One of the best known words that sounds when one wants to emphasize his persistence and determination on a subject is that he will deal with it "until the black snow falls". If we were living on HD 209458 b, this would not exist because French astronomers discovered that the exoplanet actually had black snow!
HD 209458 b is a gas giant located at a distance of 150 light years from Earth in the Pegasus Constellation. It is located very close to its parent star and completes a complete rotation around it in just 84 hours.
As follows, the temperatures that develop on this exoplanet are very high. On the side of the planet that during its orbital motion sees its parent star (that is, where it is day) the temperature reaches two thousand degrees Celsius. On the opposite side the temperature is around 500 degrees Celsius. Of course these conditions are in no way related to life for this and the scientific community has unofficially christened the planet "Osiri", the god of the dead in ancient Egypt.
HD 209458 b is a breath away from his star
The formation of snow requires water which does not exist in HD 209458 b. But the very large difference in day and night temperature on the planet creates different phenomena. One of these is the creation of atmospheric currents that carry turbulent matter from areas where there is a day in those that exist night and the opposite. This (theoretically) means that the gas masses that start from the areas where there is a day solidify when they enter the night conditions.
Eternal black snow
Scientists at the Côte d'Azur Observatory in Nice have created a three-dimensional model of the atmospheric conditions prevailing in HD 209458 b. According to this, the hot gases as they go to the night areas are converted into titanium oxide flakes. Experts describe it as "black, hot, smoky snow" falling into the interior of the planet. The researchers say that black flakes are most likely the product of a mixture of titanium dioxide with another element. Although titanium dioxide has a white and light hue the presence of some other element - e.g. of silicon oxide - gives black color to flakes.
According to the simulation, upward gaseous currents send the flakes back to the upper layers of the planet's atmosphere. "The gases solidify, fall and then return to the upper layers creating a continuous cycle of snowfall. The snowstorms at HD 209458 b will not look like they are on Earth, it's like you're in the middle of a burning forest " says Vivien Parmentier, a member of the research team. The survey appears in the online archive archive archive "arxiv.org".