The Milky Way

The Milky Way

History

Our universe is estimated to be 14 or so billion years old, but our Milky Way is estimated to be 800 million to 13.5 billion years old. The name, “the Milky Way got its name from the greek term “galaxius” which means “milky” in English (CrashCourse, 2015). However, the idea that the Milky Way is made up of stars was created by Democritus (a greek philosopher) who believed so.

Over the years, people began to know it as the Milky Way. In the past, people believed that the earth was in the center of space. This belief was incorrect as the Earth is far from the center. Instead, we are in the middle of a large and small spiral arm.

The reason we know that is because of the man named Galileo, and his telescope. Galileo used his telescope to peer into the night sky towards Sagittarius, a constellation, he noticed dust and clouds smothering the view and the true image of the sky from the naked eye, but with the telescope, he realized he could see much more. A crucial theory that was developed in the late 1700’s was the theory that there was a large group of stars that weaved together in the sky. In 1785, William Herschel created the first map of the Milky Way,He was the first to study and measure the distribution of stars in space. While counting the stars, he could see that the stars were grouped into a huge disk formation, and he was correct. (Tronomical Adventures, 2007)

Structure

It was widely believed and agreed upon that the Milky Way consisted of two major spirals. However, as was later proven, that is not the case. There are two major ones with the addition of two smaller; these spirals rotate in a clockwise motion. The larger spirals are anchored to the top and the bottom of the oval, while the smaller ones also originate from the top and bottom of the oval, but stay in between the major ones.

Each of the spirals have a name: the Sagittarius arm and Perseus arm are the larger ones, and the smaller arms are known as the Norma and Orion arms.These arms hold most of the suns, with a few of these suns being in between them.

Within the Milky Way, there are hundreds of billions of stars. The center of the Milky Way is made up of many of the red giant stars. Our Milky Way is a flat disk with everything with space within it. It’s made up of gas, dust, stars and debris. A rough estimate of the radius of our galaxy is about 100,000 light years thick. It’s so big, it takes our sun 250 million years to orbit the Milky Way; currently our sun has revolved around the Milky Way 20 times already.

In the centre of the Milky Way is a long oval shaped bar with a radiant glow, the glow in the middle is formed by groups of stars woven together, and most of them are very old, among some of the oldest in the Milky Way

Halos

Along the outer edges of the Milky Way, there is a halo built of suns within the halos. It has been thought that the suns within the halo were flung out of the spirals into the halos. According to scientists, it is believed that the Milky Way galaxy contains ninety percent of dark matter, called halo. The “luminous matter” seen through telescopes only conveys less than ten percent of the mass of the galaxy. The halo consists of the majority of the overall mass of the Milky Way. Furthermore, halo is the outer space of the galaxy and is the opposite of spiral arms as it mostly consists of darkness and old stars (Brown et al, 2014).

Appearance

The sun and the planets that orbit it comprise a galaxy, commonly known as the Milky Way galaxy (NASA, 2015). Similar to other galaxies, it contains star, gas, and dust held together by gravity. The name of “Milky Way” was based on the appearance of a “milky band of light” when seen through the sky. Many stars have been seen throughout the sky, and experts approximate that there are around one hundred billion stars that have, at the minimum, one planet that they orbit (National (Geographic, 2021). The Milky Way is called a spiral galaxy, as it can be viewed from the top or bottom and similarly looks like a spinning wheel (Dalcanton, N.d.). Scientists use star points called cepheid variables to map out the Milky Way. The further away from the center of the Milky Way galaxy, the more twist is seen. The sun is located on one of the spiral arms, around 25,000 light years from the center. In the past, our galaxy has sucked up dwarf galaxies, such as the Sagittarius Dwarf Galaxy (Universe Today, 2014). This expands our galaxy and makes it bigger, and the Galaxy has been doing so since it came into existence.

Environment

The Milky Way Galaxy is part of The Local Group, which contains the Milky Way and Andromeda galaxies. The Andromeda galaxy is a relatively small group of galaxies (Cosmos, N.d.). The Local Group has more than fifty-four galaxies, and the Milky Way is the second biggest of the group (EarthSky, 2018). The Milky Way is near the gravitational center of the Local Group ,and the group has a diameter of ten million light years. Astronomers discovered that the Local Group is near the outside of the many large clusters of galaxies, called Virgo Supercluster. There are two small satellites, M32 and M110 that are currently in the Local Group journeying (NASA, N.d.). Astronomers believe that the two large spiral galaxies, M31 and the Milky Way, will collide in the future, to create a large elliptical galaxy.

References

Brown et al. (2014, January 13) ‘’Milky Way Halo’’. Retrieved on January 3, 2021 from https://www.cfa.harvard.edu/research/oir/milky-way-halo
CrashCourse. (2015, October 22). ‘’The Milky Way: Crash Course Astronomy #37.’’ Retrieved on January 3, 2021 from https://www.youtube.com/watch?v=tj_QPnO8vpQ
Cosmos. (N.d.). ‘’Environment of Galaxies.’’ Retrieved on January 3, 2021 from https://astronomy.swin.edu.au/cosmos/E/environments+of+galaxies
Dalcanton, J. (N.d.). ‘’The Milky Way Galaxy.’’ Retrieved on January 3, 2021 from https://www.amnh.org/explore/ology/astronomy/the-milky-way-galaxy2
EarthSky. (2018, December 6). ‘’What is the Local Group?’’ Retrieved on January 3, 2021 from https://earthsky.org/astronomy-essentials/galaxy-universe-location
NASA. (2015, December n.d.). ‘’The Milky Way Galaxy.’’ Retrieved on January 3, 2021, from https://imagine.gsfc.nasa.gov/science/objects/milkyway1.html
NASA. (N.d.). ‘’The Local Group.’’ Retrieved on January 3, 2021, from https://imagine.gsfc.nasa.gov/features/cosmic/local_group_info.html
National Geographic. (2021, January 15). ‘’Milky Way Galaxy.’’ Retrieved on January 3, 2021 from https://kids.nationalgeographic.com/explore/space/milky-way/
Plaxco, J. (n.d.). ‘’The milky way galaxy.’’ Retrieved February 03, 2021, from http://www.astrodigital.org/astronomy/milkywaygalaxy.html