NASA’s IXPE Measures White Dwarf Star for First Time
By Michael Allen
For the first time, scientists used NASA’s Imaging X-ray Polarization Explorer (IXPE) to study a white dwarf star. Using IXPE’s unique X-ray polarization capability, astronomers examined a star called EX Intermediate Polar Hydra, revealing the geometry of energetic binary systems.
In 2024, IXPE spent nearly a week focusing on EX Hydrae, a white dwarf star system located in the Hydra constellation, about 200 light years from Earth. An article on the results published in the Astrophysical Journal. Astrophysics researchers based at the Massachusetts Institute of Technology in Cambridge led the study, with co-authors from the University of Iowa, East Tennessee State University, the University of Cork and Embry Riddle Aeronautical University.
A white dwarf star appears when a star lacks the hydrogen to fuse in its core, but is not massive enough to explode as a core-collapse supernovae. What remains is very dense, about the same diameter as Earth and as much mass as our Sun.
EX Hydrae is in a binary system with a main-sequence companion star, from which gas continually falls onto the white dwarf. Exactly how the white dwarf accumulates or accumulates this material and where it arrives on the white dwarf depends on the strength of the white dwarf star’s magnetic field.
In the case of EX Hydrae, its magnetic field is not strong enough to completely concentrate matter at the star’s poles. But it continues to rapidly add mass to the accretion disk, earning it the classification of “intermediate polar.”
In an intermediate polar system, matter forms an accretion disk while also being attracted toward its magnetic poles. During this phenomenon, material reaches tens of millions of degrees Fahrenheit, bouncing off other material bound to the white dwarf star, creating large columns of gas that emit high-energy X-rays – a perfect cosmic situation for IXPE to study.
“The unique polarimetry capability of NASA’s IXPE allowed us to measure the height of the white dwarf star’s accretion column nearly 2,000 miles high – without as many assumptions as previous calculations,” said Sean Gunderson, MIT scientist and lead author of the paper. “The
Information from IXPE’s EX Hydrae polarization data will help scientists understand other highly energetic binary systems.
The IXPE mission, which continues to provide unprecedented data enabling groundbreaking discoveries about celestial objects across the universe, is a joint mission of NASA and the Italian Space Agency with scientific partners and collaborators in 12 countries. It is led by NASA’s Marshall Space Flight Center in Huntsville, Alabama. BAE Systems, Inc., headquartered in Falls Church, Virginia, manages spacecraft operations in collaboration with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. Learn more about IXPE’s current mission here:
https://www.nasa.gov/ixpe
