The Biggest Thing in the Universe.

Scientists have created the first map of a colossal supercluster of galaxies known as Laniakea, the home of Earth's Milky Way galaxy and many other. This computer simulation, a still from a Nature journal video, depicts the giant supercluster, with the Milky Way's location shown as a red dot.

In the cosmic scheme of things, Earth is small. Even in our solar system, we are easily dwarfed by the planet Jupiter (more than 1,000 Earths would fit in the planet, according to NASA) and our sun (more than a million Earths would fit in there, according to Cornell University).

Even our sun looks puny when it is compared to the biggest stars we know of. The sun is a G-type star, a yellow dwarf — pretty average sized on the cosmic scale. But some "hypergiant" stars are much, much larger. Perhaps the biggest star known is UY Scuti, which could fit more than 1,700 of our suns. (Note that the margin of error is roughly 192 sun-widths, so at the lower end of the margin UY Scuti would move several ranks down the list of the biggest stars.) UY Scuti is only about 30 times more massive than our sun, however, so that shows that mass and size don't necessarily correlate in space.

Progressing up the list of big cosmic objects, other things to consider are black holes and, in particular, supermassive black holes that typically reside in the center of a galaxy. (Our Milky Way hosts one that is about 4 million times the mass of the sun.) One of the biggest supermassive black holes ever found resides in NGC 4889, which has a black hole roughly 21 billion times the mass of the sun.

Tetris Effect Background of Laniakea

There are things out there bigger than even supermassive black holes. Galaxies are collections of star systems and everything that is inside those systems (such as planets, stars, asteroids, comets, dwarf planets, gas, dust and more). Our own Milky Way is about 100,000 light-years across, NASA says; a light-year is the distance light travels in a year. It's difficult to characterize what the largest galaxies are, because they don't really have precise boundaries, but the largest galaxies we know of are millions of light-years across. The biggest known galaxy is IC 1101, which is 50 times the Milky Way's size and about 2,000 times more massive. It is about 5.5 million light-years across. Nebulas, or vast clouds of gas, also have impressively large sizes. NGC 604 in the Triangulum Galaxy is commonly cited as one of the largest; it's roughly 1,520 light-years across. 

Laniakea work in progress

Now at last we are starting to approach the biggest structures in the universe. Galaxies are often bound to each other gravitationally in groups that are called galaxy clusters. (The Milky Way, for example, is part of the small Local Group that comprises about two dozen galaxies, including the Andromeda Galaxy.) At first glance, astronomers thought that these structures were the biggest thing out there. In the 1980s, however, astronomers realized that groups of galaxy clusters are also connected by gravity and connected in a supercluster.