New technique more precisely determines the ages of stars

January 10, 2019, Embry-Riddle Aeronautical University
Embry-Riddle researchers used data captured by the Gaia satellite (shown here in an artist's impression) to determine the ages of stars. Credit: European Space Agency - D. Ducros, 2013

How old are each of the stars in our roughly 13-billion-year-old galaxy? A new technique for understanding the star-forming history of the Milky Way in unprecedented detail makes it possible to determine the ages of stars at least two times more precisely than conventional methods, Embry-Riddle Aeronautical University researchers reported Jan. 10 at the American Astronomical Society (AAS) meeting.

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, explained Embry-Riddle Physics and Astronomy Professor Dr. Ted von Hippel. 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 said.

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.

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, 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 physical behavior of electrons—to fill in the last ingredient for determining the age of the star, its mass.

Finally, by figuring out the abundance of different elements within the star, or its metallicity, researchers can further refine the age of the object, Moss and Kloc reported in two separate AAS poster presentations. Moss focused on pairs of stars with one white dwarf and one main sequence star similar to our Sun, while Kloc's research looked at two white dwarf stars in the same binary system.

"The next level of study will be to determine as many of the elements in the periodic table as possible for the main sequence star within these pairs," von Hippel said. "That would tell us more about Galactic chemical evolution, based on how different elements built up over time as formed in our galaxy, the Milky Way."

Though he emphasized that the current work remains preliminary, the team ultimately hopes to publish the ages of all within the Gaia dataset: "That could allow researchers to significantly advance our understanding of star-formation within the Milky Way."

Within the field of archaeology, von Hippel noted, carbon-dating methods made it possible to determine the age of structures, fossils, Stone Age sites and much more, thereby providing deeper insights into the evolution of life on Earth. "For today's astronomers, without knowing the age of different components of our galaxy, we don't have context. We've had techniques for dating celestial objects, but not precisely."

Explore further: White dwarf-main sequence binary identified in the open cluster NGC 752

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FredJose
1 / 5 (5) Jan 11, 2019
The old, old problem will still persist: how to get the first stars to "form" all by themselves whilst there is no known way to go past the Jeans Mass Limit naturalistically, other than using dark matter in simulation? Right now the as yet undetected and characterized dark matter has unknown physical properties and hence making up assigned magical properties that enable star-formation is clutching at straws.
rrwillsj
not rated yet Jan 11, 2019
there you go again freddymyboy. telling god what to do & how to do it correctly by your dictates.

instead of humbly appreciating the deities efforts & simply accepting that it is beyond your comprehension.

That you are refusing to accept the reality that you are a mundane dullard.

Whose prideful egotism disdains the wisdom of those anointed to bring knowledge to the ignorant.

i am a materialist atheist but even i can see the sin & folly of hubris in your demands!

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