Beyond Our Solar System

Stars, Galaxies, Black Holes and More
Exploring The Universe

Other Solar Systems

Our Milky Way Galaxy is just one of billions of galaxies in the universe. Within it, there are at least 100 billion stars, and on average, each star has at least one planet orbiting it. This means there are potentially thousands of planetary systems like our solar system within the galaxy!


Our Sun is one of at least 100 billion stars in the Milky Way, a spiral galaxy about 100,000 light-years across.

The stars are arranged in a pinwheel pattern with four major arms, and we live in one of them, about two-thirds of the way outward from the center. Most of the stars in our galaxy are thought to host their own families of planets.

The Milky Way galaxy is just one of billion of galaxies in the universe.

The universe is a vast expanse of space which contains all of everything in existence. The universe contains all of the galaxies, stars, and planets. The exact size of the universe is unknown. Scientists believe the universe is still expanding outward.

Go farther. Explore Beyond Our Solar System In Depth ›

Ten Things to Know

10 Need-to-Know Things About the Universe


Big Discovery

Edwin Hubble’s study of the stars revealed our galaxy — once thought to be the entire universe — is actually one of billions in an expanding universe.


Small Matter

Ninety-five percent of the Universe is dark energy and dark matter. The rest — everything on Earth, all the planets and stars and everything else — makes up the remaining five percent.


A Lot of Nothing

Our Universe is mostly empty space. Galaxies and clusters of galaxies that make up the visible universe are concentrated in a complex scaffold that surrounds enormous empty spaces.

First Image of a Black Hole


Cosmic Neighborhood

The Milky Way galaxy is in the Local Group, a neighborhood of about 30 galaxies. Our nearest major neighboring galaxy is called Andromeda.


More Planets Than Stars

We know of thousands of planets — called exoplanets — orbiting other stars in our galaxy. When you look up into the night sky, every star you see has, on average, at least one planet.


Common Spiral

About two-thirds of the known galaxies are spiral-shaped like our Milky Way galaxy. Most of the rest have elliptical (oval-like) shapes, and a few have unusual shapes like toothpicks or rings.


Many Galaxies

Hubble Space Telescope observations (pictured) of a tiny patch of space (a fraction of the diameter of the Moon) revealed more than 5,500 galaxies.


Is Anybody Out There?

Scientists are searching for other planetary systems could have the potential for life. So far, Earth is still the only planet known to harbor life.


No Escape

There is a supermassive black hole at the center of our galaxy. A black hole is a great amount of matter packed into a very small area, which results in a gravitational field so strong that nothing—not even light—can escape.


Billions and Billions

There may be a hundred billion galaxies in the Universe. A galaxy is full of stars: Our sun is just one of at least a hundred billion stars in our own Milky Way galaxy.

Thousands of Galaxies

FAQ: How Big is Space?

FAQ: How Big is Space?

We'll let our colleagues in Exoplanet Exploration (the search for planets orbiting other stars) handle this one:

A short video guide to distance in the cosmos. Credit:NASA/JPL-Caltech

Wondering more about distant worlds? Read this Galactic FAQ.

Pop Culture

Pop Culture

Star Trek
"Star Trek" inspired many scientists and engineers. Credit: CBS/Paramount.

The mysteries of our Universe have long captivated science fiction authors and countless, memorable books at films—many of which inspired the real life scientists and engineering currently exploring the universe.

Many scientists cite Star Trek, first aired on television in 1966 and reinvented numerous times on both small and big screen in the decades since, as an inspiration. The show followed the imagined crew of a spaceship exploring our galaxy.

Another inspiration: Science fiction author Arthur C. Clarke’s 2001: A Space Odyssey, in which a fictional astronaut is transported across the cosmos through a mysterious portal. This tale is both a memorable movie and novel. For the next generation, who knows who will be inspired by the the 2014 movie Interstellar, a fictional team of astronauts search for a habitable planet around a black hole in a distant galaxy.

The 1980 television series Cosmos, featuring Voyager mission scientist Carl Sagan, took viewers on a factual tour of the known Universe and sparked the imaginations of many present day scientists and engineers. The series was reimagined in 2014 with astronomer Neil deGrasse Tyson as the host.



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