Planetologists have discovered an extremely unusual exoplanet in the constellation Cygnus, whose atmosphere is heated to such high temperatures that clouds of titanium and iron hover in it. Their findings were published in the journal Nature.
“When we calculated the properties of the KELT-9b atmosphere, we realized that it would be entirely composed of atoms, not molecules. Based on these predictions, we tried to find iron in its atmosphere. When we looked deeper, we found even more surprises,”says Jens Hoeijmakers of the University of Geneva, Switzerland.
Astronomers call "hot Jupiters" heated gas giants that are only 2.2-75 million kilometers away from their stars. In the solar system, even Mercury approaches a star no closer than 46 million kilometers, and therefore really hellish temperatures reign in the atmospheres of such planets - about 1000-1300 degrees Kelvin.
It is much easier to find such planets than other celestial bodies, and they make up most of the exomers known to science. The discovery of "hot Jupiters" for the first time presented scientists with the fact that the atmosphere on such planets can consist of extremely exotic materials. For example, in recent years, gas giants have been discovered with lead and glass clouds, as well as air consisting of evaporated metals and rocks, in the upper layers of which it sometimes rains from rubies and sapphires.
Relatively recently, scientists have found several "hot Jupiters", whose atmospheres were heated to even higher temperatures, exceeding 2.5 thousand degrees Kelvin. In addition to the hellish heat, their air layers had an unusual structure - they were hotter on the outside and colder on the inside, like the stratosphere of the Earth.
Such anomalies have led scientists to assume that the atmosphere of these "ultra-hot Jupiters" is heated by some kind of super-powerful greenhouse effect, which can be generated by two substances - titanium oxide or vanadium oxide.
Huymakers and his colleagues proved that titanium is indeed present in the atmosphere of such worlds by observing KELT-9b, the hottest planet in the Galaxy, about 650 light years away. It is located unusually close to the luminary - a year lasts about 1.5 Earth days, due to which hellish temperatures and extremely unusual atmospheric conditions reign on its surface.
In particular, its "sunny" side is heated to a temperature of 4600 degrees Kelvin (4326 degrees Celsius), which by a huge margin covers the record of another super-hot planet, WASP-33b, whose atmosphere is heated "only" to 3200 degrees Kelvin (2926 degrees Celsius)). Due to such high temperatures, the atmosphere of KELT-9b is very rarefied and actually consists of single atoms, since molecules simply cannot form under such conditions.
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This observation prompted the authors of the article to believe that in the spectrum of KELT-9b one can find traces of those molecules that usually do not enter the atmosphere of planets and do not decay into individual atoms, including compounds of iron and titanium.
Guided by this idea, astronomers analyzed the images obtained by the HARPS-N spectrograph at the end of July last year, when this planet last passed through the disk of the star. Having cleared it of interference, scientists tried to find in it absorption and emission lines associated with various types of ions of these metals.
It turned out that both iron and titanium are present in the atmosphere of KELT-9b in large quantities. This may explain why this planet is hot to such high temperatures. Further study of the data, as the authors of the article hope, will help to understand whether water and carbon monoxide are present in the atmosphere of "ultra-hot Jupiters", which is important for revealing the chemical composition of their bowels and the history of formation.
