However, we don't expect gas giants there (and that's good news!).
Researcher of that state Yale University in the magazine Astronomical Journal. They rely on a new analysis of data collected by advanced instruments that hunt on exoplanets. Normally researchers use these data to look for signals that are caused by exoplanets. But Yale's scientists took a completely different approach. They used the data to find out which exoplanets would be overlooked by these instruments in the Alpha Centauri system.
Alpha Centauri is a triple star system that is only 4 light-years away from the earth. It consists of the stars Alpha Centauri A, Alpha Centauri B and Proxima Centauri. An exoplanet has already been discovered around Alpha Centauri B. This planet would be so close to its mother star that life is impossible there. Last year, researchers also discovered a planet around Proxima Centauri. This planet is rocky and appears to be in the habitable zone (meaning that - depending on the distance to the star - liquid water can be found on the surface).
What did we miss?
The research shows that these advanced instruments overlook a great deal. For example, they would not be able to mark small, rocky planets in the livable zone around Alpha Centauri A and B p. In very concrete terms, it means that possibly unnoticed planets circling around Alpha Centauri A that are smaller than 50 earth masses. And Alpha Centauri B may well be surrounded by undiscovered planets that are smaller than 8 earth masses. In the case of Proxima Centauri, there might also be something to discover: a planet that is 1.5 times as heavy as our earth would not be spotted by the current instruments. "Because Alpha Centauri is so close, it is our first stop outside our solar system," says researcher Debra Fischer. "And there are almost certainly small, rocky planets around Alpha Centauri A and B."
In addition, based on their study, the researchers exclude the possibility of large planets à la Jupiter in the system. "The universe tells us that small planets are the most common type of planet and our study shows that those small planets are precisely the ones that are most likely to orbit around Alpha Centauri A and B."
The absence of large planets is good news for the viability of possibly unnoticed rocky planets in Alpha Centauri. A large planet can mess with the orbit of asteroids, which means that they are more likely to hit the small planets. "We are able to exclude that large planets threaten the small, livable worlds," said researcher Lily Zhao. Moreover, the research offers tools for the future planetary hunt in this fascinating star system.