Did a rogue star change the makeup of our solar system?

July 20, 2018 by Bob Yirka, Phys.org report
Effect of a prograde, parabolic fly-by of a star with a) M=0.5 M , b) M2= 1, M and c) M2= 5 M that is inclined by 60 degree and has a angle of periastron equal zero. The perihelion distance is always chosen in such a way as to lead to a 30-35 AU disc. The top row indicates the eccentricity distribution of the matter with a central area of most particles on circular orbits and more eccentric orbits at larger distances form the Sun. The eccentricities are indicated by the different colours given in the bar. The origin of the different eccentricity populations in the original disc can be seen in bottom row, where matter indicated in grey becomes unbound from the Sun. Note that in c) the path of the perturber is not visible because it is outside the shown frame. Credit: arXiv:1807.02960 [astro-ph.GA]

A team of researchers from the Max-Planck Institute and Queen's University has used new information to test a theory that suggests a rogue star passed close enough to our solar system millions of years ago to change its configuration. The group has written a paper describing their ideas and have posted it on the arXiv preprint server.

In recent years, space scientists have begun to suspect that something out of the ordinary happened to our solar system during its early years. Many have begun to wonder why there is not as much material in the outer solar system as logic would suggest. Also, why is Neptune so much more massive than Uranus, which is closer to the sun? And why do so many of the smaller objects in the outer solar system have such oddly shaped orbits? In addressing such questions, many space scientists have begun to wonder if a star might have wandered by during the early years of the solar system—coming just close enough to pull some of the objects in the outer parts of the solar system from their prior positions.

The idea of a rogue star has been debated for some time, but the has not been embraced because of the timing—if a star had wandered by, it would have been approximately 10 million years after the birth of the solar system. But objects in the outer solar system would have still just been forming, making it unlikely that they would have been impacted by a rogue star.

In their paper, the researchers with this new effort suggest that recent research by other teams studying the formation of other solar systems has shown that the outer parts of such systems can be more developed than their inner parts. They suggest that if that were the case for our solar system, then it is possible that the outer parts had matured to the point where they could have been impacted by the of a passing star. To test their theory, they created a simulation of just such a scenario and found that it very closely matched what we are able to see today—a solar system with odd characteristics at its outer edges.

Explore further: Simulations suggest Planet Nine may have been a rogue

More information: Outer solar system possibly shaped by a stellar fly-by, arXiv:1807.02960 [astro-ph.GA] arxiv.org/abs/1807.02960

Abstract
The planets of our solar system formed from a gas-dust disk. However, there are some properties of the solar system that are peculiar in this context. First, the cumulative mass of all objects beyond Neptune (TNOs) is only a fraction of what one would expect. Second, unlike the planets themselves, the TNOs do not orbit on coplanar, circular orbits around the Sun, but move mostly on inclined, eccentric orbits and are distributed in a complex way. This implies that some process restructured the outer solar system after its formation. However, some of TNOs, referred to as Sednoids, move outside the zone of influence of the planets. Thus external forces must have played an important part in the restructuring of the outer solar system. The study presented here shows that a close fly-by of a neighbouring star can simultaneously lead to the observed lower mass density outside 30 AU and excite the TNOs onto eccentric, inclined orbits, including the family of Sednoids. In the past it was estimated that such close fly-bys are rare during the relevant development stage. However, our numerical simulations show that such a scenario is much more likely than previously anticipated. A fly-by also naturally explains the puzzling fact that Neptune has a higher mass than Uranus. Our simulations suggest that many additional Sednoids at high inclinations still await discovery, perhaps including bodies like the postulated planet X.

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rrwillsj
3.2 / 5 (5) Jul 20, 2018
If it turns out, that observations confirm the speculation of "Rogue Stars" effecting many young systems?

Would also imply the possobility that there may have been more than one such event, during the first hundred million or so years during the system formation epoch.
doogsnova
1 / 5 (8) Jul 20, 2018
The answer is yes, and much more recently. The "destroyer" aka "the comet of 1680" first penetrated into the SOL System for the first time approximately 970,000 years ago. After this first appearance of the Destroyer, it assumed an orbit that regularly carried it every 714 years back into the SOL System. It moved through the SOL System on its course about 87 times before it altered its orbital path and orbital time in the year 12,943.5 B.C. for the first time through circumstances unknown to us, namely to a constant of 575.5 years. In 13384 B.C., a small Jovian moon of approximately four kilometers in diameter was torn off by the Destroyer and was taken on a journey, with which some small asteroids followed. This was the return of Shoemaker-Levy 9 in 1994. There's much more.
FOM CO UK CR 150

antialias_physorg
3.7 / 5 (3) Jul 20, 2018
Not sure I follow their reasoning. From the linked arxiv paper they argue that early fly-bys within the first 10MYrs can have happened because it is now known that Jupiter size masses can form relatively quickly. The masses they require for their simulations, however, are vastly bigger (with the most likely in the 0.5 sun to 5 suns range)
the likelihood of a flyby drops greatly after this period due to dispersal of the initial star forming region.
A late fly-by should still be somewhere relatively close. I'm not aware of any candidate star in that range within our extended neighborhood.
andyf
5 / 5 (4) Jul 20, 2018
The answer is yes, and much more recently. Blah blah blah blah etc...

doogsnova wins todays plonker award.
Surveillance_Egg_Unit
3 / 5 (4) Jul 20, 2018
"—if a star had wandered by, it would have been approximately 10 million years after the birth of our galaxy."

10 million years seems a very short time for a 'rogue star' to be kicked out of its original orbit within the newly formed/forming Milky Way, unless the conditions within the Milky Way was so chaotic that a large enough 'rogue' star could itself be affected by another large star or enormous planetary body, so that the 'rogue star' was pulled out of its normal orbit by the force of gravity. It would then have had to careen wildly through its neighborhood and outward toward our still-nascent Solar System.
Perhaps an enormous planetary body followed in the star's path, being responsible for the anomalies of the outer Solar System.
RealScience
4.8 / 5 (5) Jul 20, 2018
"—if a star had wandered by, it would have been approximately 10 million years after the birth of our galaxy."

10 million years seems a very short time for a 'rogue star' to be kicked out of its original orbit within the newly formed/forming Milky Way...


That should read 10 million years after the birth of the SUN (or of the solar system), and NOT after the birth of the galaxy...
Surveillance_Egg_Unit
5 / 5 (4) Jul 21, 2018
Thank you, RS. I seem to have copied an error/typo from the article which I copied verbatim. I thought that there was something strange about the description as a 'birth of our 'galaxy'". But to argue against it in a PO forum most often would result in a nasty flurry of mob activity, i.e., "how dare you question the brilliant rhetoric of these amazing sacrosanct scientists/researchers/astronomers, etc.? I hope that the authors/editors/whatever will be more careful in future articles.

You seem to be the only one who caught the mistake.
someone11235813
5 / 5 (1) Jul 21, 2018
If the Sun were one millimetre in diameter the nearest star would be 40 kilometres away. With this much space between stars, it's no wonder that colliding galaxies pass right through each other. Hard to see a rogue star coming close enough to disrupt the solar system.
torbjorn_b_g_larsson
5 / 5 (2) Jul 21, 2018
Not sure I follow their reasoning.


I'm not sure either. They are competing with the Planet Nine hypothesis, but only on Sednoids. Yet they do not put its best alternative against their own best and they also insert likelihood for the entire system architecture to confuse matters. Instead their raw likelihood is 5-7 % to compare with PN capture at 20 % [ https://en.wikipe...net_Nine ] assuming at least one system ejection always occurs as system formation models and microlensing data agree on.

[Notably they also use the Late bombardment as factor. But that is an arguable feature. It was always hinging on bad sampling - no control of contamination - and statistics - fake impactor rate peaks guaranteed - and new complementary data on early Earth and Moon activity do not show it. Anyway, not a decisive factor, and they themselves note that.]

Their raw likelihood is marginal to start with, and inferior to the more predictive theory.
torbjorn_b_g_larsson
5 / 5 (2) Jul 21, 2018
Oops, they also explain the Kuiper belt "cliff" (somewhat abrupt outer edge) as PN does. But the point I was trying to describe remains, PN predict so much more.
RealScience
5 / 5 (4) Jul 21, 2018
If the Sun were one millimetre in diameter the nearest star would be 40 kilometres away. With this much space between stars, it's no wonder that colliding galaxies pass right through each other. Hard to see a rogue star coming close enough to disrupt the solar system.


Most sun-like stars are born in open clusters, so the density of stars would have been far higher than around the sun today. Second, one does not have to get close to the sun itself. So passing by at 100 AU would be ~10 meters on your sun = 1 mm scale, and the stars would average bring only a few kilometers apart.

Ah... the article is open access, and it calculates and explains the odds.
(And nowhere does it even mention the age of the galaxy - so that's just a reporter's error....)
Surveillance_Egg_Unit
3.7 / 5 (3) Jul 22, 2018
If the Sun were one millimetre in diameter the nearest star would be 40 kilometres away. With this much space between stars, it's no wonder that colliding galaxies pass right through each other. Hard to see a rogue star coming close enough to disrupt the solar system.


Most sun-like stars are born in open clusters, so the density of stars would have been far higher than around the sun today. Second, one does not have to get close to the sun itself. So passing by at 100 AU would be ~10 meters on your sun = 1 mm scale, and the stars would average bring only a few kilometers apart.

Ah... the article is open access, and it calculates and explains the odds.
(And nowhere does it even mention the age of the galaxy - so that's just a reporter's error....)

says RS

Perhaps Bob Yirka of PO had a lapse of concentration. Bad boy. Bob!
Mark Thomas
5 / 5 (1) Jul 23, 2018
PN predict so much more.


Unfortunately, each passing year of fruitless searching puts the likelihood of PN in greater doubt.

Over geological timescales, it appears the outer solar system is a lot more dynamic that we previously had reason to believe. Consider that Scholz's Star passed through the Oort cloud just 70,000 years ago, and Gliese 710 will pass through the Oort Cloud in 1.3 million years. It stands to reason that the Oort Cloud will be nothing like the idealized models we often see published if a star passes though every million years or so. If we can ever get out there, we might find objects that originated in other solar systems, objects that experienced high temperatures uncharacteristic of the outer solar system, objects scattered into all sorts of orbits, etc.

https://arxiv.org...3648.pdf

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