Astronomers are very good at hunting exoplanets with a little help from powerful ground and space-based telescopes. We are no longer searching for a planet here and there – we are exploring the entire solar system. TRAPPIST-1 has been of particular interest with the seven-planetary system, which was discovered in 2016 and 2017. A new study has confirmed that all these planets are small and rocky like Earth, and they are all surprisingly similar to each other.
The TRAPPIST-1 system was originally visualized in Chile using the TRAPPIST telescope. At that time, astronomers believed that all planets would be stony, and many are in the habitable zone of the stars. TRAPPIST-1 is a red dwarf, so potentially habitable planets are very close with the solar years measured on Earth days. All seven exoplanets are closer to TRAPPIST-1 than Mercury is to our Sun.
Under the leadership of Eric Agole at the University of Washington, the rays were able to estimate the mass of all the planets as they transition to the stars. Combined with orbital time, scientists have a better handle on both the mass and diameter of the exoplanet. This means that we can also detect mass – and here where things are strange. They are all eight percent less dense than if they had the same structure as the Earth.
This number is easily within the range astronomers would expect, but planetary composition varies greatly. We have never found such a solar system Company. Here at home, we have gas giants like Jupiter which are much denser than the Earth. Even among rocky worlds in our solar system, there is a significant variation in density. For example, Mars is about 70 percent denser as Earth.
The team has come up with three possible explanations for the low density, each of which will be altered, which look like those close to these planets. The planets may have a structure similar to that of the Earth, with the exception of low iron content. If they have iron cores like the Earth, they will be slightly smaller. Alternatively, iron can be spread evenly throughout the exoplanet with oxygen, essentially forming large balls of rust with no iron core. The third possibility is slightly more complicated. The low density can also be explained by the deep seas covering the four outer planets. This is less likely because the water content must be so as to leave the planets with the same density.
We can learn which of these options is correct before long. The TRAPPIST-1 system is a popular target for astronomers because there are too many planets to study all in one place. It is also in the grand scheme of things at least. The 40-light-year difference will not be a problem for devices such as the upcoming Web Space Telescope, but with current technology it will take hundreds-thousands of years to travel there.