Astronomy – a dust map of the Milky Way

Although quite tidy, the space between the stars is not completely empty: the “interstellar medium” is made up of gas and microscopic dust particles. With an average of a few to a few thousand particles per square centimeter (in the “dense” molecular clouds), the cosmic emptiness is usually still significantly better than the best vacuum that can be achieved on Earth – such as the one at the core research center CERN, which comes to a few hundred atoms per cubic centimeter.

However, the distances in the universe are huge, so that even an extremely low partial density is noticeable when observing objects. The star light is absorbed and scattered in many ways during the passage by interstellar matter. The so -called extinction or weakening of the light depends on the wavelength: dust particles absorb light with shorter wavelengths (blue light) stronger and somewhat less strongly with longer wavelengths (red light). Stars always appear somewhat glowers and reddish than they are. But how much is the extinction, or in other words: What does the observed star look “in reality”? Since the distribution of the matter in the Milky Way is only known, astronomers have to fall back on estimates in order to interpret the light of observed objects.

In a new one Study Astronomers have now created the most detailed three -dimensional map of the cosmic dust in the Milky Way. To do this, they used spectra of the ESA mission »Gaia« and the Chinese telescope Lamost-and programed help in the context of machine learning.

The “Gaia” spacecraft through the entire sky in the optical area for a good ten years and measured their position, direction of movement and brightness with previously unequal precision for almost two billion stars of the Milky Way. A spectrum has been recorded for part of the objects, but which is relatively low: different, very close together wavelengths can therefore be relieved.

For the new study, 130 million star spectra of »Gaia« was selected and supplemented with information on the lamost pattern of the largest Chinese optical telescope, which provided very high-resolution spectra for around one percent of the selected stars. Together, the basic properties of the stars such as their surface temperature could be determined very precisely.

The only thing missing is the dust, because: what would the real star spectrum look like on earth if the light took its long (but thanks to »Gaia« well -known) path through the Milky Way?

The insterstellar gas dust clouds are the birthplaces of stars.

With the help of an artificial neural network, as is used in machine learning, the astronomers generated a variety of model spectra that the computer compared with the 130 million “Gaia” spectra. Under the use of statistical procedures, a three -dimensional map of the interstellar dust could be created in the Milky Way.

The dust was even good for a surprise. So far, it was expected that light of all wavelengths in dense dust regions were almost equally absorbed. However, it was shown that even with a medium dust -dust -dust, smaller wavelengths are significantly more effective than larger ones. According to the astronomers, the wavelength dependency could be due to the presence of a certain molecular group, the polycyclic hydrocarbons. Mostly very unhealthy on earth, the connections in space could possibly play an important role in the development of life.

The dust as well as its composition and distribution are also of considerable interest for other areas of astrophysics. After all, the mighty insterstellar gas dust clouds are the birthplaces of stars-and ultimately also the place of contemporary planets such as the earth.