A Rare Earth-Sized Planet in a Habitable Zone was Just Discovered by NASA

 By David Nield

January 14, 2023 

A possible image of the exoplanet TOI 700 e

                                     Planets that are similar to Earth seem to be a good place to start when looking for life outside of our Solar System. We may now add the promising lead known as celestial object TOI 700 e to that list.

It has been determined that TOI 700 e orbits inside the habitable zone of its star, TOI 700. That's the area of space where water would likely be present in large amounts on its surface and be at a temperature conducive to a liquid state. These sorts of planets are regarded as being "just perfect" for life as we know it because they are too warm for an ice cap yet are still chilly enough for vapour to condense.

TOI 700 e was discovered by NASA's Transiting Exoplanet Survey Satellite, or TESS, who also gave it the name (TOI means TESS Object of Interest). The other planet in this system's habitable zone is TOI 700 d, which was discovered in 2020.

According to planetary scientist Emily Gilbert of the NASA Jet Propulsion Laboratory (JPL) in California, "This is one of just a few systems containing several, tiny, habitable-zone planets that we know of."

"The TOI 700 system is thus a fascinating possibility for further investigation. The scenario also demonstrates how further TESS observations help us identify ever-smaller planets because planet e is around 10% smaller than planet d."

TOI 700 e and 700 d are depicted in the foreground and background, respectively, of an illustration. (JPL-Caltech, NASA, Robert Hurt)

A M dwarf star, or TOI 700, is a tiny, cold star that is around 100 light-years from Earth in the Dorado constellation. The planets must be closer to these stars in order for the temperatures to be warm enough for water to not freeze because they are neither as large nor as hot as our own Sun.

Regarding TOI 700 e, it is thought to be mostly stony and 95% the size of Earth. It is located in the "optimistic" habitable zone, which is a region where water could have once been present. The smaller "conservative" habitable zone, where liquid water may be present for the bulk of a planet's life, is where TOI 700 d is located.

These exoplanets (planets beyond our Solar System) are visible to telescopes as frequent blips in their parent stars' light as they transit them. Earth-like planets like this one are a rare treat since bigger planets, which have greater surface area shielding the star's light, offer better prospects for observation than tiny, rocky planets.

One orbit of TOI 700 e takes 28 days, but TOI 700 d, which is slightly further away from its neighbour, takes 37 days. It needed additional data to prove that the silhouette indeed represented a new planet because TOI 700 e is smaller than TOI 700 d.

According to astronomer Ben Hord from the University of Maryland, "If the star was a bit closer or the planet was a little bigger, we could have been able to discover TOI 700 e in the first year of TESS data." However, the signal was so weak that we need an extra year of transit observations to locate it.

Any strategy we can discover to focus the hunt for life—which TESS is watching 100 million stars—will be helpful. One of the finest methods we have for accomplishing that is to find exoplanets in their respective habitable zones.

It is believed that TOI 700 e and TOI 700 d are tidally locked, meaning that one side of the planet is constantly facing its star (in the same way that the same side of the Moon is always visible from Earth). It is true that the possibility of sophisticated life developing successfully is decreased when one side of a planet is continually roasting in the sun.

Even if these "just right" planets aren't precisely ideal for supporting life, they can nonetheless help us locate solar systems that could be more suitable. Astronomers can learn more about the development of our home and how nearby planets got to be in their current orbits by investigating star systems similar to the one we are in.

"TOI 700 e is a key example that we have a lot more to learn," says astronomer Joey Rodriguez from Michigan State University. "Even with more than 5,000 exoplanets discovered to date."