The Milky Way

The galaxy that we are located in is the Milky Way galaxy. It includes the sun, earth, and the solar system. Its name came from the Greeks who regarded it as "the path to heaven." Greek myths thought of it as milk spilled by the goddess Hera as she nursed her son Hercules. In the early 1960s, an Italian astronomer Galileo, who was the first to study stars with a telescope, proved that our galaxy was made up of a band of stars. By studying the Milky Way's shape, other astronomers correctly thought that the sun and its planets were part of the collection of stars in the shape of a huge powder puff. That grouping of stars came to be called the Milky Way. Milky Way refers to the portion of the Milky Way galaxy that can be seen by the naked eye.

Our galaxy is full of dust and gas, lit by the radiation of stars within them (more than 500 billion stars). Each galaxy is made up of clusters of stars, for these clusters are the building blocks of all galaxies. The Milky Way is large, but is one of millions of galaxies in the universe.

Scientists classify galaxies by their shape based on a method used by an American astronomer, Edwin Hubble. He identified three main types of galaxies: spirals, ellipticals, and barred spirals. A spiral galaxy is one composed of a flattened, star-forming disk component which may have spiral arms and large central galactic bulge. An elliptical galaxy is a galaxy in which the stars are distributed in an elliptical shape in the sky, ranging from highly elongated to nearly circular in appearance. A barred-spiral galaxy is a spiral galaxy in which a bar of material passes through the center of the galaxy, with the spiral arms beginning near the ends of the bar.

The Milky Way is a typical spiral galaxy, which has several arms that extend from the central bulge. Each arm extends from the central bulge and is named based on the name of the constellation that its stars appear to be in when seen from earth. For example, the spiral arm our sun lives in is the Orion arm. This arm is located between the Sagittarius and the Perseus arm.

The main portion of the Milky Way galaxy consists of four parts: the disk, Galactic Halo, Galactic Halo, Galactic Corona, and the core. The disk is a large spiral structure on which we are located. The disk is surrounded by the Galactic Halo, which contains old stars and the disk like a spherical shell, and it extends a distance of 31,000 light-years beyond the disk's edge. The Galactic Halo is surrounded by the Galactic Corona 160,000 light-years. The core of the galaxy accounts for 40% of the galaxy's total mass, but it cannot be seen. Through the use of radio astronomy and computers, nonoptical information into images, which describe a strange arena of swirling clouds and spinning disks, energized by intense magnetic forces, exploding stars - maybe a blackhole, but it is not certain.

The time it takes for the Milky Way Galaxy to rotate, at 1.4 million miles per hour, is one Galactic year. A Galactic year is equal to 230 million Earth years. The sun is about 30,000 light years from the core. The sun travels at a speed of over 600 thousand mph, pulling the earth and the rest of the solar system along with it. Even at that speed, it takes the sun 225 million years to travel around the core.

Our Galaxy is one of 30 nearby galaxies that are clustered around two chief members of the group: Our Galaxy and the Andromeda Galaxy. The Andromeda Galaxy is slightly larger than ours and is located about 2 million light years from earth. Like our own, this galaxy consists of a flattened, circular galactic disk(flattened region of gas and dust that bisects the galactic halo in a spiral galaxy; a region of active star formation) that extends to a galactic bulge (thick distribution of warm gas stars around the galactic center). The disk and bulge are embedded in a roughly spherical ball of faint old stars known as the galactic halo, where globular clusters and other old stars reside.

The Milky Way and the 30 neighboring galaxies make up the Local Group. The combined gravities of the Local Group holds them together. This cluster of galaxies is also known as a galaxy cluster.

The entire solar system is located in the Milky Way. It contains billions of stars, gas, and dust. As said by the Greeks is "the path to heaven." Maybe if the mystery is solved about the cenetr of our galaxy, we all would be on that path, but that is just one of the many mysteries of the universe.

This page was written by Monet Samuel in the Astronomy Class of BCC/ Broward County July 1998