Running head: MILKY WAY GALAXY
Milky Way Galaxy
MILKY WAY GALAXY
The Spiral structure of the Milky Way Galaxy from Radio Observations
The study of the study of the Milky Way structure is vital importance for a better understanding
of the universe. This study digs deeper into the structure of Milky Way Galaxy’s with emphasis
to its spiral arms. Multiple data sources were sought including the NASA websites. As found out,
the Milky Way is a disk shaped galaxy composed of four spiral arms, two large and the rest are
smaller. The spiral arms are regions of actively forming new stars dominated by young stars,
dust and gas. Dust and gas are primary materials for the formation of new stars. This dust is also
responsible for the reddish appearance of the stars since it absorbs more blue light than red.
Besides the disk, there are numerous older stars, which appear white in color according to the
picture by COBE. Additionally, the Milky Way contains a dark halo, extensive but void of
luminous stars. The extensive halo was discovered due to the gravitational pull it exerts on
existing visible matter.
The Milky Way is a collection of close to a billion stars bound by gravitational forces.
The solar system is part of the Milky Way (Clements, 2015). As such sun is among the hundred
billion stars that make the Milky Way. The desire to know more about the universe has always
driven scientists into deeper research. A greater understanding of Milky Way, a galaxy in which
the earth is positioned is not only satisfies the curious minds of millions of people around the
world but it also amazing considering its interesting features. More importantly, events that
occur around the galaxy may eventually determine the fate of the earth. A better understanding
of major events and process may position scientist at a vantage position to predict and impeding
danger such as collision with terrestrial bodies and save the situation if possible (Oort &
Westerhout, 1958). NASA has always searched the sky for potentially hazardous phenomena or
object. In a recent undertaking NASA reactivated WISE, an Infrared survey, to scan the sky in
2013 after two years of hibernation in a mission to enable it to identify objects that may harm to
the planet earth (NASA, 2015). The structure of the Milky Way, the galaxy in which the earth
and the entire solar system is located, takes a central position in this study.
The study of the galaxy dates back to more than 322 BC where most of the available
information was based on speculation. Aristotle noted propositions by Democritus and
Anaxagoras who thought the galaxy was composed of distant stars. In contrast Aristotle thought
that the Milky Way originated from exhalation of large stars being ignited in upper atmosphere
(Kormendy & Bender, 2018). Although their views were largely criticized by other scholars,
their views marked the start of a long journey of study that is yet to complete. Many more
scholars after Aristotle publicized their findings about the galaxy based on observations (Oort &
Westerhout, 1958). In 1048 Abū Rayhān, a Persian astronomer asserted that the Milky Way
comprised countless nebula star-like fragments. Later, Avempace, an Andalusion astronomer
came up with a new idea claiming the galaxy was made up of stars that were reflected in the sky
to make them appear as a continuous mass of luminous object.
A more scientific approach to explore the universe took place in 1610 when Galileo
Galilei observed the sky using a telescope. His approach proved that galaxy was in deed made of
MILKY WAY GALAXY
stars. Other ideas such as the galaxy rotate along with all the stars and other bodies and existence
of multiple galaxies would later follow (Kormendy & Bender, 2018).
Efforts to describe the shape of the galaxy took shape in 1785 when William Herschel
attempted counting stars in various regions of the sky and came up with a diagram to describe
the Milky Way’s shape. A more advanced telescope was developed in 1845 enabling Lord Rose
to prove the existence of a spiral shaped nebulae and an elliptical one (Oort & Westerhout,
In 1920, an astronomical debate about the shape and size of the universe between Harlow
Shapley and Heber D. Cutis was held in the National History Museum located in Washington
DC. Curtis believed that the universe was composed of several galaxies citing that there were
spiral nebulae outside the Milky Way while Shapley held that the universe had only one galaxy
and the other phenomena were just gas clusters (Kormendy & Bender, 2018)).
Although Curtis and Shapley’s debate ended in controversy, it sparked new efforts to pin
down the nature of the universe. A few years later, Edwin Hubble brought the controversy to an
end by proving that there were spiral nebulae external to the Milky Way and composed of stars
rather than gas clusters (Kormendy & Bender, 2018)). He used an innovated Hooker’s telescope
to produce astronomical photographs with enough resolution to distinguish individual stars in the
These approaches by early scientist to the study of the Milky Way w...