An international team of researchers has managed to accurately measure the distance between two massive young stars in the PDS 27 system. They found that the objects are 4.5 billion kilometers (2.8 billion miles) apart, making them the closest pair of baby stars ever observed.
The discovery, reported in Astronomy & Astrophysics: Letters, is very important for theoretical models. Astronomers have been struggling to find examples of young, close, massive binaries. And without observations, it is not possible to test theoretical models.
“With PDS 27 and its companion we have now found the closest, most massive young stellar objects in binaries resolved to date,” lead author Dr Evgenia Koumpia, from the School of Physics and Astronomy at the University of Leeds, said in a statement. “There is a shortage of known young massive binary systems in charted space. High mass stars have comparatively short lifespans, burning out and exploding as supernovae in only a few million years, making them difficult to spot. This limits our ability to test the theories on how these stars form.”
The paper also reported the discovery of a second system of young massive binary stars, called PDS 37. The stars in the system are a bit further apart. The team estimates the distance between them to be about 6.3 to 8.1 billion kilometers (3.9 to 5 billion miles).
“PDS 27 and PDS 37 are rare and important laboratories that can help inform and test the theories on the formation of high mass binaries," Dr Koumpia continued. “How these binary systems form is quite a controversial question with several theories having been put forward. Observational studies of binaries in their early stages are crucial to verifying the theories of their formation.”
The stars in PDS 27 weigh roughly 10 times the mass of our Sun and the system is located 8,000 light-years from Earth. The observations were possible thanks to the PIONIER instrument on the European Southern Observatory’s Very Large Telescope Interferometer (VLTI). The instrument combines the light from four different telescopes.
“The discovery of massive young binary stars provides a crucial step forward in being able to answer many of the questions we still have about these stellar objects,” said study co-author Professor Rene Oudmaijer, also from the School of Physics and Astronomy at Leeds. "The next big question – which we have tended to avoid so far because of observational difficulties – is why so many of these massive stars are in binary systems?"
Massive stars are important players in the galaxy. Their stellar winds, energy, and eventual explosive death shape the galactic environment. Their evolution is complex but this study provides an important piece of the puzzle.