Alpha Centauri may have mini Earths-like planets: study

Alpha Centauri - the closest star system to our planet - may be home to small, rocky Earth-like worlds that have been previously overlooked, according to a study.
Astronomers at Yale University in the US have taken a fresh look at Alpha Centauri star system and found new ways to narrow the search for habitable planets there.
The study, published in the Astronomical Journal, ruled out the existence of a number of larger planets in the system that had popped up in previous models.
"The universe has told us the most common types of planets are small planets, and our study shows these are exactly the ones that are most likely to be orbiting Alpha Centauri A and B," said Professor Debra Fischer.

The Alpha Centauri system is located 1.3 parsecs (24.9 trillion miles) from Earth, making it our closest neighbouring system.
It has three stars: Centauri A, Centauri B, and Proxima Centauri. Last year, the discovery of an Earth-like planet orbiting Proxima Centauri set off a new wave of scientific and public interest in the system.

"Because Alpha Centauri is so close, it is our first stop outside our solar system. There is almost certain to be small, rocky planets around Alpha Centauri A and B," said Fischer.
The findings are based on data coming in from a new wave of more advanced spectrographic instruments at observatories located in Chile.

"The precision of our instruments has not been good enough, until now," Fischer said.
Researchers determined that for Alpha Centauri A, there might still be orbiting planets that are smaller than 50 Earth masses.
For Alpha Centauri B there might be orbiting planets than are smaller than eight Earth masses; for Proxima Centauri, there might be orbiting planets that are less than one-half of Earth's mass.
The study eliminated the possibility of a number of larger planets, which takes away the possibility of Jupiter- sized planets causing asteroids that might hit or change the orbits of smaller, Earth-like planets.
"This is a very green study in that it recycles existing data to draw new conclusions," said graduate student Lily Zhao.

"By using the data in a different way, we are able to rule out large planets that could endanger small, habitable worlds and narrow down the search area for future investigations," he said.
This new information will help astronomers prioritise their efforts to detect additional planets in the system, the researchers said.