Are we in a universe or galaxy?

Q: Are universe and galaxy different?

Hint: The term universe refers to everything that exists, including galaxies and the space between them. A galaxy is a massive cluster of stars (millions or billions) held together by gravity. The Milky Way is the name of the galaxy in which we live.

Portion of Hubble Extreme Deep Field. Every spot and smudge in this image is a galaxy. Credit: NASA, ESA

Many people are not clear about the difference between our Solar System, our Milky Way Galaxy, and the Universe.

Let’s look at the basics.

Our Solar System consists of our star, the Sun, and its orbiting planets (including Earth), along with numerous moons, asteroids, comet material, rocks, and dust. Our Sun is just one star among the hundreds of billions of stars in our Milky Way Galaxy. If we shrink the Sun down to smaller than a grain of sand, we can imagine our Solar System to be small enough to fit onto the palm of your hand. Pluto would orbit about an inch from the middle of your palm.

On that scale with our Solar System in your hand, the Milky Way Galaxy, with its 200 – 400 billion stars, would span North America (see the illustration on the right). Galaxies come in many sizes. The Milky Way is big, but some galaxies, like our Andromeda Galaxy neighbor, are much larger.

The universe is all of the galaxies – billions of them! NASA’s telescopes allow us to study galaxies beyond our own in exquisite detail, and to explore the most distant reaches of the observable universe. The Hubble Space Telescope made one of the deepest images of the universe, called the Hubble Extreme Deep Field (image at the top of this article). Soon the James Webb Space Telescope will be exploring galaxies forming at the very beginning of the universe.

You are one of the billions of people on our Earth. Our Earth orbits the Sun in our Solar System. Our Sun is one star among the billions in the Milky Way Galaxy. Our Milky Way Galaxy is one among the billions of galaxies in our Universe. You are unique in the Universe!

You can observe objects in our solar system and even see other galaxies at a star party near you-and rest assured that everything you are seeing is a part of the same universe as you! Find out more by using our club and event finder and connect with your local astronomy club.

Discovering the Ultimate Source of Energy on Earth: The Sun! (Photo Credit: Warren Rupp Observatory)

Last Updated: June 2017

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Exploring The Universe

Other Solar Systems

Our Milky Way galaxy is just one of the 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!

Introduction

Our Sun is one of at least 100 billion stars in the Milky Way, a spiral galaxy about 100,000 light-years across. And where are we in the Milky Way? Our Sun lies near a small, partial arm called the Orion Arm, or Orion Spur, located between the Sagittarius and Perseus arms.

The Latest

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 the billions of galaxies in the universe.

The universe is a vast expanse of space that 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?

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

Read: Our Milky Way Galaxy: How Big is Space?

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

Wondering more about distant worlds? Read this Galactic FAQ.

Pop Culture

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

The mysteries of our universe have long captivated science fiction authors and filmmakers.

Many scientists say they were inspired by the science fiction television series "Star Trek" – which first aired on television in 1966 and has been reinvented numerous times on both small and big screens in the decades since. The original show followed the crew of the starship Enterprise on a five-year mission to explore 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. The next generation may be inspired by the 2014 movie "Interstellar" – where a fictional team of astronauts searches for a habitable planet around a black hole in a distant galaxy.

The 1980 television series "Cosmos" – which featured 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.

Resources

NASA Topics: Solar System and Beyond

NASA’s Exoplanet Portal

NASA Astrophysics

Are we in our own galaxy?

Our Sun (a star) and all the planets around it are part of a galaxy known as the Milky Way Galaxy. A galaxy is a large group of stars, gas, and dust bound together by gravity. They come in a variety of shapes and sizes. The Milky Way is a large barred spiral galaxy.

Are universe and galaxy different?

Hint: The term "universe" refers to everything that exists, including galaxies and the space between them. A galaxy is a massive cluster of stars (millions or billions) held together by gravity. The Milky Way is the name of the galaxy in which we live.

Is Earth inside a galaxy?

Earth is in the second largest galaxy of the Local Group - a galaxy called the Milky Way. The Milky Way is a large spiral galaxy. Earth is located in one of the spiral arms of the Milky Way (called the Orion Arm) which lies about two-thirds of the way out from the center of the Galaxy.

Is Earth considered a universe?

The universe is everything. It includes all of space, and all the matter and energy that space contains. It even includes time itself and, of course, it includes you. Earth and the Moon are part of the universe, as are the other planets and their many dozens of moons.