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 Graphene and quantum dots put in motion a CMOS-integrated camera that can see the invisible
30.05.2017 | ICFO-The Institute of Photonic Sciences

nachricht New Method of Characterizing Graphene
30.05.2017 | Universität Basel

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: New Method of Characterizing Graphene

Scientists have developed a new method of characterizing graphene’s properties without applying disruptive electrical contacts, allowing them to investigate both the resistance and quantum capacitance of graphene and other two-dimensional materials. Researchers from the Swiss Nanoscience Institute and the University of Basel’s Department of Physics reported their findings in the journal Physical Review Applied.

Graphene consists of a single layer of carbon atoms. It is transparent, harder than diamond and stronger than steel, yet flexible, and a significantly better...

Im Focus: Strathclyde-led research develops world's highest gain high-power laser amplifier

The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.

The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

3D printer inks from the woods

30.05.2017 | Life Sciences

How circadian clocks communicate with each other

30.05.2017 | Life Sciences

Graphene and quantum dots put in motion a CMOS-integrated camera that can see the invisible

30.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>