Scientists inch closer to precisely weighing Milky Way

Researchers in the US have determined the mass of the Milky Way to be 210 billion times the mass of the Sun with an uncertainty of only 20 percent.

The study used streams produced by certain stars and statistical tools applied by internet search engines to rank websites to measure the weigh our galaxy. The researchers at Columbia University decided to give the Milky Way a more precise physical checkup as our home galaxy's precise weight is still unknown.

"Such measurements have been tried before with different streams, but the results were always quite ambiguous," said study co-author professor Kathryn Johnston.

"Our new measurement breaks these ambiguities," Johnston said.

The Milky Way consists of roughly 100 billion stars that form a huge stellar disk with a diametre of 100-200 thousand light years. The Sun is part of this structure, hence, when we look into the sky, we look right into a gigantic disk of stars.

The vast number of stars and the huge extent on the sky make it hard to measure fundamental quantities for the Milky Way, such as its weight. In this study, the researchers used stars outside this disk, which orbit around the Milky Way in a stream-like structure, to weigh the Milky Way to high precision.

The team demonstrates that such streams, produced by dissolving globular clusters, can be used to measure not only the weight of our Galaxy, but can also be exploited as yardsticks to determine the location of the Sun within the Milky Way.

"Globular clusters are compact groups of thousands to several millions of stars that were born together when the universe was still very young," said lead researcher Andreas Kupper.

The researchers used data from the Sloan Digital Sky Survey, which scanned the sky of the Northern Hemisphere for about 10 years to create a comprehensive catalog of stars in the sky.

From the improved precision of Milky Way weight, the scientists hope to learn about the formation and composition of our home galaxy, and to understand how the Milky Way compares with other galaxies in the Universe.

The study was published in The Astrophysical Journal.