When it comes to finding life outside our solar system, planets that closely resemble Earth seem like a good place to start. We can now welcome the celestial object TOI 700 e in this group of promising tracks.
TOI 700 has been confirmed to orbit inside the habitable zone of its star, TOI 700. This is the region of space where significant amounts of water on its surface would be at an appropriate temperature for a liquid form. . Too hot for a blanket of ice, but cold enough for vapor to condense, these types of planets are considered “perfect” for life as we know it.
Credit goes to NASA’s Transiting Exoplanet Survey Satellite, or TESS, for finding TOI 700 e, and giving it its name (TOI stands for TESS Object of Interest). It is the second planet in the habitable zone of this system, joining TOI 700 d which was spotted in 2020.
“It’s one of the few systems with multiple small habitable planets that we know of,” says planetary scientist Emily Gilbert of NASA’s Jet Propulsion Laboratory (JPL) in California.
“This makes the TOI 700 system an exciting prospect for further tracking. Planet e is about 10% smaller than planet d, so the system also shows how additional TESS observations are helping us find smaller and smaller worlds. .”
TOI 700 is a small, cool star (known as the M dwarf star), located about 100 light-years away in the constellation Dorado. These stars are nowhere near as big or as hot as our own Sun, so the planets must be closer to them for conditions to be warm enough for water not to freeze.
As for TOI 700 e, it is believed to be 95% the size of Earth and mostly rocky. It is within the “optimistic” habitable zone – an area where water may have existed at one time. TOI 700 d lies in the narrower “conservative” habitable zone, where astronomers believe liquid water could exist for most of a planet’s existence.
Telescopes see these exoplanets (planets outside our solar system) as regular flashes in the light of their parent stars as they pass in front of them, in what is called a transit. With more surface area blocking starlight, larger planets provide easier-to-see opportunities than smaller, rocky worlds, making Earth-like discoveries like this a rare treat.
The TOI 700 e takes 28 days to complete a single orbit, while the TOI 700 d – which is a little further away than its neighbor – takes 37 days. Because TOI 700 e is smaller than TOI 700 d, more data was needed to confirm that the silhouette truly represents a new planet.
“If the star was a little closer or the planet a little bigger, we might have been able to spot TOI 700 th in the first year of TESS data,” says astrophysicist Ben Hord of the University of Maryland. “But the signal was so weak that we needed an additional year of transit observations to identify it.”
TESS monitors around 100 million stars, so any way we can find to narrow down the search for life will be helpful. Finding exoplanets in their respective habitable zones is one of the best ways we have to do this.
Both TOI 700 e and TOI 700 d are thought to be tidally locked: in other words, one side of the planet always faces its star (in the same way that the same side of the Moon is still visible from Earth). Certainly, the fact that one side of a planet is constantly baking in the sun reduces the likelihood that complex life will get off to a smooth start.
While these “perfect” planets aren’t exactly perfect for life, they tell us a thing or two about finding solar systems that might be better suited for it. By studying star systems like the one we find ourselves in, astronomers can also better understand the evolution of our home and how neighboring planets came to their current orbits.
“Even with more than 5,000 exoplanets discovered so far, TOI 700 e is a key example that we still have a lot to learn,” says astronomer Joey Rodriguez of Michigan State University.
The research has been accepted for publication in the Astrophysical Journal Lettersand is currently available on arXiv.