Wandering Star has changed the orbit of the Earth — says Harvard astronomer

18/11/2012

A new theory suggests that during the "hot" phase of the history of our solar system, a wandering star passed close to developing the solar system and pulled our developing planets out of alignment with the solar equator.


According to Konstantin Batygina astronomer at the Harvard-Smithsonian Center for Astrophysics (Cambridge, Mass.) of the journal Nature, the theory explains why, because of which the Earth revolves around the sun at an angle of 7 degrees with respect to the solar equator.

Constantine theory indicates that young stars can develop in clusters, with disks of matter surrounding them, and almost always distributed in the equator, being attracted by the nearby star. Next protoplanetary disks can be removed from the second star of the equatorial orbit. He believes that a rogue star long past, and are unlikely to return.

In the journal Nature, Batygin writes that the existence of a gaseous giant planets whose orbits lie close to the host star (a "hot Jupiter"), can be largely attributed to the planetary migration connected with the viscous evolution of protoplanetary nebulae. Recent observations Rossiter-McLaughlin effect during the passage of the planets showed that significant fraction hot Jupiter are in orbits which are offset relative to the axis of rotation of the star host. This finding calls into question the importance of the managed disk migration as a mechanism of a hot Jupiter.

The geometric representation of the problem. These figures show a schematic representation of a "rough" neighbor planets through a managed disk migration in binary systems. Adiabatic reaction of self-gravitating disk for long-term perturbations of stellar companion lead to a recession of the ascending node, as determined by the orbital plane of the stellar companion. Recession is the angular momentum vector relative to the disk angular momentum stellar binary orbital angular momentum seems to lead to a shift in the angle between the axis of rotation of the star and the disk in the reference frame stars.
 

 



Batygin shows that irregular orbits may be a natural consequence of the disk migration in binary systems whose orbital plan does not correlate with the axis of rotation of individual stars. Gravitational torques associated with the dynamic evolution of protoplanetary disks idealized because of massive disturbances distant bodies, lead to a shift in the orbital plane of the disc with respect to the rotating poles of the host star.

As a result, Batygin suggested that in the absence of a strong connection between the disk and the angular momentum of the host star, or sufficient dissipation, which acts to rebuild the stellar rotation axis and orbits of the planets, the fraction of planetary systems (including systems "Neptune's hot" and " super-Earth "), whose angular momenta are shifted with respect to its native stars will be comparable to the level of the primary star of the set.

The structure in dusty protoplanetary how planetary systems form.
 

Photo: Observatory Gemini / AURA artwork by Lynette Cook.

Inclination (angle between the orbit of the planet and the star rotation) of the detected planetary orbits are in the range of almost perfectly flat prograde to almost perfectly flat retrograde systems. Earlier, the mismatch between the orbit of the planet and the axis of rotation of the star have been attributed to post-nebular interaction of several bodies. In particular, the Kozai cycles with tidal friction, diffusion "planet-planet", secular and chaotic back-and-forth motions have been proposed as ways to form irregular planet. These mechanisms are likely responsible for several specific examples (eg, extreme eccentricity HD80606b is almost always due to Kozai resonance with a stellar companion HD806078).

However Batygin writes, it is unlikely that they can explain the uneven population as hot Jupiters. For example, the Kozai mechanism can be suppressed by force apsidal precession mnogoplanetarnoy system. In addition, as part of the planet-planet scattering and the secular chaos, the permitted range of options is limited, since the creation of the orbits near requires that the time frame for the tidal capture was significantly lower than the growth of eccentricity, which requires a corresponding tidal heating, but quite small, not excessive, so as not to blow the planet for its Roche lobe.

"I think it is quite plausible idea," says Josh Winn, an astronomer at the Massachusetts Institute of Technology in Cambridge, which measures the orbital inclinations of several hot Jupiters, — the journal Science onlline. "The best thing to do — to test the hypothesis." If Batygin rights, says Wynn, the imbalances need to be as common in solar systems that do not have hot Jupiters, because the slope of the disk does not require a hot Jupiter. So far, NASA's Kepler spacecraft measured the tilt of only one mnogoplanetnoy system: three planets around Kepler 30, each having an orbit that line up with the equator of the star. In the future, Winn plans to follow in other mnogoplanetnyh systems and test the theory Batygina.

Another mnogoplanetnaya solar system has a known tilt: our own. "I think somewhere in the Milky Way, is a star that is responsible for our slope," — says Batygin. He suspects that our sun was once the companion star, which moved the solar nebula is 7 °, and then disappeared from the scene after having the planet.

Citation: Konstantin Batygin

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