# Orbiting around an object of variable mass

• awygle
In summary, the conversation discusses the hypothetical scenario of a satellite in orbit around an object that experiences a sudden change in its mass. The speakers acknowledge the unlikelihood of such an event occurring in nature, but also mention the possibility of artificially creating similar reactions through the use of engines. However, in terms of Newtonian gravity, changing the mass would not pose a problem and could be accounted for in the trajectory. In contrast, relativity does not allow for a sudden change in mass.

#### awygle

I'm curious - what would happen if a satellite was in orbit around an object which suddenly lost a large piece of its mass, or gained a large amount of mass? Of course this seems extremely unlikely to occur in nature, but I suppose similar reactions could be produced by using engines to counter the gravitational pull.

The problem with "what would happen if XXX ?" questions, where XXX violates physical laws, is that any answer is possible of course. You cannot use the system of laws of nature anymore to consider what would happen if something is defined from the start to violate them.

Now, in purely Newtonian gravity, there's no problem: just change the value of M, and take the last values of position and velocity as the new initial values of the new trajectory. The diminished pull (because the new value of M is smaller) can be indeed set equivalent to the effect of any other force in the opposite direction, yes.

In relativity, you can't "suddenly change mass".

## 1. How does the mass of an object affect its orbit around another object?

The mass of an object does not directly affect its orbit around another object. The orbit is primarily determined by the gravitational force between the two objects, which depends on the masses of both objects and the distance between them.

## 2. Can an object of variable mass be in a stable orbit?

Yes, an object of variable mass can be in a stable orbit. As long as the total mass of the system remains the same, the gravitational force and resulting orbit will also remain stable.

## 3. How does the varying mass of an orbiting object affect its speed?

The speed of an orbiting object is determined by its distance from the object it is orbiting and their respective masses. As the mass of the orbiting object changes, its speed may also change in order to maintain a stable orbit.

## 4. Can the mass of an orbiting object change during its orbit?

Yes, the mass of an orbiting object can change during its orbit. This can happen due to factors such as fuel consumption, collisions with other objects, or even the shedding of material. However, as long as the total mass of the system remains constant, the orbit will not be significantly affected.

## 5. How do scientists account for variable mass when calculating orbits?

When calculating orbits, scientists take into account the changing mass of an object by using the conservation of mass principle. This means that the total mass of the system remains constant, and any changes in the mass of an object will be reflected in its speed and orbit.