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For this method to work, von Hippel and his team must measure the star’s surface temperature, whether it has a hydrogen or helium atmosphere, and its mass. The surface temperature can be determined from a star’s color and atmospheric constituents.
“The star’s mass matters because objects with greater mass have more energy and take longer to cool,” said von Hippel, director of Embry-Riddle’s Physical Sciences Department Observatory and 1.0-meter Ritchey-Chretien telescope. “This is why a cup of coffee stays hot longer than a teaspoon of coffee. Surface temperature, like spent coals in a campfire that’s gone out, offer clues to how long ago the fire died. Finally, knowing whether there is hydrogen or helium at the surface is important because helium radiates heat away from the star more readily than hydrogen.”
Determining the precise masses of stars, particularly for large samples of white dwarfs, is very difficult. Now, astronomers have a new method to determine white dwarf masses.
Leveraging Gaia Satellite Data
The method takes advantage of data captured by the European Space Agency’s Gaia satellite, an ambitious mission to create a three-dimensional map of the Milky Way. Von Hippel, with recent Embry-Riddle graduate Adam Moss, current students Isabelle Kloc, Jimmy Sargent and Natalie Moticksa, and instructor Elliot Robinson, used highly precise Gaia measurements of the distance of stars.
Just as a car’s speedometer may appear to give two different readings from the driver’s perspective versus the passenger’s seat, celestial objects can appear to be in different locations, depending upon the viewer’s vantage point. The Gaia measurements, based on the geometry of two different lines of site or “parallaxes” to objects, helped Embry-Riddle researchers determine the radius of stars based on their brightness. They could then use existing information on the star’s mass-to-radius ratio – a calculation driven by the …