Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Coronal activity may be ’buried alive’ in red giant stars, say Colorado researchers

08.01.2003


When Earth’s sun expands into a red giant star in roughly five billion years, long after Earth has become uninhabitable, the hydrogen core will be burned out and the bloated outer shell will be cool and murky.



But according to new research by the University of Colorado at Boulder, such red giants still retain surface magnetic storms and coronas -- the very hot and patchy outer atmosphere of the sun and sun-like stars -- at temperatures of millions of degrees Fahrenheit that often signal stellar youth.

The red giant coronal regions, however, appear to be submerged in the extended outer shell known as the chromosphere, "buried alive" in these red giants.


Low-mass stars like the sun begin their lives as fast-spinning dwarfs exhibiting high levels of magnetic activity including giant solar flares that could affect early life on planets like Earth, said Professor Tom Ayres of the astrophysical and planetary sciences department. As sun-like stars age and ultimately expand into red giants, the rotation slows or even stops, he said.

"Rotation is thought to be a key ingredient in the coronal magnetic activity," said Ayres. "Once the rotation halts, the surface magnetic storms should cease."

In 1990, scientists proposed these red giant stars were a coronal graveyard, said Ayres. "But new evidence, surprisingly, indicates that there probably still is coronal activity buried beneath the murky atmospheres of these dying stars."

The submerged violent activity may be tied to the remarkable winds that blow off red giant stars, said Ayres. "These mysterious winds travel at a mind-boggling 100,000 miles per hour and are so strong they literally blow away much of the stellar ’outer envelope’ during the terminal phases of the star’s life."

The team imaged two bright stars, Arcturus and Aldebaran, thought to have been very sun-like until their evolution into red giants millions of years ago. They used NASA’s powerful Chandra X-Ray Orbiting Observatory, ultraviolet instruments on the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer, or FUSE.

"We indirectly detected the presence of hot coronal gas through UV emissions of highly charged carbon and oxygen detected by FUSE," he said. "Apparently magnetic storms still occur on the surfaces of red giants but do not rise very high into the thick chromosphere of warm gas – about 10,000 F -- that surrounds the cooler layers that measure about 5,000 F."

Ayres said the chromosphere is opaque to X-rays but is more transparent in the UV, allowing the hot emissions from the surface magnetic storms to escape. "With only the X-ray view, we might have thought the magnetic activity in the "coronal graveyard had entirely faded away," he said. "Now, the UV perspective has revealed that the activity is merely ’buried alive’ and that we will have to dig deeper to fully understand the inner workings of these dying stars."


A paper on the subject by Ayres, Alexander Brown and Graham Harper, all research associates at CU-Boulder’s Center for Astrophysics and Space Astronomy, or CASA, was presented at the 201st annual meeting of the American Astronomical Society held in Seattle Jan. 6 to Jan. 12.

The data were obtained from NASA’s Chandra X-Ray Observatory and several other instruments, including FUSE -- which was partly assembled and built at CU-Boulder’s CASA -- and the Hubble Space Telescope. The work was supported by in part by grants from the Smithsonian Astronomical Observatory, the Space Telescope Science Institute in Baltimore and NASA.

Additional Contact:
Jim Scott, (303) 492-3114

Tom Ayres | EurekAlert!
Further information:
http://www.colorado.edu/

More articles from Physics and Astronomy:

nachricht First evidence on the source of extragalactic particles
13.07.2018 | Technische Universität München

nachricht Simpler interferometer can fine tune even the quickest pulses of light
12.07.2018 | University of Rochester

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Research finds new molecular structures in boron-based nanoclusters

13.07.2018 | Materials Sciences

Algae Have Land Genes

13.07.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>