New understanding of Sun’s infancy possible

The ability to view in depth images of a nearby star has provided an international team of astronomers with the chance to understand the Sun’s behaviour billions of years ago.

Using interferometry, scientists combined the light of separate telescopes to create the resolving power of a 330m telescope, to produce the first direct image of surface structures on the binary star Zeta Andromedae. The star is 181 light years away from Earth.

Found in the northern constellation of Andromeda, Zeta Andromedae showed signs of starspots – similar to sun spots found on our Sun. However the patterns of these spots differ from those on the Sun, as they were found near Zeta’s northern pole region as well as across its lower latitudes. On our Sun they are only found near its equator. The researchers believe these results challenge conventional thinking of how magnetic fields of stars influence their growth.

Professor Stefan Kraus, Associate Professor in astrophysics at Exeter University, said: “Most stars behave like giant rotating magnets and starspots are the visible manifestation of this magnetic activity. Imaging these structures can help us to decipher the workings that take place deep below the stellar surface.”

As Zeta Andromedae is a binary star, itself and a smaller unknown object orbit each other. This increases the speed of Zeta’s rotation, 40km per second compared to the Sun - which rotates at two kilometres per second. As Zeta’s rotation is so rapid, it resembles the stage at which a new star is being created, said Heidi Korhonen, from the University of Copenhagen and co-author of the study.

The scientists said they have evidence from how the starspots are distributed, that magnetic fields can suppress heat flow across large areas of Zeta’s surface. As astronomers rely on the temperatures of stars to measure their age, further research on these extended cool regions is needed to see if they affect temperature measurements.

Dr Rachael Roettenbacher, from the University of Michigan, said: “It's important to understand the Sun's history because that dictates the Earth's history - its formation and the development of life. We see the starspots [on Zeta Andromedae] in both hemispheres and at all different latitudes. This can't be explained by extrapolating theories about the Sun's magnetic field.

"The better we can constrain the conditions of the solar environment when life formed, the better we can understand the requirements necessary for the formation of life."

The findings were published in Nature.