How rare is an earth-like planet?
24 September 2022
For centuries, humans have wondered if Earth is the only one in the universe or similar planets exist. But with the discovery of NASA’s Kepler Space Telescope, all that has changed.
It has become clear that planets like ours exist in the universe. Planets like ours exist in the universe and have yet to be seen with our own eyes.
Since its launch in 2009, Kepler has discovered more than 2,000 exoplanets and provided us with a vast amount of information about their orbits and sizes. The planets are found very widely in mass, composition, and orbital distance, including giant gas giants orbiting very tight to their stars, called sizzling Jupiters, circumpolar planets orbiting two stars called circumpolar planets, and rocky planets with the possibility to become Earth-like.
Earth-like planets have rocky surfaces and are about 0.5 to 1.5 times the size of Earth. In other words, they are in the sweet spot of an orbital distance that is neither too close nor too far away, and liquid water may exist on the surface. The presence of water is very important because it means that the planet can support life.
Kepler taught us that there are many such planets in the universe. We know that there are more habitable planets in our galaxy alone than people are living on Earth. One out of every two sun-like stars we see in the night sky has an Earth-like rocky planet in its habitable zone.
Earlier this year, a planet orbiting the nearby red dwarf star Proxima Centauri made headlines. The planet, called Proxima b, orbits in the star’s habitable zone, may have water, and is similar to Earth in size, about 1.3 times the size of Earth.
We know that such planets exist, but we have yet to see them. More specific detection methods are needed to determine the properties of terrestrial planets, such as whether water and oxygen exist. Recent technological innovations have made it possible to image terrestrial planets outside our solar system directly. That is what we desire with Project Blue.