# Relativistic effects of a low orbit around supermassive objects

• Sotnas
In summary, the conversation discusses the idea of sending humans to orbit a massive object like a neutron star or black hole. The questions raised include whether this is possible without killing the astronauts, the challenges of entering and maintaining such an orbit, and what the astronauts would see from their window. It is noted that the intense gravitational forces would make survival nearly impossible and the major challenge would be braking to enter the orbit. The possibility of using fictional technology to reduce the effects of tidal forces is also mentioned. The conversation also mentions the potential structure and heat differences on the surface of a neutron star and the potential for time dilation for the astronauts in orbit. The effects of a magnetar's powerful magnetic field are also discussed as a potential danger for the astronauts.
Sotnas
Hi everyone, first post here. Lurking for a while but it was time to register..
I'm trying to conceptualize an idea in which humans are sent to orbit a very massive object, like a neutron star, a magnetar or even possibly a black hole. I would like the ship to be relatively close to the surface that is spinning at maybe 50 hz, and also, the ship should be stationary above its surface.

So my questions are 1) can I do this without killing the astronauts,
2) What would be the major issues in entering and maintaining such an orbit?

3) What would they see, looking out the window up to the sky? Considering the relativistic effects of them spinning around the object at speeds near C.

I'd appreciate any thoughts on the subject!

/D

A black hole has nothing that could be described as "spinning surface".

Orbiting an object with 1 solar mass with 50 Hz needs an orbital radius of ~100km and an orbital speed of ~35000km/s or .1c. For a rough approximation, we can still neglect relativistic effects.

1) Tidal accelerations would be ~40000g/m. That means head and feet feel accelerations of 40000g relative to the center of the body. There is absolutely no way to survive this, the astronauts would get ripped apart in milliseconds. Even the strongest materials available today would struggle to maintain the integrity of a spacecraft with a "height" (as seen as radial distance) of more than a few meters, and I think the other directions are even worse (as compression is harder to manage compared to tension)

2) The major issue in entering this orbit: assuming the environment of the massive object is empty enough to avoid collisions with gas/objects: braking. Coming from a point far away, the spacecraft would have to accelerate (backwards) by .05c on its own somehow. Nuclear propulsion methods might be able to deliver this, chemical rockets are completely pointless here.

3) Towards the neutron star or similar: probably nothing, as the object is so hot it will make a human eye blind quickly.
Towards the neutron star or similar, with appropriate shielding: a small white disk.
Towards everything else, with even better shielding against the neutron star radiation: probably blurry lines from all the other objects (apparently) swirling around you with a rate of 50 Hz.

Thanks mfb, great feedback... didnt take tidal forces into account. Guess I need to figure out some fictional technology that will help reduce these effects, but not eliminate them alltogether. The environment should be totally empty - it's a lone object approaching the solar system.

If we assume the spaceship has appropriate light filtering system - kindof what they had on the movie Sunshine while approaching the sun. Would the neutron star have any kind of structure or heat differences on the surface that would translate into a more interesting view?

Another thing is, for plot reasons I need the astronauts in orbit to have much more time available to them than Earth time. If the neutron star will enter the solar system in 5 years time, could I use relativistic effects to make their stay in orbit last a lot longer than 5 years (for them).

Would the neutron star have any kind of structure or heat differences on the surface that would translate into a more interesting view?
I would guess so (especially for pulsars), but I don't know.

Another thing is, for plot reasons I need the astronauts in orbit to have much more time available to them than Earth time. If the neutron star will enter the solar system in 5 years time, could I use relativistic effects to make their stay in orbit last a lot longer than 5 years (for them).
I don't see how this would work in any even remotely realistic way. If you need more "thinking time", use more astronauts or a better computer. If you need more manual work, use more astronauts or more machines. What other reason is there for more time for astronauts?

What I am trying to get is, once they enter the strong gravitational field do they locally still have (the on Earth calculated) 5 years before the event happens, or will they have less time, because their clock is now ticking slower relative to earth?

There are two different effects: as seen from Earth they are moving fast (special-relativistic time dilation gives them more time), but at the same time they are close to a massive object (gravitational time dilation gives them less time). In an orbit, as far as I remember the second effect wins, so they have a bit less than five years.
I don't see the relevance of this, however.

If it's a magnetar, then you would also have to watch out for the effects of an extremely powerful magnetic field-

..The magnetic field of a magnetar would be lethal even at a distance of 1000 km due to the strong magnetic field distorting the electron clouds of the subject's constituent atoms, rendering the chemistry of life impossible. At a distance halfway to the moon, a magnetar could strip information from the magnetic stripes of all credit cards on Earth. As of 2010, they are the most magnetic objects ever detected in the universe.

http://en.wikipedia.org/wiki/Magnetar#Magnetic_field

## 1. How does the strong gravitational pull of a supermassive object affect objects in low orbit?

The strong gravitational pull of a supermassive object, such as a black hole, causes significant distortions in space-time. This can result in time dilation, where time appears to move slower for an object in orbit compared to an object at a greater distance. This effect is known as gravitational time dilation and is a key component of the theory of general relativity.

## 2. Are there any physical effects experienced by objects in low orbit around a supermassive object?

Yes, there are several physical effects experienced by objects in low orbit around a supermassive object. These include tidal forces, where the difference in gravitational pull between the side of the object facing the supermassive object and the side facing away causes stretching and compression of the object. This can also result in spaghettification, where an object is stretched and torn apart due to extreme tidal forces.

## 3. Can objects in low orbit around a supermassive object reach speeds close to the speed of light?

Yes, objects in low orbit around a supermassive object can reach incredibly high speeds, but they will not reach the speed of light. This is due to the effects of time dilation and the fact that as an object approaches the speed of light, its mass increases, making it more difficult to accelerate further.

## 4. How does the relativistic effect of low orbit around a supermassive object affect satellite communication?

The relativistic effects of low orbit around a supermassive object can cause small changes in the timing of signals sent between satellites and ground stations. This is known as gravitational redshifting and can affect the accuracy of GPS systems and other satellite communications. However, these effects are generally very small and can be corrected for with advanced technology.

## 5. Are there any potential dangers for objects in low orbit around a supermassive object due to relativistic effects?

Objects in low orbit around a supermassive object are at risk of being pulled into the object itself due to the strong gravitational pull. This is known as the "Roche limit" and can result in objects being torn apart by tidal forces. Additionally, the high speeds and intense radiation near supermassive objects can pose a danger to spacecraft and astronauts in low orbit.

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