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
1
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.
2
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.
3
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
4
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.
5
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.
6
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.
7
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.
8
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.
9
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.
10
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:
- 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
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
Resources
NASA Topics: Solar System and Beyond
NASA’s Exoplanet Portal
NASA Astrophysics