Outside the Solar System, at about 670 light-years from planet Earth, an Ultra-Hot Jupiter was found: KELT-9b. The exoplanet was detected back in 2016 with the use of Kilodegree Extremely Little Telescope.
The most intriguing thing about KELT-9b is, well, its temperature. The 4,300 degrees Celsius makes it the hottest planet ever-known so far. The Sun’s temperature is 5,505 degrees Celsius, but the Sun is a star, not an ex planet. You might imagine that its color might be something closer to red, but KELT-9 is a B-type star, and that means it is a blue planet.
KELT-9b is a giant planet, with a mass of 2.8 times larger than Jupiter. It has half the density of Jupiter because it is nearly twice its radius, and because it receives an extreme amount of radiation from its host star, named KELT-9.
More about KELT-9b, the hottest exoplanet ever spotted
The star’s atmosphere outer boundary nearly reaches the hot planet’s Roche lobe, which means that it is experiencing rapid atmospheric escape. Also, KELT-9b orbits its host in just one day and a half. That’s fast, considering the 365 days necessary for Earth to orbit the Sun.
Because of the fast revolution around the host star, the exoplanet doesn’t have time to spin around its axis. That makes the planet to have a hidden face towards the star. Just like the Moon does with the Earth. Also, on the hidden part, it is always nighttime. Because of the hot day side, the hydrogen gas molecules are not stable, and they are broken into their component atoms.
The elements reform on the night side before getting back to the dayside, where they get shred again. It’s like a cooling system. Scientists are now interested in the exoplanet’s atmosphere and the way radiation and flow balance each other out, as heat and gases flow from the hot dayside to the cool night one. The dark side of the hottie will be revealed someday.