Unveiling the Darkness: Dark Matter and Dark Energy
(Image Credit: Live Science)
(Image Credit: Astronomy Magazine)
(Image Credit: SciTechDaily)
September 6, 2023
Tsz Kiu Amanda Leung
9th Grade
Diocesan Girls' School
We live in a world of protons, neutrons, and electrons. However, if we examine the universe as a whole, all light and atoms, “normal matter,” only make up about 5% of the cosmos. If so, what exactly is the remaining 95%, and how do we find it?
A concept first proposed in the 1930s by Fritz Zwicky, dark matter was only confirmed by Vera C. Rubin and her colleagues in the 1960s, making it a very recent discovery. Our universe is mainly dark matter and dark energy, where dark matter makes up about 27% and dark energy roughly 68%. One view of dark matter is that it is non-baryonic - that is, it is not made up of protons and neutrons, but other particles, such as leptons, quarks, or axons. Scientists generally agree that dark matter is a new, invisible type of particle that our sensory equipment cannot pick up. Since light passes through dark matter, we have not seen dark matter directly. Instead, we discovered its existence by analyzing gravitational events and calculations influenced by the mass of dark matter. Another theory is that dark matter can be explained by changing our theories on gravity - perhaps there is another system of gravity that could describe why and how dark matter behaves.
How exactly do we find the invisible? Scientists study dark matter by observing the gravitational effects of it on visible objects. Gravity bends rays and affects what we can see in space, just as water distorts light. Astronomers use gravitational lensing, which entails observing the gravity of massive galaxy clusters that contain dark matter and affect the light from other galaxies behind the cluster. Using mathematical models, scientists consistently determine that there is about five times as much dark matter as normal matter in the universe. Dark matter also binds galaxies that would otherwise break apart.
Abell 1689, one of the biggest and most massive known clusters
(Image Credit: HubbleSite)
Image of the massive galaxy cluster Cl 0024+17 (ZwCl 0024+1652)Blue shading has been added to indicate the location of dark matter that is mathematically required to account for the nature and placement of the gravitationally lensed galaxies that are seen.
(Image Credit: NASA, ESA, M.J. Jee and H. Ford (Johns Hopkins University)
Dark matter is considered crucial for galaxies, which are surrounded by a halo of it. But for every rule comes an exception, and dark matter is no different. In 2018, Imaging from the Dragonfly Telephoto Array, the Sloan Digital Sky Survey, the MMT, the Gemini North telescope, and the Hubble Space Telescope showed an oddity in the ultra-diffuse galaxy NGC 1052-DF2: it is deficient in dark matter. Further observations from The Hubble Space Telescope in 2021 confirmed this discovery. This changes the way we think about galaxies, as they do not have an observable central region, spiral arms, or a disk. There is also no evidence that they have a central black hole. This oddball galaxy was a shock after many years, as it challenged the preconception of how galaxies worked. This discovery also spurred research into the formation of galaxies.
NGC 1052-DF2
(Image Credit: Wikipedia)
Dark energy is a newer and possibly more groundbreaking discovery. Before its discovery, we thought the expansion of the universe would gradually slow due to the effects of gravity. However, through numerous observations, we found that the cosmos is expanding increasingly over time. Dark energy drives this expansion of the universe against gravity, yet not much more is known. Why dark energy exists also remains a mystery.
Throughout history, we have sought to discover more about the universe through improving technology. Through Galileo's telescope, we saw parts of the cosmos previously invisible to us, and greatly increased our understanding of space. Modern innovations such as the James Webb Space Telescope by NASA and the Euclid spacecraft mission by the European Space Agency have already greatly advanced our understanding of dark matter, black holes, and energy. As aerospace technologies improve, it is certainly possible to uncover more mysteries of space.
Reference Sources
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“Dark Matter and Dark Energy’s Role in the Universe.” Science, 3 May 2021,
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“Dark Energy, Dark Matter.” NASA,
https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy.
“Dark Energy and Dark Matter.” Dark Energy and Dark Matter | Center for Astrophysics,
https://pweb.cfa.harvard.edu/research/topic/dark-energy-and-dark-matter.
Dark Matter Goes Missing in Oddball Galaxy - Hubblesite.Org, 28 Mar. 2018,
https://hubblesite.org/contents/news-releases/2018/news-2018-16.html.
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