Humans have been fascinated by stars for thousands of years. Studies of the stars go as far back as the first civilization in human history, Sumeria, located in Mesopotamia (1). Ancient civilizations would study the stars and incorporate them into their architecture, literature, art, calendars, mythology, and religion. Even now, humans study the stars in hopes of learning the universe’s secrets. However, recent advancements in technology have allowed for more abundant information about the stars.
A star used to be considered a celestial being in the heavens (2), but now it is known as being a bright ball of hydrogen and helium held together by gravity. A star is created when a gas cloud heats up to the point where the cloud starts to fall into itself due to gravity (3). Nuclear fusion at the core of the star slowly stops the star from collapsing, and the fusions produce heat and photons.
There are many different types of stars, so they are classified by their spectra and temperature (4). The Morgan-Keenan system uses the letters O, B, A, F, G, K, and M to categorize the temperature of stars. The scale begins with O being the hottest and ends with M being the coolest (5). This system classifies all stars, including yellow dwarfs, red giants, blue giants, supergiants, white dwarfs, and neutron stars (6). Even the Sun is classified within this system, despite the fact that the sun was not considered a star until the late 1800’s (7).
Humans have also discovered just how many stars there are, and how far they reach. While there can only be estimates, in the Milky Way alone there is estimated to be approximately 100 billion stars (8). Furthermore, most people believed that the Milky Way made up the entire universe. Edwin Hubble disproved this with the discovery of Andromeda (9), and Hubble estimated that there were 100 billion galaxies in the known universe, which put the number of stars in the universe up to 1 billion trillion (10).
The stars located in different galaxies are so far away that when people look up at them in the sky, they are seeing the light of the star as they were in the past because the light is still traveling throughout the universe (11). Overall, stars have always and will always be a topic of interest to anyone who looks at them. Whether stars are seen as celestial beings or balls of gas, they continue to astound anyone who studies them.
(1) “Sumerian Astronomy and Calenders.” Crystalinks.com,
(2) “Ancient Greek Astronomy and Cosmology.” Www.loc.gov, Library of Congress,
(3) Temming, Maria. “What Is a Star? | Types of Stars.” Sky & Telescope, 18 Apr. 2017, www.skyandtelescope.com/astronomy-resources/what-is-a-star/.
(4) Spectra is simply the plural form of spectrum.
(5) “The Morgan-Keenen System.” StarPartycom, starparty.com/topics/astronomy/stars/the-morgan-keenan-system/.
(6) “Star Classification.” EnchantedLearning.com, Enchanted Learning, www.enchantedlearning.com/subjects/astronomy/stars/startypes.shtml.
(7) “Ask A Solar Physicist FAQs – Answer.” Stanford Solar Center, solar-center.stanford.edu/FAQ/Qsunasstar.html.
(8) “How Many Stars Are in the Milky Way?” Space.com, Google, www.google.com/amp/s/amp.space.com/25959-how-many-stars-are-in-the-milky-way.html.
(9) Andromeda is a spiral galaxy, and was the first galaxy other than the Milky Way ever discovered.
(10) “Hooker 100-Inch Reflector.” Amazing Space, amazing-space.stsci.edu/resources/explorations/groundup/lesson/scopes/mt_wilson/discovery.php.
(11) Plait, Phil. “Are the Stars You See in the Sky Already Dead?” Slate.com, Google, www.google.com/amp/amp.slate.com/blogs/bad_astronomy/2013/08/13/are_the_stars_you_see_in_the_sky_already_dead.html.