An illustration of the potentially habitable exoplanet TOI 700 e. NASA.

TOI 700: An Alien System With Two Potentially Habitable Worlds

Astronomers have discovered a second Earth-sized planet orbiting its star in the so-called habitable zone.


To this date (as of writing), NASA has confirmed the existence of 5,241 exoplanets. Nearly 10,000 more are awaiting confirmation. Astronomers estimate that there are hundreds of billions of planets in the Milky Way. However, we do not have the necessary technology to discover some of the most distant. Nevertheless, we are making significant progress in exploring the vastness of our galaxy. Now, astronomers using data from TESS (Transiting Exoplanet Survey Satellite) have found an Earth-sized planned dubbed TOI 700 e. This world is exciting because it is beloved to be 95 percent the size of Earth and rocky in nature. But what makes it even more appealing to astronomers is that the planet orbits its host star, TOI 700, in the habitable zone, the proper distance from a star where liquid water can exist on the surface of a planet.

TOI 700, a system of particular interest

The star system TOI 700 is a very interesting one. This is because previous studies have discovered three exoplanets orbiting the star called TOI 700 b, c, and d. Exoplanet TOI 700 d also orbits the star in the habitable zone. However, scientists were unsure whether there was another world, a fourth planet, orbiting TOI 700. With an additional 12 months of data from TESS, scientists were able to discover the planet, and the finding is exciting. “This is one of only a few systems with multiple, small, habitable-zone planets that we know of,” said Emily Gilbert, a postdoctoral fellow at NASA’s Jet Propulsion Laboratory.

TOI 700, an M Dwarf

The star TOI 700 is what astronomers call a Red Dwarf or M Dwarf. These are the smallest main sequence stars in the galaxy and are only a fraction of the Sun’s size and mass. They are born in much greater abundance than more massive stars, which means our galaxy is dominated by them. In fact, Red Dwarfs are believed to make up as much as seventy-five percent of our galaxy’s stellar population. TOI 700 is located some one hundred light-years from Earth, in the constellation Dorado.


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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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