DARK MATTER -The Unknown Matter.!

Next to dark energy, the second largest component of the universe is dark matter. It can't be seen directly, but it's effect can be observed from its interaction with the rest of the universe through its gravity.The truth is , we understand little of what it is, and more of what it is not.

It doesn't interact with baryonic matter and it's completely invisible to light and other forms of electromagnetic radiation, making dark matter impossible to detect with current instruments. But scientists are confident it exists because of the gravitational effects it appears to have on galaxies and galaxy clusters .

WHAT DO WE KNOW SO FAR?

IS IT DARK ?

Dark matter can't be seen directly and it radiates no light, so it can't be stars or planets.

Dark matter is called dark because it does not appear to interact with observable electromagnetic radiation, such as light, and is thus invisible to the entire electromagnetic spectrum, making it extremely difficult to detect using usual astronomical equipment.

IS IT DETECTABLE?

It is too dense and small to absorb or emit enough radiation to be detectable by current imagining technology.

Later we can learn the direct and indirect detection experiments .

IS IT A CLOUD OF NORMAL MATTER?

If a dark matter was normal matter particles called Baryons, it would be detected using reflected light- but it is undetectable,so it is not baryons.

IS IT A ANTIMATTER?

Antimatter wipes out on contact & produces gamma rays.Astronomers do not detect antimatter in dark matter.

IS IT A BLACK HOLE?

Light bends with gravity lenses of black holes. There have not been enough lensing events to account for the amount of dark matter that exists.

WHO FIRST DISCOVERED IT?

Dutch astronomer Jacobus Kapteyn first suggested the existence of dark matter in 1922 while studying stellar velocities
Swiss astrophysicist Fritz Zwicky inferred the existence of dark matter during his work on galactic clusters in 1933.He is also best in other works like Neutron stars ,Gravitational lensing ,Supernovae...
In 1939, American astronomer Horace Babcock reported on the presence of dark matter gleaned from his measurements of galaxy rotation curves.
The late American astronomer Vera Rubin teamed up with the instrument maker Kent Ford in the 1960s and 1970s ,and together they used their new spectrograph to measure the velocity curves of spiral galaxies ,they found that most of them contain six times as much dark matter as visible matter.

[click on above scientist names to known about them]

WHY DO WE CARE?

The Higgs boson & dark matter may be connected . Both investigation are about the ways subatomic particles interact, & what the fundamental structure of the universe looks like. A better understanding of subatomic particles is essential to making modern theoretical physics make sense.
Experts like Neil deGrasse Tyson believe that if dark matter makes up around 25 percent of the known universe , dark energy probably makes up about 70 percent of the known universe . Dark energy may be the reason the reason seems to be expanding .
Dark energy & dark matter are intimately connected . E=MC² ,remember?

HOW WE ARE SEARCHING FOR IT ?

PARTICLE COLLIDER

Large particle collider -The world's largest machine designed to test various theories of particle physics.

COSMOLOGY INSTRUMENTS

WMAP- Spacecraft that measured temperatures of the Cosmic Microwave Background.

Plank -NASA-ESA space observatory that mapped the universe revealing the oldest lights which traveled billions of years.

DIRECT DETECTION EXPERIMENTS:

CDMS- At soudan Mine in Minnesota
LUX- Large Underground Xenon experiment at Sanford Underground Laboratory in South Dakota.
ArDM- at Canfranc Underground Laboratory in spain.
XENON-deep underground at Italian Gran Sasso laboratory.

INDIRECT DETECTION EXPERIMENTS:

Gamma ray detectors-Fermi Space Telescope,ground based Cherenko Telescope Array.
Neutrino Telescope- Icecube Neutrino observatory, Antares telescope
Antimatter detectors- Pamela,AMS-O2,other X-rays & Radio facilities.

IS THERE ANY GALAXY IN THE UNIVERSE WITH NO DARK MATTER?

NGC1052-DF2 is a large, but very diffuse galaxy located some 60 million light-years away. This image of the galaxy, which is thought to contain a negligible amount of dark matter, was captured by the Advanced Camera for Surveys on the Hubble Space Telescope.

To determine how quickly the globular clusters were rotating around DF2, the researchers analyzed the absorption lines of spectra taken with the Keck Observatory. This allowed them to determine each cluster’s velocity, which they then used to calculate the overall mass of the galaxy.

Difference between with Dark matter & without Dark matter:

Left side :

The galaxy without Dark matter.

Right side:

The galaxy with Dark matter.

Astronomers infer the existence of dark matter largely based on the fact that the rotation curves of galaxy's are not what you would expect without some form of hidden mass spread through the entire galaxy. In this simulation, the galaxy on the left shows what rotation would look like without the effects of dark matter, while the right shows rotation with dark matter.

SOURCE:

http://www.astronomy.com/news/2019/03/ghostly-galaxy-without-dark-matter-confirmed

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

https://www.space.com/20502-dark-matter-universe-mystery-infographic.html

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

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