A new technique for understanding the star-forming history of the Milky Way is unprecedented detail has now made it possible to determine the ages of stars at least two times more precisely.
The study was presented by the Embry-Riddle Aeronautical University at the January 10 meeting of the American Astronomical Society (AAS) meeting.
According to Embry-Riddle Physics and Astronomy Professor Dr. Ted von Hippel, current star-dating techniques, based on assessments of stars in the prime or main sequence of their lives that have begun to die after exhausting their hydrogen, offer a 20-percent, or at best a 10-percent margin of error. Embry-Riddle’s approach, leveraging burnt-out remnants called white dwarf stars, reduces the margin of error to 5 percent or even 3 percent, he added.
Dr. Ted von Hippel went on to say that for the method to work, his team must measure the star’s surface temperature, whether it has a hydrogen or helium atmosphere, and it’s mass.
Dr. von Hippel said, “The star’s mass matters because objects with greater mass have more energy and take longer to cool,” adding, “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.”
Now, astronomers have a new method to determine white dwarf masses and takes advantage of data captured by the European Space Agency’s Gaia satellite.
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.
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 physical behaviour of electrons – to fill in the last ingredient for determining the age of the star, its mass.
By figuring out the abundance of different elements within the star, or its metallicity, researchers can now further refine the age of the object, Moss and Kloc reported in two separate AAS poster presentations.