LUCKY SEVEN
Up to seven habitable planets may orbit distant stars
Somewhere in the Universe, it is possible that there could be a star that’s orbited by seven habitable planets, an astrobiologist at the University of California, Riverside, has calculated.
The search for life in outer space is typically focused on what scientists call the ‘habitable zone’ – the area around a star in which an orbiting planet could have liquid water oceans and conditions for life as we know it.
Dr Stephen Kane and his team created a model system in which they simulated planets of various sizes orbiting their stars. They used an algorithm that accounted for gravitational forces exerted by the host star and any orbiting planets, and tested how they would interact with each other over millions of years.
They found it is possible for some stars to support as many as seven habitable planets, and that a star like the Sun could potentially support six planets with liquid water – though the existence of Jupiter, a large gas giant, makes it impossible in our Solar System.
Currently, only a handful of stars are known to have multiple planets in their habitable zones, but Kane and his team now plan to search for stars surrounded by smaller planets. These stars will be prime targets for telescopes such as the one at NASA’s Jet Propulsion Laboratory’s Habitable Exoplanet Observatory, and could offer insight into forces that might change life on our own planet one day.
“Although we know Earth has been habitable for most of its history, many questions remain regarding how these favourable conditions evolved with time, and the specific
drivers behind those changes,” Kane said. “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.”