Are we alone? This is a question that we have asked ourselves ever since we started studying space. At first there were our 7 heavenly neighbors in our solar system, and later hundreds of new planets were found all across the galaxy. Currently we know of over 4000 extrasolar planets, but only a very small fraction of those are potentially habitable. Habitability depends on many factors like the planets composition, distance to its host star, activity of the host star, etc. Only 17 such planets are known to us at the moment, and this includes Earth! For this reason, finding a new one is a big deal.
TOI 700-d Discovered in Dorado Constellation
TOI 700-d is the newest member to join this prestigious club, an earth like planet that was found recently by NASA’s Transiting Exoplanet Survey Satellite (or TESS for short). It is about 101 light-years away and circles a red dwarf in the Dorado constellation, making one orbit every 37 days. It gets about 87% of the solar energy that we do here on Earth, which makes the two planets very similar. Astronomers think that it may be tidally locked, which means that it only ever shows one side to the star, just like we only ever see one side of our moon.
TESS Space Telescope Searching for Exoplanets
The planet is an undetectable speck in the sky, and is only found because it dims its host star by a little bit when it passes in front of it. In fact, this is exactly what TESS is built for. It makes constant and extremely accurate brightness measurements of a large number of stars. Afterwards these measurements can be scanned for periodical dips that they call ‘transits’. They even found two more planets in that system by using this method, but these are too close to the star to be habitable. Commenting upon the exciting discovery, Paul Hertz, Director of the Astrophysics Division in the Science Mission Directorate at NASA, stated:
“TESS was designed and launched specifically to find Earth-sized planets orbiting nearby stars. Planets around nearby stars are easiest to follow up with larger telescopes in space and on Earth. Discovering TOI 700 d is a key science finding for TESS… In 11 months of data, we saw no flares from the star, which improves the chances TOI 700 d is habitable and makes it easier to model its atmospheric and surface conditions.”
Determining Mass Key to Understanding Density
It is currently unknown if the planet has an atmosphere, or if it even is a rocky world like our own. The planet could very well be a gas planet, like a small Neptune. We can’t really tell until the planets mass is determined, which unfortunately is not an easy task. For this a very large telescope would be needed, much bigger than anything that we currently have or will have in the future. Therefore, direct observations seem out of the question.
A work around for this problem is to estimate the possible masses of the planet, along with other properties that we cannot yet measure. An exact number is not easy to find, but we know that for example it’s not going to be lighter than the Moon or heavier than Neptune. Using these estimates, the team made around 20 models that simulated the planet and its host star. From these simulations, they found that in most cases the planet would be habitable. The worst-case scenario resulted in a 91 C surface temperature, which would be bad for us but not unmanageable for some extreme lifeforms. On top of that, none of the models made the oceans evaporate.
When we find enough planets like this one, we might be able to figure out what makes worlds habitable, and perhaps finally answer weather or not we are alone.