Models and observations show that both stars and planets are formed as a cloud of material collapses into a disk. If the process runs in one line, then the planets will form from the same disk and thus move in the same plane. And because the material from the same disk will come into the star, bringing it to its inertia ̵
Except when he does not. Anything that upset even the flow of material – from collecting disks to the passing star – can break this process. We saw the results: planets that form disks and planetary orbits that do not match the equator of the star.
The researchers now report a complex, four-star system in which the planet-forming disk is arranged perpendicular to the stars so that it runs over their poles.
Practice against theory
To some extent, this type of system was predicted. The calculations suggest that binary stars must have complex interactions with all the discs that surround them. In some cases, this will strictly impose the arrangement, as the gravitational pull will force the disc to align with the equators of the stars. But if the disk goes far enough from this plane, the gravitational interactions will turn the plane of the disk perpendicularly so that it goes above and below the poles of the two stars.
Although we had calculations that suggest this is probably not observed in any binary stars. This has led an international team of astronomers to carefully consider the star system HD 98800.
Even without planets, the HD 98800 is quite complex, consisting of two pairs of double stars. This has led to a really cruel nomenclature, with one binary called "A" and its two stars called "a" and "b", while the second binary is called "B" and is grouped with stars "a" and "b" . Hence, the paper is full of discussion of the binary BaBb system. The two binary systems are separated by about 54 times that distance, or about 1.8 times the Sun-Neptune distance. All four stars in the system look young and the material disc was set in orbit around the BaBb pair in the 1980s. The inner edge of this disk is set by the two stars it travels while the outer edge is bounded by the second set of stars further. based on these initial observations was not clear. That's why the researchers turned to the ALMA telescope. The hardware allows them to fine-tune the stars orbits in the system and track the material in the surrounding disk.
ALMA for Poor Data
ALMA is sensitive to wavelengths emitted by carbon monoxide, which is a simple material in the discotheques that make up the planet. This allowed researchers to make a high-resolution disk on the disk, including its orbital speed, which causes the different regions of the disk to emit red and blue light depending on whether they are moving to or away from us. Then they build different disc models based on ALMA data
Models show a number of things. First, they assume that the disk can not just be a hard material, as it will quickly be thrown out of the orbit. This means that there is a gas allowing friction and gravitational attraction to keep the disk intact. That is, we have found a disk that forms a planet, not a residual disc of residue that has not merged into planets.
The second trace that comes from the models is that there are two possible disc orientations for the binary. stars and one is perpendicular to the plane of the stars' orbit. In other words, the disk rotates above and below the poles of the stars. Given that this has already been predicted by orbital calculations, the researchers suspect that this is what we are looking at.
Finally, the authors simulated a disk that is slightly aligned with true vertical, and discovered that gravitational interactions would bring it back to vertical alignment in less than 1000 years. This shows that the current configuration is stable that would naturally form from any disk that has started somewhere near this alignment. It is convenient that the additional binary system in this four-star system offers a possible explanation. If this was a relatively late arrival – which means that the two binary systems formed separately and then only gravitationally bound, then its arrival could discard the orientation of the disk. Alternatively, the disc could be thrown out of the center by the same processes that cause it to happen with solo stars: an uneven distribution of cloud material from the material that gives birth to the systems.
One final luck came out of Alma's observations: the material in the disk seems to be condensed into powder particles, a key early step that allows the formation of the planet. So at some point in the future there may be planets circling the system, embellished with two suns and two very bright, very close stars.
Astronomy of Nature 2019. DOI: 10.1038 / s41550-018 -0667-x (for DOIs).