Thanks to the Hubble Space Telescope, a team of astronomers have detected a vast dust structure of about 240 billion kilometers in diameter enveloping the young star HR 4796A. An interior dust ring, narrow and bright, was already known, sign of an ongoing planetary formation process.
HR 4796 is a binary star system located about 220 light-years from the Sun in the constellation Centaurus. This star system consists of a white star and a red dwarf. The main star is about twice as massive as the Sun and twenty times brighter, while its age is estimated at 8 million years.
Scientists already knew that the system was surrounded by a dust disk – a sign of an ongoing planetary formation process – but it would seem that the structure is actually much larger and more complex than previously thought. For researchers, this field of fine dust debris was probably created as a result of collisions between planets developing near the star. The pressure of the star’s light, 23 times brighter than the Sun, then pushed the dust far into space.
“The images unambiguously reveal the debris ring embedded in a much larger, morphologically complex and biaxially asymmetric exo-ring diffusion structure,” the researchers wrote in an article recently published in The Astronomical Journal.
In other words: it’s massive and weird. More extended in one direction than in the other, the structure seems “crushed” on one side. This may be due to the movement of the host star through the interstellar medium, such as the bow wave of a boat crossing a lake. The researchers also suspect the presence of a tug: the binary companion of the star (HR 4796B), located about 86 billion km from the primary star.
Although long hypothetical, the first evidence of a debris disk around a star was discovered in 1983. Later photographs revealed a similar phenomenon around the southern star Beta Pictoris. By the end of the 1990s, Hubble’s second-generation instruments – which had the ability to block the glare of a central star – made it possible to photograph many more discs. About 40 of these systems have been listed so far, largely by Hubble. Recall that HR 4796 is only eight million years old – our Sun is 4.5 billion.
Understanding these structures could help us understand how stars evolve, and even how planets form around these young stars. Our own solar system was probably formed from a dust disk, after all.