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New Research Finds Dark Matter Half What We Previously Thought

dark matter

Image credit: ESO/L. Calçada. Artist’s impression of the Milky Way and its dark matter halo.

By application of a very old technique to examine the borders of the Milky Way, a group of astronomers from Australia has roughly calculated the amount of dark matter in our galaxy. Quite interestingly, based on their estimation, there might be half as much of dark matter in the Milky Way as once thought. Their research has been released in the latest edition of The Astrophysical Journal.

As kind of the elusive substance, dark matter is unable to absorb, emit or reflect light, which means that it is not visual to both our eyes as well as the instruments applied to identify normal matter. Since dark matter is unable to interact with the electromagnetic force, what is clear that it does exist because it can leave gravitational effects on visual matter. Even without being seen, but according to the calculation made by physicists, dark matter composes nearly twenty-five percent of the universe and just 4% of the universe is made up by dust, stars and planets as well as the stuff of our bodies, which we call “normal” matter, while the rest of it is known as dark energy.

Although with difficulty in studying dark matter, scientists are capable of making measurement of its mass by the method developed by James Jeans, a British astronomer in the early 19th Century.

This technique pioneered long before researchers were even sure about the existence of knew dark matter, is used to measure the speed at which stars are travelling throughout the Milky Way. Astronomers have been doing the work for some period of time, but they had never applied it to probe the very edges of our galaxy, which is just they are trying to do in their newest research.

To look out so far away, the distance of about 5 million billion kilometers from our planet, they were capable of getting measurements which ensured them to have the calculation of the mass of dark matter in the Milky Way. Though it was discovered to be a quite large figure, some 800,000,000,000 times the mass of the Sun, this is just half of the estimates previously made.

According to Professor Geraint Lewis, co-author of the paper, the new measurement made by the team is much helpful in solving a problem, which has been regarded as tough one in the cosmological world for nearly fifteen years.

As Dr. Prajwal Kafle, the lead author said, the Lambda Cold Dark Matter theory which was widely known as the concept of formation and evolution of galaxy, had predicted that lot of huge satellite galaxies existed around the Milky Way. But to surprise of scientists, when their latest measurement was applied, the theory predicted that only three existed, namely, the Small Magellanic Cloud, the Large Magellanic Cloud, and the Sagittarius Dwarf Galaxy. That is just the result of our  observation.

Source: International Centre for Radio Astronomy Researchsiliconrepublic and The Astrophysical Journal

Journal reference: Kafle, Prajwal Raj, et al. “On the Shoulders of Giants: Properties of the Stellar Halo and the Milky Way Mass Distribution.” The Astrophysical Journal 794.1 (2014): 59.