— There are three types of binaries: visual, which means you can actually see the two stars in a telescope (no orbiting binaries have a wide enough separation to be seen with the naked eye); spectroscopic, which means you can see the presence of the orbit due to the Doppler shifting of the stellar spectral lines; and …

A binary system is simply one in which two stars orbit around a common centre of mass, that is they are gravitationally bound to each other. Actually most stars are in binary systems. They share a common focus which is the centre of mass or barycenter of the system and orbit around this point.

Or, more intriguingly, the two stars might both supernova and collapse into two orbiting black holes that would throw off gravitational waves at the speed of light as their orbits slowed. When they finally merge, they would form one big black hole, giving off one last, intense blast of gravitational waves.

Yes. These are called binary stars. Depending upon the relative mass of the stars, one could have a situation where one of the stars basically orbits the other star because the more-or-less stationary star is much more massive than its binary companion.

Stars die because they exhaust their nuclear fuel. Really massive stars use up their hydrogen fuel quickly, but are hot enough to fuse heavier elements such as helium and carbon. Once there is no fuel left, the star collapses and the outer layers explode as a ‘supernova’.

Stars rarely collide, but when they do, the result depends on factors like mass and speed. When two stars merge slowly, they can create a new, brighter star called a blue straggler. Stars that collide with a black hole are ultimately consumed. …

Galaxies die when the stars that live in them stop forming. Now, for the first time, astronomers have witnessed this phenomenon in a distant galaxy. Scientists were able to glimpse a galaxy as it ejected almost half of the gas it uses to form stars.

The merging of galaxies will radically affect their shape. For example, two spiral galaxies can merge and form an elliptical galaxy. Sometimes even more than two galaxies can collide with each other. Although galaxies have a lot of starts, it is very unlikely that starts from both galaxies actually collide.

Our galaxy, the Milky Way, is falling towards the Andromeda galaxy. In about 4 billion years, these galaxies will collide. Eventually, in about 6 billion years, these galaxies will merge. The combined system will settle down, perhaps resembling an elliptical galaxy.

The Milky Way is currently undergoing minor mergers with both the Sagittarius and Canis Major dwarf galaxies. The large number of disturbed galaxies in these six regions of the Hubble Ultra Deep Field show that interactions between galaxies were even more common in the past than they are today.

We have a universe with three dimensions and if you include space-time, four. So in Stranger Things, characters don’t travel to another dimension but rather another version of Earth in a parallel universe. Hypothetically, this holds true. If space-time goes on forever, it only makes sense that it must repeat itself.