Astrophysicists Reveal Amount of Dark Matter is Less Than Previously Thought

SciTech Daily ^ | 10/09/2014 | Source: International Center for Radio Astronomy Research

[Red Badger]

New research from the University of Western Australia reveals that the amount of dark matter in the Milky Way is half as much as previously thought.

Australian astronomers used a method developed almost 100 years ago to discover that the weight of dark matter in our own galaxy is 800,000,000,000 (or 8 x 1011) times the mass of the Sun.

They probed the edge of the Milky Way, looking closely, for the first time, at the fringes of the galaxy about 5 million billion kilometers from Earth.

Astrophysicist Dr Prajwal Kafle, from The University of Western Australia node of the International Center for Radio Astronomy Research, said we have known for a while that most of the Universe is hidden.

“Stars, dust, you and me, all the things that we see, only make up about 4 per cent of the entire Universe,” he said.

“About 25 per cent is dark matter and the rest is dark energy.”

Dr Kafle, who is originally from Nepal, was able to measure the mass of the dark matter in the Milky Way by studying the speed of stars throughout the galaxy, including the edges, which had never been studied to this detail before.

He used a robust technique developed by British astronomer James Jeans in 1915 — decades before the discovery of dark matter.

Dr Kafle’s measurement helps to solve a mystery that has been haunting theorists for almost two decades.

“The current idea of galaxy formation and evolution, called the Lambda Cold Dark Matter theory, predicts that there should be a handful of big satellite galaxies around the Milky Way that are visible with the naked eye, but we don’t see that,” Dr Kafle said.

“When you use our measurement of the mass of the dark matter the theory predicts that there should only be three satellite galaxies out there, which is exactly what we see; the Large Magellanic Cloud, the Small Magellanic Cloud and the Sagittarius Dwarf Galaxy.”

University of Sydney astrophysicist Professor Geraint Lewis, who was also involved in the research, said the missing satellite problem had been “a thorn in the cosmological side for almost 15 years.”

“Dr Kafle’s work has shown that it might not be as bad as everyone thought, although there are still problems to overcome,” he said.

The study also presented a holistic model of the Milky Way, which allowed the scientists to measure several interesting things such as the speed required to leave the galaxy.

“Be prepared to hit 550 kilometers per second if you want to escape the gravitational clutches of our galaxy,” Dr Kafle said.

“A rocket launched from Earth needs just 11 kilometers per second to leave its surface, which is already about 300 times faster than the maximum Australian speed limit in a car!”

Publication: Prajwal Raj Kafle, et al., “On the Shoulders of Giants: Properties of the Stellar Halo and the Milky Way Mass Distribution,” 2014, ApJ, 794, 59; doi:10.1088/0004-637X/794/1/59

PDF Copy of the Study: On the Shoulders of Giants: Properties of the Stellar Halo and the Milky Way Mass Distribution

Image: ESO/L. Calçada

[Red Badger]

Artist’s impression of the Milky Way and its dark matter halo (shown in blue, but in reality invisible). Credit: ESO/L. Calçada

Video at link:

This animation shows a supercomputer simulation of a galaxy like the Milky Way and its invisible dark matter halo. We zoom in to the galaxy and can see knots of dark matter where we would expect to see many satellite galaxies, but they don’t exist in the real Universe. That’s the missing satellite problem. Credit: Prof Chris Power and Dr Rick Newton, ICRAR. Music by Reuben Christman

[Red Badger]

Space Ping!

If you didn’t know how much there was in the first place, how would you know half of it was missing?.............

[PIF]

Still awaiting explanation of the Great Attractor, and what it is.

[RetSignman]

That damn Glowbull Warming is up to it’s nefarious ways again.

[bigbob]

wonder how much is in Moochele’s trunk?

[Red Badger]

Still awaiting explanation of the GRAVITY, and what it is...............

[Red Badger]

That would be a really big Black Hole......................

[HandyDandy]

Are they going to now have to doublecheck ALL their findings using common core math?

[showme_the_Glory]

I like dark chocolate but not Milky Way. Snickers is better.

[Don Corleone]

Astrophysicists Reveal Amount of Dark Matter is Less Than Previously Thought

Bush's fault!

[Dead Corpse]

Aahh man... I was hoping to get a ton of this Unobtainium to play with on my forge this weekend...

[UCANSEE2]

Still awaiting explanation of the Great Attractor, and what it is.

It's like the drain at the bottom of a pool.

[Verginius Rufus]

Isaac Newton explained how gravity works, more or less (some corrections by Albert Einstein). But I don't think he explained why there is gravity to begin with.

OK, so every particle of matter attracts every other particle of matter. But why? Why doesn't matter just mind its own business and not bother any other bits of matter? Cosmic busybodies. Matter must be "Progressive."

And why does light keep traveling for billions of years? Don't the light beams ever get tired?

[Red Badger]

Unobtainium can be had by the shipload.
All you have to do is get to the nearest Pulsar and back...............

[Attention Surplus Disorder]

I’m offended.

How will I ever get my fair share of dark matter now?

This sucks, it’s completely unfair.

Think I’ll take down the convenience store down the block. I’ll wait til it’s dark. They can suck on their dark matter. Yeah.

[Dead Corpse]

I don’t own a ship. Ergo, I don’t need an entire shipload of it.

Just wanted to see if I could hammer it into a decent set of mitten gauntlets and a set of pauldrons.

[HandyDandy]

Describing the effects of Gravity is not the same as knowing what it is.

[Red Badger]

Gravity is just the label we put on something that we don’t know how it works but know that it does.

Mass depresses the fabric of space-time, creating a ‘gravity well’, or so they tell us. Every bit of mass depresses it to some extent.

If you had a universe where only two atoms of hydrogen existed, and they were a billion light years apart, they would eventually collide or settle into a stable orbit around a central point............

[Red Badger]

Well, I don’t know about ‘pauldrons’ but you could probably hammer it into a Ron Paul...................

[mikrofon]

They probed the edge of the Milky Way, looking closely, for the first time, at the fringes of the galaxy about 5 million billion kilometers from Earth

They probably haven't factored in that Negative Energy barrier ....