The Milky Way galaxy may be home to as many six billion Earth-like or potentially habitable planets, as per a new study. Scientists have predicted that these exoplanets orbit sun-like stars and have rocky terrain along with amiable temperatures. For instance, it is not hot enough to dry up surface water and not cold enough to freeze it. Astronomers have been screening exoplanets for Earth-like features but have mostly stumbled upon gas or ice planets, which are similar to Neptune. Spotting Earth-like planets have been a challenge due to their small size and distance from their stars. Earlier estimates suggest that there are 0.02 potentially habitable planets for every Sun-like star or the G-type star, according to the study.
So researchers have devised a new method to identify the numbers. And according to their calculations, there could be as many as 0.18 Earth-like planets per G-type star. "Our Milky Way has as many as 400 billion stars, with seven percent of them being G-type. That means less than six billion stars may have Earth-like planets in our Galaxy," astronomer Jaymie Matthews, a co-author of the study from the University of British Columbia (UBC), Canada, said in a statement. Identifying exoplanets could aid in understanding how planets form and evolve. It can also help scientists plan future missions dedicated to finding exoplanets, they explain. “If we can identify another Earth-like planet, it comes full circle, from thinking that everything revolves around our planet to knowing that there are lots of other Earths out there," Sara Seager, professor of planetary science and physics at MIT said.
In this study, the team used data on 200,000 stars gathered by NASA's Kepler Mission that operated from 2009 to 2018. The space telescope surveyed the Milky Way to hunt for Earth-like planets. "I started by simulating the full population of exoplanets around the stars Kepler searched," astronomer Michelle Kunimoto from UBC in Canada explained.
"I marked each planet as 'detected' or 'missed' depending on how likely it was my planet search algorithm would have found them. Then, I compared the detected planets to my actual catalog of planets. If the simulation produced a close match, then the initial population was likely a good representation of the actual population of planets orbiting those stars," she added. Previously, Kunimoto discovered 17 new exoplanets using Kepler data, in addition to recovering thousands of already known planets.
Their calculations showed that there might be as many as one Earth-like planets for every five Sun-like stars in the Milky Way Galaxy, totaling about 6 billion of such exoplanets. Their size could be between 0.75 and 1.5 times the mass of Earth. They orbit a G-type star at a distance between 0.99 and 1.7 astronomical units (AU). 1 AU is the mean distance between the Earth and the Sun. According to ScienceAlert, the estimated numbers may be much smaller. What is more, scientists do not know whether these planets harbor life. For instance, Mars is 1.5 AU from the Sun, and yet the Red Planet is inhospitable.
The study is published in The Astronomical Journal.