By Huzayfa Mallick
The Earth is in the middle of nowhere. Famously, we’re a pale blue dot floating somewhere in the middle of the universe. A miniature planet traveling through the vast and endless void of outer space. With that in mind, it makes sense to question our place in the universe; most importantly, where are we?
Figure One: Photo of Earth from Voyager 1 (can you find our planet?)
For many years, this question has remained a mystery to scientists across the world (and still is to some extent!). However, due to the pioneering work of brilliant scientists over hundreds and hundreds of years (Galileo Galilei as an example), we can form a decent answer based on what we know now.
Let’s start with what we already know. The Earth is part of a larger solar system consisting of a star (the Sun), as well as 8 planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. We might think that the Earth we live on is massive, but it isn’t even in the same conversation as the solar system. For reference, the spacecraft Voyager 1 started its mission in 1977 and took a picture of the Earth in 1990, after traveling 6 billion kilometers. Although Voyager 1 had traveled that far, it wasn’t even remotely close to the edge of the solar system.
Figure Two: Perspective of Voyager 1 when taking photo of the Earth
Looking beyond the ‘neighborhood’ that is the Solar System, our star system is part of a massive galaxy, famously known as the Milky Way. The Milky Way is a spiral galaxy approximately 13.6 billion years old. In the grand scheme of things, all the objects within our galaxy (stars systems, interstellar objects, etc.) are orbiting around the center of the Milky Way, comparable to a rotating disk, all due to the force of gravity. With regards to the magnitude of gravitational force required to hold together such a system, it is no surprise that the center of the Milky Way has a supermassive black hole known as Sagittarius A, which scientists were recently able to capture a picture of, as you may have seen in the news.
In addition to what has been discussed above, there are many other distinguishable components of the Milky Way that we can look at. As mentioned above, it is important to understand that the Milky Way is a spiral galaxy, easily distinguished by its two main spiral arms (Perseus and Scutum Centaurus). Adding on, the Galactic Bulge is a feature unique to spiral galaxies, representing a dense group of stars located near the center of the Milky Way, as shown in the diagram below. The area outside the bulge is known as the Galactic Disk and is where the Solar System is located. For reference, our Solar System is located approximately 25,000-30,000 light years from the middle of the Milky Way, with the galaxy spanning approximately 100,000 light years across. This implies that it would take light 100,000 years to travel across the entire Milky Way, which goes to show how massive the galaxy is.
Figure Three: Components Of The Milky Way
Figure Four: Labeled Diagram Of The Milky Way
Looking beyond the limitations of the Milky Way, galaxies are typically grouped together in clusters. The Milky Way is in the same cluster as the Andromeda Galaxy, making up a cluster known as the Local Group, which is part of a larger group of galaxies known as the Virgo Supercluster. You may have heard of the Andromeda Galaxy as it is set to collide with the Milky Way in the next several billion years. However, due to the size of the two galaxies, the collision is not expected to impact many of the individual star systems but will be changing the view of the night sky for the future, as shown in the video below.
References
AccuWeather. (2017, February 8). Future night sky after Milky Way and Andromeda merge [Video]. Youtube. https://www.youtube.com/watch?v=k1Dm6taJRZQ
Briggs, A. (2023, March 3). What is a galaxy? All you need to know. EarthSky. Retrieved November 10, 2023, from https://earthsky.org/astronomy-essentials/definition-what-is-a-galaxy/
Pultarova, T., Dobrijevic, D., Tillman, N. T., & Howell, E. (2023, April 18). Milky Way galaxy: Everything you need to know about our cosmic neighborhood. Space.com. Retrieved November 10, 2023, from https://www.space.com/19915-milky-way-galaxy.html
The National Aeronautics and Space Administration. (n.d.). Galaxies. NASA Science. Retrieved November 10, 2023, from https://science.nasa.gov/astrophysics/focus-areas/what-are-galaxies/
The National Aeronautics and Space Administration. (n.d.). The Milky Way Galaxy. NASA Science. Retrieved November 10, 2023, from https://science.nasa.gov/resource/the-milky-way-galaxy/
The National Aeronautics and Space Administration. (n.d.). Voyager 1's Pale Blue Dot. NASA Science. Retrieved November 10, 2023, from https://science.nasa.gov/resource/voyager-1s-pale-blue-dot/
The National Aeronautics and Space Administration & Jet Propulsion Laboratories. (n.d). [Computer generated image showing the Voyager 1 spacecraft when taking a picture of the Earth]. NASA Science. https://science.nasa.gov/_ipx/w_1024&f_webp/https://smd-cms.nasa.gov/wp-content/uploads/2023/06/Animated_GIF_showing_the_family_portrait_image_from_the_perspective_of_Voyager_1_in_1990-1-e1687939529369.gif%3Fw=2000
The National Aeronautics and Space Administration & Jet Propulsion Laboratories. (1990). [Photograph of the Earth taken by Voyager 1]. NASA Science. https://science.nasa.gov/_ipx/w_1024&f_webp/https://smd-cms.nasa.gov/wp-content/uploads/2023/09/PIA23645_PaleBlueDotRevisited_1600.jpg%3Fw=1600
The National Aeronautics and Space Administration, Jet Propulsion Laboratories & Hurt, R. (n.d). [Photograph showing the components of the Milky Way]. NASA Science. https://science.nasa.gov/_ipx/w_1024&f_webp/https://smd-cms.nasa.gov/wp-content/uploads/2023/09/ssc2008-10b1.jpg%3Fw=2000
The National Aeronautics and Space Administration, Jet Propulsion Laboratories & The European Space Agency. (2016). [Photograph showing a diagram of the Milky Way]. ESA Science & Technology. https://cdn.sci.esa.int/documents/33580/35361/1567240240682-ESA_Gaia_Milky_Way_Anatomy_625.jpg
What Is a Galaxy? (2022, July 13). NASA Space Place. Retrieved November 10, 2023, from https://spaceplace.nasa.gov/galaxy/en/
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