Some of the peculiarities of our solar system – a cloud surrounding comets, dwarf planets in strange orbits and, if there really exists, a possible Nine Planet far from the sun – were linked to the narrow approach of another star in our system. The childhood threw things or helter-skelter.
But the star muskets are really able to collide with planets, comets and asteroids, distributing full planetary systems?
Astronomers at the University of Berkeley and Stanford think they've now found a smoker's weapon.
A planet that orbited a new binary star could be disturbed by another pair of stars that skated too close to the system between 2 and 3 million years ago, shortly afterwards the planet was formed from a dust and swirl gas disc.
If confirmed, the most prominent arguments that set aside the stellar ones help to sculpt planetary systems and can determine whether or not planets with stable orbits.
"One of the mysteries derived from the study of exoplanets is that we see systems where planets are misaligned, although they are born on a circular and flat disk," said Paul Kalas, assistant professor of astronomy at UC Berkeley. "Perhaps a cosmic tsunami affects these systems and reorganizes everything about them, but we have not had any proof. Our work gives rare observational evidence for one of these flies, gently influencing one of the planetary systems in the galaxy."
Astronomers are already looking for a stellar bypass in the past of our solar system, but since it probably spent 4,600 million years ago, most tests became cold. The star system that astronomers studied, identified only by the number 106906 and located about 300 light years from the Earth in the direction of the Crux constellation, is very young, only about 15 million years ago.
Kalas and Robert De Rosa, former postdoctor of UC Berkeley, now a researcher at Stanford's Kavli Institute of Astrophysics and Cosmology of Particles, describe their findings in an accepted publication for publication in Astronomical magazine and is now available online.
Stars of Rogue
Kalas, who studies new and newly formed planetary systems to try to understand what happened in the early years of our own solar system, first focused on HD 106906 in 2015 after it was discovered to have a massive planet in a highly unusual orbit. The planet, nicknamed HD 106906 b, has a mass of about 11 Jupiters and orbits the HD 106906 – recently revealed as a binary star – in an inclined orbit at about 21 degrees from the plane of the disk that contains all the rest of the material to the star. Its current location is at least 738 times farther from its star than the Earth is from the sun, or about 18 times farther from its star than Pluto is from the sun.
Kalas used both the Gemini Planet Imager on the Gemini Telescope of the Chilean Andes as the Hubble Space Telescope to see more closely the HD 106906 and found that the star also has a comet belt. The strange orbit of the planet and the fact that the dust disk itself is asymmetrical indicates that something has interrupted the new system.
Kalas and his colleagues, including De Rosa, proposed that the planet had been expelled from its solar system due to interactions with another planet that had not yet been seen in the system or by a passing star. Kalas and Rosa now believe both have passed: the planet was expelled in an eccentric orbit when it was dangerously close to the central binary star, a scenario proposed in 2017 by theoretician Laetitia Rodet and her collaborators at the Grenoble Observatory in France. The repeated gravitational releases of the binary rapidly expelled the planet into interstellar space, but the starfish rescued the planet by shaking its orbit at a safer distance from the binary.
The space observatory Gaia gave them the data they needed to prove their hypothesis. Gaia, launched in 2012 by the European Space Agency, collects precise measurements of distance, position and movement for 1,300 million stars in the Galaxy of the Milky Way, a catalog of 10,000 times greater than the predecessor of Gaia, Hipparcos.
Kalas and Rosa gathered Gaia's information in 461 stars in the same group as the HD 106906 and calculated their positions back in time. He inverted the cosmic watch, so to speak, and found that another binary star system could reach about 3 million years ago. to alter the planetary system.
"What we did here is really to find the stars that could have given HD 106906 the extra gravity shot, a second kick so that it would become long, as well as a hypothetical Nine planet would be in our solar system," said Kalas.
They also discovered that the binary star entered a trajectory that was within about 5 degrees of the system disk, which made it even more likely that the encounter had a strong and lasting impact on the HD 106906.
That double touch may be important to stabilize planets, asteroids and comets around the stars, said Kalas.
"Studying the HD 106906 planetary system is like going back in time to see the cloud of Oort comets forming around our new sun," he said. "Our giant planets gravitationalally kicked countless comets at a great distance, many were expelled completely, becoming interstellar objects such as" Oumuamua ", but others were influenced by passing stars. That second kick by a stellar steering wheel can separate the orbit of a Comets from any encounter with the planets, saving him from the prospect of expulsion. This chain of events preserved the material from the most primitive solar system in a freezing away from the sun for billions of years. "
Kalas hopes that future observations, such as an updated catalog of Gaia measurements, will clarify the meaning of the flyby on the HD 106906.
"We started with 461 suspects and we discovered two that were on the crime scene," he said. "Your exact role will be revealed as we gather more evidence."
The work was supported by the National Science Foundation (AST-1518332), the National Aeronautics and Space Administration (NNX15AC89G) and the Nexus for Exoplanet System Science (NExSS), a research coordination network sponsored by the Directorate of the NASA Science Mission ( NNX15AD95G).