“New Study: Gravitational Lensing Sheds Light on Dark Matter Debate”

Physicists believe that most of the matter in the universe is made up of invisible matter that we know only through its indirect effects on the stars and galaxies that we can see.

We’re not crazy! Without this “dark matter”, the universe as we see it would be meaningless.

But the nature of dark matter is an ancient mystery. But, New study Written by Alfred Amroth of the University of Hong Kong and colleagues, published in natural astronomyuses the gravitational bending of light to bring us one step closer to understanding.

Invisible but everywhere

The reason we think dark matter exists is because we can see the effect its gravity has on the behavior of galaxies. In particular, dark matter appears to make up about 85% of the mass of the universe, and most of the distant galaxies we can see appear to be surrounded by a mysterious halo of matter.

But it’s called dark matter because it doesn’t emit, absorb, or reflect light, making it very difficult to detect.

So what are these things? We think it must be some kind of unknown fundamental particle, but we’re not sure yet. All attempts to detect dark matter particles in laboratory experiments have so far failed, and physicists have debated their nature for decades.

Scientists have proposed two main hypothetical candidates for dark matter: a relatively heavy character called a weakly interacting massive particle (or WIMP), and a very light particle called an axion. In theory, WIMPs behave like discrete particles, whereas axions behave very much like waves due to quantum interference.

It’s hard to tell the difference between these two possibilities – but a little detour around a distant galaxy provides a clue.

Einstein’s gravitational lens and rings

When light passes through the universe by a massive object such as a galaxy, its path is curved because – according to Albert Einstein’s theory of general relativity – the massive object’s gravity distorts space and time around it.

As a result, sometimes when we look at a distant galaxy, we can see a distorted image of another galaxy behind it. And if everything lines up perfectly, the light from the background galaxy will surround the nearest galaxy.

This distortion of light is called “gravitational lensing”, and the circles it can create are called “Einstein loops”.

By studying how rings or other lenticular images are distorted, astronomers can study the properties of halos of dark matter that surround nearby galaxies.

Axion vs. WIMPs

And that’s exactly what Amroth and his team did in their new study. They looked at several systems in which multiple copies of the same object are visible in the background around the foreground lensing galaxy, with a particular focus on a system called HS 0810+2554.

Using detailed modeling, they figured out how the image would be distorted if dark matter was created from WIMPs versus how it would be if dark matter was created from axes. The WIMP model doesn’t look like the real thing, but the axion model accurately reproduces all the features of the system.

These findings suggest that axions are a more likely candidate for dark matter, and their ability to explain lensing anomalies and other astrophysical observations has irritated scientists.

particles and galaxies

The new research builds on previous studies that also suggest axions are the most likely form of dark matter. For example, one study see the axion dark matter effect on the cosmic microwave background, transient final Examining the behavior of dark matter in dwarf galaxies.

While this research won’t end the scientific debate about the nature of dark matter, it does open new avenues for testing and experimentation. For example, observations of gravitational lensing could in the future be used to investigate the wave properties of axons and possibly measure their mass.

A better understanding of dark matter will have implications for what we know about particle physics and the early universe. It can also help us better understand how galaxies form and change over time.