by Astronomers have used a principle first proposed by Albert Einstein 100 years ago to map the distribution of dark matter in unprecedented detail. The team’s approach was able to reveal the presence of dark matter “clumps” between galaxies, showing how this mysterious substance is distributed on small scales.
Fluctuations in observed dark matter, detected between a distant quasar (or a bright light source supported by a supermassive feeding black hole) and the distance between that quasar and Earth can help constrain the properties of unobservable matter.
Dark matter worries scientists because, although it makes up about 85% of the universe, it is invisible. This is because dark matter does not interact with any electromagnetic radiation, including visible light, or it does so incredibly weakly.
This means that the particles that make up dark matter – whatever it is – cannot be atoms that contain electrons, protons and neutrons. These are the bars that make up the everyday things that make up the stars, the planets, our bodies and everything we see around us every day.
It is this puzzle that has led to the intensive search for these so-called dark particles.
Related: We still don’t know what black matter is, but here’s what it isn’t
Until now, the only way scientists could prove the existence of dark matter was to observe the effect it has on “normal” matter through gravity. Indeed, when astronomers did this, they discovered that if the galaxies were not made up of mostly dark matter, the objects in them would fly apart as quickly as they spin too fast to be held together by the gravitational pull of the visible matter inside them.
Not only are galaxies believed to be shrouded in dark matter halos to prevent such a catastrophe, but some dark matter models also suggest that there should be clumps of dark matter inside galaxies and filling the space between them.
A group of researchers from Japan, led by Kindai University’s Kalki Taro Inoue, intend to use the Atacama Large Millimeter / submillimeter Array (ALMA) to better understand the distribution of dark matter around a distant, large galaxy and find clumps of mysterious matter. in the intergalactic space.
To do this, they observed light from a quasar called MG J0414+0534, which is 11 billion light-years from Earth, using an effect called gravitational lensing.
Putting a dark object under a cosmic magnifying glass
Gravitational lensing is a concept that first appeared in Einstein’s theory of gravity, general relativity, published in 1915. This concept is very different from Newton’s concept of gravity because it rethought the fabric of space and time — combined as 4-dimensional space-time — as. A dynamic element of the universe, not just a static stage on which cosmic events play out.
Einstein saw matter as causing a bend or “warp” in the fabric of space-time. The greater the mass, the greater the bending of spacetime. This can be represented as a simple 2D object placed on a stretched rubber sheet. A bowling ball makes a bigger dent in the paper than a tennis ball, just as a galaxy makes a bigger curve in space-time than a star.
What’s more, something really cool happens when a supermassive object comes between Earth and a distant light source like another galaxy, a star, or in this case, a quasar. Light usually travels in a straight line to Earth, but when it passes this curved side of space, its path turns, too. Masses near our planet that cause such bending lead to extreme deviations.
This means that light from the same source can take different paths around a large object and thus can reach the telescope at different times. This can cause one object to light up and be magnified in an image or appear in multiple places in a single image.
The intervening object, therefore, is referred to as a gravitational lens.
Gravitational lensing can help scientists see objects that are usually too distant and faint to observe. For example, the James Webb Space Telescope (JWST) has been using gravitational lensing to great effect to see galaxies in the early universe.
But beyond helping scientists study the subject of gravitational lensing, the result could be used to map the distribution of matter in the galaxy that acts as a natural lens in the first place. That includes dark matter mapping.
In this way, astronomers have been able to map the distribution of visible matter, and then estimate the distribution of dark matter in the lensing galaxy.
Inoue and team did this to the dark matter in the galaxy while conducting their distant quasar study, causing MG J0414+0534 to appear four times in one ALMA observation. This allowed researchers to capture the galaxy at a higher resolution than ever before, and map its dark matter to a scale of 30,000 light years.
They were able to take the use of gravitational lensing to another step.
With ALMA’s high resolution, astronomers have been able to map the distribution of dark matter that resides between galaxies and the line of sight to a quasar 11 billion light-years away. The results presented by the researchers help to confirm the so-called “cold dark matter” (CDM) model of the universe, which suggests that dark matter is made up of slow-moving particles.
That’s because the CDM dark matter model predicts that dark matter should exist inside galaxies and outside them, distributed in intergalactic space.
The team’s research was published Thursday (September 7) in the Astrophysical Journal.
#Black #lumps #typing #Einsteins #theory #general #relativity
