An Earth-sized rogue planet discovered in the Milky Way
phys.org
phys.org
On a related note, it's possible to have rogue solar systems as well: https://medium.com/starts-with-a-bang/ask-ethan-can-stars-es...
Here is is our linnaean classification of species. Look how these species are breaking the species barrier!
Nature, meanwhile, isn't very fussy about the concept of species. It's not even strict about the concept of an organism.. even cells or any of the classifications we use to understand bundles of biology.
A planet is a thing that orbits our sun. Hey, exoplanets! A planet is a thing that orbits a star. Hey, rogue planets. Hey, rogue solar system! Meanwhile, the universe isn't all that fussy about solar systems or galaxies.
Our minds don't seem to naturally make as much of a distinction between abstraction and manifestation as we do.
That said, it isn't always easy, I feel like it was only 5 years ago I started to realize this myself as I got more interested in models, categories and taxonomies. And I feel this is a common mistake people make prior to being experts themselves (in any field), is confusing the abstraction for the concrete.
A very simple example is how tomatoes are both fruits and veggies, in reality, tomatoes are tomatoes, but in culinary science, it is more useful to consider a tomato a vegetable, because most recipes that call for fruits wouldn't be good with tomatoes in them. On the other hand, in botanical science, it is categorized a fruit, as fruit describes the category of seed-bearing structures in flowering plants.
This shows how various studies will use different models, categories and taxonomies to work with that is best adapted for their end results.
The beauty of such models is that they can help innovation, by allowing us to reason about more than we can at once. That's the benefit of any abstraction. But in doing so, we also reduce reality to a simplification, albeit one that ideally allows us to figure out something which meets our requirements and provide us the practical benefits we were looking for, like say figuring out how to build a machine that can fly.
So my advice would be to stop arguing semantics, because so often people will debate what is what: "no tomatoes arn't fruit that's ridiculous they are vegetable". Well who cares, they are what works best, and if you're baking, its better to consider them a vegetable, but if you're gardening, you'll be better considering them fruits. So instead start arguing about the models, it's better they be fruits when gardening because of x,y,z practical reasons that apply to gardening.
Even something as minor as the category of a tomato, would matter very much to a tomato farmer when, hypothetically, all vegetable farms qualify for a higher level of government subsidies than fruit farms. Or to a retailer when, again hypothetically, fruits and vegetables are charged different sales tax rates.
What the farmer in your example cares about is the legal classification of tomatoes in context of subsidies and taxation. That's an entirely different thing that biological, or culinary classification, and needs to be explicitly separated. If it isn't it leads to idiocy.
Real life examples of such inane reasoning can be seen with some very popular complaints about "stupid EU bureaucracy" - for example, that EU "decided that snails are fish" (they aren't, they just get bucketed with fish for some trade deal). People really do use it as a serious argument.
And sure, instead of legal classifications, one can discuss ethics related examples. Such as what makes for the good life? Something as simple as saying, the good life is based on some common sense notion of good or the good life is different for everyone and dependent on unique personal circumstances, already assigns numerous categories implicitly. That doesn't mean that both of those notions of the good life cannot be right. It does mean that we need categories to discuss and reconcile their differences, if we wish to have a pluralistic and liberal [in the 19th century sense of the word] society.
> In this respect our task must be to account for such experience in a manner independent of individual subjective judgement and therefore objective in the sense that it can be unambiguously communicated in ordinary human language. "The Unity of Human Knowledge" (October 1960) Niels Bohr
The periodic table comes to mind.
Exceptions to the rule are the thing that drive new science.
It isn't Eureka we're looking for its, huh, thats funny.
The remaining gas and dust that is swirling around the star flattens out into a disk (because of angular momentum). Planets gradually form in this disk, again via accretion (snowball effect).
Related to this, I wonder what the minimum resources a rogue planet has to have for human habitation in the future. Obviously there won't be sunlight, which means that we will have to generate all of our energy in some other way. Nuclear fission? Fusion?
Also if you find some water you could split it for oxygen and use methalox rocket propulsion locally.
Plants to consume the carbon dioxide, giving you calories and the oxygen back.
Otherwise you are just a Hobo jumping on a passing train and hoping it ends up somewhere hospitable so that your great great great great great ... great... great... great... great grandchild, an lineage born and lived entirely on the train, has a place to call home.
Without FTL, to spread over the galaxy we'll need to adjust our thinking on long time-scales for any of it to make sense or be possible anyway. We'll be a different species really (or _several_ different species).
If I were to bet, I'd say our more lasting contribution to the galaxy will more likely be mechanical (AI) descendants rather than ourselves, and next most likely would be barely recognizable biological dscendants (not necessarily that different from us physically, but in terms of society and mentality). That's all assuming we make it off of Earth and then away from Sol at all in any lasting way.
If you can live for 10,000 or 100,000 years then being limited to lightspeed isn't such a bummer. You can visit interesting places.
https://www.fourmilab.ch/cship/flythru.html
You'd have hundreds of years of media to catch up on when you got back.
If the AI doesn't absorb us somehow, I suspect it'll limit our ability to contaminate the rest of the galaxy.
(In the infosphere the Earth shines alone in darkness, the sole star.)
The machine will keep us in a bottle to feed off of our data.
...
Come to think of it, why wouldn't it "farm" us over a larger volume?
If an AI comes from space, it's likely billions of years old and we are as interesting as fungus.
> I don't see how humanity is a source for information beyond the initial growth phase (assuming it's created here on Earth).
Setting aside the possibility that Earth life is already an ancient alien nanotech AI ( https://en.wikipedia.org/wiki/Panspermia ), and assuming that humans are unique in the Universe, the rest of the entire Universe is pretty much predictable. There may be some poetic physics going on out there (I mean, of course there is, the Universe is beautiful!) but unless there's another planet of insane ape-men out there somewhere ours is the only show in town.
I imagine that the limitations of organic lifespan limitations will disappear with our species.
The most we can hope for is that AI somehow takes us with it.
Everything we do is survivorship bias. On Earth we may be the gardeners, but in space we're just the seeds.
The planet doesn't offer much to help the travel, yet you need to get out of its gravity well when you arrive.
Weirdly enough I never came up to a similar scenario in countless sci-fi books. I'd imagine it would be so expensive that if we were capable of it we would probably wouldn't need/want it as other alternatives would be much more efficient, right?
The thought of designed solar system is interesting - what if we FTL is an unbeatable barrier - we might just be stuck here and populate our system with hundreds of rogue passerby planets!
So with perfect efficiency, working just from conservation of energy, this would require around 13 days of the entire energy output of the sun. Or around a trillion years at Earth's current energy consumption.
Keep in mind how they detected this: they looked at the gravitational distortion of light caused by the planet's influence. We are used to seeing this gravitational lensing with black holes, which is visibly obvious even to an untrained human eye. The effect exists for every object with mass, but it's extremely tiny for planet-mass objects. For planet detection without a host star, it is the best measurement we have, but it's very finnicky and doesn't contain very much information compared to spectral analyses, motion around a host star, etc.
From that paper's abstract:
> Although in practice [rogue planets] do not emit any light, they may be detected using gravitational microlensing via their light-bending gravity. Microlensing events due to terrestrial-mass rogue planets are expected to have extremely small angular Einstein radii (~ 1 µas) and extremely short timescales (~ 0.1 day). Here, we present the discovery of the shortest-timescale microlensing event, OGLE-2016-BLG-1928, identified to date (tE ≈ 0.0288 day = 41.5 min). Thanks to the detection of finite-source effects in the light curve of the event, we were able to measure the angular Einstein radius of the lens θE = 0.842 ± 0.064 µas, making the event the most extreme short-timescale microlens discovered to date. Depending on its unknown distance, the lens may be a Mars- to Earth-mass object, with the former possibility favored by the Gaia proper motion measurement of the source. The planet may be orbiting a star but we rule out the presence of stellar companions up to the projected distance of ∼ 8.0 au from the planet. Our discovery demonstrates that terrestrial-mass free-floating planets can be detected and characterized using microlensing.
(Jupiter mass does come up, but only in the context of a binary system - when ruling out that this planet is orbiting a star, they can only rule out a parent body larger than a few Jupiter masses.)
There would have to be 25 times as many rogue planets as the mass of all systems, and most of the mass in a system is in its sun, so 25 Earths, Jupiters and Saturns are barely a blip.
There's still more than 5 times more dark matter than any matter we see, though. But I thought if it's extremely hard to detect rogue planets, then what if there's whole bunch of them, like really 6 times more than other matter including stars. And there's no clouds around them for some reason (example reason is that they were expelled from their formation clouds by gravitation dance with other planets there).
What's the theory that predicted this? After billions of years, I would expect all planets be attached (gravitationally) to a star, shouldn't they?
> Indeed, a few years ago, Polish astronomers from the OGLE team from the Astronomical Observatory of the University of Warsaw provided the first evidence for the existence of such planets in the Milky Way.
Wait. Evidence is not the theory. Did they predict this or discover it?
> After Jupiter had accreted large amounts of nebular gas, it could have gravitationally scattered the planetesimals remaining nearby into orbits which led to escape from the Solar System.
But this was purely speculative. It wasn't until many years later that the planet was actually observed.
> After billions of years, I would expect all planets be attached (gravitationally) to a star, shouldn't they?
I am not sure what you mean by that. All planets are formed in disks surrounding a star (or possibly a brown dwarf); rogue planets are planets that were able to escape the influence of that star. It might take billions of years before they get close enough to another star in the galaxy to fall into its influence.
> that were able to escape the influence of that star.
What's the mechanism here? Is it something with greater mass that pulled it into an escape?
>What's the mechanism here? Is it something with greater mass that pulled it into an escape?
I'm a layman. Take what I say with skepticism, but I think in this case the parent poster was referring to any mechanism that ends up with a planet getting out of the orbit of the star. One such potential mechanism is gravitational slingshotting.
Let's imagine you have a planet orbiting a star. A satellite flies in towards the planet. As the spacecraft passes by the planet, it gets some of the momentum of the planet as the planet is moving around the star. The planet loses that momentum. This increases the satellite's velocity in relation to the sun. The satellite can reach escape velocity and escape the influence of the star.
Edit: alternatively to reading my explanation, you could read Wikipedia's: https://en.wikipedia.org/wiki/Gravity_assist#Explanation
There's an amazing gif of Voyager 2's slingshots. Pay attention to the velocity as it passes planets: https://en.wikipedia.org/wiki/Gravity_assist#/media/File:Ani...
I don't see why a similar thing couldn't happen to planets.
Play with a few orbital simulators. Many are quite simple, but others allow a great deal of flexibility. It's actually quite a tricky business to get more than a few massive bodies into stable orbits -- gravity alone leads to extremely chaotic systems.
Planets are formed around stars, but some escape due to gravitational slingshotting etc.. Some of those might be caught again, but why would you think all are?
In the UK there was a recent series on “The Planets” by Brian Cox - one of the things I learnt was how a large has giant had migrated over time from the outer solar system to the inner and back out to the outer. That type of event have caused a slingshot to accelerate a planet like Venus into a highly elliptical orbit, one which might be further accelerated by other planets to a point where it reached escape velocity - especially if combined with large collisions.
This would happen in the same way the voyagers gained speed as it flew past the gas giants in the 80s.
It’s unlikely, but there are a lot of solar systems and a lot of planets.
Predicting the location of a given rogue planet would be like predicting the position if a tractor in a given field in Nebraska. However once you see the tractor is there you can start to predict how it got there.