- Distance: 40 Lightyears
- Star: TRAPPIST-1
- Constellation: Aquarius
TRAPPIST-1d was discovered on May 2, 2016, via the transit detection method. Not much was known about the planet nor its star initially. Further analysis found that TRAPPIST-1d is a little smaller than Earth. It is around 30% smaller in terms of mass compared to Earth, at least. Being smaller is not technically a bad thing, however. The signs for TRAPPIST-1d were initially promising.
We know it has a hydrogen-poor atmosphere, a lot like Earth. Meaning there is a potential we could breathe the air. Yet the problem is that it is tidally-locked while it orbits an ultracool dwarf star. Of course, we do not use “ultracool” to mean it’s awesome. Rather, this means the star’s surface temperature is 2700 K or under. It is on the edge of the habitable zone around TRAPPIST-1. Yet it gives off very little visible light, in spite of being about 50 times closer to its star than the Earth is to the Sun. The host star even gives off 4.3% more sunlight. Yet the small nature of the host star does not help. In spite of this, it is said that TRAPPIST-1 shines 3,000 times brighter than Earth’s Moon. Further analysis found that the atmosphere might make the planet uninhabitable, as it is claimed to be a lot like Venus than Earth.