A new study using the Very Large Telescope (VLT) of ESO showed that
Most of the bright stars of very high mass, responsible for the evolution of galaxies, do not live in isolation.
Almost three quarters of these stars have a nearby companion, far more than previously supposed.
Surprisingly, the majority of these pairs interact violently, occurring, for example, mass transfer of a star to the other.
It is believed that about one third of these pairs will eventually merge, forming a single star.
The discovery, published in the journal Science on Thursday, used the VLT ( Very Large Telescope ) of ESO.
The Universe is a place with many aspects and many of the stars are quite different from the sun
The international team used the VLT to study type O stars, which have temperatures, masses and luminosities very high. These stars have short lives and violent, playing a key role in the evolution of galaxies.
They are also linked to extreme events, such as “star vampire”, where the smaller star sucks matter from the surface of most companion, and gamma-ray bursts.
“These stars are genuine monsters,” says Hughes Sana (University of Amsterdam), author of the study. “They have 15 or more times the mass of our Sun and may be up to one million times brighter. These stars are so hot they glow with a blue-white and have surface temperatures that exceed 30 000 degrees Celsius.”
The astronomers studied a sample of 71 stars of type O, both isolated and in pairs (binary systems) in six upcoming young star clusters in the Milky Way. Most of the observations used ESO telescopes, including the VLT.
Evolution of Galaxies
By analyzing the radiation emitted by these objects with unprecedented detail, the team found that 75% of all type O stars are part of a binary system, a higher proportion than had been assumed until now, and the first accurate determination of this value .
More importantly, the team found that the proportion of these pairs where the stars are sufficiently close to each other so that there is interaction between them (either through stellar fusion, or by mass transfer of the so-called star vampire) is much higher than expected, a result that has profound implications for our understanding of evolution of galaxies.
The type O stars are only a fraction of 1% of the stars in the universe, but the phenomena that are associated with the violent means that have a disproportionate effect on its surroundings.
The winds and shocks that come from these stars may give rise both to stop the star formation, its radiation causes the hazy glow, their supernovae enrich galaxies with heavy elements essential to life and is still associated with gamma ray bursts, which are among the most energetic phenomena in the universe. The type of the stars are involved in so many mechanisms which move the galaxies.
“The life of a star is greatly affected by the fact this is very close to each other,” says Space Telescope Science Institute ,( USA), coauthor of the study. “If two stars orbit very close to each other, will eventually merge. But even that does not happen, one of the stars usually removes surface material of another.”
Universe does not accept simplifications
The mergers between stars, which the team estimates that will be the final destination of about 20-30% of type O stars, are violent phenomena. But even the comparatively calm backdrop of stars vampires, what happens in 40-50% of cases, has profound effects on how stars evolve.
Until now, astronomers thought that the binary systems of stars of high mass, where the components orbit very close to each other, were an exception, something needed to explain exotic phenomena, such as binary X-ray pulsars or black holes double binaries.
This new study shows that to correctly interpret the universe, we can not make this simplification: these double stars of high mass are not only common, their lives are also fundamentally different from those that exist as single stars.
For example, in case of vampire star, the star smaller, lower mass, rejuvenates while sucking fresh hydrogen from its companion. Its mass will increase substantially and will survive his companion, living much longer than a single star with the same mass.
However, the star becomes a victim without your envelope before have the opportunity to become a bright red supergiant. Instead, its core is exposed to hot blue. This phenomenon shows that the stellar population of a distant galaxy may appear much younger than it is in reality, both stars rejuvenated vampire victims decreased as the stars become hotter and blue in color, so staying with the appearance of younger stars.
Knowing the true proportion of binary stars with high mass interaction is therefore crucial in order to properly characterize these distant galaxies.
“The only information that astronomers have of distant galaxies is provided by the radiation that reaches the telescope. Without making assumptions about what is responsible for this radiation, we can not draw conclusions about the galaxy, such as young or how massive it is. This study shows that the common assumption that most stars exist in isolation can be misleading, “concludes Hughes Sana.
To understand what proportion of these effects and how this new perspective will affect the new view of galaxy evolution is now necessary to model binary stars, very complicated.
So take some time before these considerations are included in the models of galaxy formation.
Most stars are classified according to their spectral type or color.
This parameter is, in turn, connected with the mass of the stars and its superficial temperature.
From the bluer (and therefore the warmer and greater mass) to the redder (and hence the cooler and less weight), the following classification is the most common, B, A, F, G, and K M.
The type of the star have a surface temperature of about 30 000 degrees Celsius or higher, and have bright colored pale blue. Its weight is 15 or more times the mass of the sun
The stars that make up the binary systems are usually very close to each other in order to be seen as two separate points of light directly.
However, the team was able to detect the binary nature of the instrument using UVES ( Ultraviolet and Visible Echelle Spectrograph ) on the VLT.
The spectrographs split the light emitted by stars, a process similar to a prism that separates the sunlight into a rainbow.
Printed in the stellar radiation patterns are faint lines caused by chemicals present in the atmospheres of stars, which darken specific color of radiation.
When astronomers observe stars only, these patterns, called absorption lines, are well fixed, but in binary systems, the lines coming from the two stars are slightly displaced relative to one another due to the motion of the stars.
Features such as these lines and are displaced from one another, or the way moving in time, allow astronomers determine the movements of the stars and thus its orbital characteristics including whether the stars are sufficiently close together so that there is exchange of material or even melting.
Hydrogen from star
The existence of the enormous number of star vampire is now identified according to another phenomenon previously unexplained.
About a third of the stars that explode as supernovae have, surprisingly, very little hydrogen.
However, the proportion of supernovae poor in hydrogen is in accordance with the proportion of vampire stars in this study.
It is expected that stars vampires deem rise to hydrogen-poor supernova on its victims, since the hydrogen-rich outer layers have been uprooted by the star’s gravity vampire before the victim has had the opportunity to explode as a supernova.