So far, over 4,000 exoplanets have been found and they come in all different sizes, temperatures, orbits, etc… For example, some exoplanets are gas giants that are larger than Jupiter, while others are rocky worlds about the same size as Earth. They can be exceptionally hot or have very cold temperatures. They can complete a full orbit around their star (or stars) in just a few days or much longer, and some don’t even have a host star.
Some exoplanets have been described as “hot Jupiters” and recent studies have revealed new and surprising facts about them. First of all, the fact that scientists have found hot Jupiters is amazing as they once believed that they were so unlikely that they probably didn’t even exist. These are exceptionally hot giants that orbit their star at an incredibly close range.
So far, astronomers have detected over 700 hot Jupiters in our Milky Way Galaxy and the data collected by NASA’s Spitzer Space Telescope allowed experts to focus in on a specific number of them. In fact, 49 hot Jupiters were chosen to be extensively studied for the new research project.
Jean-Michel Desert, who is an astronomer at the University of Amsterdam, stated, “Hot Jupiters – all of them are quite peculiar,” adding, “But we do see families of [these] exoplanets.” To better understand this, they are grouped into three families – “cooler” hot Jupiters with atmospheric temperatures as high as 1,300 degrees Fahrenheit (704 degrees Celsius); “hot” hot Jupiters with temperatures between 1,300 and 3,100 degrees Fahrenheit (704 to 1,704 degrees Celsius); and ultra-hot Jupiters with temperatures hotter than 3,100 Fahrenheit (over 1,704 degrees Celsius).
As for what the researchers found, one surprise was that the “cooler” hot Jupiters didn’t have any methane in their atmospheres as stated by Claire Baxter from the University of Amsterdam, “To not find methane in any of the planets [at temperatures lower than about 1,300 degrees Fahrenheit] was surprising with the basic assumptions we had made.”
On the ultra-hot Jupiters, carbon monoxide and methane were mixed together in their atmospheres. “Seeing the evidence for vertical mixing in a statistical sense is an important step because it is predicted by models and was also previously seen in brown dwarfs [a kind of failed star],” Baxter explained, “Now we have collected evidence that this effect is also seen in exoplanet atmospheres.”
Another thing they discovered was that hot Jupiters have approximately the same amount of metal content as their stars which contradicts previous theories that they had a much higher amount.
This is a very important step in learning more about hot Jupiters and with future observations from the James Webb Space Telescope as well as the European Space Agency’s ARIEL mission, astronomers will be able to gather even more data regarding these giant exoplanets.
The research was published in Astronomy & Astrophysics.