You possibly can truly see the wave of the Milky Means galaxy by mapping its stars
Spiral galaxies are one of the most famous types of galaxies. Most people see them as large round disks and know that our Milky Way galaxy is one of their numbers. What most people don’t realize is that many spiral galaxies have some sort of distortion effect that, when viewed from the edge, can make them appear to be forming a wave. Now, under the direction of Xinlun Chen at the University of Virginia, scientists have studied millions of stars in the Milky Way and have begun to develop an image of a “wave” going through our own galaxy.
Since humans are currently unable to view the Milky Way in an edge orientation, they have to resort to brute force methods to develop models for the wave of our galaxy. Fortunately, scientists now have the tools to do so in the form of the Sloan Digital Sky Survey and ESA’s Gaia satellite.
The “integral galaxy” is one of the spiral galaxies with the most visible distortion.
The team’s method was to identify and track the movements of as many stars as possible. To do this, they used the APOGEE spectrograph (Apache Point Observatory Galactic Evolution Experiment), which is part of the SDSS. These preliminary data allowed them to look at both the chemical compositions and the motions of hundreds of thousands of stars. While this motion data was helpful in creating the image of the wave of the Milky Way, it was not enough to complete it.
Additional data was needed, supplied by Gaia – detailed distances to these hundreds of thousands of stars. By combining the distance data with the movement data, the team was able to create a full 3D map of the Milky Way, or at least as good an approximation of a map as can be made within its boundaries.
SDSS YouTube video shows storage in the galaxy.
Photo credit: SDSS YouTube Channel
What this map can show us is the “wave” that is present in so many spiral galaxies, including our own, although it is not as common as elsewhere. Another discovery from this dataset was that the wave itself travels through the galaxy, orbiting the galaxy approximately every 440 million years.
Many factors could have caused such a long-lived and ever-expanding wave. However, the team suspects that a theoretical collision with an earlier satellite galaxy about 3 billion years ago caused the original ripple. It then kept going long after the introductory force had been released and will continue to do so for a long time. Perhaps it will be long enough before we send a probe outside the galaxy to observe the Milky Way’s own wave from one edge.
SDSS – The Milky Way makes the wave
Newsweek – Something appears to have collided with the Milky Way and created a huge wave in the galactic plane
UT – A giant wave sweeps through the Milky Way, unleashing new stellar nurseries
UT – This distorted circle is actually a galaxy that looked very similar to the Milky Way just after the Big Bang
Lead photo credits: Adrian Price-Whelan / 2mass