Probably "moving group". If they're still gravitationally bound, then "open cluster" is a better term.
Mutual attraction on macro scales such as stars, planets, and galaxies, is caused by gravity. Gravity can be better stated as the geometric shape on the macro scale of the universe, which is shaped and formed by the energy-momentum in the universe.
Motion and mutual gravitational attraction.Another Perspective:Gravity is the only thing required, which is fortunate because it's the only thing there is.
The mutual attractive force of gravity keeps the Earth in its orbit around the Sun.
An electric charge cannot be carried in the interior of a hollow container. Due to mutual repulsion, the charges will migrate to the larger external surface.
They can invest their own income/profits in a mutual fund but they cannot invest the depositors money in a mutual fund
We know of no way to shield anything from the force of gravity. The only way we know to reduce the mutual gravitational force that draws every two objects together is to either reduce the product of their masses somehow, or else to move them farther apart.
The mutual attraction that objects have for each other is typically due to gravity. Gravity is a fundamental force of nature that causes all objects with mass to be attracted to each other. The strength of this attraction depends on the mass of the objects and the distance between them.
Mutual Defense Treaty or Pact.
Symbiotic organisms live together for mutual benefit, such as lichens formed by fungi and algae, nitrogen-fixing bacteria in the roots of legumes, and cleaner fish that remove parasites from larger fish. These relationships can provide advantages like protection, food, or shelter for both species involved.
The force of gravity is greatest between two masses whose product is greatest, and which are closest together. You're already as close to the earth's total mass as you can get, and there's nothing you can do to change the earth's mass. So the only way to increase the mutual force of gravity between the earth and another body is to increase the mass of the secondary body. In fewer words: Eat more. Get heavier.
NATO?
Gravity causes a 'mutual' force between every two masses, that attracts each of them toward the other one. The mutual force between the sun and earth is what keeps the earth in its orbit around the sun.