See the Milky Way's 3-D structure

James Marshall
August 2, 2019

Our location deep inside the very big structure means we can't observe our galaxy externally, forcing us to envision its form from within. The difference between these can tell us how far away a star might be from our sun.

"The internal structure and history of the Milky Way are still far from being well understood, in part because it is extremely hard to measure distances to stars in the outer regions of our galaxy", Dorota Skowron, the study's lead author, said.

Over the years, astronomers have employed various attempts to map our galaxy, including star counts, radio observations of gas molecules, and even extrapolations of similar spiral galaxies nearby.

Using that fluctuation, the team produced a 3D model of the galaxy, confirming work that previously demonstrated the galaxy was flared at its edges. A better way to map the Milky Way would be to directly measure our distance to a large sample of stars strewn across the galactic disk.

More research like this to map the ages and locations of stars in the Milky Way could can help scientists piece together how our galaxy formed.

The new three dimensional map has been published in the journal Science.

"Our map shows the Milky Way disk is not flat".

The map showed that the galaxy's disk, far from flat, is significantly warped and varies in thickness from place to place, with increasing thickness measured further from the galactic center.

This enables astronomers to calculate their distance with great precision.

"A key question would be whether there is a similar, possibly opposite warp [on the other side] too", he said. "Warping may have happened through past interactions with satellite galaxies, intergalactic gas or dark matter (invisible material present in galaxies about which little in known)". Our galaxy gets thicker with distance from the core.

To create the 3D map, Skowron and her colleagues charted the location of Cepheid variable stars.

To make the map, astronomers looked to its bright, pulsing stars called cepheids. In total, the researchers observed the galactic disk for six years, taking 206,726 images of the sky.

Richard de Grijs, an astronomer at Macquarie University and co-author on the Nature Astronomy study, said that both the previous study and the new study rely on Cepheids that sit on our side of the Milky Way. The results of the simulation look remarkably similar to the real map.

"They essentially confirmed our earlier conclusions regarding the 3D shape of the Milky Way's disk, including its flaring in the outer regions", Chen said.

Cepheids are easy to study because they pulsate at regular intervals and burn hundreds (or sometimes thousands) of times brighter than our sun. "Yet they found pretty much the same result, which is comforting!" "Cepheid variables are bright supergiant stars and they are 100 to 10,000 times more luminous than the sun, so we can detect them on the outskirts of our galaxy". "We can see with our own eyes, and inside our own galaxy, that star formation is not a constant process, but indeed is happening in bursts". And now astronomers from the United States and Europe have put together a new 3D model of the galaxy based on the distance between stars. Skowron doesn't believe that seeing the other side will dramatically increase the number of Cepheids they find. Infrared telescopes, she said, could do the trick.

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