Astronomy & Astrophysics is publishing the first detection of a magnetic field on the star Vega, one of the brightest stars in the sky. Using the high-sensitivity NARVAL spectropolarimeter installed at the Bernard-Lyot telescope (Pic du Midi Observatory, France), a team of astronomers  detected the effect of a magnetic field (known as the Zeeman effect) in the light emitted by Vega.
Vega is a famous star among amateur and professional astronomers. Located at only 25 light years from Earth in the Lyra constellation, it is the fifth brightest star in the sky. It has been used as a reference star for brightness comparisons. Vega is twice as massive as the Sun and has only one tenth its age. Because it is both bright and nearby, Vega has been often studied but it is still revealing new aspects when it is observed with more powerful instruments. Vega rotates in less than a day, while the Sun's rotation period is 27 days. The intense centrifugal force induced by this rapid rotation flattens its poles and generates temperature variations of more than 1000 degrees Celsius between the polar (warmer) and the equatorial regions of its surface. Vega is also surrounded by a disk of dust, in which the inhomogeneities suggest the presence of planets.
This time, astronomers analyzed the polarization of light emitted by Vega  and detected a weak magnetic field at its surface. This is really not a big surprise because one knows that the charged particle motions inside stars can generate magnetic fields, and this is how solar and terrestrial magnetic fields are produced. However, for more massive stars than the Sun, such as Vega, theoretical models cannot predict the intensity and the structure of the magnetic field, so that astronomers had no clue to the strength of the signal they were looking for. After many unsuccessful attempts in past decades, both the high sensitivity of NARVAL and the full dedication of an observing campaign to Vega have made this first detection possible.
The strength of Vega magnetic field is about 50 micro-tesla, which is close to that of the mean field on Earth and on the Sun. This first observational constraint opens the way to in-depth theoretical studies about the origin of magnetic fields in massive stars. This detection also suggests that magnetic fields exist but have not been detected yet on many stars like Vega, but farther and more difficult to observe. Astronomers believe that this discovery will be a key step in understanding stellar magnetic fields and their influence on stellar evolution. As for Vega, it is now the prototype of a new class of magnetic stars and will definitely continue fascinating astronomers for years.
 The team includes F. Lignières, P. Petit, T. Böhm, and M. Aurière (Laboratoire d'Astrophysique de Toulouse-Tarbes, CNRS/Université de Toulouse, France).
 Radiation is not only characterized by its wavelength and its intensity, but also by its polarization state. The polarization state of waves, including light waves, describes the orientation of their vibrations. A light wave can either be non-polarized, linearly or circularly polarized depending on the orientation of the electric field as the wave travels. In particular, the polarization state of radiation gives information about the presence of a magnetic field in the medium where the radiation was emitted. Hence, polarization data allow astronomers to study stellar magnetic fields.
First evidence of a magnetic field on Vega. Towards a new class of magnetic A-type stars, by F. Lignières, P. Petit, T. Böhm, and M. Aurière.To be published in Astronomy & Astrophysics, 2009, vol. 500-3
New quantum liquid crystals may play role in future of computers
21.04.2017 | California Institute of Technology
Light rays from a supernova bent by the curvature of space-time around a galaxy
21.04.2017 | Stockholm University
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...
Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.
A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
21.04.2017 | Physics and Astronomy
21.04.2017 | Health and Medicine
21.04.2017 | Physics and Astronomy