A rough 80 percent of the universe’s mass is made up of material that cannot be observed directly by scientists. Its strange property is that it does not emit light or energy. What is the reason for its dominance, then?
The universe is believed to contain more matter than is visible to the naked eye since at least the 1920s. There has been a growing level of support for dark matter since then, and although there have not been concrete discoveries of dark matter, there have been considerable possibilities.
“Motions of the stars tell you how much matter there is,” Pieter van Dokkum, a researcher at Yale University, said in a statement. “They don’t care what form the matter is, they just tell you that it’s there.” Van Dokkum led a team that identified the galaxy Dragonfly 44, which is composed almost entirely of dark matter. [Image Gallery: Dark Matter Across the Universe]
It consists of protons, neutrons, and electrons, which make up the baryonic matter that we know and love. It is possible for dark matter to be made of baryonic and non-baryonic matter. Dark matter must make up roughly 80% of the universe in order to bind its elements together. There might simply be more regular, baryonic matter missing, making detection difficult.
White dwarfs, brown dwarfs, and neutron stars are examples of possible candidates. Black holes with supermassive mass may also play a role. To account for the missing mass, scientists would need to observe more hard-to-spot objects while other elements suggest dark matter is more exotic.
The majority of scientists believe dark matter consists of nonbaryonic matter. Known as WIMPS (weakly interacting massive particles), WIMPS are tens to hundreds of times heavier than protons. Unfortunately, they are difficult to detect because their interactions with “normal” matter are so weak. Though yet undiscovered, neutralinos are the leading candidate as they are heavier and slower than neutrinos.
A second candidate is sterile neutrinos. Particles called neutrinos do not belong to the regular matter we are familiar with. Normally neutrinos do not interact with ordinary matter, so they pass through Earth and its inhabitants. The sterile neutrino, a hypothetical dark matter particle, is proposed as a fourth type of neutrino. Only gravity would interact with the sterile neutrino.
“One of the outstanding questions is whether there is a pattern to the fractions that go into each neutrino species,” Tyce DeYoung, an associate professor of physics and astronomy at Michigan State University and a collaborator on the IceCube experiment, told Space.com.
Dark matter also appears to exist in the form of uncharged photinos, another theoretical particle.
According to a statement by the Gran Sasso National Laboratory in Italy (LNGS), “Several astronomical measurements have corroborated the existence of dark matter, leading to a world-wide effort to observe directly dark matter particle interactions with ordinary matter in extremely sensitive detectors, which would confirm its existence and shed light on its properties. However, these interactions are so feeble that they have escaped direct detection up to this point, forcing scientists to build detectors that are more and more sensitive.”
If gravity is to continue to describe objects within the solar system correctly, perhaps the laws of gravity need to be revised.
Here are five revelations about Dark Matter:
1. Dark matter exists everywhere
Only 5% of the universe is occupied by planets, stars, asteroids, and galaxies. Where does the rest of the money come from? The mystery lies there.
Dark matter is the term we use to describe all the mass in the universe that is still invisible. Dark energy makes up about 70% of the universe, while dark matter makes up the remaining 25%. Even though we cannot see or understand it, we are aware that it is out there.
There is no visible evidence of it. Observing dark matter is incredibly challenging, as we have no way to see it. Since this strange substance does not interact with light, it is completely invisible.
How can we be sure it exists? There are strange ways in which it alters the universe, and that is something we can observe.
2. Galaxies are bound together by dark matter
The space it impacts can be felt, even though dark matter is invisible.
Dark matter exerts gravitational force, causing other matter to gravitate towards it. Even whole galaxies – like the Milky Way – are held together by the gravitational power of dark matter. Due to its ability to mesh galaxies together, dark matter is often compared to a giant spider’s web.
3. As a result, space appears distorted
Taking a look at the sky can also enable us to observe the effects of dark matter. Exoplanets are often stretched and irregularly shaped when observed by astronomers.
As a result of dark matter’s gravitational pull, this phenomenon is called gravitational lensing. It bends light around galaxies so violently that appearances of them are distorted.
4. There are spaceships searching for signs
Does gravity create dark matter or is it a particle? There’s no way to prove either theory true or false yet, and more research needs to be done before either can be proven to be accurate.
There must be occasional collisions between dark matter particles, an interaction which produces radiation. Thus, advanced detectors have been fitted to spacecraft to help find signs of this radiation. There have been a few interesting findings, but we are still searching for hard evidence.
5. Our understanding of dark matter is advancing
We still don’t know a lot about dark matter, and some mysteries are unlikely to ever be solved. The truth is becoming closer to us as technology advances.
Despite the complexity, elusiveness, and mystery of dark matter, scientists around the world will continue the search – and what they discover could transform our very conception of the universe.
Dark matter: how do we know it exists?
The existence of dark matter is unknown if it is not visible to scientists?
Studying how large objects move in space helps scientists calculate the mass of those objects. In the 1970s, astronomers examining spiral galaxies anticipated seeing material in their centers moving faster than at the edges. Instead, they found the stars of both galaxies traveled at the same speed, indicating there was more mass inside than could easily be seen. Additionally, studies of the gas in elliptical galaxies suggest that there is a greater need for mass than is present in visible objects. If all the mass contained within clusters of galaxies could be measured with conventional astronomical instruments, they would break apart.
A lens can be constructed from massive objects in the universe through the way that light bends and distorts. Astronomers have used galaxy clusters to increase their understanding of dark matter in the universe by studying how light is distorted by them.
The results of all of these methods strongly suggest that much of the matter in the universe remains unseen.
Dark energy vs. dark matter
Dark matter constitutes over a quarter of the universe’s composition despite making up the majority of the universe’s matter. There is a great deal of dark energy in the universe.
As the universe expanded outward following the Big Bang, it began to expand inward. As gravity drew the objects together, they thought it would eventually run out of energy and slow down as it became less powerful. But studies of distant supernovae reveal today’s universe expands faster than it did in the past, not slower, showing itself to be expanding faster. Only dark energy could overcome gravity, if the universe contained enough energy.