Sun Has Likely Entered New Evolutionary Phase, Say Astronomers

by Bruce Dorminey

The Sun has likely already entered into a new unpredicted long-term phase of its evolution as a hydrogen-burning main sequence star — one characterized by magnetic sputtering indicative of a more quiescent middle-age. Or so say the authors of a new paper submitted to The Astrophysical Journal Letters.

Using observations of other sunlike stars made by NASA ’s Kepler Space Telescope, the team found that the Sun is currently in a special phase of its magnetic evolution.

Heretofore, the Sun was thought to have been just a more slowly rotating version of a normal yellow dwarf (G-spectral type) star. These results offer the first real confirmation that the Sun is in the process of crossing into its magnetic middle age, where its 11-year Sunspot cycles are likely to slowly disappear entirely. That is, from here on out, the Sun is likely to have fewer sunspots than during the first half of its estimated 10 billion year life as a hydrogen-burning star.

“The Sun’s 11-year sunspot cycle is likely to disappear entirely, not just get less pronounced; [since] other stars with similar rotation rates show no sunspot cycles,” Travis Metcalfe, the paper’s lead author and an astronomer at the Space ScienceInstitute in Boulder, Colo., told me.

Metcalfe says this transition takes a few hundred million years, but once the Sun completely crosses this Rubicon of middle age, it will remain magnetically inactive for the rest of its hydrogen-burning life.

We now understand that every star goes through this phase, says Metcalf, and that the Sun has a peculiar magnetic cycle for its rotation rate because it is in the middle of the transition to a less magnetically-active state. And he notes that this new realization does help explain why the Sun’s current surface activity doesn’t jibe with patterns seen on many other sunlike stars….. READ MORE

Source: Fobes via SWLing