In my setting I want to destroy the world in a way where people have:

  1. Plenty of notice of the impending demise
  2. No chance of stopping it
  3. They can't engineer a way to survive on earth
  4. The rest of the inner solar system is also rendered uninhabitable

I plan to do this by having a large extra solar object, that was previously undetected, on an intercept course with our solar system and will likely be captured into an eccentric orbit of the sun in the inner solar system. This would hopefully cause all the inner planets from mercury to mars to either be thrown out of their orbits or eaten by the new arrival. I was planning on having this object be a brown dwarf or a super Jupiter.

The problem I'm not sure about is: if an object that big was under a century away I think we could have seen and discovered it already.

So my question is: What is the largest astronomical object that could be overlooked, assuming modern or near future technology, until it was only a few decades away from intercepting our solar system?

  • 3
    xkcd.com/1633 – user25818 Aug 30 '17 at 16:17
  • There are no Super Jupiters in Solar system (including the outer reaches), but nothing can prevent a rogue one to drop by. We will have at least a year advanced notice. Brown dwarfs, on the other hand, are much better visible, there is virtually no chance of any of them coming during human's lifespan. – Alexander Aug 30 '17 at 16:42
  • Planet Nine is postulated, and I believe is a Super Jupiter. en.wikipedia.org/wiki/Planet_Nine – DPT Aug 30 '17 at 16:57
  • "similar study in 2014 focused on possible higher-mass bodies in the outer Solar System and ruled out Jupiter-mass objects out to 26,000 AU" Planet Nine is believed to be of Uranus/Neptune class. – Alexander Aug 30 '17 at 17:01

Black Hole

A black hole passing by and attracted by the gravity of our sun would be insanely devastating and probably undetectable until is really close to see their effects in the outer rim of our solar system.

https://en.wikipedia.org/wiki/File:A_star_is_consumed_by_a_black_hole.ogv

Supernova

Not exactly an object getting inside our system but there is already a theory that a "relativy closer" supernova caused a mass extintion on our planet.

https://en.wikipedia.org/wiki/Ordovician%E2%80%93Silurian_extinction_events

The gamma ray burst could strip the planet from his ozone layer in an instant allowing that the sun radiation reach the earth killing almost all live.

  • Neither of these fit the qualifications that the user asked for. – jdunlop Aug 30 '17 at 18:27
  • @jdunlop sorry, but how a rogue black hole wouldn't fit the description? – Tridam Aug 30 '17 at 19:37
  • The question asks for something that can be detected with a few decades advance notice. – ths Aug 30 '17 at 21:14
  • A moderately sized black hole could eventually be detected as the effects of gravitational lensing become more and more apparent. Astronomers would notice the growing distortion in a part of the sky and conclude that it's likely a black hole, since there's no light being produced. The fact that the distortion is getting worse either means the black hole is growing very quickly (Extremely unlikely) or approaching (A lot more likely). – Daniel Canlin Masterson Aug 31 '17 at 12:02
  1. Plenty of notice of the impending demise
  2. No chance of stopping it
  3. They can't engineer a way to survive on earth
  4. The rest of the inner solar system is also rendered uninhabitable

Numbers 1 and 4 are easily possible and conceivable with earth's current knowledge etc.

Number 2 and 3 are interesting. You can write it such that they can't stop it, regardless of their technology level, by introducing another element, something like an independent pandemic scenario or other global catastrophe - Rise of our robot overlords or something.

In practice, we humans don't seem to worry about doom scenarios until it is close enough to really matter. then, we freak out. This happened with Y2K and is happening more obviously now with global climate change, and nuclear proliferation in some parts of the world. I think the number of years till collision is immaterial. Plenty of people won't worry about events that are far out there - They think there is no reason to, for something far in the future.

So, through a combination of normal human social behavior and/or independent world events, you could make it so that by the time we took it seriously we would be out of time.

As for #3, a collision or other huge event will disrupt plant's severely(decreased sunlight.) if it did in the dinosaurs, it could do the same to us. We starve - And getting to that point is ugly (I bet some people start cannibalizing.) I suppose we could make biodomes, but there are definitely ways to make your planet inhospitable. Maybe some folks make it, but there would be a pretty big collapse.

Transit of a Pulsar through the inner solar system;

  1. Just like a comet or asteroid you'd have to be looking right at it to spot it, but it's an emitter not a reflector so we could spot it much farther away we'd know about it from 10s or even 100s of light-years away.

  2. Unless you can make a significant change to the velocity of either the solar system or an object that weighs 2-3 times what the Sun does it's going to happen.

  3. & 4. The radiation output would be enough to sterilise a huge swath of the solar system, not just Earth, tidal forces would create massive Roche Tides on Earth and the other rocky worlds, think force a 10 earthquake everywhere on the planet for days or weeks during the transit. Long term the gravitational perturbations would also turn the whole solar system into a shooting gallery for millennia to come with Main Belt, Kuiper and Oort objects thrown in every direction.

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