Astronomers believe there could be many more exoplanets out there in the habitable zone, providing the solar system does not have a gas giant. In many solar systems, a gas giant planet can pull out planets from the habitable zone – the region in space surrounding a star which is neither too hot nor too cold and could support life.
One only has to look at the evidence in our solar system, where the giant Jupiter – by far the biggest planet in the solar system, being more than 100 times the size of Earth – pulls the likes of Mars away from the habitable zone.
This is the conclusion of a study from University of California Riverside astrobiologist Stephen Kane who published his work in the Astronomical Journal.
Mr Kane said: “[Jupiter] has a big effect on the habitability of our solar system because it’s massive and disturbs other orbits.”
Compared to another solar system, such as TRAPPIST-1, where there is no gas giant in the solar system, more planets are in a suitable region of space.
For example, our solar system has one habitable planet – Earth – while TRAPPIST-1 has three.
Mr Kane: “This made me wonder about the maximum number of habitable planets it’s possible for a star to have, and why our star only has one. It didn’t seem fair!”
An algorithm from Mr Kane’s team showed gas giants, which have much more of a gravitational pull, can draw out planets from a habitable zone.
The algorithm also revealed up to seven planets could fit in the habitable zone, massively increasing the chances of finding suitable-for-life planets.
Mr Kane said: “More than seven, and the planets become too close to each other and destabilize each other’s orbits.”
Not only does the study reveal that there may be more planets out there which could be habitable for life, but it could also show how Jupiter’s gravitational pull could have implications for the future of our planet.
Mr Kane continued: “Although we know Earth has been habitable for most of its history, many questions remain regarding how these favourably conditions evolved with time, and the specific drivers behind those changes.
“By measuring the properties of exoplanets whose evolutionary pathways may be similar to our own, we gain a preview into the past and future of this planet—and what we must do to maintain its habitability.”