These gigantic structures, which contain hundreds or even thousands of galaxies bound together by gravity, offer important ...

Space. It's really, really big. How big is it? Well, according to astronomers, the observable universe is around 92 billion light-years in diameter, but that's all we can see (hence the word ...

Astronomers have long estimated that ordinary matter – basically, anything other than dark matter – makes up only a fraction of the known universe. The conclusion stemmed from a complex calculation ...

Will the universe keep existing forever? An astrophysicist explains how scientists aren’t entirely sure, but they can make predictions.