Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Stellar cartography

19.03.2019

The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.

A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes and interferometers.


Stellar environment of the star II Pegasi. Shown is the magnetic-field extrapolation out to 2.2 stellar radii. Magenta: negative polarity, green: positive polarity, closed loops are in white.

AIP

This technique, referred to as Doppler imaging or Doppler tomography, requires a high-resolution spectrograph, usually a large telescope, lots of observing time, and nifty analysis software.

Each atomic spectral line can be seen as a compressed one-dimensional “image” of the stellar surface, which, if the star rotates, becomes broadened by the Doppler-effect. If a star has spots on its surface, just like our Sun has sunspots, the Doppler-broadened spectral line profiles will be selectively deformed.

A time series of such spectral line profiles taken over a full stellar rotation can then be converted to a temperature (or brightness) image of the otherwise unresolved stellar surface, just like in medical brain tomography.

But PEPSI can go a major step further. Because its two polarimeters also feed polarized light to the spectrograph, PEPSI captures the otherwise hidden profile deformation due to the Zeeman-effect.

The Zeeman-effect is the splitting and polarization of spectral lines due to an external magnetic field. Combined with the rotational Doppler-effect it allows the reconstruction of the star’s surface magnetic field geometry. The cartography in polarized light is thus called Zeeman-Doppler-Imaging.

In a dedicated observing run with PEPSI attached to the effective 11.8m LBT a team of AIP astronomers was able to obtain a unique time series of polarized high-resolution spectra of the rotating star II Pegasi. “II Peg has a rotation period of 6.7 days and is thus manageable with the LBT in terms of the required observing time”, says the PEPSI Principal Investigator (PI) and author of the II Peg study Prof. Klaus Strassmeier from the Leibniz Institute for Astrophysics in Potsdam, Germany (AIP).

“And with seven clear nights we were very lucky as well”, adds the PEPSI project scientist Ilya Ilyin. The already complex polarized spectra were analyzed with the special inverse mapping code iMap developed at the AIP. Once applied, the surprise was big when warm and cool starspots were reconstructed from the PEPSI data and they appeared with opposite polarity.

“The warm features had positive polarity on II Peg while most of the cool features had negative or mixed polarity”, says iMap-PI Thorsten Carroll. The spot distribution on II Peg has no direct analogy on the Sun. The individual spots found on this star are huge compared to the Sun, about thousand times larger than sunspots.

“We explain the co-existing warm spots of II Peg due to heating by a shock front caused by the plasma flow between regions of different polarities”, concludes Strassmeier. "Both as a spectrograph and as a spectropolarimeter, PEPSI is unique in today's worldwide suite of astronomical instruments and will make significant contributions to stellar physics", adds Christian Veillet, LBT Observatory's Director.

"The need to characterize the stars hosting exoplanets, as well as the planets themselves through transit observations, should also make PEPSI a sought-after instrument to the members of the LBT community.”

Wissenschaftliche Ansprechpartner:

Prof. Dr. Klaus G. Strassmeier, 0331-7499-223, kstrassmeier@aip.de
Dr. Thorsten Carroll, 0331-7499-207, tcarroll@aip.de
Dr. Ilya Ilyin, 0331-7499-269, ilyin@aip.de
Dr. Christian Veillet (LBT Observatory), +1 (520) 621-5286, cveillet@lbto.org

Originalpublikation:

K. G. Strassmeier, T. A. Carroll, & I. V. Ilyin, Warm and cool starspots with opposite polarities. A high- resolution Zeeman-Doppler-Imaging study of II Pegasi with PEPSI, A&A, in press; arXiv:190211201S

Weitere Informationen:

http://bit.ly/Stellar_Cartography
https://pepsi.aip.de
http://www.lbto.org
http://bit.ly/PEPSI_Movies

Dr. Janine Fohlmeister | idw - Informationsdienst Wissenschaft
Further information:
http://www.aip.de

More articles from Physics and Astronomy:

nachricht Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun
18.04.2019 | University of Warwick

nachricht In vivo super-resolution photoacoustic computed tomography by localization of single dyed droplets
18.04.2019 | Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences

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: Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

A stellar flare 10 times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter

  • Coolest and smallest star to produce a superflare found
  • Star is a tenth of the radius of our Sun
  • Researchers led by University of Warwick could only see...

Im Focus: Quantum simulation more stable than expected

A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.

Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...

Im Focus: Largest, fastest array of microscopic 'traffic cops' for optical communications

The technology could revolutionize how information travels through data centers and artificial intelligence networks

Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...

Im Focus: A long-distance relationship in femtoseconds

Physicists observe how electron-hole pairs drift apart at ultrafast speed, but still remain strongly bound.

Modern electronics relies on ultrafast charge motion on ever shorter length scales. Physicists from Regensburg and Gothenburg have now succeeded in resolving a...

Im Focus: Researchers 3D print metamaterials with novel optical properties

Engineers create novel optical devices, including a moth eye-inspired omnidirectional microwave antenna

A team of engineers at Tufts University has developed a series of 3D printed metamaterials with unique microwave or optical properties that go beyond what is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

Fraunhofer FHR at the IEEE Radar Conference 2019 in Boston, USA

09.04.2019 | Event News

 
Latest News

New automated biological-sample analysis systems to accelerate disease detection

18.04.2019 | Life Sciences

Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

18.04.2019 | Physics and Astronomy

New eDNA technology used to quickly assess coral reefs

18.04.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>