#planetary migration

Planetary Migration

Mercury, Venus, Earth, Mars, Jupiter, Saturn .. You probably know what comes next, but .. what if I said Neptune, Uranus ? 

The planets like the stars seem like clockwork, fixed in their specific orbits or places in our night sky, but have the planets in our solar system always been this way ? 

Planets migrate, and the larger planets migrate a lot more, and there’s a lot of different reasons for it. 

Other Stars

The stars in our sky are not fixed, most stars in our night sky are moving around the centre of the galaxy in a spur from one of the main arms, and while they generally follow a similar track, they do so at different speeds and different tracks. Some stars are heading in very different directions, Tau Ceti for example is heading at breakneck speed and is likely to leave the galactic plane before returning back in again. 

All this jostling around means stars come close and then move away. A star that moves particularly close will disrupt the orbits, either pushing planets inwards, or pulling them outwards. 

When stars are born, they are usually not alone, born in close knit clusters, and that closeness for many millions of years after the birth can drive a large amount of gravitational influence on the newly developing planetary bodies.

Orphaned Exoplanets

It is thought the galaxy is likely full of orphaned planets, kicked out of their system and left to wonder the galaxy without a host star, until that is, a star comes close enough to acquire it. Some believe the planet Uranus may have been such a planet, although it’s disputed. Additional planets would then disrupt all the other planets. 

Resonance

Planets when they orbit pull and tug on each other, the larger the planet, the more it can do this. Jupiter is key in our solar system. So much so, a book written in the 1970s called “The Jupiter effect” predicted all kinds of disasters are a result of planetary alignment. The truth is, we wouldn’t be here without it, Jupiter has helped stabilise the planets orbits using resonance. 

The moons of Jupiter are a good example of this, you can see how the moons orbit in a set pattern. This is because they have maximum impact on each other at their closest approach, and minimum at the furthest. A system such as this left to its own devices slowly conforms to a resonance pattern, and in doing so, it’s orbit becomes more stable held together by each in the system.

Chaotic Systems

In the early Solar System, just after the planets were born, the solar system was still full of gas and dust, and that leftover debris exerted it’s own gravitational pull and push, leading to planets moving about. One study from 2019 suggested Jupiter started out life 5 times further out and was pulled in by these bodies of gas, and over 700,000 years it finally found its location.

Another theory is that Neptune was nearer Saturn, but migrated out further than Uranus. 

Exoplanets soon to be swallowed by their star

Tess has discovered hot Jupiters around dying solar-like stars with some of the shortest known orbital periods. These exoplanets are in fact migrating towards their suns and should soon be swallowed up there on the scale of a few million years or so. Their study could give valuable information on the evolution of planetary systems and of course the end of the Solar System. You will also be…

The four planets of the Kepler-223 star system seem to have little in common with the planets of Earth's own solar system. And yet a new study shows that the Kepler-223 system is trapped in an orbital configuration that Jupiter, Saturn, Uranus, and Neptune may have broken from in the early history of the solar system.

"Exactly how and where planets form is an outstanding question in planetary science," said the study's lead author, Sean Mills, a graduate student in astronomy & astrophysics at the University of Chicago. "Our work essentially tests a model for planet formation for a type of planet we don't have in our solar system."

These puffy, gaseous planets, far more massive than Earth, orbit close to their stars. "That's why there's a big debate about how they form, how they got there, and why don't we have one," Mills said.

The Fifth Giant Planet

The Fifth Giant Planet

  The Fifth Giant Planet By Judith E Braffman-Miller

Strange things happened in our Solar System when it was young and forming. During the later stages of Solar System formation, massive protoplanets and planetesimals (the building blocks of planets) performed a chaotic gravitational ballet that caused many planetesimalsto be rudely tossed into new and dangerous orbits by…

Jupiter the Destroyer

We should be thankful that the early solar system was not conducive for life. During those early days, Jupiter was less constrained by its current orbit and swung through the early solar system, annihilating a first generation of inner planets, as reported by new evidence in the Proceedings of the National Academy of Sciences (PNAS).

Based on a simulation of early planetary formation, the destructive behavior of an adolescent Jupiter may explain why our solar system has so little in common with other planetary systems. In these other systems, large rocky planets orbit extremely close to their host star — much closer than the distance between Mercury and the Sun. Jupiter's wanderings is a possible reason to our solar system's lack of inner rocky planets.

After the planetary apocalypse, Jupiter eventually settled into its current orbit, while the much of the debris of these first generation planets plunged into the Sun. The remnants that did not suffer a fiery fate would eventually coalesce into the modern inner planets of Mercury, Venus, Earth, and Mars — another reminder that we are nothing more than the recycled remains of our planetary progenitors.

-DC

Original PNAS paper: http://bit.ly/1CNpgOI

Further reading: http://bit.ly/19NYGtC http://bit.ly/1ComHlG http://bit.ly/1IsQbzA

Why are Venus and Earth about the same size, as shown in the NASA image above, but Mars is definitely smaller than both?

"Planetary scientists have long wondered why Mars is only about half the size and one-tenth the mass of Earth. As next-door neighbors in the inner solar system, probably formed about the same time, why isn’t Mars more like Earth and Venus in size and mass? A paper published in the journal Nature this week provides the first cohesive explanation and, by doing so, reveals an unexpected twist in the early lives of Jupiter and Saturn as well."

The authors of the paper did hydrodynamic simulations that best reproduced the relatively small mass of Mars by assuming a starting disk of material whose outer edge was about where the Earth's orbit is now.  They attribute this to an inward migration of Jupiter to about 1.5 times this distance early in the Solar System's history followed by a later outward migration to about 5 times the Earth's orbital radius.  It also explains some of the properties of the extant asteroid belt.