New data from Gaia bring us closer to revealing how massive stars are formed


An international team of astronomers, with the participation of the Center for Astrobiology (CAB, CSIC-INTA), has used data from the ESA Gaia mission to study characteristics and properties of the largest group gathered to date of massive stars in the process of formation, known as Herbig Ae / Be stars. The analyzes indicate that the variability and emission in the infrared detected are due to the presence of irregular disk-shaped structures seen in profile. The study also finds that the more massive stars scatter these discs at a much faster rate than the less massive ones.

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Star formation is a phenomenon of which there are still many unknowns to be solved. In particular, very little is known about the formation of massive stars, which have several times more mass than our Sun, which in comparison has a fairly modest size. One of the main difficulties that astronomers face when studying massive stars is that they form at an amazing speed, in just a few million years, which is only a moment in the time scale of the universe. For this reason, we know very few stars that are in the process of formation, with the consequent complication to study their general characteristics and shed light on the still unknown processes by which they acquire their enormous size.

Fortunately, this spring the astronomical community has experienced an authentic revolution. After two years of observations, the space probe Gaia of the European Space Agency (ESA) has measured distances to more than one billion stars and other celestial bodies.

In the present study, carried out by an international team of astronomers with the participation of the Center for Astrobiology (CAB, CSIC-INTA) and recently published in the Astronomy & amp; Astrophysics, have compiled a vast majority of the known massive stars that are in the process of formation. These are the so-called Herbig Ae / Be stars. Taking those stars for which Gaia had measured distances, in particular 252, and also using data obtained by other telescopes, both on land and in space, its main parameters, temperature and luminosity have been calculated; like other physical values ​​that allow us to explore their stages of formation and the interstellar medium that surrounds them. With all the data obtained, a global study of the main characteristics of the star sample has been carried out, resulting in the largest homogenous analysis of this type of stars to date.
For Miguel Vioque, lead author of the study," thanks to this approach and the accuracy of the distances measured by Gaia, it has been confirmed that the variable brightness observed in many stars in formation is due to the presence of Accretion discs, seen in profile ". The accretion discs are gigantic flat structures formed by gas, ice and dust, which rotate around the young star and slowly fall towards it. In addition, this study has also found that these disks are much smaller for stars that have approximately seven times or more the mass of the Sun.

Ignacio Mendigutía, CAB researcher and co-author of the study, points out that "the results obtained will serve to better understand the interaction of the stars in training with their environment; a complex mixture of gases, dust, ice and magnetic fields. In addition, they will help enormously to discover new stars of this type, since now a homogenous data set is available that describes its main characteristics ". In addition, "other research teams will be able to use the data from this study to deepen their understanding of how stars form in the universe," concludes Mendigutía.

This study is part of the STARRY project, which is funded by the European Union within its Horizon 2020 Research and Innovation program through the MSCA agreement ITN-EID No. 676036.

Figure: artistic impression of a star of Herbig Ae / Be. © ESO and L. Calçada.


Fuente: UCC-CAB

Fecha: 2018-12-21


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