Astronomers discovered an Earth-sized planet located in the habitable zone of a nearby star that could potentially contain liquid water. A group of NASA exoplanet astronomers (Josh Schlieder and his students Emily Gilbert, Tom Barclay, and Elisa Quintana) were looking at data from TESS (Transiting Exoplanet Survey Satellite) when they found the planet and it’s really not that far from Earth. In fact, it’s so close that its atmosphere may potentially be observed by using the James Webb Space Telescope or even large ground-based telescopes.
The Earth-sized exoplanet’s host star is called TOI-700 (or TESS of Interest number 700) and it’s relatively small and dim. It’s only around 40% of the size of our own sun and approximately 1/50 of its brightness. It’s located in the constellation Dorado – which can be viewed from the Southern Hemisphere – and is approximately 100 light-years away from Earth. To put this into better perspective, Proxima Centauri, which is the closest star to us, is located 4.2 light-years away from us and would take us around 20,000 years to travel there. So, although it’s quite far away, it’s still relatively close in comparison to other stars and exoplanets that have been found.
In the past decade, around a dozen Earth-sized exoplanets have been discovered that are located in the habitable zone of their host stars; however, most of them are between 600 and 3,000 light-years away from us and are pretty much impossible to study and observe.
Three planets surround TOI-700 and are simply named b, c, and d. Planet d is the one that’s located in the habitable zone and is around the same size as Earth. What’s even more interesting is that it orbits its star every 37 days. Planet b is also Earth-sized but orbits its star at a very close range (Planet c is mini-Neptune sized). For comparison, Venus receives twice the amount of sunlight that Earth gets and the planet is dry and extremely hot. Planet b receives five times that amount of sunlight.
And since liquid water is essential for life, it’s very important for astronomers to figure out if there is any on Planet TOI-700 d and what its atmosphere is like. Based on different models studied by the astronomers, if the planet’s atmosphere has a combination of methane or carbon dioxide, or water vapor, it could possibly be habitable. Hopefully the James Webb Space Telescope will be able to confirm or deny these hypotheses when it’s launched next year.