Thread by @weatherindia

#MilkyWayGalaxy Hosts At Least 30 Crore Potentially Habitable Planets; Closest Around 20 Light-Years Away - by @MrigDixit

weather.com/en-IN/india/sp…

(📸: NASA Ames/JPL-Caltech/T. Pyle)

For starters, an #Earth-like planet is essentially any planet that is rocky, roughly the same size as the Earth, and orbiting a G-type star—often called a yellow dwarf star—like the Sun.

The planet must also be orbiting at the 'Goldilocks’ distance—positioned in the habitable zone around the star—in order to be able to host liquid water, and potentially life, on its surface.

Moreover, as per #NASA’s estimates, at least four habitable planets may be located just 30 light-years of our Sun, and the closest Earth-like world is likely to be at most about 20 light-years from us.

The planet hunter mission

The significant details of the new study come from the remarkable Kepler Space telescope, which played a crucial role in investigating the presence of planets in our home galaxy.

The mission was retired by @NASA in 2018—after it ran out of fuel—but it left behind a legacy of rich space data.

(Image credit: NASA)

During the nine years journey, Kepler identified 4,034 candidate exoplanets with a potential of being habitable worlds, but later out of these only 2,300 were actually validated. The telescope also revealed that there are billions of planets in our galaxy.

To hunt for habitable planets, space scientists usually look at three main parameters, which includes being rocky, orbiting a star similar to the Sun, and the hosting conditions viable to keep water in the liquid state.

Finding habitable worlds

Astronomers confined their search to exoplanets between a radius of 0.5 and 1.5 times than that of our planet to sharpen the study focus.

They further narrowed down the planets that are mostly rocky and orbiting stars of age and temperature similar to that of our Sun.

These calculations were done through the help of a final dataset of planetary signals obtained through Kepler along with the data about each star’s energy output collected by the European Space Agency's Gaia mission.

(Image credit: ESO/M. Kornmesser/NASA)

The data obtained from Gaia was significant in understanding the amount of energy emitted by a host star and how much of it is received by the orbiting planet.

The researchers are still trying to decode the exact effect of the star’s energy on the planet and the formation of liquid water.

But the conservative estimate highlights that the occurrence rate of such planets is 50%, meaning half of the Sun-like stars have rocky planets capable of hosting water. That’s roughly 30 crore planets in the Milky Way.

While 30 crore forms the most conservative estimate, research from the University of British Columbia has earlier shown that there may be more than 500 crore Earth-like planets present in our Milky Way galaxy.

The #MilkyWay galaxy consists of 40,000 crore stars, and out of these, about seven per cent, i.e. around 2,800 crore stars, are G-type like the Sun.