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Galaxies and the Distant Universe
Color image of the Milikay Way Galaxy with notations about each arm.
Annotated artist's view of our Milky Way Galaxy. Recent observations show that our galaxy is a barred spiral.

The International Year of Astronomy and the celebration of the 400th anniversary of the telescope continues this month with a focus on galaxies and the distant, ever expanding universe. NASA's featured April object is the majestic Whirlpool Galaxy. But, let's begin with our own galaxy ... the Milky Way.

In 1609, when Galileo pointed his newly built telescope toward the fuzzy band of light in the night sky that we now know of as the Milky Way, he discovered that it was actually made up of countless individual stars. Fast-forward 400 years. Now, 21st century NASA telescopes peer through the dust that hides the center of our Milky Way galaxy to study distant galaxies in amazing detail and to explore the most distant regions of the observable universe.

Our home galaxy, the Milky Way, is about 100,000 light years in diameter and has about 200 billion stars.

Astronomers used to believe that the Milky Way had four arms making up its spiral structure. Using new data from NASA's, researchers have discovered that the Milky Way galaxy is actually a "barred spiral" made up of two major arms named Perseus and Scutum-Centaurus that are wrapped around a dense, bar-shaped core of stars. Two minor spiral arms named Sagittarius and Norma are less dense and are located between the major arms.

A new, third spiral arm which lies across the bar of the galaxy, was discovered via a radio telescope survey of Milky Way gas. Named the "Far-3 Kiloparsec Arm," it is shorter than the two major arms. While the major arms of our galaxy have the highest density of both young and old stars, the minor arms are filled with gaseous material and contain the elements that create an environment for new star formation. Just one of the hundreds of billions of stars in the Milky Way, the Sun is located between the Sagittarius and Perseus arms, near the partial arm called the Orion Arm, [sometimes called the Orion Spur].

The universe is made up of clusters of galaxies that are not evenly spaced. Sometimes these galaxies, drawn together by gravity, collide and form a brand new galaxy. This galactic mixing creates many interesting shapes and patterns such as spirals, ellipses and bars.

Many of the oldest galaxies in the universe are so distant from us (many billions of light years away) that even the most advanced telescopes are only able to observe them as fuzzy, oval-shaped blobs. Andromeda, our nearest galactic neighbor, is a more than 2.3 million light-years away.

Color image of the Whirlpool Galaxy.
From small telescopes on the Earth's surface, the Whirlpool Galaxy (M51) can look fuzzy. But, in 2005, the Hubble Telescope snapped the clearest image ever of M51 and its companion galaxy. Credit: S. Beckwith (STScI) Hubble Heritage Team, (STScI/AURA), ESA, NASA

And even further away lies the beautiful Whirlpool Galaxy. The 51st entry in Astronomer Charles Messier's famous catalog of fuzzy objects, the Whirlpool Galaxy is the focus of April International Year of Astronomy celebrations. Located in the constellation Canes Venatici, the Whirlpool Galaxy can be observed with a small telescope under good viewing conditions. The Whirlpool galaxy is particularly interesting to view because from Earth we get a "top-down" view of the galaxy and can see its spirals. When first observed by Lord Rosse in 1845 it was the first galaxy recognized to have a spiral-oval shape.

If you want to do some amateur astronomy of your own but don't have access to a telescope, consider building your own. A simple, easy to build and use telescope, the Galileoscope was created with the intention that it be available to millions of people worldwide.

To observe the Whirlpool Galaxy in the April night sky, look for the last bright star in the handle of the Big Dipper (away from the Dipper's bowl). This large galaxy with its clear spiral structure is cataloged as NGC 5194. Its spiral arms and "lanes" of dust sweep in front of its companion galaxy (NGC 5195). The two galaxies are about 31 million light-years distant and are part of the small constellation Canes Venatici. Although the Whirlpool Galaxy looks fuzzy and faint from small, Earth-bound telescopes, the Hubble Space Telescope's Advanced Camera for took the sharpest picture of M51 in January, 2005.

To celebrate the Kepler telescope's successful launch last month, NASA is holding a Kepler teachers workshop on Saturday, April 25th at the National Air & Space Museum in Washington, DC. The one-day workshop will help teachers understand the Kepler Mission and how to create hands-on activities for middle and high school students. Each workshop attendee gets to take home a transit model which includes an orrery made from LEGOs a Vernier light sensor, interface and graphing software.

Last Updated: 2 February 2011

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Last Updated: 2 Feb 2011