Astronomers with the space telescope “Hubble” failed to detect young stars with irregular brightness variations in the Central part of the cluster Westerlund 2. This supports the idea that the radiation from the hot massive stars not able to give the young stars, located next to form planetary systems. Article published in the journal the Astrophysical Journal.
In young star clusters can be detected a number of stars located at nearly the same distance from the observer, having approximately the same age and chemical composition but different masses. This diversity allows the use of young star clusters as natural laboratories to study the evolution of stars to the main sequence and their circumstellar disks.
Many of these clusters, however, is too bright, contain abundant dust cloud or have a high level of crowding of stars, which for a long time, observations were limited to very close, as well as more diffuse regions of star formation, such as the Great Orion nebula or a cluster of Snowflakes. With the advent of the space telescope “Hubble” has become possible to study populations of stars to the main sequence in a more distant or compact young massive clusters — as in the milky Way and in galaxies of the Local group.
A team of astronomers led by Helen Sabbi (Elena Sabbi) from the Institute of space research published the results of observations “Hubble” for compact young stellar cluster Westerlund 2, which is within the scope of starburst Gum 29, located 20 thousand light years from the Sun in the constellation Carina. Westerlund 2 is one of the most massive young clusters in the milky Way (his age — about 1-2 million years) and contains many stars OB-type, including a heavy binary system WR 20a, consisting of stars of class of wolf–Rayet with masses of 83 and 82 solar masses.
The data of the telescope showed that almost a third of the stars to the main sequence in the cluster are variable. 11 percent of such stars identified as stars of T Taurus with weak chromosphere lines, 52 per cent like the classic star T style Calf, 5 percent show irregular changes in brightness (in the English language they are called dippers), 26 percent of flare busters, and the remaining 6 percent are zatmenie double stars.
In addition, the researchers found no stars with irregular brightness variations in the Central region of the cluster with a radius four light years. If we consider that the irregular brightness variations are often associated with the presence of the star or the circumstellar disk of planetesimals, the opening can be explained by the influence of powerful streams of ultraviolet radiation from a large number of massive stars in this region. Such stars estimated to be able to dissipate the circumstellar disks in less than two years, that would deprive the star-the mistress of the ability to form a planetary system. Further observation of the accumulation and the search for stars with circumstellar disks with the help of the space telescope “James Webb” should help to understand the processes in the cluster.
Earlier we talked about how the Hubble has confirmed the breach interstellar comet Borisov after its close approach to the Sun, celebrated its thirtieth anniversary with the two nebulae, and helped to find the elusive black hole of intermediate mass.