendez from the University of Sao Paulo, Brazil, the leader of the team and coauthor of the paper in which the findings were published, in a statement.

Jupiter is thought to have played a key role in the formation of Earth, possibly clearing out debris and enabling small rocky planets like Earth and Mars to form by swinging through the inner Solar System early in its life like a wrecking ball. It therefore stands to reason that finding a similar planet in a similar orbit in another planetary system could be a sign that the system formed in a similar way to ours.

Studying the star HIP 11915, 186 light-years from Earth, the international team found that it has a gas giant that is not only almost identical in mass to Jupiter, but orbits at a similar distance from its host star. That planet has 0.99 times the mass of Jupiter and orbits at 4.8 astronomical units (one AU is the distance from Earth to the Sun). Jupiter orbits at 5.2 AU. The team notes that the size of the exoplanet cannot yet be determined, owing to the method of its discovery – radial velocity – which relies on measuring the planet's influence on its host star.

While other Jupiter-like planets have been found before, this is the first time that such a planet has been found in this configuration. What’s more, the star itself is similar in mass, composition and age to our Sun.

“From the spectrum of HIP 11915, we can tell that its composition is similar to the Sun,” coauthor on the study Megan Bedell from the University of Chicago told IFLScience. It’s thought that our Sun’s chemical composition is fairly unique, possibly due to forming rocky planets in the past. “If it’s true, then HIP 11915 has the chemical signature of a rocky planet host,” Bedell added.

Jupiter is thought to have swept through the early Solar System, illustrated, allowing rocky planets like Earth to form. NASA.

The discovery of a Jupiter-like planet is arguably more important though, considering the key role that we think Jupiter may have played in the formation of Earth as we know it. “Current theories suggest that Jupiter enabled the formation of our inner Solar System because it migrated into Mars' current orbital distance and cleared out [some of the] debris from the inner Solar System with its gravity,” said Bedell. This enabled the smaller rocky planets to form, due to the limited debris available, rather than larger gas giants.

“After Jupiter migrated back out again, smaller planets like Earth and Mars were able to form without as much interference. So if this is true, then having a Jupiter-like planet would make small rocky worlds more likely to form," said Bedell.

At the moment, the team is unable to confirm or deny whether there are rocky planets in the HIP 11915 system, although this could be possible with the ESO's upcoming rocky planet-hunting ESPRESSO instrument, due to be installed on the Very Large Telescope (VLT) in Chile next year.

But the discovery of this gas giant in a relatively long-period orbit could be a step toward finding Earth-sized planets in the habitable zones of Sun-like stars. So far in planet hunting, gas giants have almost exclusively been found in close orbits around their stars, turning them into so-called “hot Jupiters”.

“This discovery is, in every respect, an exciting sign that other solar systems may be out there waiting to be discovered,” Bedell said in a statement.