Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Starquakes reveal stellar secrets

15.08.2002


Looking into the interior of the Earth or the Sun is a bit similar to examining a baby in its mother`s womb using an ultrasound scan. Light cannot penetrate the area, so we make pictures in these cases using sound waves, which human ears cannot hear. With SOHO, ESA has probed deeply into the Sun using the sound-waves principle, and with great success. The future missions, Solar Orbiter and Eddington, will look inside our Sun and other stars, respectively, in a similar way.



Here on Earth, when scientists recorded slight shakes, or seisms, coming from earthquakes even on distant continents, they began to estimate the routes and the changing speeds of the waves passing through the Earth`s interior. This revealed our planet`s molten core. Nowadays, oil prospectors routinely thump the ground to get seismic echoes from deep-lying strata. Scientists combine earthquake records from seismometers worldwide, to make 3D pictures of the rocks far beneath our feet.

Seismology is the study of earthquake waves. Studying solar sound waves is called helioseismology, from helios, a Greek word for Sun. When you transfer your focus onto the stars, as Eddington will do, you are studying asteroseismology. Although the Sun and stars are made of very hot gas rather than rocks, basic principles about deducing the routes and speeds of internal waves still work.


Sound waves do not travel through space, but scientists can register their activities by subtle changes in the light of the Sun and the stars. The reverberating waves make the visible surface of the Sun rise and fall roughly every few minutes, and the motions affect the wavelength and brightness of the light. The simplest helioseismic telescopes observe the whole Sun oscillating. They detect sharply defined `notes` rather like a musical chord. From these, scientists can deduce the internal layers of the Sun with amazing precision, all the way down to its superheated core.

SOHO`s MDI instrument registers the waves at a million points across the visible surface. It has detected vast streams of hot gas flowing unseen beneath the surface. Most remarkably, MDI can look right through the Sun to observe stormy sunspot regions forming on the far side, which swing into view when the Sun rotates on its axis.

When the next generation of solar spacecraft looks more closely at selected parts of the Sun, helioseismologists are sure to make more sensational discoveries. For ESA`s Solar Orbiter, due for launch around 2012, key targets will be regions near the poles.

"Our special chance to detect sub-surface flows near the poles is one of the most exciting aspects of the Solar Orbiter mission," says Bernhard Fleck, ESA`s Project Scientist for SOHO and study scientist for the Solar Orbiter. "We think these hidden streams of gas have a strong influence on the Sun`s magnetic behaviour, and so can affect its storminess."

For astronomers, the Sun is a fairly typical middle-aged star seen in close-up. All the other stars are so far away that asteroseismologists can observe oscillations only of the whole star. However, as with the Sun, these can provide information never available before about the internal make-up of the stars. Much of what astronomers think they know about the Universe`s structure and evolution depends on their understanding of how stars work. Knowing a star`s age is an important part of this study.

Canadian, Danish, and French satellites will pioneer the field in the next few years, probing between them hundreds of stars. ESA`s Eddington spacecraft, due to fly in 2008, will therefore not be the first space mission to study asteroseismology. However, it will go much farther by examining as many as 50 000 stars, from the smallest to the largest, and from the oldest to the youngest, with an accuracy never seen before. For example, previously, if you wanted to state the age of a 100-million-year-old star, you would have to estimate in the range 80 to 120 million years. Eddington allows you to specify it to be almost exactly 104 million years old.

The sound waves in the Sun and the stars are pitched far too low for human beings to hear, but it is fairly simple to convert them to audible frequencies. To listen to the `Song of the Sun`, go the following site: http://soi.stanford.edu/results/sounds.html

Monica Talevi | alfa
Further information:
http://www.esa.int

More articles from Physics and Astronomy:

nachricht 'Growing' active sites on quantum dots for robust H2 photogeneration
08.07.2020 | Chinese Academy of Sciences Headquarters

nachricht On-chip spin-Hall nanograting for simultaneously detecting phase and polarization singularities
08.07.2020 | Light Publishing Center, Changchun Institute of Optics, Fine Mechanics And Physics, Chinese Academy

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: Excitation of robust materials

Kiel physics team observed extremely fast electronic changes in real time in a special material class

In physics, they are currently the subject of intensive research; in electronics, they could enable completely new functions. So-called topological materials...

Im Focus: Electrons in the fast lane

Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber from the Max Planck Institute for Polymer Research (MPI-P) in Mainz has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell. Clever alignment of these "electron highways" could make perovskite solar cells even more powerful.

Solar cells convert sunlight into electricity. During this process, the electrons of the material inside the cell absorb the energy of the light....

Im Focus: The lightest electromagnetic shielding material in the world

Empa researchers have succeeded in applying aerogels to microelectronics: Aerogels based on cellulose nanofibers can effectively shield electromagnetic radiation over a wide frequency range – and they are unrivalled in terms of weight.

Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic...

Im Focus: Gentle wall contact – the right scenario for a fusion power plant

Quasi-continuous power exhaust developed as a wall-friendly method on ASDEX Upgrade

A promising operating mode for the plasma of a future power plant has been developed at the ASDEX Upgrade fusion device at Max Planck Institute for Plasma...

Im Focus: ILA Goes Digital – Automation & Production Technology for Adaptable Aircraft Production

Live event – July 1, 2020 - 11:00 to 11:45 (CET)
"Automation in Aerospace Industry @ Fraunhofer IFAM"

The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM l Stade is presenting its forward-looking R&D portfolio for the first time at...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Contact Tracing Apps against COVID-19: German National Academy Leopoldina hosts international virtual panel discussion

07.07.2020 | Event News

International conference QuApps shows status quo of quantum technology

02.07.2020 | Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

 
Latest News

Shock-dissipating fractal cubes could forge high-tech armor

08.07.2020 | Materials Sciences

Scientists use nanoparticle-delivered gene therapy to inhibit blinding eye disease in rodents

08.07.2020 | Health and Medicine

'Growing' active sites on quantum dots for robust H2 photogeneration

08.07.2020 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>