When you see something unexpected happen once, it can be seen as an outlier. When you see it 3 or 4 times, it indicates you may need to update your definition of unexpected. When the unexpected seems to be the norm… it’s time to rethink things. In recent years, scientists the world over have been working to directly determine the temperatures of exoplanets, and over and over, these alien worlds have appeared cooler than expected. This seems to indicate that planets must be holding onto heat differently from what was expected. Now, researchers at Cornell University have published a paper in the Astrophysical Journal Letters that uses updated models to try and get simulations to better match reality. In this work, led by Nikole Lewis, they reviewed more than 4100 detected exoplanets, looking for temperature measurements, and working to understand what they actually mean. One of the big issues is that we can’t generally disentangle the temperatures of the near and far side of these worlds – we often end up with an averaged measurement of the day and night time sides of the planet. This averaging can distort our understanding, and gives us a lower measurement than may be representative of the planet.
“Hot Jupiters” are worlds snuggled so close to their host stars that they orbit in just a few days, have one side permanently locked to face their star, and are blasted with so much energy that their day side can get distorted – bloating up, making the world look a bit like an egg, with the fat end facing the star.
When we look at these planets we can’t see their 3D shape, and if we try and transform from what we measure in the 2D sky to that 3D reality with the wrong assumptions, we’ll end up with temperatures that are 1000’s of degrees off. New models from Cornell look for specific key molecules in the planets’ atmospheres, and these molecules can more precisely indicate temperatures through both their existence, and their excitation levels.
These aren’t models we can easily use today – we just don’t generally have the telescopes and spectrographs needed to resolve molecules in most of these world’s atmospheres. But we can start… and when that next generation of space telescopes and massive earth-based scopes are built, we will be ready to more accurately understand their 3D temperature variations.