New measurements suggest there is about half as much mysterious dark matter in the Milky Way as researchers previously believed.
Researchers used a century-old measurement method to determine the weight of dark matter in our galaxy is 800,000,000,000 (or 8 x 1011) times the mass of the Sun, the International Centre for Radio Astronomy Research (ICRAR) reported. To make its findings the research team also looked at the edges of the Milky Way for the first time.
"Stars, dust, you and me, all the things that we see, only make up about [four] percent of the entire Universe," said astrophysicist Prajwal Kafle, from The University of Western Australia node of the International Centre for Radio Astronomy Research. "About 25 percent is dark matter and the rest is dark energy."
The researchers measured the mass of dark matter in our home galaxy by looking at the speed of stars reaching to the outer edges, which have never before been studied in detail.
"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," 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."
The study provides a comprehensive model of the Milky Way that allows scientists to measure things such as the speed required to leave the galaxy.
"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!" Kafle said.