The Hubble Telescope captured an image of NGC 5917 (spiral galaxy). This is an interesting object due to the established contact with the galaxy MCG-01-39-003 (not visible on the frame, but located at the bottom right).
The concept of "mass" in most cases is compared with "weight", although it is a question of different things. Mass is the substance of an object and always remains itself without reference to a position. If you go to the moon, where gravity is much lower than ours, then the mass remains stable. In fact, changes occur with weight, because it is a force created by another massive object. Gravity - a way of "communication" of cosmic bodies. We weigh less on the earth satellite, but not because they lose mass. Just the mass of the moon is less than the Earth, so the force of gravitational influence decreases. Understanding this difference is extremely important when we try to understand how objects in space interact. Without massive gravitational “dialogues”, the planets will stop making revolutions around the star, and the galaxies will stop contacting, like NGC 5917, with a neighbor. Galactic contact can lead to interesting effects. They are capable of generating someone else’s mass (stars, dust and gas), as well as distorting the shape or creating waves that lead to active star formation. But sometimes they are so absorbed in the interaction that they merge into a single object. If NGC 5917 decides to unite, then the next distant generations will be able to admire it.