# What will happen to Earth when the starnappers strike?

The things that pop into my mind in the middle of the night…

Those evil but incredibly advanced at science Alpha Centaurions have decided that they need to add another star to their system (I don’t know why, keeping up with the Jones, probably) and have decided our Sun is just the right size and hue to fit their decoration scheme.

So they send out their SuperSpace Tug with the latest AmazoTractorBeamThingy. It latches onto the Sun (yes, quite a tricky challenge, but as I said they have advanced science) and start dragging it home.

What I want to know is, what will happen to the planets of our solar system?

Will they be dragged along by the Sun’s gravity, with their orbits more or less disturbed/the same?

Will only some planets go along (the closest ones, maybe) while the rest are lost? Or only the ones that happened to be moving in approximately the ‘right’ direction at the time the Sun gets yanked off?

Or will they all be left in the cold and dark? <sniff>

If a planet is left behind, I assume they will head off in whatever direction at whatever speed they happened to be traveling at when this, ah, disruption occurred? If so, what’s their likely fate? Will they travel ‘forever’ or eventually smash into something, or end up orbiting some other star?
Drawing on a knowledge of physics that consists of one course in High School mumblety years ago, I’m guessing that what mostly counts is how fast the Sun is pulled away, plus the mass of the Sun and a particular planet and the distance between them.

Let’s say that it will take 100 (Earth) years for the Evil ACs to haul our sun the 4.3 light years.

Some googling got me:

Distance from Earth to Sun: 149.6 million kilometers (average)

Mass of Earth: 5.976e24 kg

Mass of Sun: 1.989e+30 kg
But I don’t know how to proceed any further.

Anyone?

Nothing would happen, Chuck Norris wouldn’t permit it.

It depends how fast they move the sun. If they move it ***very ***slowly, the entire solar system will move along with it. On the other hand, if they just yank it out of here, we’re in deep doodoo. The planets will fly off on their own (possibly shedding moons along the way), depending on their vector at the time of the Big Yank. They’d probably eventually get sucked into something’s gravitational field, but of course there’s no way to predict what or where or when. Those darn Alpha Centaurians.

Then we’re in deep doodoo. The OP has it leaving at 4.3% of the speed of light. That gets it out to the distance of Neptune’s orbit in 4 days and that’s pretty quick. Most of the planets will just mosey off on their own, as you say. If any happen to be more or less in the path of the departing Sun then in all likelihood they will leave in a quicker, albeit unpredictable, way.

Since the Alpha Centaurians have extra suns I say we go over there and get ourselves an extra star.

Assume the Sun is given a sudden delta-v “kick” in one direction. In the Sun’s reference frame, that’s equivalent to all the planets being given a delta-v in the opposite direction.

If that delta-v is small compared to a planet’s current orbital speed, then the orbit will be altered only a little. Probably, the orbit will be made more eccentric (more elliptical) — unless by coincidence the delta-v happens to undo the eccentricity it already has.

If the delta-v is about sqrt(2) times the planet’s current orbital speed, or larger, then the planet will effectively achieve escape velocity in the Sun’s reference frame, and will no longer be bound to the Sun. It will “drift” off into interstellar space. Unless — again by coincidence — you’ve set the two bodies on a collision course, in which case the planet will suffer Sudden Massive Existence Failure.

So note then that the fate of a planet, in the your scenario, depends not only on the Sun’s delta-v but also the planet’s current speed. It would easily be possible to lose some of the planets but not all, depending. (However, for a delta-v of 4.3% light-speed, you’d certainly leave all of them behind.)

Well, look, the plans have been on display for fifty of your Earth years, so you’ve had plenty of time to lodge any formal complaint and it’s far too late to start making a fuss about it now.

If you can’t be bothered to take an interest in local affairs that’s your own lookout.

Sounds like ‘left in the cold and dark’ is the consensus. :mad:

Two thoughts:

1. Why are we leaving a valuable property like our favorite star just lying around unprotected, anyway? I understand the National Guard and the Army and all are kind of busy these days, but couldn’t we throw up a barbed wire fence at least?
2. In the meantime, maybe I’ll sell my stock in SunBlocks Ltd. and invest the money in GrowLight Industries instead.

So we’re left in the cold and dark. Does Earth freeze over completely? Does any sort of life survive? If Earth eventually got pulled into another star’s orbit, could it support life again or would it be completely dead? Does the moon stay in orbit around Earth or does it get knocked out of orbit as the sun pulls away?

But the plans were in a disused basement with a sign on the door reading ‘Beware of the leopard!’

Excuse me, but I’ve got to lie in front of this bulldozer…

I’m not a geologist, but until one comes by, I’ll take a couple guesses…

The Earth’s interior radiation would continue to exist even without the Sun, and would be a heat source of a kind. I don’t think it’s anywhere near enough to keep the surface from freezing over. It is enough though, I think, to keep the Earth geologically active for a very long time. So there would still be volcanoes, continental drift, deep ocean vents, and so on. Perhaps the anaerobic bacteria that live around such vents could keep up a living.

It’s possible that once the Earth was frozen over it would stay that way forever, even if you brought back the Sun or a Sun-like star to the same distance. The albedo of ice is very high (at least in the optical band), so most of the incident sunlight would be bounced back into space, and wouldn’t warm anything enough to melt it. It’s a bad situation that tends to re-enforce itself.

I believe it’s conjectured that the Earth actually was in a permanent ice-ball state very early in its history. Then, we collided with the massive object that resulted in the Moon forming — which collision also melted enough ice to make liquid oceans, and broke the vicious circle. (Liquid water has a very low albedo. It absorbs a lot of light, making heat, and then spreads that heat around to warm everything else.)

This historical scenario I read anyway in Scientific American, or somewhere like it. I don’t know how much evidence there actually is for the Ice-Ball Era.

I suppose if you temporarily warmed up the Earth a lot, to restore the oceans and the atmosphere, and then turned down the heat to current-day levels, then you’d probably have a planet that could still support life. But since no plants or oxygen-breathing animals would have survived the freezing, you’d have to wait and hope for it all to re-evolve.

Assuming the Sun is pulled away in a trajectory that doesn’t take it very close to the Earth-Moon system — “close” on the scale of the Moon’s orbital radius that is — then the Earth and Moon should continue orbiting each other just as they do now.