Andromeda Galaxy

This picture of the Andromeda Galaxy was taken using an ultraviolet light camera that was mounted on NASA's Swift Spacecraft. The picture is actually a composite image made by linking together 330 individual smaller pictures of the Andromeda Galaxy that the Swift Spacecraft took while it was floating through outer space.

All About the Andromeda Galaxy

The Andromeda Galaxy is a spiral shaped galaxy, just like our galaxy, the Milky Way. It's the closest neighboring galaxy to our Milky Way. Astronomers estimate that Andromeda is about 2.5 million light-years(2.4×10¹⁹ km) from Earth. The Andromeda galaxy is actually the most distant object from Earth that can be seen by the naked eye (meaning you can see it in the sky without using a telescope). Andromeda can only be seen with the naked eye on very dark, clear nights (usually when there's no moon and no clouds).

Nicknames and Scientific Names for Andromeda:

In addition to being called the Andromeda Galaxy, it is also known as Messier 31, M31, NGC 224, and the Great Andromeda Nebula.

Andromeda's Size and Location

The Andromeda Galaxy is part of a group of galaxies called the Local Group, which also contains our galaxy, the Milky Way, another famous galaxy called the Triangulum Galaxy, and about 30 other smaller galaxies. Astronomers disagree about the size of Andromeda. Some believe that it's the largest galaxy in the Local Group, because it contains the most stars. Others believe that our Milky Way is the largest galaxy in the Local Group and that the Andromeda Galaxy is the second largest galaxy in the Local Group.

It's hard for scientists to compare the two galaxies and know for sure which one is the biggest, because both galaxies are incredibly massive, both galaxies are continuing to expand, both galaxies are constantly moving, and Andromeda is light years away from Earth (so there's no way right now that scientists could travel there or even send a spacecraft to Andromeda to take pictures).

The Andromeda Galaxy and the Milky Way (our galaxy) are neighbors. They are both part of the Local Group of Interconnected Galaxies.

How to Spot the Andromeda Galaxy in the Night Sky

If you want to find the Andromeda Galaxy in the night sky, you should first locate the constellation it shares its name with. While it may sound confusing the galaxy of Andromeda is just north of a group of stars called the constellation Andromeda.

When you look at the Andromeda Galaxy on a dark night without a telescope, it looks like a long, hazy patch or a glowing smudge in the sky. To the naked eye, the Andromeda Galaxy looks like it's about as long as the Moon. In reality, it's billions of times larger than the Moon. Andromeda just looks so small, because it's so far away from Earth. If you look at Andromeda with binoculars, you can see its spiral shape. There is a concentrated bulge (or lump) of matter at the center of the spiral. Around the bulge, you can see a fuzzy glowing disk shaped spiral. This spiraling part of the galaxy is made of gas, dust, planets, and stars.

Follow these steps to find Andromeda yourself at night: http://www.wikihow.com/Find-the-Andromeda-Galaxy

Watch this video to learn how Andromeda got its spiral shape: http://www.nature.com/news/galactic-collision-gave-andromeda-its-arms-1.15329

Andromeda is Moving Towards Us

Andromeda's spiral of gas, dust, planets, and stars is moving. It's swirling around the big bulge in the center of the galaxy. Our galaxy (the Milky Way) and Andromeda are both spiraling toward each other in outer space at a speed of about 70 miles per second. The two galaxies are still really, really far away from one another. However, astronomers predict that Andromeda and the Milky Way will collide (crash into each other) in about 4 or 5 billion years. When the two galaxies collide, they will form a super elliptical shaped galaxy called the Milkomeda Galaxy. As a result of the collision with Andromeda, the sun will no longer be at the center of our galaxy.

Click here to watch a video and learn more: http://www.space.com/15946-galaxy-smash-milky-andromeda-collision-video.html

This series of photo illustrations shows the predicted merger between the Milky Way and Andromeda as seen from Earth. The first frame is the present day; the last frame is 7 billion years from now. --NASA

How Many Stars are In the Andromeda Galaxy?

While the Milky Way contains more dark matter than the Andromeda Galaxy, the number of stars in Andromeda is more than double the number of stars in our galaxy. In 2006, the Spitzer Space Telescope was used to count the stars in Andromeda. Using this powerful telescope to make observations, Astronomers counted about a trillion stars in Andromeda. If the trillion stars in Andromeda could be divided up equally, every living person on Earth (7.14 billion people)---including you--could have about 140 stars. In comparison, the Milky Way only has 200-400 billion stars. If all the stars in the Milky Way were divided up equally among every living person on Earth, each person would get less than 60 stars.

The number of stars in Andromeda is about one trillion =1,000,000,000,000

The number of stars in the Milky Way is about three billion = 3,000,000,000

This is a picture of the Andromeda Galaxy that was taken using two different space telescope cameras. One telescope camera used infrared light to show the dust strips in the galaxy where new stars are forming (the red, yellow, and orange coloring). The other telescope used x-ray imaging (the blue coloring) to show stars that are dying.