Double Star System Flipped its Planet-Forming Disc into Pole Position

Astronomers have finally found a double star system that has flipped its surrounding disc beyond the orbital plane of its stars.

According to the latest research published in the journal ‘Nature Astronomy’, an international team of astronomers used the Atacama Large Millimeter/Submillimeter Array (ALMA) to locate a double star system that has flipped its planet-forming disc to a position that leaps over the orbital plane of those stars. They acquired high-resolution images of the disc (which is about the size of the Asteroid belt) and analyzed them to confirm the existence of such a double star system.

Scientists have been theorizing about such a system for quite some time now but no physical evidence was there to support these claims, prior to this research. The observations of ALMA clearly show a thick hoop of gas and dust at right angles to the binary star orbit. Dr. Grant M. Kennedy, a Research Fellow at the Department of Physics and Center for Exoplanets and Habitability of the University of Warwick, explained that these polar discs could be pretty common in our universe by saying,

“Discs rich in gas and dust are seen around nearly all young stars, and we know that at least a third of the ones orbiting single stars form planets. Some of these planets end up being misaligned with the spin of the star, so we’ve been wondering whether a similar thing might be possible for circumbinary planets. A quirk of the dynamics means that a so-called polar misalignment should be possible, but until now we had no evidence of misaligned discs in which these planets might form.”

The orbit of this double star system was known to the researching team because of the previous observations. They figured out the exact orientation of the ring of gas and dust in the system and combined these pieces of information to determine that the dust ring is completely consistent with the polar orbit. In simpler words, the stars of the double star system are orbiting each other in one plane while the disc surrounds them at right angles to their orbits. It resembles a giant ferris wheel, which has the carousel at the center. Talking about the chances of planet formation in such double star systems, Kennedy said,

“Perhaps the most exciting thing about this discovery is that the disc shows some of the same signatures that we attribute to dust growth in discs around single stars. We take this to mean planet formation can at least get started in these polar circumbinary discs. If the rest of the planet formation process can happen, there might be a whole population of misaligned circumbinary planets that we have yet to discover, and things like weird seasonal variations to consider.”

Researchers further elaborated that the ring would appear (from the surface) as a perpendicular, broad band rising from the horizon if there were any planets or planetoids near the inner edge of the ring. The planets orbiting such a double star system would experience abrupt changes in their seasons because the variation of illumination throughout the binary orbit also affects the season on a polar circumbinary planet. Under this polar configuration, the stars would appear to move in and out of the disc plane. Consequently, objects may have two shadows from time to time. Dr. Daniel Price, a Co-author of the study from the Center for Astrophysics (MoCA) and School of Physics and Astronomy at Monash University, referred to these changes in the following words:

“We used to think other solar systems would form just like ours, with the planets all orbiting in the same direction around a single sun. But with the new images, we see a swirling disc of gas and dust orbiting around two stars. It was quite surprising to also find that that disc orbits at right angles to the orbit of the two stars. Incredibly, two more stars were seen orbiting that disc. So if planets were born here there would be four suns in the sky!”

On this occasion, Price also praised the ALMA telescope for its amazing discoveries. He acknowledged that it has helped us a lot to improve our understanding of other solar systems. He said,

“ALMA is just a fantastic telescope, it is teaching us so much about how planets in other solar systems are born.”