29 Jul 2019

"Dragonfly 44" A weird galaxy made of 99% dark matter!

A milkyway sized weird galaxy made of 99% dark matter

 


What we know about dark matter is nothing. From decades we are trying to solve the mystery of dark matter but we still can’t detect them.

We are using very advanced instruments like Hubble telescope and even International space station (ISS) and many more powerful telescopes which is also present on the Earth, but we have not detected them yet.

Here should be a question, if we don’t have detected it yet then how do we know, even it exists?

Well, we know how much dark matter is because we know how much it affects the universe's expansion. Dark energy is roughly 68% and dark matter is 27% while normal matter is just 5% in this universe.
As we haven’t observed dark energy yet, so only we have explanations in the name of information.

This Universe consists 95% of dark matter and dark energy that means we only see the 5% of this universe but the rest 95% is present everywhere as a dominant factor.

Now, what if a milkyway sized galaxy found to be containing 99.99% of dark matter and just 0.01% of ordinary matter?

Astronomers have discovered a galaxy as big as the Milky Way that consists almost entirely of dark matter, a mysterious and invisible substance that scientists have been trying to figure out for decades.

Only one-hundredth of one percent (0.01%) of the galaxy is ordinary, visible matter like stars and planets. The other 99.99 percent of the stuff in this galaxy can't be seen, but their effects can se observed.

This dark galaxy was first detected in 2015 by using Dragonfly Telephoto Array in New Mexico and was named Dragonfly 44.

This Dragonfly Telephoto Array is combination of eight telephoto lenses and cameras, which is designed to look at the objects in the universe which are not bright enough to see from other telescopes.

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Pieter van Dokkum of Yale University and colleagues found the Dragonfly 44 galaxy in the Coma Cluster, 300 million light years from the Earth.

This distance is easily close enough far a telescope to see, as Hubble telescope can se billions of light year away, but still no one noticed these galaxies hidden in dark before.

Dragonfly 44 is one of the largest and the brightest galaxy they have found in Coma Cluster, which is a group of at least 1,000 galaxies. Dragonfly 44 is as big as milkyway galaxy but emits only 1% as much light.

Discovery of Dragonfly 44 galaxy

Pieter van Dokkum and his team realize something unusual about Dragonfly 44, that was a galaxy hold it together with so few stars. There wouldn’t be enough gravity and the stars should drift out. But here the suspect which was responsible for holding the stars and forming the galaxy was the dark matter.

But, how much dark matter? For finding this, they used one of the largest telescope on the Earth, located at the W. M. Keck Observatory in Mauna Kea, Hawaii named Keck II.

They used a tool on the Keck II telescope called the Deep Imaging Multi-Object Spectrograph (DEIMOS) to study the movement of stars in the galaxy.

In their observations, van Dokkum and his team found evidence of way more mass than they could actually see. Only 0.01 percent of the galaxy is made of ordinary, visible matter, that is made of atoms containing electrons, protons and neutrons.

But the other 99.99 percent of Dragonfly 44's mass is the dark matter. Of all the stuff in this Milky Way-size galaxy, we can see almost nothing.

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"This has big implications for the study of dark matter," van Dokkum said.

"It helps to have objects that are almost entirely made of dark matter so we don't get confused by stars and all the other things that galaxies have.

The only such galaxies we had to study before were tiny. This finding opens up a whole new class of massive objects that we can study."

Although, 47 similarly faint galaxies were observed, far dimmer than the other galaxies within the Coma cluster. How these galaxies form is still a mystery.

Nature reports that a quasar at the heart of the galaxy may have destroyed the gas reserves that normally would’ve formed conventional stars, or that interactions with other galaxies in the Coma cluster might be responsible for the phenomenon.

The team is searching for more massive dark galaxies that are closer to Earth so they might uncover signals that reveal a dark matter particle.


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