White dwarf stars are quite literally dying stars, they are the burned-out cinders which have exhausted the very hydrogen that sustained them and now scientists believe that by using a new type of measurement they can use those stars to determine the true age of the Milky Way.
A study published on Wednesday in the journal Nature, astronomer Jason Kalirai describes a new technique for measuring the mass and age of old stars based on their current white dwarf status.
According to Kalirai:
“If we want to assess when components of the Milky Way formed, we need the ages of the stars.”
The scientists research focuses on the halo portion of the Milky way, a section that is nearly 500,000 light-years in diameter around the bulge and disk of the galaxy. The halo is composed mostly of old stars which had given scientists a hard time in determining the precise age of the stars through the use of old fashioned measurements and temperature readings.
For his own tests Kalirai examined light from newly formed white dwarf stars in Messier 4 (a nearby cluster known to be 12.5 billion years old). He then used the spectra information about hydrogen from the Messier 4 stars to determines the stars’ masses since the age of a star is directly related to its mass.
According to the LA Times:
“The more massive a star, the more pressure at its core and the faster it burns through its hydrogen supply. Less massive stars burn more slowly.
Turning to four newly formed white dwarfs in the Milky Way’s halo, Kalirai found that they were more massive than newly formed white dwarfs in Messier 4. That allowed him to calculate that their progenitor stars were also heavier, which means the halo stars were younger — about 11.4 billion years old, give or take 700 million years.”
The new process for measuring white dwarfs to determine stellar ages has been around for more than a decade however better data collection techniques and more powerful telescopes have just now made the theory available for testing purposes. In this test Kalirai used data culled from the Keck Observatory in Hawaii and the European Southern Observatory in Chile.
Next up for Kalirai will be outer Halo measurements.