Space
High Magnetism Found In Stars' Cores, According To Astronomers
Rosanna Singh
First Posted: Oct 23, 2015 12:14 PM EDT
For the first time, astronomers have fully examined the mysterious inside of stars, only to discover that they are highly magnetized, according to a news release.
"In the same way medical ultrasound uses sound waves to image the interior of the human body, asteroseismology uses sound waves generated by turbulence on the surface of stars to probe their inner properties," said Jim Fuller, a Caltech postdoctoral researcher, who co-led the study.
The scientists used a technique called asteroseismology to calculate the magnetic field strengths in the fusion-powered hearts of dozens of red giants, which are stars that are further evolved versions of our sun. Asteroseismology enables astronomers to study the internal structure of pulsating stars by the interpretation of their frequencies.
This new finding will enable astronomers to fully understand the mechanisms behind the life and death of stars, the magnetic fields that determine the rotation rate of stars, and how stars evolve. Up until now, astronomers have studied the magnetic fields of stars' surfaces and they have used supercomputer models to simulate the fields near the cores, where the nuclear-fusion process takes place, according to the researchers.
"We still don't know what the center of our own sun looks like," Fuller said.
Red giants' physical make-up is different from other main sequence stars like the Sun, which make them ideal for asteroseismology. The core of the red giants is denser than younger stars. However the sound waves do not reflect off the cores, as they do in stars like the Sun. The sound waves are transformed into another category of waves known as gravity waves, according to the researchers.
"It turns out the gravity waves that we see in the red giants do propagate all the way to the center of these stars," said Matteo Cantiello, co-lead author of the study and stellar astrophysics specialist from UC Santa Barbara's Kavli Institute for Theoretical Physics (KITP).
"Depending on their size and internal structure, stars oscillate in different patterns," Fuller said.
In the oscillation pattern (the dipole mode), one hemisphere of the star becomes brighter while the other hemisphere becomes dimmer. Astronomers observed these oscillations in a star by measuring how its light varies over time, according to the news release.
Strong magnetic fields in a star's core can cause filed disruptions of the gravity waves, which causes some of the waves to lose energy and become trapped in the core. The researchers created the term "magnetic greenhouse effect" to describe this process, since it is similar to the greenhouse effect, where atmospheric gases trap heat from the Sun.
The trapped gravity waves inside a red giant causes some of the energy of the star's oscillation to be lost, and the outcome is smaller than the dipole mode, according to the researchers.
In 2013, NASA's Kepler space telescope detected the dipole-mode dimming in several red giants. They found that the internal magnetic fields of the red giants were 10 million times stronger than the earth's magnetic field.
By studying the interior magnetic fields of stars, researchers can develop a better understanding about the origin of powerful magnetic fields on the surfaces of some neutron stars and white dwarfs, which are two categories of stellar corpses that form when stars die.
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First Posted: Oct 23, 2015 12:14 PM EDT
For the first time, astronomers have fully examined the mysterious inside of stars, only to discover that they are highly magnetized, according to a news release.
"In the same way medical ultrasound uses sound waves to image the interior of the human body, asteroseismology uses sound waves generated by turbulence on the surface of stars to probe their inner properties," said Jim Fuller, a Caltech postdoctoral researcher, who co-led the study.
The scientists used a technique called asteroseismology to calculate the magnetic field strengths in the fusion-powered hearts of dozens of red giants, which are stars that are further evolved versions of our sun. Asteroseismology enables astronomers to study the internal structure of pulsating stars by the interpretation of their frequencies.
This new finding will enable astronomers to fully understand the mechanisms behind the life and death of stars, the magnetic fields that determine the rotation rate of stars, and how stars evolve. Up until now, astronomers have studied the magnetic fields of stars' surfaces and they have used supercomputer models to simulate the fields near the cores, where the nuclear-fusion process takes place, according to the researchers.
"We still don't know what the center of our own sun looks like," Fuller said.
Red giants' physical make-up is different from other main sequence stars like the Sun, which make them ideal for asteroseismology. The core of the red giants is denser than younger stars. However the sound waves do not reflect off the cores, as they do in stars like the Sun. The sound waves are transformed into another category of waves known as gravity waves, according to the researchers.
"It turns out the gravity waves that we see in the red giants do propagate all the way to the center of these stars," said Matteo Cantiello, co-lead author of the study and stellar astrophysics specialist from UC Santa Barbara's Kavli Institute for Theoretical Physics (KITP).
"Depending on their size and internal structure, stars oscillate in different patterns," Fuller said.
In the oscillation pattern (the dipole mode), one hemisphere of the star becomes brighter while the other hemisphere becomes dimmer. Astronomers observed these oscillations in a star by measuring how its light varies over time, according to the news release.
Strong magnetic fields in a star's core can cause filed disruptions of the gravity waves, which causes some of the waves to lose energy and become trapped in the core. The researchers created the term "magnetic greenhouse effect" to describe this process, since it is similar to the greenhouse effect, where atmospheric gases trap heat from the Sun.
The trapped gravity waves inside a red giant causes some of the energy of the star's oscillation to be lost, and the outcome is smaller than the dipole mode, according to the researchers.
In 2013, NASA's Kepler space telescope detected the dipole-mode dimming in several red giants. They found that the internal magnetic fields of the red giants were 10 million times stronger than the earth's magnetic field.
By studying the interior magnetic fields of stars, researchers can develop a better understanding about the origin of powerful magnetic fields on the surfaces of some neutron stars and white dwarfs, which are two categories of stellar corpses that form when stars die.
Related Articles
Hubble Spots Big Bang Frontiers: 250 New Galaxies Discovered
A Black Hole Shreds Star Into Pieces
For more great science stories and general news, please visit our sister site, Headlines and Global News (HNGN).
See Now: NASA's Juno Spacecraft's Rendezvous With Jupiter's Mammoth Cyclone