Polish and Belgian astronomers committed an unexpected discovery associated with the composition of the atmosphere (comes) of distant comets. It was first shown that in the gas shell around the ice bodies there are atoms of iron and nickel, which are usually sublimated from the kernel with a much higher temperature. Metals in the gaseous phase were even identified from those comets that are three times further from the Sun than the Earth, as well as the first interstellar comet 2i / Borisov. Two articles of scientists are published in the magazine Nature.
Scientists collected data for 20 years using a high-precision spectrograph of Uves (Ultraviolet and Visual Echelle SpectroGraph) installed on the VLT (Very Large Telescope) telescope in Chile. This tool made it possible to distinguish the lines of individual chemical elements in the comet comet spectrum at different distances from the Sun (from 0.68 to 3.25 astronomical units).
The emission lines of iron and nickel atoms were revealed, which are very weak and are located in the blue region of the spectrum, where they are lost against the background of bright radiation. According to scientists estimates, metals are present in the amount of only one gram for every 100 kilograms of water vapor. This explains why metals remained unnoticed for many years of observations.
An interesting feature is that both iron and nickel are porovna, although the Ni / Fe ratio is usually 10 times less, which is observed at the Sun, meteorites and some other comets close to the solar crown. Equal proportion indicates that the source of metals is a special substance on the surface of the cometic kernel, and the sublimation of this substance occurs at low temperatures (below thousand kelvins). For example, metal organic compounds may be (such as [Fe (PaH) +), FE carbonyls (CO) 5 and Ni (CO) 4 or even pseudocarbins (unusual carbon molecules with iron atoms).
The presence of nickel atoms was revealed at the comet 2i / borisov at that time at a distance of 2.32 astronomical units (A.E.), which is equivalent to the equilibrium temperature of 180 Kelvinov. As Polish scientists write, the source of nickel is a certain nickel-containing molecule with the time of life a few minutes if the comet was at the same distance from the Sun as the Earth (one AE). This is consistent with the fact that Belgian astronomers have discovered on remote comets, and this emphasizes the relationship between local and interstellar celestial bodies, although it is not yet known how much the analogues of small bodies of the solar system are in the Milky Path.