Thursday, May 24 , 2018, 2:22 pm | Overcast 62º

 
 
 
 
Advice

UCSB Physicists and Colleagues Discover Magnetic Cores of Pulsating Stars

Jim Fuller, Matteo Cantiello and Lars Bildsten, researchers whose findings on stars’ magnetism appears in the journal ‘Nature.’
Jim Fuller, Matteo Cantiello and Lars Bildsten, researchers whose findings on stars’ magnetism appears in the journal ‘Nature.’ (Bill Wolf / UC Santa Barbara Current photo)

Using a recently developed technique to detect magnetic fields inside stars, a group of astronomers — including Matteo Cantiello and Lars Bildsten from UC Santa Barbara’s Kavli Institute for Theoretical Physics (KITP) — has discovered that strong magnetic fields are very common in stars. The group's findings appear in the journal Nature.

“We have applied a novel theoretical idea that we developed just a few months ago to thousands of stars and the results are just extraordinary,” said Cantiello, a specialist in stellar astrophysics at KITP.

Previously, only a very small percentage of stars were known to have strong magnetic fields. Therefore, current scientific models of how stars evolve do not include magnetic fields as a fundamental component.

“Such fields have simply been regarded as insignificant for our general understanding of stellar evolution,” said lead author Dennis Stello, an astrophysicist at the University of Sydney in Australia. “Our result clearly shows this assumption needs to be revisited because we found that up to 60 percent of stars host strong fields.”

Until now, astronomers have been unable to detect these magnetic fields because such fields hide deep in the stellar interior, out of sight from conventional observation methods that measure only the surface properties of stars.

The research team turned to asteroseismology, a technique that probes beyond the stellar surface, to determine the presence of very strong magnetic fields near the stellar core.

“The stellar core is the region where the star produces most of its energy through thermonuclear reactions,” Cantiello explained. “So the field is likely to have important effects on how stars evolve since it can alter the physical processes that take place in the core.”

Most stars — like the sun — are subject to continuous oscillations.

“Their interior is essentially ringing like a bell,” noted co-author Jim Fuller, a postdoctoral scholar from the California Institute of Technology in Pasadena. “And like a bell or a musical instrument, the sound produced reveals physical properties, such as size, temperature and what they are made of.”  

The researchers used very precise data from NASA’s Kepler space telescope to measure tiny brightness variations caused by the ringing sound inside thousands of stars. They found that certain oscillation frequencies were missing in 60 percent of the stars due to suppression by strong magnetic fields in the stellar cores.

“It’s like having a trumpet that doesn’t sound normal because something is hiding inside it, altering the sound it produces,” Stello said.   

This magnetic suppression effect had previously been seen in only a few dozen stars. However, the new analysis of the full data set from Kepler revealed that this effect is prevalent in stars that are only slightly more massive than the sun.

According to Cantiello, such intermediate mass stars are hotter and more luminous, and their cores are stirred by convection.

“We believe that the magnetic field is created by this ‘boiling’ sequence and stored inside the star for the remaining evolutionary phase. Astrophysicists previously have suggested this but it was very speculative; now it seems clear that this is the case,” he said.

“This is a very important result that will enable scientists to test more directly current theories for how magnetic fields form and evolve in stellar interiors,” said co-author Bildsten, the director of KITP. “When a star dies, the presence of strong magnetic fields can have a profound impact, possibly resulting in some of the brightest explosions in the universe.”

This research could potentially lead to a better general understanding of stellar magnetic dynamos, including the one controlling the sun’s 11-year sunspot cycle, which is known to affect communication systems and cloud cover on Earth.

“So far, the study of stellar magnetic dynamos principally relied on computer simulations, which now can be tested using these new exciting observations,” said Fuller. 

Julie Cohen writes for the UCSB Office of Public Affairs and Communications.

 

Support Noozhawk Today

You are an important ally in our mission to deliver clear, objective, high-quality professional news reporting for Santa Barbara, Goleta and the rest of Santa Barbara County. Join the Hawks Club today to help keep Noozhawk soaring.

We offer four membership levels: $5 a month, $10 a month, $25 a month or $1 a week. Payments can be made through PayPal below, or click here for information on recurring credit-card payments.

Thank you for your vital support.

Become a Supporter

Enter your email
Select your membership level
×

Payment Information

You are purchasing:

Payment Method

Pay by Credit Card:

Mastercard, Visa, American Express, Discover

Pay with Apple Pay or Google Pay:

Noozhawk partners with Stripe to provide secure invoicing and payments processing.

  • Ask
  • Vote
  • Investigate
  • Answer

Noozhawk Asks: What’s Your Question?

Welcome to Noozhawk Asks, a new feature in which you ask the questions, you help decide what Noozhawk investigates, and you work with us to find the answers.

Here’s how it works: You share your questions with us in the nearby box. In some cases, we may work with you to find the answers. In others, we may ask you to vote on your top choices to help us narrow the scope. And we’ll be regularly asking you for your feedback on a specific issue or topic.

We also expect to work together with the reader who asked the winning questions to find the answer together. Noozhawk’s objective is to come at questions from a place of curiosity and openness, and we believe a transparent collaboration is the key to achieve it.

The results of our investigation will be published here in this Noozhawk Asks section. Once or twice a month, we plan to do a review of what was asked and answered.

Thanks for asking!

Click Here to Get Started >

Reader Comments

Noozhawk is no longer accepting reader comments on our articles. Click here for the announcement. Readers are instead invited to submit letters to the editor by emailing them to [email protected]. Please provide your full name and community, as well as contact information for verification purposes only.

Daily Noozhawk

Subscribe to Noozhawk's A.M. Report, our free e-Bulletin sent out every day at 4:15 a.m. with Noozhawk's top stories, hand-picked by the editors.

Sign Up Now >