Trickery up a Cosmic Sleeve: A Galaxy missing Dark Matter

Author: Ted Isidor

Editors: Ken Saito Artists: Lucy Chen

Matter is within us. It makes up the entire universe including our very bodies. On a clear night, the sky is always full of sparkling wonders. Stars paint the sky, filling in for the dark space that surrounds each; no matter where you look, a star is there.

Stars are made of matter as well. Many of them tend to join together with other stars in groups called galaxies. When light emitted from a star travels across or near a galaxy, the path of the light ray bends instead of following a straight path. Many photos taken by instruments like the Hubble Space Telescope seem distorted because of this gravity. The funny thing about the process of gravitational lensing, which is the scientific name for this process, is that it is not “normal matter” which is causing the bending of light’s path but it is actually something more mysterious: something that astronomers are still perplexed by to this day, called dark matter.

Dark matter is a substance (to say the least) that doesn't want to be known. It does not emit any light (making it impossible to see visually) and cannot be artificially made, making it especially difficult to study. One thing that is known, however, is that dark matter interacts with matter through gravity. Although we know the characteristics of dark matter to a certain extent, what’s all the hype about it? The two main pillars that will be discussed on the importance of dark matter are its scale and influence on the universe. In the case of the amount of dark matter in the universe, it is believed that dark matter makes up around 27 percent according to CERN, which is a big percentage when compared to the fact that the matter we view and touch all around us only makes up about 5% of the universe. Additionally, dark matter is believed to be the only thing keeping galaxies intact. In an article by ScienceDaily discussing the disappearance of dark matter in a galaxy, which will be discussed further in later segments, dark matter is referred to as being a glue that holds galaxies together. According to previous scientific knowledge, galaxies without dark matter did not exist. However, astronomers, using the Hubble Space Telescope, have recently found such a galaxy in the universe. Of course, such a discovery has caused an uproar and a spark of curiosity for those who look up at the night sky.

Dark matter is a tricky subject to deal with, so how are astronomers able to justifiably state that the galaxy they are studying is missing a lot of dark matter? According to the article written by NASA addressing the topic named “Mystery of Galaxy’s Missing Dark Matter Continues,” acknowledged this finding was intended to provide more proof of a similar finding in the past. Both papers measured the amount of dark matter present in the galaxy of study through stellar motion, meaning that they studied how the stars are moving because the movement of stars is highly affected by gravity. A way of visualizing this is with a trampoline, a bowling ball, and a golf ball. If you place the bowling ball in the middle of the trampoline and roll the golf ball along with the trampoline, its motion seems to get closer and closer to the bowling ball. If the bowling ball was lighter, then the path the golf ball takes would be drastically different. Yet, the issue with the previous study as noted in the article by NASA was that the researchers had to find a way to ensure and increase the accuracy of the distance between the galaxy and Earth if it were to be closer to Earth, “The galaxy, therefore, would need dark matter to account for the observed effects of the total mass.” As a result of this, the current paper published utilized the Hubble Space Telescope to get a more accurate distance, which turned out to be larger than what was originally thought. This increased distance further strengthened the argument that the galaxy in question DF2 lacks dark matter.

The mystery of why DF2 lacks dark matter will most likely cause theorists to hypothesize ways in which galaxies lacking dark matter are able to form, undoubtedly challenging our current knowledge of this substance. Likewise, the uniqueness of DF2 has the potential to drive engineers to develop more sophisticated telescopes dedicated to studying such galaxies and for dark matter in general. More importantly, the discovery of a galaxy without dark matter causes scientists to believe that dark matter does in fact exist, which is a revolutionary claim since as stated before, humanity has yet to find a way to directly study dark matter. Dark matter truly leaves us in the dark. It refuses to be known yet its presence is everywhere. It is a necessity that allows for our universe to take its form, causing both astronomers and physicists alike to search for a true understanding of the subject. Questioning the mystery of the state of the galaxy DF2 is a question of dark matter, whose answers may lie in the future or in an idea in your mind. It is a matter of time until we can develop a full understanding of dark matter and the structure of DF2. For now, the darkness prevails.

 

Citation:

Carruthers, Tom. “Gravitational Lensing.” Curious, 14 Dec. 2017, www.science.org.au/curious/space-

time/gravitational

lensing#:~:text=As%20the%20light%20emitted%20by,This%20is%

20called%20gravitational%20lensing.&text=Weak%20gravitational%20lensing

%20results%20in%20galaxies%20appearing%20distorted%2C%20stretched

%20or%20magnified.

CERN. “Dark Matter.” CERN, home.cern/science/physics/dark-matter.

Jenner, Lynn. “Mystery of Galaxy's Missing Dark Matter Deepens.” NASA, NASA, 15 June 2021,

www.nasa.gov/feature/goddard/2021/mystery-of-the-galaxys-missing-dark-matter-deepens.

Nagaraja, Mamta. “Dark Energy, Dark Matter.” NASA, NASA, 2021,

science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy.

O'Neill, Mike. “Cosmic Mystery Deepens: Oddball ‘See-Through’ Galaxy's Missing Dark Matter.”

SciTechDaily,

SciTechDaily, 20 June 2021,

scitechdaily.com/cosmic-mystery-deepens-oddball-see-through-galaxys-missing-dark-matter/.

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