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I'm working on a setting for an RPG, and I'm trying to build my planet so it's unique and interesting, but also semi-plausible. My question is, could you have a planet in stable orbit around a magnetar that sustained life as we know it, an earth of sorts, and what would the effects on the planet be?

I know magnetars have a short lifespan during which they are highly magnetic, but this planet will have been an experiment by someone. So they've stabilized the star so that it remains as is, producing a strong magnetic field. I would also like the planet to have a few moons, but I want the planet orbiting squarely withing the region where the two gravitational fields would interact.

My thoughts on possible ramifications lead me to a couple of things. Traveling rocks that are naturally magnetic, possibly floating landmasses, depending on the strength of the field, an animal-type species that has perfect sense of location due to magnetic sensitivity, and perhaps travel via magnetic ships that ride the field.

EDIT: Another note, if there's a different way to get the effects I'm looking for, floating landmasses and such, aside from orbiting a magnetar, I'm interested in hearing about it.

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    $\begingroup$ You'd have to deal with the high energy gamma and x-ray radiation for a start... I don't remember hearing of a magnetar before, so thanks for that! $\endgroup$ – AndyD273 Aug 26 '15 at 14:28
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    $\begingroup$ nightninja and @AndyD273, magnetars are fun (at least, i think so), mostly because they have a tendency to rip apart atoms. I doubt a planet could exist in what would be the habitable zone of a magnetar. $\endgroup$ – Frostfyre Aug 26 '15 at 14:47
  • $\begingroup$ Also, there are several animal species on Earth that use electro-/magnetism. Hammerhead sharks are believed to navigate using the Earth's magnetic field, for example. So that part of your question is conceivable. $\endgroup$ – Frostfyre Aug 26 '15 at 14:49
  • $\begingroup$ @Frostfyre Are they different than other neutron stars? I kinda thought that anything that got to close to a neutron star kinda got crushed down into neutronium. I could be thinking of something else... Even if a planet could exist in that area, and if life wasn't sterilized by the radiation, you gotta wonder what magnetic fields that strong would do. In Blindsight, the author has strong magnetic fields that disrupt human brain/nerve signals, causing temporary blindness and stuff. And Crichton listed evidence that strong magnetic fields could shrink things... for what that's worth. $\endgroup$ – AndyD273 Aug 26 '15 at 15:12
  • $\begingroup$ @AndyD273 Magnetars are a type of neutron star; they are the most magnetic objects in the universe we know of. $\endgroup$ – Frostfyre Aug 26 '15 at 15:30
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There are a number of problems, lets solve them one at a time:

Having a planet in the first place:

If the planet was captured by the Magnetar after it was formed then that would explain it surviving the supernova. You would need some interesting interactions in order to explain a stable non-elliptical orbit but it's theoretically possible for capture to happen.

Providing light and heat:

The Magnetar won't do it. You have two choices here:

  • Internal heating of the planet by gravitational or magnetic forces - this would give you an ice crust with liquid water beneath.
  • A binary system with another star and the Magnetar orbiting that other star. Your planet could orbit the Magnetar or orbit the combined binary. Either way you would get temperature variations depending on your distance from the light star.

Note that Magnetar research has suggested that a binary pair may be needed for Magnetar to form in the first place - or that it would help them form anyway.

Not getting ripped to shreds by the magnetic field

This is hard to answer, but remember that the strength of the field varies for different Magnetars and also that the further you are from the Magnetar the weaker the field will become. In other words you just need to move the planet out until it is far enough from the star to survive.

Ramifications:

Traveling rocks that are naturally magnetic It depends what you mean by travelling, magnetic rocks could plausibly be pulled along the ground or even act like tides on an ocean under the influence of the field.

possibly floating landmasses, depending on the strength of the field No. Sorry. That would never be stable. They would either fly up into the air or fall to the ground.

an animal-type species that has perfect sense of location due to magnetic sensitivity

Highly unlikely - since magnetic sensitivity would just let it sense where the Magnetar is, and the planet is constantly moving through the agnetars field.

travel via magnetic ships that ride the field.

Slightly more plausible than floating land since you can have something actively working to stabilize them. It still doesn't really make sense though. You have a powerful magnetic field but the planet is already moving through that at massive speed. You could probably generate electricity off it though...

Your how-else question might be covered here: What could cause rock formations (small stones, boulders, islands...) to levitate?

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  • $\begingroup$ Thanks! I'll take a look at that other link. I'm leaning towards an artificial planet orbiting a regular star, that way I can explain away a lot of things. We'll see though, still very much in the brainstorming phase. $\endgroup$ – nightninja Aug 28 '15 at 12:34
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If you are so close to the magnetar the star produces enough heat and light to create temperate regions, we are thinking several million kilometers distance from the star.

The planet will be tidally locked, one facing the magnetar, the other facing away. The planet will have its hydrogen stripped away on the sunlit side very very quickly - on the sunlit side the radiation will be somewhat comparable to a blast furnace situated inside chernobyl when it's melting down. That's lethal. The dark side however will have a very much oxygenated atmosphere. This planet will be showered in particles, which is plausible to produce an industrial effect of sorts. The illumination on the dark side may then be caused by a magnetosphere glow (aurora equatorialis) reaching all the way around the planet. Heat is provided by atmospheric convection, i.e. storms and rain. It would be a world with very little coriolis. The landscape would be material deposited after a supernova, and there may very well be mining going on for rare stable element 120. It would be a hellish place, obviously.

I can not rationalize in to existence pandora floating stuff.

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You have a big problem with the tides.

I've seen neutron stars listed as having a luminosity of 1E-6 of the sun. Lets work from that and see what happens.

Energy goes at the square root of distance, thus we need to be a sqrt(1E-6) of the distance the Earth is--1/1000th of the distance.

Tides, however, go at the cube root of distance. Thus our planet experiences a solar tide 1000x what Earth does. On Earth the average solar tide is 25cm. That means on your planet is 250m.

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Not possible, because if you are close enough for the heat then all matter that is composed by chemical bonds gets shred because the magnetic field of magnetars would steal the electrons breaking all chemical bonds. If you are far away enough for chemical binding to be able to exists, then you would not have enough heat, for not saying that even if chemical bonds can happen, it would still be difficult for things like neurons to work under such magnetic field, and probably chemical reactions would not work very well, because the interference of the magnetic field, thus not allowing life science life is based in lotta of chemical reactions.

Magnetars are the most dangerous and hazardous celestial object you can be around, it would be way safer to be orbiting a black hole.

If you want something similar to a magnetar but more life friendly you can try with neutron stars, after all magnetars are a special class of neutron stars, but not all neutron stars are a magnetar, and a neutron star still would be cool and dangerous, but would still be probable to support life.

In general a magnetar is not a good idea, a magnetar does not have a "strong magnetic field" they have the magnetic field that is unthinkable high

For you to understand, for levitating a frog in the air you need 16 tesla, because with such a strong magnetic field even water becomes magnetic, a magnetar have magnetic fields rounding between 1.000.000 tesla and 1.000.000.000.000 tesla. a 16 tesla is a "strong magnetic field", 1 million tesla is not a "strong magnetic field" is a monster worse than a black hole.

TL;DR Not, life is not going to be able to survive a planet orbiting a magnetar, even if the planet is in a very far away orbit, and somehow has a internal way of being warm and has his own ways of providing light to itself, even so far away the magnetic field would still mess enough whit chemical reaction for the chemical reactions required for life failing constantly and thus bringing death in a few hours, and that is for life that comes from outside the magnetar, it would be impossible for life to be produced in such a planet or reproduce if bringed from other place

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It is shockingly difficult to get significant magnetic effects from a magnetar on an orbiting planet. I know because I developed my own setting involving a magnetar planet, did a bunch of calculus, and talked with an astrophysicist specializing in neutron stars to check my work. Without going into all the messy mathematical details, I'll give you the high-level conclusions.

The problems are three-fold:

  1. Because they are dipolar, magnetic fields drop off proportional to the inverse cube of distance. There is a minimum distance at which a planet can orbit defined by the Roche limit, and it's far enough away that even the extreme fields of a magnetar just aren't that impressive anymore. Yeah, if you arrange things just right, you can end up with a planet where magnetic computer memory is useless, 'cause it just gets reset by the ambient field all the time... but that doesn't take much, and you certainly won't end up with floating rocks, practically-levitating vehicles, or locally-significant electrical induction. Biological magnetic navigation is fine, but you don't need a magnetar for that--Earthling organisms can already do it.

  2. In a Newtonian universe plus electromagnetism, you could imagine a magnetar with a field so colossally huge that all of the issues from (1) are resolved. However, you still have several sub-problems:

    a. Magnetic levitation depends on a field gradient, not a constant field strength. The gradient of a magnetar's magnetic field over the surface of a planet will be both tiny, no matter how strong the field is, and highly variable in direction with respect to the ground. Also, static magnetic levitation is unstable, so you won't get naturally floating rocks, let alone continents, unless they are composed of some kind of natural superconductor.

    b. If the magnetar's magnetic field is not exactly aligned with its axis of rotation, and if the planet does not orbit exactly in the magnetar's equatorial plane, then you will end up with a rapidly-oscillating magnetic field across the planet, which is not useful for continuously levitating things and will result in significant heating and magnetic drag. The heating might be a good thing, but the magnetic drag makes this an unstable scenario--the planet will rapidly be moved to a higher orbit where the magnetic effects are insignificant.

  3. In reality, we do not live in a Newtonian universe. Which means that we have to consider the effects of the light cylinder--the cylinder defined by the radius from the star's rotation axis at which an object co-rotating with the magnetar would have to move at light speed. Well inside the light cylinder, the magnetic field is well-approximated by a rotating classical field, but as you approach the light cylinder the field becomes highly distorted, and effectively "cut off" at that surface. Outside of the light cylinder, the field in the star's equatorial plane is effectively zero, and follows a fairly complex function of stellar latitude, central radius, and magnetic inclination above and below that plane. So if the planet orbits in the magnetar's eqatorial plane, it will see no significant magnetic effects at all; if its orbit is inclined, it will experience complex but regular variations in field strength and direction as it passes above and below the equatorial plane.

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