A team of astronomers have learned that one recently developed method for identifying the age of stars needs to be recalibrated, especially for stars older than the sun. With the recalibration, there would be new implications that the Earth's sun might be on the edge of a transition to a weaker magnetic field.
As stars age, their rotations slow down and by modelling this process, scientists can accurately predict or estimate the age of stars. Dubbed as gyrochronology, this method has been utilized for many years now.
Stars expel mass in the form of stellar wind and this reacts with the star's magnetic field, creating a brake system on its rotation. However, the researchers, led by astronomer Jennifer van Saders of the Carnegie Institution for Science, found that older stars actually do not slow down like younger stars. This change in deceleration is caused by a shift in the behavior of the aging magnetic field of the star.
The researchers recommend that the method of determining the age of stars should be recalibrated, taking into consideration how stars that are older than the sun spin.
Recalibration Of Gyrochronological Calculation
Stars rotate around an axis just like other planets and as they age, their spinning power slows down due to the magnetic field acting on its stellar wind. In a way, the magnetic field acts like a brake system.
When stars grow older, the computation of their age might change too. This is why the researchers urge that the recalibration of the gyrochronological calculation for stars is important.
"The ability to determine a star's age is important for improving our understanding of the life cycles of astronomical systems - for cataloging how the star and the objects near it have changed through history and for predicting how they might change in the future," van Saders said.
"Gyrochronology has the potential to be a very precise method for determining the ages of the average sun-like star, provided we can get the calibrations correct," she added.
How Can Astronimists Test Gyrochronology Calibrations For Older Stars?
Scientists used data from the Kepler space observatory to test the gyrochronology calibrations for older stars. They discovered that standard models predict more slowing down of magnetic fields as the stars grow older.
They conclude that the braking mechanism of the magnetic fields in moderately aged stars and older stars is weaker. If their findings are true, the Earth's sun may be close to a critical transition to a weakened braking power because of the changes in its magnetic field.
The study was published in the journal Nature.
Magnetic Fields Are Common In Stars, Not Rare As Previously Thought
Once thought as rare, magnetic fields are in fact common in stars, an international team of astronomers found. This new work sheds light on the understanding of how stars evolve and their ultimate fate.
A team of astronomers at the University of Sydney have discovered that strong magnetic fields are common in massive stars. Using data from NASA's Kepler Mission, they found that stars that are more massive than the sun actually contain internal magnetic fields up to 10 million times that of Earth.
The discovery might give insight on the evolution and fate of stars in space, including the Earth's sun.
"This is tremendously exciting, and totally unexpected," said astrophysicist Dennis Stello, lead researcher and an associate professor at the University of Sydney.
"Because only 50 percent of stars were previously thought to host strong magnetic fields, current models of how stars evolve lack magnetic fields as a fundamental ingredient. Such fields have simply been regarded insignificant for our general understanding of stellar evolution," he added.
The work was also based on a previous endeavor initiated by the Californian Institute of Technology. The discovery entails that measurements of stellar oscillations or sound waves inside stars could be utilized to determine the presence of magnetic fields in stars.
The research will help scientists test theories of how magnetic fields of stars form and evolve. This could potentially lead to a better general understanding of magnetic dynamos within stars, including the one controlling the sun's cycle.
