Milky Way much larger than previously estimated

The Milky Way galaxy is at least 50 percent larger than is commonly estimated, according to new findings which reveal that the galactic disk is contoured into several concentric ripples.

The research, conducted by an international team led by physics professor Heidi Jo Newberg from Rensselaer Polytechnic Institute in New York, revisited astronomical data from the Sloan Digital Sky Survey.

"In essence, what we found is that the disk of the Milky Way is not just a disk of stars in a flat plane - it is corrugated," Newberg said. As it radiates outward from the sun, we see at least four ripples in the disk of the Milky Way.

"While we can only look at part of the galaxy with this data, we assume that this pattern is going to be found throughout the disk," he said in a paper which appeared in the Astrophysical Journal.

"Importantly, the findings show that the features previously identified as rings are actually part of the galactic disk, extending the known width of the Milky Way from 100,000 light years across to 150,000 light years," said Yan Xu, scientist at the National Astronomical Observatories of China.

Going into the research, astronomers had observed that the number of Milky Way stars diminishes rapidly about 50,000 light years from the centre of the galaxy.
"And then a ring of stars appears at about 60,000 light years from the centre," Xu said.

What we see now is that this apparent ring is actually a ripple in the disk. And it may well be that there are more ripples further out which we have not yet seen, he said.