It is not the first discovery of comets in other stars: four examples had already been known before. However, based on the new observations, welsh estimates that these so-called exocomets in the lactic trabe are probably found in as many stars as planets.
Comets are collections of ice and dust that are common in our solar system. These "dirty snowballs" have diameters of only about 5 to 20 kilometers. Normally they make their rounds far away from the sun. But when they are thrown out of their orbits and come close to the sun, they thaw and form a huge tail. The material of this elongated cloud of gas and dust absorbs the star’s light at certain wavelengths, leaving characteristic dark lines in the spectrum of starlight. In this way, the team around welsh found comets in three observation campaigns at a total of six stars. "These exocomets are more common and easier to detect than previously thought," welsh explained in a release from his university.
The astronomers had studied young stars of spectral class A, which are only about five million years old. Astronomers have not spotted planets in these stars, but the young suns are surrounded by coarse disks of gas and dust that normally form planets. In addition, undiscovered planets must have thrown the comets out of their original orbit so that they could approach their respective home star far enough to thaw out. Welsh believes that with optimized instruments, comets can also be detected in older stars of spectral classes G and F, where most of the more than 850 exoplanets discovered so far have been found.