New discovery casts doubt on how the Solar System formed

Astronomers have discovered a new type of star system that defies everything we know about the formation of the Solar System.

More…

CrazyNeutrino said:

New discovery casts doubt on how the Solar System formed

Astronomers have discovered a new type of star system that defies everything we know about the formation of the Solar System.

More…

—-

Surely not everything.

tauto said:

CrazyNeutrino said:

New discovery casts doubt on how the Solar System formed

Astronomers have discovered a new type of star system that defies everything we know about the formation of the Solar System.

More…

and maybe not our solar system.

—-

Surely not everything.

CrazyNeutrino said:

New discovery casts doubt on how the Solar System formed

Astronomers have discovered a new type of star system that defies everything we know about the formation of the Solar System.

More…

Known as a ‘binary-binary’, the system has two stars orbiting each other incredibly closely (like a traditional binary system), but the primary star also has two massive structures of its own in orbit. This is the first binary-binary system ever discovered – and its existence suggests that we might be very wrong about how solar systems are born.

I’ve sort of been saying this for a while, but not in this context. There are two ways that solar systems can develop. By cold accretion or by hot shedding of momentum. Conventional astronomy says that all planets form by cold accretion and all multiple stars form by hot shedding of momentum. But there is a continuum of orbits between the hot jupiter planets and the multiple stars, so hot shedding of momentum also provides a simpler explanation of hot Jupiters.

Now let’s consider this binary-binary in this context.

> The system is made up of two stars that are only 22 astronomical units apart, which is roughly the distance between the Sun and Uranus. … While in terms of stars, that’s pretty damn close to each other.

Wrong, totally wrong. It’s really quite unusual for binary stars to be that far apart. Most binary stars (spectroscopic binaries) orbit closer together than 0.5 astronomical units.

> But what’s weird about this system is that the primary star has two massive structures orbiting it – a giant planet that’s around 12 times more massive than Jupiter, and a brown dwarf that’s 57 times more massive than Jupiter. That’s incredibly big, but both those objects are only between 0.1 and 1.5 astronomical units away from their star.

Not a problem for either the cold accretion or hot shedding on momentum formation models, unless there’s more in the technical paper than in the review. Let’s check.

> It is the first close binary system with more than one substellar circum-primary companion. Our dynamical simulations show the system is stable if the binary orbit has a large semi-major axis and a low eccentricity.

OK so far.

I note is that both 12 and 57 are minimum masses, and given the secondary star orbit inclination it’s very likely that both are significantly heavier than that. Not a planet.

> Nature of the system and its formation and evolution. The large masses of these two substellar objects suggest that they could be formed as stars with their binary hosts: a large molecular cloud collapsed and fragmented into four pieces

Yes, that’s what I’ve called the hot momentum shedding model.

> This scenario might be relevant for the binary stars but seems problematic for the two substellar objects on orbits within ∼1 AU because it is unclear whether fragmentation on such a small scale can occur.

Oh rubbish. It occurs all the time. The smaller the scale, the easier the fragmentation process. Unless there’s something peculiar about the rotation rate of the primary that the paper isn’t mentioning.

> Perhaps a more plausible explanation is that the two substellar objects were formed like giant planet in a protoplanetary disk

Yes, that’s what I’ve called the cold accretion model. Glad they’ve added the word “perhaps”. It’s less plausible (Unless there’s something peculiar about the rotation rate of the primary or the orientation of the orbital planes that the paper isn’t mentioning) but possible.

> A commonly recognized issue is that the binary perturbations generally inhibit the growth of planetesimals in the disk

Yes.

OK, I’ve read enough. A very interesting discovery, and far from easy to find.

Surely solar systems could form in a number of different ways not just cold accretion and depending on how they form it determines the make up and positions of the planets

Cymek said:

Surely solar systems could form in a number of different ways not just cold accretion and depending on how they form it determines the make up and positions of the planets

different types of elements?

different types of states of matter?

CrazyNeutrino said:

Cymek said:

Surely solar systems could form in a number of different ways not just cold accretion and depending on how they form it determines the make up and positions of the planets

different types of elements?

different types of states of matter?

First and foremost, different amounts and patterns of turbulence in the collapsing pre-solar cloud. eg. binary and multiple star systems.

Secondly, the different types of elements, governing whether the collapsing objects will be primarily rocky or gaseous bodies. eg. density of planets.

Thirdly, the chaos generated by the combination of gravity and inelastic collisions between the coalescing bodies. eg. planetary spin, composition of the atmosphere.

Different states of matter (eg. the “ice line”) comes into play in determining the relative sizes of inner and outer planets.