know the structure of the Milky Way

( Milky Way / Google Image)

The star system where the Sun is called the Milky Way or also called the Milky Way. Initially, the Milky Way galaxy is described as a spiral structure with four arms are composed of stars, each is an arm Norma, Scutum-Centaurus, Sagittarius and Perseus. There are also ribbons of gas and dust in the galaxy's center. Sun is located on a small arm called the Orion Arm, which is located between the Sagittarius and Perseus.

The model is based on radio observations in the 1950s of the gases in galaxies lasted until revised in the 1990s. Based on the results of a large infrared sky survey, discovered the existence of a large band consisting of stars in the Milky Way galaxy. Infrared rays can penetrate the dust, and so telescopes designed to collect infrared rays can be viewed more clearly into the center of the galaxy is filled with dust and various objects. Then, in 2005, astronomers began using infrared detectors on Spitzer Space Telescope to obtain more detailed information regarding these bands. A group of astronomers led by Robert Benjamin of the University of Wisconsin found that ribbon running from the Galactic center towards the outside of the broader and longer than previously thought. Benjamin then develop special software to calculate such stars as well as measure its density. The calculations were done on the Scutum-Centaurus arm showed an increase in their numbers, as that should be in a spiral arm. While measuring the Sagittarius and Norma arms showed no increase in their numbers. 4th arm, Perseus arms enveloping the outermost part of the Milky Way, can not be seen in the latest images taken by Spitzer.

These findings suggest that the Milky Way galaxy has two spiral arms, as well as the structure of the galaxies banded in general. The main arm, arms, Scutum-Centaurus and Perseus arms, have the greatest densities were composed of young stars and bright and the stars are older, known as red giants (red-giant stars). Benjamin said the two major arms are visible in touch with the near and far ends of the main.

Though galaxy arms appear to be feature complete, but in reality stars in it are constantly moving in and out in the arm. This is caused by the movement of the stars as they orbit the galactic center.

The distribution of stars in the galactic disc-shaped large flat containing about a hundred billion stars with a diameter of about 100,000 light-years away and the sun is located about 30,000 light years from the galactic center. Flat shape of this galaxy due to rotational motion and the sun around the center of the galaxy at a rate of 250 km / s and with a period of 200 million years. The galaxy's core is the main part of the galaxy is composed of stars that form a relatively flat disc with a convex in the middle. The stars at the galactic core is located close to one another. Older stars are found in the central bulge with a thickness of 20,000 light years (6,100 pc). Save younger are found in the spiral arms. The galactic center is located in the constellation Sagittarius. The north pole is in Coma Berenices, polar selatanya in Sculptor. The sun is in the corner of the spiral arms CarinaCygnus approximately 32,000 light years (9,800 pc) from the center of the galaxy. It is estimated that billions of galaxies aged 12-14 years and consists of 100 billions of stars. Flaring out from the galactic core are like a spiral disk churned out from the galactic core called spiral arms.

The diameter of the Milky Way about 100,000 light-years away and the sun is located about 30,000 light years from the galactic center. The spiral arms are composed of cosmic gas and dust clouds are a lot of so-called interstellar medium. Along with the gas and dust clouds, there are a lot of young stars, some of which are very hot and very bright. In a cloud of gas and dust between stars in the spiral arms is still the formation of new stars.

( Star / Google Image )

 In addition it also contains a lot of galactic star clusters (starclustrs), a group of stars that may have the same origin and age. There are two types of star clusters are open clusters and globular clusters. Open cluster is usually named after the galactic cluster which is the most common group and has a number of thousands, which usually consists of several hundred stars are not bound by gravity so strong together and move together in space. Open cluster is located on the main galaxy disk and is usually located inside or close to the spiral. And hundreds of globular clusters formed speroidal layering system of this dish and each cluster contains several hundred thousand stars. In addition, there is a star that is not a member of any group but the numbers far exceeded star clusters and are on the whole area of ​​the cluster stars. Random Stars and star clusters have formed something called the galactic halo. Halo includes regions whose volume far beyond the area of ​​the galaxy's main disk. Galactic radio emission suggests that the halo contains gas and their X-ray radiation from the gas. This indicates that the gas is very hot in the order of 106 K. The hot gases just lie on the inside of this and called the corona halo galactic. The closer to the direction of the galactic core, especially near convex disc nucleus in the center of galaxies, stars and clusters of halo is more dense than the area far from the galactic core. Halo has a thickness of at least 100,000 TC and even the direction of the galactic plane diameter can be up to two or three hundred thousand light-years away and stretched far beyond the circumference of the galaxy's main disk.