Nearly one-third of disk galaxies in the nearby universe are warped, resembling a potato chip in shape. Our Milky Way galaxy is also a warped disk galaxy.
The Milky Way's Warped Disk
The Milky Way's disk, like a spinning top, wobbles due to the influence of the surrounding dark matter halo. This wobbling is called precession, and it's an important factor in understanding galactic dynamics.
Challenges of Measuring Precession
Previous methods for measuring precession were indirect and not very accurate. These methods relied on tracers that could be influenced by other factors in the galaxy.
A New Era: The Motion-Picture Method
A new "motion-picture" method uses Cepheid variable stars to track the warp's movement over time. This allows scientists to create a 3D picture of the disk's warp at different ages.
Cepheid Variable Stars: Nature's Chronometers
Cepheid variable stars are pulsating stars that brighten and dim at predictable rates. The pulsation period of a Cepheid variable star is directly related to its luminosity.
Unveiling the Dark Matter Halo's Shape
By studying the precession of the warp, scientists were able to determine the shape of the dark matter halo. The Milky Way's dark matter halo is slightly oblate, like a flattened sphere.
The Power of Big Data
This study used data from the Gaia spacecraft and LAMOST telescope. This vast dataset allowed scientists to analyze a large sample of Cepheid variable stars.
The Milky Way's Grand Design
Understanding the precession and the shape of the dark matter halo helps us understand the Milky Way's evolution.This knowledge can be applied to study other galaxies and the large-scale structure of the universe.