Kepler spots four rogue Earth-mass exoplanets floating in space, unbound to any star Astronomers have discovered four faraway Earth-mass exoplanets that appear to be floating in space all by themselves without a parent star to orbit. The strange bodies were unearthed by a team of astroboffins led by the University of Manchester in the UK after digging through data collected by NASA’s now-decommissioned Kepler …
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No. We had plenty of evidence that stars form from nebula. We had an example that planets could form along side a star. We had models of nebula evolution & star formation that naturally evolved planets.
In other words: we had a well-grounded theory, and an example where it actually happened.
That's not "speculation" any more than the finding of Neptune was based on "speculation".
with Gabrielle Drake springs to mind.
When I've tried simulating star system formations I got a surprisingly high ejection rate, pretty much every system would lob at least one into the firmament in its early years.
I wrote that shit myself, must have a hunt for some astro modelling that can use a GPU!
I have the Universe Sandbox on Steam.
When I fire up the model of our solar system and put it in rapid advance, it generally takes around ten to fifteen minutes before one of the inner planets gets ejected.
I suppose the Universe Sandbox uses the GPU.
In any case, I think it is quite frightening to imagine that there are scores of planets out there that are just roaming around, not bound to a star. And to think that Hollywood has already made a film about that.
The planet you're looking for is normally called Theia. Spoiler: it was spiralling away when it had a little prang and didn't get ejected intact (or possibly, at all).
Thank you for the link, I didn't know about that one.
But I suspect they did actually mean Vulcan, which was the hypothesized planet to explain why Mercury's orbit kept mismatching from what Newtonion laws predicted (this was before Einstein's General Relativity was shown to be a better explanation).
In Search of Planet Vulcan, by Richard Baum and William Sheehan, a very good book on the state of astronomy then, and why astronomers were so determined to find it.
?!
The OPs point was "Maybe that’s where Vulcan went?" But Vulcan couldn't go somewhere because, as you say, it never existed and could never have existed.
Theia has a reasonable chance of having been real; the best competing theory has the earth-moon system formed from a head on between two even bigger planetary bodies.
But thanks for reminding me of Vulcan. Next time we have an argument about dark matter I will bring it up because it's almost an exact parallel: an anomaly that is most simply explained by an unobserved mass which turns out actually to be an error in our theory of gravitation.
You can't simply rewind the process unfortunately, the three body problem makes orbital mechanics chaotic in the long term, since differences in initial position of even a couple of feet have huge impacts given enough time. This is as true going backwards as it is forwards.
Closest we can come is running many, many simulations and comparing the results to our modern solar system. That has suggested at least two points that are relevant to this study.
The first is that either there isn't enough mass in the outer solar system - the region occupied by Uranus and Neptune - or that they are too widely separated. This suggests there was at one point another planet in the region that was ejected. If the Uranus and Neptune swapped places as part of the same interaction it would help match up our theories of how planets develop with the observed characteristics of the pair.
The second is Jupiter. The conventional view is that the Sun created the planets, but those same simulations have suggested Jupiter may have formed independently. that is when the Sun first ignited it was already there. If left undisturbed it may have remained as a planet formed in isolation, or possibly continued to accrete material from the protostellar nebula from which the Sun was formed to become a star in its own right.
"I have the Universe Sandbox on Steam.
When I fire up the model of our solar system and put it in rapid advance, it generally takes around ten to fifteen minutes before one of the inner planets gets ejected."
Unfortunately that's simply a demonstration of the limts of modelling continuous changes on a computer. In Newtonian mechanics and relativity, time is continuous*, and that's what the equations used to calculate motion and gravitational effects require. But that's not actually possible to simulate, so to actually model things you instead take an existing state, advance time by a small amount, and calculate what the new state should now be. As the time step used gets smaller, the results get more similar to a real continuous chage, but conversely as the time step gets bigger, the results diverge further from reality.
With motion under gravity specifically, the big problem is that there is no such thing as angular movement - at any point in time all objects have an instantaneous linear velocity plus whatever forces happen to be acting on them. If you use small enough time steps, you get something close enough to true continuously curved motion. But if the time step is too large, your objects actually move through polygons instead.
Universe Sandbox is an interesting one, because although it's presented as a game, it is an entirely valid gravitational simulator. But because it is presented as a game, it's not at all obvious to most people how to get results that actually mean anything. A large part of the work doing these kinds of simulations is figuring out what settings you need in order to produce a valid result, and under what conditions the result remains valid. For example, if you want to figure out where the Earth will be next year, you'll be fine with fairly coarse time steps. But if you want to know where the Earth will be in a million years, any errors early on will be magnified throughout the simulation and you'll get with complete nonsense at the end. This is the problem with chaotic systems.
So ultimately you end up with a compromise between accuracy and computing time. If you could use arbitrarily small time steps, you could simulate everything with perfect accuracy, but it would take an infinite time to get a result. The larger you make your time steps, the easier it is to finish your simulation in a sensible time, but the more you need to worry about whether the results actually mean anything. In Universe Sandbox, putting things into rapid advance actually means greatly increasing the time step used, and generally produces complete nonsense as a result. It would be possible to use it to get a real answer to what will happen to the Solar System millions of years from now, but it would likely take weeks or months of computing time on a regular PC.
tl;dr - Universe Sandbox does not give an accurate picture of how often planets get eject from star systems. I'm also pretty sure it doesn't use the GPU for anything other than rendering.
* It's generally treated as continuous in quantum physics as well, but in that case there are arguments about whether it might be quantised instead.
Why are there downvotes on this? It's polite, informative and sounds very reasonable.
If you downvote a post I think you should post a reply to refute the post too unless it's obvious like say, the post says the brontosaurus is not valid unit of measurement or claims the Flying Spaghetti Monster does not exist.
"In any case, I think it is quite frightening to imagine that there are scores of planets out there that are just roaming around, not bound to a star."
So, potentially lots of planets out there with no accompanying stars? That could be a lot of matter out there in the dark.
Honour to your holdfast, honour to your teyn!
Literally just finished DotL, which I spied unloved in the basement of Booth's in Hay on Wye last month.
Cracking first novel (many authors have a bit of a wobble in early books before they find their literary feet), wonderful world-building and full of themes which emerge later in his better-known works.
"This was foreseen by George R.R. Martin in his 1977"
Preceded by at least two stories:
When Worlds Collide from 1933. Silly by today's standards, but it deals with rogue planets entering solar system.
A Pail of Air, a short story from 1951, deals with the Earth having been hurtled away from solar system.
> But one group of planets with similar masses to Earth previously spotted by Kepler don’t seem to be gravitationally bound to any stars at all
One evening their star said it would go out to buy cigarettes, and a couple hours later its planets realized it had never actually smoked...
As far as we humans are concerned, pretty close... It might not mean immediate destruction if it doesn't hit Earth, but it will certainly throw a spanner in the delicate, fine-tuned orbital system, resulting in orbits changing and bad things eventually happen.
That been said, it doesn't really have to hit anything (unlikely anyway), a simple flyby of a weighty Earth-sized planet would create enough perturbations in the inner planets' orbits, and most certainly eject a massive hailstorm of asteroids out from the eponymous belt.
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