Gravitational wave astronomy and dark matter really exist?

Monika Sachan

LIGO and gravitational wave detector detects the gravitational wave, and this gravitational wave effect helps to find the dark matter’s properties with the help of the Pulsar technique. These are all types of observations taken by gravitational wave astronomy and there is the other type of black hole researchers haven’t yet seen, but think could exist and would be considered to be dark matter. These are primordial black holes.

What is Gravitational-wave astronomy?

Gravitational-wave astronomy is a sub-branch of observational astronomy which uses to detect the gravitational wave and collect observatory data about objects within the universe like a black holes, neutron stars, and processes including those of the early universe just after the big bang theory. It is done with an electromagnetic spectrum.

Ground-based detectors like LIGO and Space-based detectors like LISA are part of gravitational wave astronomy.

Is dark matter particle made up of weakly- interacting particles?

If the dark matter is made up of weakly interacting particles, one general questions generate in our mind that it can form objects equivalent to stars, planets but the answer is no because of reasons:

  1. It has a less efficient method to lose energy.

Losing energy is essential for forming the object. Dark matter seems to lack the means to lose energy, simply because it is not able to communicate strongly in ways other than gravity.

  • It has less a range of interactions needed to form structures.

            Ordinary matter interact in different ways like stars form through gravity and they emit energy in the form of neutrons and electromagnetic radiation, but there is no evidence that dark matter is capable of a wide range of interactions.

Cosmic microwave background:

Cosmic microwave background is electromagnetic radiation which is a part of the early stage of the university. This is useful to understand the scientists how the early universe was formed. Both dark matter and ordinary matter do not have the same properties. In particular, in the early universe, the ordinary matter was ionized and interacted strongly with radiation via Thomson scattering. Dark matter does not interact with radiation, but it does affect the cosmic microwave background by the gravitational potential, and affects the density and velocity of ordinary matter.

This is the oldest light we can see beyond back both in time and space 14 billion years ago, long before the Earth or even our galaxy existed. The cosmic microwave background is very close to a perfect blackbody but contains very less temperature anisotropies of a few parts.

In 2013, data from the European Space Agency’s Planck space telescope was released, showing the highest accurate picture of the CMB yet. The results support the Lambda-CDM model. It showed more proof that dark matter and dark energy mysterious forces that are likely expansion of the universe.

Bullet Cluster:

If dark matter does not exist in the real world, then the next explanation must be general relativity, the prevailing theory of gravity is incorrect and should be modified. The collision of two galaxy clusters, the Bullet Cluster, provides a challenge for the modified prevailing theory of gravity because its visible center of mass is far displaced from the baryonic center of mass.

The components of cluster pairs like star, gas, and dark matter behave differently during the collision. When they collide, the distributed normal matter sticks together and heats up while the galaxies and dark matter pass through it which creates the effect that we observed.

New Research Finds That the Supermassive Black Holes Could Make From Dark Matter:

In December 2020 a new theoretical study has proposed the creation of supermassive black holes from dark matter. The international team found that supermassive black holes could form directly from dark matter in high-density zones in the centers of galaxies. The result has key implications for cosmology in the early Universe and is published in Monthly Notices of the Royal Astronomical Society.

In the explanation of model, exactly shows that how supermassive black holes initially formed is one of the biggest problems in the study of the universe. Supermassive black holes have been observed as early 800 million years after the Big Bang, and how they could grow so quickly could remain unexplained.

Standard formation models involve normal baryonic matter the atoms and elements that make up stars, planets, and other visible objects collapsing under gravity to make black holes, which then grow over time. However, the new work investigates the potential existence of stable galactic cores made from dark matter, and surrounded by a diluted dark matter halo, finding that the centers of those structures could become so concentrated that they may also collapse into supermassive black holes once a critical threshold is reached.

“This model shows how dark matter haloes could harbor dense concentrations at their centers, which may play a crucial role in helping to understand the formation of supermassive black holes,” added Carlos.

Primordial black holes:

Scientists have seen the gravitational effects on dark matter, so they know that there something must be going on to cause those effects. But so far, they have never tried to directly detect a dark matter particle, so they’re not sure exactly what dark matter is like.

One idea is that some of the dark matter could be primordial black holes that are a hypothetical type of black hole that formed a fraction of a second after the Big Bang. Primordial black holes could have masses100,000 times less than a paperclip, up to about 100,000 times greater than the Sun.

These pockets of dense matter mostly photons in the early universe under the high density and heterogeneous conditions might have collapsed under their gravity and formed early black holes.

“I think it’s an interesting theory, as interesting as a new kind of particle, If primordial black holes do exist, it would have profound implications on the conditions in the very early universe,” says Yacine Ali-Haimoud, an assistant professor of physics at New York University.

Primordial black holes belong to the class of massive compact halo objects (MACHOs). They are naturally a good dark matter candidate: they are collision-less and stable, and they have non-relativistic velocities, by using gravitational waves to learn the properties of black holes; LIGO might be able to prove or constrain this dark matter theory.

One way to detect this is to constraint their mass and abundance is by hawking radiation, small black holes emit the Hawking radiation at a rate inversely proportional to their mass and escaping the evaporation process.

Unlike normal black holes, primordial black holes don’t have a minimum mass threshold they have to succeed in to make. If LIGO were to see a black hole less massive than the sun, there might be a primordial black hole. Even if primordial black holes do exist, it is unknown that they account for all of the dark matter in the universe. Still, finding proof of primordial black holes would expand our fundamental understanding of dark matter and how the universe began.

Ancient Black Holes would give access to hidden secrets:

The researcher could study and experiment that a merger of two primordial black holes, never-before-seen objects that are considered a dark horse candidate for the dark matter the invisible, unidentified something that produces most of the matter within the universe. Hypothesize to have formed from density fluctuations in the very early universe, these ancient black holes could still exist today and will explain the mass discrepancy identified within the recent LIGO observations.

“Ancient black holes would give us access to secrets we would never otherwise be able to do,” wrote Hooper, in an email to The Daily Galaxy. “If primordial black holes are real, they’d have potential to solve a whole host of the biggest problems in cosmology, not the least being the mystery of dark matter, considered to be the backbone to the structure of the universe.”

Reference:

https://www.space.com/33892-cosmic-microwave-background.html

https://en.wikipedia.org/wiki/Cosmic_microwave_background

https://astronomy.com/news/2019/07/primordial-black-hole

https://www.symmetrymagazine.org/article/what-gravitational-waves-can-say-about-dark-matter

https://astronomy.com/news/2019/07/primordial-black-holes

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