Astronomers are observing relations between stars with utter curiosity. They are witnessing how one star, typically bigger, absorbs a smaller and less powerful one. Scientists call it “stellar cannibalism” as one object is seen to be eaten by another. Now an international team of astronomers made an interesting discovery – a case of stellar cannibalism turned a star into a brown dwarf.
Scientists were observing a system, named J1433, consisting of a low-mass object orbiting a white dwarf. This binary system is 730 light-years away from us. White dwarf is just a remnant of a star and is the centre of this system, while the other star is orbiting it in a very tight circle, which takes only 78 minutes to complete.
As was mentioned before, this system has features of stellar cannibalism – the bigger and more massive white dwarf is stripping away mass from the other star. This process is turning the smaller star into a brown dwarf. This is very interesting, because all other brown dwarves that scientists observed actually are ‘failed stars’ – objects that were supposed to be normal bright stars, but did not have enough mass to come to a vivid shine of hydrogen fusion. In this case the process in which brown dwarf appeared was completely different. At the beginning there was a normal star, but then during billions of years it was stripped of its mass.
Of course, astronomers had to use very impressive advanced devices in order to research this system. They employed X-Shooter instrument at the Very Large Telescope in Cerro Paranal, Chile. X-Shooter enables scientists to analyse astronomical objects simultaneously all the way from the ultraviolet to the infrared, which allowed them to discover that a different process of brown dwarf formation is indeed possible.
Juan Venancio Hernández Santisteban, lead author of the study from the University of Southampton, said: “Our knowledge of binary evolution suggests that, if the companion star can survive the transition, brown dwarfs should be common in this type of system. However, despite several efforts, only a few candidate systems with tentative evidence for brown-dwarf companions had previously been found”.
White dwarf in this system is also much hotter, heating up the brown dwarf unequally. The difference between the day and night sides of the brown dwarf is 57 degrees Celsius, but the difference between the hottest and the coldest parts is a full 200 degrees Celsius. Scientists say that mapping the temperature of this object is a significant achievement. Although it is one of many cases of the stellar cannibalism it is very interesting as it changed perception about the formation of the brown dwarves and allowed scientists to really put advanced astronomy equipment through its paces.