Research Highlights

Solar cycle 25 has begun

Since December 2019, solar activity has been on the up. This is consistent with predictions, to which MPS researchers contributed.

September 15, 2020

In the past one and a half years, the Sun has been rather dull: hardly a sunspot covered its surface, hardly a solar flare hurled radiation and particles into space. As observational data now show, for the last nine months solar activity has been slowly picking up again. Already in December 2019, our star passed its activity minimum, an event which occurs approximately every eleven years. This confirms predictions made by the Solar Cycle 25 Prediction Panel, an international panel of experts organized by NASA and NOAA (National Oceanic and Atmospheric Administration), in March last year. The panel, whose members include Dr. Robert Cameron from the Max Planck Institute for Solar System Research (MPS) in Germany, expects the Sun to be as tame in the now beginning solar cycle 25 as it has been in the previous eleven years.
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Gigantic, red and full of spots

About eight percent of red giants are covered by sunspot-like, dark areas. These stars rotate faster than others of their kind.

July 13, 2020

Starspots are more common among red giant stars than previously thought. In the journal Astronomy & Astrophysics, researchers led by the Max Planck Institute for Solar System Research (MPS) in Germany report that approximately eight percent of red giants exhibit such spots. They are the expression of strong magnetic fields at the stellar surface. These magnetic fields are created deep inside the star in a process that requires, among other things, convection and a fast rotation of the star. Although red giants are generally regarded as slowly rotating stars, those with starspots are apparently an exception. The new publication offers a comprehensive analysis of the reasons for their short rotation periods ranging from forced synchronization with another, closely neighboring star, to the swallowing of a star or planet, to a fast initial rotation speed in an early phase of development.
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Mystery of solar cycle illuminated

In the convection zone of the star, the plasma currents make a huge turnover that lasts about 22 year.

June 25, 2020

Solar activity fluctuates in a rhythm of about eleven years, which is reflected among other things in the frequency of sunspots. A complete magnetic period lasts 22 years. Scientists have long been puzzling over what causes this cycle. It must be related to the conditions beneath the "skin" of our star: A layer of hot plasma - electrically-conductive gas - extends from the surface to 200,000 kilometers below. The plasma within this convection zone is constantly in motion. A team of scientists from the Max Planck Institute for Solar System Research, the University of Göttingen and New York University Abu Dhabi has now succeeded in drawing the most comprehensive picture of the plasma flows in nort-south-direction to date. The researchers have found a remarkably simple flow geometry: the plasma describes a single turnover in each solar hemisphere, which lasts for about 22 years. In addition, the flow in the direction of the equator at the bottom of the convection zone causes spots to form closer and closer to the equator during the solar cycle.
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A faint resemblance of Sun and Earth

The star Kepler-160 and its companion KOI-456.04 are more reminiscent of the Sun-Earth system than any previously known exoplanet-star pair

June 04, 2020

The star Kepler-160 is probably orbited by a planet less than twice the size of the Earth with a star-planet distance that could permit planetary surface temperatures conducive to life. The newly discovered exoplanet, which was found by a team of scientists led by the Max Planck Institute for Solar System Research (MPS) in Göttingen is more than just another potentially habitable world. One of the key properties making it resemble the Sun-Earth system more than any other previously known world, is its Sun-like host star. Most of the Earth-like exoplanets known so far are in orbit around a faint red dwarf star emitting their energy mostly as infrared radiation rather than as visible light. The light shed on KOI-456.04 by its Sun-like host star, however, is very much like the daylight seen on our home planet. Moreover, the orbital period of KOI-456.04 around its Sun-like star is almost identical to an Earth year.
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Older Press Releases

18 Earth-sized exoplanets discovered,May 2019
ERC synergy grant for solar physics at the MPS, October 2018
New External Scientific Member at the MPS, September 2018
A new twist on stellar rotation, September 2018
Giant swirls on the Sun, May 2018
Otto Hahn Medal for Jan Langfellner, June 2017
Finding new Earths: PLATO spacecraft to be built, June 2017
New Max Planck Fellow appointed at the MPS, April 2017
Full Braking at Alpha-Centauri, February 2017
Distant star is roundest object ever observed in nature, November 2016
Slow appearance of sunspots challenges theory, July 2016
Eavesdropping on Aliens, March 2016
Giant hurricanes on the Sun, August 2014
Stellar inventory: Searching for other Earths, February 2014
Interior rotation of a distant star revealed, July 2013
Unexpectedly slow motions below the Sun's surface, July 2012


Selected Old Research Highlights

Giant swirls on the Sun

Waves similar to those controlling weather on Earth have now been found on the Sun.

May 7, 2018

Solar Rossby waves are waves of vorticity that move in the direction opposite to rotation. They have maximum amplitudes in the Sun’s equatorial regions.

A team of scientists led by the Max Planck Institute for Solar System Research (MPS) and the University of Göttingen has discovered new waves of vorticity on the Sun. As described in today’s issue of Nature Astronomy, these Rossby waves propagate in the direction opposite to rotation, have lifetimes of several months, and maximum amplitudes at the Sun’s equator. For forty years scientists had speculated about the existence of such waves on the Sun, which should be present in every rotating fluid system. Now, they have been unambiguously detected and characterized for the first time. The solar Rossby waves are close relatives of the Rossby waves known to occur in the Earth’s atmosphere and oceans.

A new twist on stellar rotation

Researchers have observed a twist in the rotational patterns of distant stars, which may explain the presence of starspots on their surface.

September 20, 2018

Sun-like stars rotate differentially, with the equator rotating faster than the higher latitudes. The blue arrows in the figure represent the rotation speed. Differential rotation is thought to be an essential ingredient for generating magnetic activity and starspots.

The research project called WHOLESUN aims at understanding the origin of solar magnetic activity by studying the Sun in its entirety. It is funded through a prestigious Synergy Grant from the European Research Council (ERC), awarded to a team of four European Principal Investigators from the Max Planck Institute for Solar System Research (MPS) in Germany, the University of St Andrews in the UK, the CEA research centre in France, and the University of Oslo in Norway. The researchers will pool their expertise in solar physics over the next six years to determine how the magnetic field is generated in the solar interior to create sunspots on the solar surface and eruptions in the solar atmosphere. To this end, the team will attempt to model the Sun as a whole using supercomputers and incorporating observational knowledge from space missions.

ERC Synergy Grant for solar physics at the MPS

The European Research Council will fund an ambitious solar physics project at the MPS over the next six years.

October 23, 2018

The research project called WHOLESUN aims at understanding the origin of solar magnetic activity by studying the Sun in its entirety. It is funded through a prestigious Synergy Grant from the European Research Council (ERC), awarded to a team of four European Principal Investigators from the Max Planck Institute for Solar System Research (MPS) in Germany, the University of St Andrews in the UK, the CEA research centre in France, and the University of Oslo in Norway. The researchers will pool their expertise in solar physics over the next six years to determine how the magnetic field is generated in the solar interior to create sunspots on the solar surface and eruptions in the solar atmosphere. To this end, the team will attempt to model the Sun as a whole using supercomputers and incorporating observational knowledge from space missions.

Slow appearance of sunspots challenges theory

Scientists find that sunspots rise to the surface much more slowly than predicted

July 13, 2016

Solar active region as seen by the Helioseismic and Magnetic Imager on board the NASA Solar Dynamics Observatory. The dark circular regions are sunspots; these regions of strong magnetic field are dark as they are cool. The image of Earth is shown for scale.  

Credit: MPS. The HMI data were used courtesy of NASA/SDO and the HMI science team and processed at the German Data Center for SDO (GDC-SDO), funded by the German Aerospace Center (DLR).

Solar active regions consist of strongly magnetic sunspots and surrounding regions of more diffuse magnetic field. These regions are the origin of solar activity which controls space weather and causes beautiful phenomena such as aurora but in some cases also damage to satellites or power grids. Solar active regions are thought to be the result of magnetic flux concentrations - bundles of magnetic field lines - rising from deep in the solar interior and penetrating the surface. A team consisting of researchers from the Max Planck Institute for Solar System Research (MPS), The University of Göttingen, NorthWest Research Associates, and the High Altitude Observatory of the National Center for Atmospheric Research has now shown that these magnetic flux concentrations move upward through the solar interior at speeds of not more than about 150 m/s. This is much slower than predicted by the prevailing current model. For their study, which is published today in the journal Science Advances, they compared satellite observations and computer simulations.

Distant star is roundest object ever observed in nature

Scientists measure the shape of a pulsating star with unprecedented precision.

November 16, 2016

The star Kepler 11145123 is the roundest natural object ever measured in the universe. Stellar oscillations imply a difference in radius between the equator and the poles of only 3 km. This star is significantly more round than the Sun. 

Stars are not perfect spheres, several mechanisms can change their shape. One mechanism is rotation: the more quickly a star rotates, the more flat it becomes due to the centrifugal force. Since distant stars appear as points in the sky, measuring their shape is a challenging task.  A team of researchers led by Prof. Dr. Laurent Gizon from the Max Planck Institute for Solar System Research (MPS) and the University of Göttingen succeeded in measuring the oblateness of a slowly rotating star. In their study, which is published on 16 November, 2016 in the journal Science Advances, they determine for the first time stellar oblateness with unprecedented precision using asteroseismology – the study of the oscillations of stars. The technique is applied to a star 5000 light years (47,000,000 billion kilometers) away from Earth and reveals that the difference between the equatorial and polar radii of the star is only 3 kilometers – a number that is astonishing small compared to the star’s mean radius of 1.5 million kilometers.

Interior Rotation of a Distant Star Revealed

2013

With the help of asteroseismic data obtained by the CoRoT space telescope, scientists were able to determine the interior rotation of a Sun-like star - and characterise an exoplanet.

Star-planet system HD52265 observed by the COROT satellite.  (Image: Mark A. Garlick / markgarlick.com)

A team of scientists led by researchers from the Max Planck Institute for Solar System Research (Germany) and the University of Göttingen (Germany) have unambiguously measured the internal rotation of a Sun-like star and determined the inclination of its rotation axis for the first time. Their calculations show that the star rotates about 2.3 times faster than the Sun, with the axis of rotation inclined at 30 degrees to our line of sight. The star, HD52265, is located more than 90 light years away in the constellation of Monoceros. The results also prove that the body known to accompany the star is indeed an exoplanet and not - as previously argued - a small companion star called a brown dwarf. This is the first time that asteroseismology, the study of a star's internal oscillations, has been used to constrain the mass of an orbiting companion of a Sun-like star. The results were published in the journal "Proceedings of the National Academy of Sciences of the United States of America" (PNAS).

Seismic constraints on rotation of Sun-like star and mass of exoplanet, Gizon et al., 
Proceedings of the National Academy of Sciences of the United States of America (PNAS), Early Edition, 29. Juli 2013 
doi:10.1073/pnas.1303291110

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