Scientists have revealed that our galaxy, Milky Way, contains just half the dark matter than what was previously thought.
Dark matter is the invisible matter that makes up most of all the galaxies. A group of astrophysicists from Australia have now remeasured the dark matter in the Milky Way by observing the speed of the stars and the edges of our galaxy. The measuring technique was developed by British astronomer James Jeans about 100 years back.
Dr. Prajwal Kafle, a researcher from the University of Western Australia, revealed that our galaxy is about 800 million times bigger than the mass of the Sun, half of what was estimated previously.
Dr. Kafle learned that majority of the universe is actually hidden. Dust, stars, people and more make about just 4 percent of the universe. About a quarter of the universe is dark matter and the rest is believed to be dark energy.
The astrophysicist explains that the current impression of the formation of our galaxy and its evolution is called the Lambda Cold Dark Matter theory. This theory states that there are some bigger satellite galaxies located near the Milky Way. These galaxies may be visible to us but we are unable to see them.
"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," Dr. Kafle said.
Professor Geraint Lewis, an astrophysicist from the University of Sydney, also helped in the study and revealed that the notion of missing satellites has posed a big problem for astrophysicists for many years. However, Dr. Kafle's latest research suggests that the problem is not as big as thought previously but it still needs to be addressed.
The study is significant as it gives more information about the dark matter in the Milky Way and a general model of our galaxy. This also allowed the scientists to unravel a few more interesting facts, such as the speed needed to exit from the galaxy.
Dr. Kafle suggests that, in order to exit from the gravitational pull of our galaxy, an object has to travel at 550 kilometers per second.
"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!" says Dr. Kafle.
The study is published in the Astrophysical Journal.
