60 stars of the so-called Delta Scuti type - like this one called beta Pictoriser - have been analyzed in depth by  an international research team involving DTU Space. (Illustration: ESO)

Scientists measure complex vibration patterns in young stars

Wednesday 13 May 20

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Victoria Laura Antoci
Senior researcher
DTU Space

An international cooperation

The article in Nature is a the result of an international cooperation involving DTU Space at the Technical University of Denmark and the Stellar Astrophysics Centre (SAC) at the University of Aarhus. The cooperation comprises 35 co-authors representing 24 research institutions in 10 countries. SAC is part of an international network researching stars. The work is based on observation from NASA's TESS-mission, where DTU Space contributes with both scientific research and technology.

 

Researchers from DTU have contributed to an international study that have been able to detect and map elusive pulsation patterns for 60 young, large stars that up until now have been difficult to study. The results have been published in the journal Nature.

By using observations from the NASA spacecraft TESS, an international research group involving researchers from DTU Space and the University of Aarhus's Stellar Astrophysics Center has been able to detect and map elusive pulsation patterns for 60 stars, called Delta Scuti stars, that up until now have been difficult to study. 

This discovery will revolutionize scientists’ ability to study details like age, size and composition of this type of stars - all members of a class named after the bright star Delta Scuti. 
It is for the first time that such systematic patterns could be identified in a significant number of stars. These results have now been published in the reputed scientific journal Nature.
 
"These new results are both amazing and important, we can now finally see the forest for the trees and perform detailed analyses of these stars and study aspects that have eluded us for the past 120 years, since the prototype has been discovered. We will be able to characterize the interiors of these stars in detail, and study the mechanism sustaining these pulsations precisely,” says astrophycisist and senior researcher at DTU Space, Victoria Antoci , who is a co-author of the article published in Nature.

The 60 stars belong to a class of variable stars named after Delta Scuti, a star visible to the human eye in the southern constellation Scutum that was first identified as variable in 1900. Since then, astronomers have identified thousands more like Delta Scuti.

"These new results are both amazing and important"
Victoria Antoci, senior researcher at DTU Space

Younger than the sun, but larger

Delta Scuti stars, in general, have a mass that is 1.5-2 times larger than that of the sun and are thought to be younger than approximately 1.5-2 billion years.

However the sample of 60 stars observed here are all younger than roughly 500 million year, many of them less than 200 years – in comparison the Sun is 4.6 billion years old.

On average, they rotate around their axis about 1-2 times a day, which is 30-60 times faster than the sun, making it difficult to decipher their patterns of pulsation, which are key to more knowledge of the star.
 
“Delta Scuti stars clearly pulsate in interesting ways, but the patterns of those pulsations have so far defied understanding,” says lead author of the article in Nature, professor Tim Bedding at the University of Sydney who cooperates with the Stellar Astrophysics Center in Aarhus University.

“To use a musical analogy, many stars pulsate along simple chords, but Delta Scuti stars are complex, with notes that seem to be jumbled. TESS has shown us that’s not true for all of them.”
 
Delta Scuti stars have been frustrating targets for scientists because of their complicated oscillations. Being able to find simple patterns and identify the modes of oscillation is game changing.

Now the scientists have a regular series of pulsations for these stars that can be compared with models, resulting in a precise age determination that is otherwise difficult to obtain. It will allow them to measure these stars much more efficiently using asteroseismology, in principle the same way as seismologists study the Earth by analyzing movements on its surface to gain knowledge about its interior.

Understanding the astrophysical phenomena oparating in Delta Scuti stars might even provide new insights into how the Sun works and why it is a relatively stable and calm star.

Comprehensive DTU Space involvement

The discoveries were made using data from TESS, a NASA Astrophysics Explorer mission launched 2018 and led and operated by MIT and managed by NASA's Goddard Space Flight Center.

DTU Space is also involved in the TESS-mission, having provided the star tracker system that is being used for navigation of the spacecraft and being part of the TESS Science Team that primarily are working on discovering and characterizing thousands of exoplanets around nearby bright stars.

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