An accretion disc around a black hole. Credit: Image courtesy of University of Leicester
Astronomers have discovered a previously unknown link between the way young stars grow and the way black holes and other exotic space objects feed from their surroundings. The study shows how the ‘flickering’ in the visible brightness of young stellar objects (YSOs) – very young stars in the final stages of formation – is similar to the flickering seen from black holes or white dwarfs as they violently pull matter from their surroundings ie accretion.
The relatively cool accretion discs around young stars, whose inner edges can be several times the size of the Sun, show the same behaviour as the hot, violent accretion discs around planet-sized white dwarfs, city-sized black holes and supermassive black holes as large as the entire Solar system, supporting the universality of accretion physics.
The study found a relationship between the size of the central object and the speed of the flickering produced by the disc, suggesting the physics of the accretion must be very similar around these different astronomical objects despite them being completely different in other ways, such as size, age, temperature and gravity. The new observations were obtained with Kepler/K2 and ULTRACAM, examining accreting white dwarfs and young stellar objects.
Accretion discs are responsible for the growth and evolution of most celestial objects, from young protostars to ancient supermassive black holes. NASA’s Kepler/K2 telescope can ‘listen’ to the seemingly random brightness variations produced by accretion discs, revealing how they all sound the same once scaled by their physical size. Accretion therefore is a universal process operating in the same way across all astrophysical objects. http://www.alphagalileo.org/ViewItem.aspx?ItemId=157287&CultureCode=en
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