There could be 6 billion Earth-like planets in our galaxy, astronomers say

VANCOUVER, British Columbia — Anyone who’s ever looked up at the stars has probably wondered if they could live in those distant solar systems. One new study of our galaxy says there may be more real estate out in space than you might think.

Astronomers, using data from NASA’s Kepler telescope, say the Milky Way galaxy could be home to nearly six billion Earth-like planets. The study found that the galaxy contains billions of G-type stars, which are the same type as the Sun. Each one of those solar systems could have planets sitting in a “habitable zone” just like the Earth.

“Our Milky Way has as many as 400 billion stars, with seven per cent of them being G-type. That means less than six billion stars may have Earth-like planets in our Galaxy,” University of British Columbia astronomer Jaymie Matthews says in a statement.

What makes ‘Earth-like’ planets so much like Earth?

The UBC astronomers say Earth-like planets need to meet several requirements to fit the interstellar bill.

First, they must be a rocky and roughly Earth-sized planet which orbits a G-type sun. That planet must then be inside the star’s habitable zone, which is the area around a sun that a planet can support liquid water and possibly life.

In our solar system, Earth is the only planet sitting in that zone — not too far so that all water will freeze and not too close to bring water to a deathly boil. This special area in space is sometimes called the “Goldilocks zone” as NASA continues the search for life in outer space.

Exoplanets are still rare, hard to find

Six billion Earth-like planets, also known as exoplanets, may sound like a very crowded galaxy but astronomers say locating them is more like finding a needle in a haystack. UBC researchers note there’s no guarantee every habitable zone even has an exoplanet in it.

“My calculations place an upper limit of 0.18 Earth-like planets per G-type star,” study co-author Michelle Kunimoto says. That’s about one exoplanet for every five stars just like ours in the galaxy.

The study adds that planets like Earth are typically missed by astronomers because they are relatively small compared to other planets. They also orbit far enough away from their suns that telescopes studying distant stars miss many planets in those systems.

New discovery

Kunimoto used a technique called “forward modeling” to attempt to overcome those deep space disadvantages. The astronomer compared data Kepler has compiled on these stars and their exoplanets to her own catalogs 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,” Kunimoto explained.

After looking at 200,000 stars the Kepler telescope has examined, the study discovered 17 new exoplanets out in deep space. It also confirmed the location of thousands of previously spotted planets which, just like Goldilocks said, might be “just right” for life.

The team’s research was published in The Astronomical Journal.

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