Department of Physics and Astronomy assistant professor Joey Rodriguez was a senior researcher on the project. Rodriguez was a member of the original team that discovered the TOI-700 system in 2020.

“We found this planet and it was about 20 percent larger than the Earth, it was sitting inside the habitable zone of the star it orbited,” Rodriguez said. “That’s exciting — that’s where we think it’s possible water could exist. Liquid water, which is one of the ingredients we think is important for life. What made this system so exciting was that it’s nearby.”

Upon the initial discovery of the system, there was a possibility of another exoplanet within the host star’s orbit. Over the last few years, the team has been working to confirm its existence.

“It’s about the size of the Earth, it’s a little bit smaller, about 95 percent of the size of the Earth,” Rodriguez said. “But we originally thought it was going to be much farther out, twice the period of the planet. It ended up being in between planet C and planet D. What was really exciting was that it’s on the inner edge of the habitable zone of the same system.”

TOI-700 e furthers the research of planets the size of Earth. The exoplanet is well lit by the host star, making the discovery especially significant.

“We don’t actually know much more about them beyond that,”Massachusetts Institute of Technology assistant professor Andrew Vandenburg said. “We don’t know if they have rocky surfaces like Earth, we don’t know if they have atmospheres like Earth that might be able to host and sustain life as we know it. And we would love to learn more about that, and that’s where our field is going in the next 20 years, if we want to really understand if these Earth-sized planets that we know are common are actually Earth-like.”

TOI-700 e’s proximity to its star is similar to that of Venus’ relativity to the sun. In comparison, TOI-700 b is a similar distance from where Earth is to the sun.

Rodriguez said this discovery showcases the beginnings of a “mini version of our own solar system.”

Further research must be conducted to discover TOI-700 e’s makeup. The exoplanet’s proximity to its host star allows for the team to look more closely, allowing the next steps towards determine if it's capable of supporting life.

“You might guess that it’s like Earth based on the size, and I would say you’re probably right, that would be my guess as well,” Vanderburg said. “But we just don’t know, and in general we don’t know if there can be puffy planets with these thick envelopes, these thick atmospheres, the size of Earth. Understanding that is really the key to understanding what the potential locations for life in our universe are.”

Studying the atmosphere’s biological signatures over the course of time will allow for further conclusions to be drawn about the exoplanet’s habitability and its similarity to Earth. The next step is to find out which planets are necessary to study for this evidence. 

“It’s starting to inch ourselves closer to actually answering that question of, are we alone, is there life elsewhere?” Vanderburg said.

Rodriguez said he believes this will be heavily debated.

“There’s many things that can cause those combinations and developments we’re gonna look for that are not biological,” Rodriguez said. “It’s these first steps in one day answering that question because we’ve gotta find the planets that are well suited and could potentially have life so that we can go study them in extensive detail.”

TOI-700 e’s discovery provides an opportunity to learn more about Earth due to its possible similarity. With that, the ethics concerning the treatment of the planet in the present.

“The way I like to think about these planet discoveries is that they’re not really telling us about other planets and places we might go, they’re telling us about our own planet and how special it is,” Vanderburg said. “We get this impression that, on Earth, that we’re special and own this planet, and maybe that gives us the confidence to do stuff to it that may not be the best for the planet.”