On this super-hot exoplanet - a real "iron curtain" instead of the sky

For the first time in history, astronomers have discovered iron andtitanium in the atmosphere of a planet outside the solar system. This exoplanet - KELT-9b - is the hottest alien world we have ever found. The planet is so hot that its temperature is even higher than that of most stars. The hot exoplanet is located about 620 light-years from Earth in the constellation Cygnus - astronomers call such "super-hot Jupiters." KELT-9b is a giant gas world similar to Jupiter, the largest planet in the solar system. However, its mass is three times larger than the Jupiterian and its diameter is two times, and the orbit is located very close to the parent star of the exoplanet, KELT-9.

Superhot Jupiter is an unofficial term.for hot exoplanets like Jupiter, whose temperatures exceed 1700 degrees Celsius. They are “so hot that they have some similarities with stars, although they are planets,” says Kevin Hen, an astrophysicist at the University of Bern in Switzerland. KELT-9b can reach temperatures of 4300 degrees.

The hottest planet

This record heat allowed astronomersdetect iron and titanium in the atmosphere of KELT-9b. Although scientists have long suspected that these elements are present on some exoplanets, iron is one of the most common elements in the Universe - they are difficult to detect in a cool environment because atoms are mostly “trapped in other molecules,” says Hen. But KELT-9b is so hot that clouds do not condense in its atmosphere, allowing individual atoms of iron and other metals to fly separately.

Titanium was seen in an exoplanet atmosphere andearlier - but not in atomic form. In September 2017, astronomers working with the Hubble Space Telescope announced that they had discovered titanium dioxide in the atmosphere of the Kepler-13A exoplanet.

Astronomers can detect various elements,by studying the spectrum of light emanating from an object in space. Because the exoplanet does not emit its own light, Hyun and his research team studied the telescope data collected during solar transit, when the exoplanet passed right in front of its star.

Which is convenient, the data already existed beforeHyun and his co-authors decided to do this research. After his colleagues at the University of Geneva used spectral data to search for hydrogen in the KELT-9b atmosphere, “they actually stored the data in a box because there was no reason to look for iron or titanium,” says Hen. "Then, a few months ago, we conducted a theoretical study that predicted that iron and titanium should be there, and this motivated us to search."

Using data from a year ago fromGalileo National Telescope in La Palma, Spain, scientists began a hunt for metals in the spectrum of light that shone through the atmosphere of KELT-9b for a 5-hour transit. These data were collected using a HARPS spectrograph.

“Different atoms and molecules show differentsignatures when you split the light into a spectrum, ”says Hen. “With sufficient resolution, enough data, each molecule can be provided with a unique signature.” A search for signatures of iron and titanium - the elements that, according to Hen and his team, should be in the atmosphere of KELT-9b - will require "a combination of powerful computing, a thorough study of spectroscopic databases and a scrupulous collection of details," wrote Hen.

Hyun's team turned to Simon for helpGrimm, an astrophysicist at the University of Berne, a specialist in calculating the opacity of atoms and molecules. “These opacities are not easy to calculate, because you need to evaluate the forces and shapes of millions and billions of spectral lines.”

Previous studies in whichsearch for hydrogen in the atmosphere KELT-9b, saw strong lines of hydrogen absorption in the spectrum, without conducting any complex cross-correlation analyzes to find iron and titanium, in contrast to the Hyun study. The astronomers who collected the data for the search for hydrogen did not have a theoretical motivation for a serious search for metals like iron.

Another study published July 2 atmagazine Nature Astronomy, showed that hydrogen actually "boils" from the atmosphere of KELT-9b and is sucked in by the parent star of the planet. “Perhaps the heavy metal also escapes because a powerful hydrogen escape“ pulls ”the heavy elements into the upper atmosphere,” says Fei Yan of the Max Planck Institute of Astronomy, lead author of the study.

While iron and titanium in the atmosphere KELT-9bwere an important discovery, Hyun says the discovery technique itself is interesting. Because the same method will be used to detect biosignatures. However, it is unlikely that astronomers will find any signs of life on this hellish planet.