Absence of Stellar Pulsations Baffles Astronomers

August 23, 2004

Readings done by a Canadian-Austrian team present a puzzle for astronomers. Expected surface phenomena, which provide information about stellar structures, could not be evidenced from readings obtained by means of a Canadian microsatellite. The precise satellite readings leave no doubt on the data published in NATURE. The project, organised in co-operation with the Institute of Astronomy at the University of Vienna and supported by the Austrian Science Fund (FWF), challenges the existing understanding of the structure of stars.

The phenomenon of pressure-driven oscillations at the surface of the sun has been known for more than 25 years. Astronomers use these pulsations to gain knowledge on the structure of the sun. Prof. Werner W. Weiss and his team from the Institute for Astronomy at the University of Vienna together with a Canadian team could for the first time conduct such observations on another star using a Canadian microsatellite. But contrary to all findings of terrestrial studies and previous calculations, there is no evidence for the surface pulsations.

"Good Vibrations" of the Stars
Prof. Weiss illustrates the astronomers’ interest in the surface pulsations thus: "It sounds paradoxical, but the surface pulsations provide us with knowledge of stellar structures. Just as seismology explores the interior of the earth by measuring quakes, the new discipline known as asteroseismology analyses the surface pulsations of stars to study their structures." One uses oscillations caused by these pulsations that move to the stellar core, where they are reflected and thrown back to the surface. The oscillations vary according to the nature of the surroundings and are measurable, thus providing indirect information about the interior of a star.

However, the surface pulsations cannot be directly measured. So the asteroseismologists measure the slight variations in the light intensity caused by these pulsations. The newest tool to be employed in this study is the Canadian microsatellite known as MOST (Microvariability and Oscillations of Stars) that is managed by Prof. Jaymie Matthews at the University of British Columbia, Canada. The satellite is situated 820 km above the earth and measures the light intensity of remote stars.

"The earth’s atmosphere is really cumbersome for measuring light. It works like a filter. MOST avoids this problem with a telescope that penetrates deep into space. Thus with a telescope of aperture 15 cm, we can achieve a higher precision in observation of a bright star than with an eight-metre telescope from earth," explains Prof. Weiss. The precision of the satellite telescope was actually confirmed by control surveys, which data was also received by a Viennese earth station, financed by the Austrian Space Agency and developed by the Vienna University of Technology.

Contradictory Findings = New Questions
The MOST's first object for readings was Procyon, a star that lies in the constellation of Orion when viewed from the earth. Seven independent readings from the earth as well as theoretical calculations anticipated a minimum of 0.002% of oscillations of light intensity caused by pulsations, which was not a problem for MOST that can read oscillations up to 0.0003%. For all the precision, no significant surface oscillations could be determined for Procyon.

Prof. Weiss states: "This finding has interesting consequences for astronomy. It is possible that other gaseous movements, created by temperature differences at the surface of the star, cause an interfering signal that is superimposed on our readings. Then our data will be exceptionally valuable for future readings. It can also be that we must review our model calculations."

Astronomers would then be required to critically question the current knowledge about the inner structure of stars. The fact that even a budding specialist discipline such as asteroseismology challenges the foundation of a scientific area is a significant point for FWF. For it assuredly advances its adherence to creativity, quality and innovation as the most important criteria for funding.

Source: PUBLIC RELATIONS FÜR RESEARCH AND DEVELOPMENT

Explore further: Pulsations detected in a hot, helium-atmosphere white dwarf

Related Stories

Pulsations detected in a hot, helium-atmosphere white dwarf

December 30, 2016

(Phys.org)—Astronomers have recently discovered non-radial oscillations in a hot, helium-atmosphere white dwarf designated PG 0112+104. The newly detected 11 independent pulsation modes in this white dwarf could be essential ...

The mystery of the pulsating blue stars

August 9, 2017

In the middle of the large Chilean Atacama desert, a team of Polish astronomers are patiently monitoring millions of celestial bodies night after night with the help of a modern robotic telescope. In 2013, the team was surprised ...

Allo, allo? A star is ringing

December 21, 2005

Astronomers have used ESO's Very Large Telescope in Chile and the Anglo-Australian Telescope in eastern Australia as a 'stellar stethoscope' to listen to the internal rumblings of a nearby star. The data collected with the ...

Pulsating star sheds light on exoplanet

July 29, 2013

A team of researchers has devised a way to measure the internal properties of stars—a method that offers more accurate assessments of their orbiting planets.

Recommended for you

AI and 5G in focus at top mobile fair

February 24, 2018

Phone makers will seek to entice new buyers with better cameras and bigger screens at the world's biggest mobile fair starting Monday in Spain after a year of flat smartphone sales.

Archaeologists find ancient necropolis in Egypt

February 24, 2018

Egypt's Antiquities Ministry announced on Saturday the discovery of an ancient necropolis near the Nile Valley city of Minya, south of Cairo, the latest discovery in an area known to house ancient catacombs from the Pharaonic ...

Walking crystals may lead to new field of crystal robotics

February 23, 2018

Researchers have demonstrated that tiny micrometer-sized crystals—just barely visible to the human eye—can "walk" inchworm-style across the slide of a microscope. Other crystals are capable of different modes of locomotion ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.