A new survey indicates that anything up to 170 rogue planets are in the local neighborhood. The good news is that if they’re not rogue planets, they’re possibly brown dwarfs. The rogues don’t emit visible light. They have to be tracked with infrared light. It’s not even entirely clear how to differentiate between big planets and brown dwarfs.
It’s only recently that the idea of huge numbers of rogue planets roaming the galaxy has been accepted as accurate. The idea of a rogue planet has been around in science fiction for about a century. The fact, meanwhile, has got people fascinated and diligently mapping things.
Therefore, of course, things instantly got a lot more complicated. The original theory of rogue planets was that they were slingshot out of parent systems. The problem with that idea is that there are so many of these planets, probably billions of them.
They can’t all have been fired out of their systems. It’s asking a bit too much of gravity and coincidence. So the new theory is that they form independently through some unknown process. (There’s a very useful video from Anton Petrov’s What the Math that clarifies this rather difficult new range of issues.)
That’s the beauty of the word “unknown”. You don’t have to commit to any theory but honest, preferably sincere, ignorance.
In practical terms, however, if we’re going sightseeing out there, it’s not a very useful expression. Like the Wall of Fire of interstellar plasma, this is a game-changer, and in some ways, possibly a good one.
Mapping the rogues.
This may well become one of the biggest data sets in history:
Rogue population density – What’s where, and how many of them? What sort of population distribution?
Identifying them as definite rogues, brown dwarfs, etc. Basic cartography meets basic astronomy.
Composition – What are they made of? May well be a lot of stuff we haven’t seen before if they’ve been formed by “unknown” processes. Combinations and types of elements could be very different. Asteroids in our own system have things that don’t form naturally on Earth, for example. Let alone whole planets.
Ahem – What’s coming our way?
There’s a little caveat or two on all this clinical theorizing about rogues:
We see a LOT, like vast numbers, of weird-looking systems. Hot Jupiters that orbit their stars in a few hours. Inverted (to us) systems with rocky planets on the outer orbits. Add any combination, and it’ll be out there somewhere.
Is it so far out of the ballpark to assume that rogue planets can also be captured by stars? Probably not. We’re too early in the process to be able to prove that one way or another, but hardly a huge leap of logic, is it?
If we think rogue asteroids and comets are a problem, what about joyriding rogue planets? They could shake up the entire gravitational balance of the Solar System. An extra Jupiter, for example, could cause a rain of objects to get displaced and come and say hello like one did in the Cretaceous.
If we happen to have 170 mapped “unknowns” fluttering about nearby, maybe we should be paying attention? Even a near miss could have a sizeable bit of the Oort Cloud in a reconfigured orbital mess, pretty quickly.
Fond as we all are of the idea of billions of tons of ice and rock running around in the system, and landing on our heads, a bit of forewarning won’t hurt. This is not theory. It’s quite possible one or more of these things can do us some damage. There’s plenty of evidence of various events in the past that may well have involved some external players affecting Earth.
The other major plus here is that even the core astrophysics for evaluating rogues will be very useful, long term. At the moment, the knowledge base is all in our system. Some external experience wouldn’t hurt and will be inevitably required later in space travel.
Some thinking to do
So far, in what can be called the post-Hubble era, we’ve discovered that most of our assumptions about interstellar and galactic space have been absurdly simplistic. If we’d tried to get to deep-ish space with the “market image” of space in the 1960s, failure would have been inevitable.
It’s literally taken a couple of generations to get the basics right. That process can be expected to continue for a long while yet. If there’s one absolutely clear and unambiguous message about space, it’s that “boldly going” means “bring your brain”. Don’t leave home without it, etc.
Don’t happen to have any golden tablets handy, (who’d put one online, anyway?) but my guess for the First Commandment of Space Exploration is
THOU SHALT GET IT RIGHT.
Fortunately, the James Webb Telescope has just now been deployed. At least we’ll be able to see more of what we’re tripping over every day or so.
