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Short solar cycle detected
on distant star

Posted: 27 August 2010

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Scientists using the Convection Rotation and Planetary Transits (CoRoT) space mission have uncovered a short solar magnetic cycle on a distant star using stellar seismology.

Stellar seismology is a technique used by scientists to 'listen' to the heartbeat of stars, like HD 49933, which is located 100 light years away in the constellation Monoceros. “Essentially, the star is ringing like a bell,” says National Center for Atmospheric Research scientist Travis Metcalfe. “As it moves through its starspot cycle, the tone and volume of the ringing changes in a very specific pattern, moving to higher tones with lower volume at the peak of its magnetic cycle.”

Using CoRoT, scientists have listened to the heartbeat of a distant star using a technique called stellar seismology. Image: Institute of Astrophysics of the Canaries, IAC.

Although magnetic cycles have been detected previously in other stars, this is the first time a cycle has been discovered using stellar seismology. Analysing 187 days worth of data the team detected regions of intense magnetic activity like our own star's sunspots. But HD 49933 is much bigger and hotter than our Sun, and its magnetic cycle much shorter – less than a year, the shortest ever observed in another star. The brief cycle will allow astronomers to observe an entire solar sequence much more quickly than stars with longer cycles, such as the Sun's 11-year cycle.

As well as helping to learn how magnetic activity varies from star to star, understanding the magnetic environment of other stars could point astronomers in the direction of potentially habitable planets. “Understanding the activity of stars harboring planets is necessary because magnetic conditions on the star’s surface could influence the habitable zone, where life could develop,” says CEA-Saclay scientist Rafael Garcia, the study’s lead author.

The team plan to extend their survey by using data from NASA's Kepler mission. “If it turns out that a short magnetic cycle is common in stars, then we will potentially observe a large number of full cycles during Kepler’s mission,” says Metcalfe. “The more stars and complete magnetic cycles we have to observe, the more we can place the Sun into context and explore the impacts of magnetic activity on possible planets hosted by these stars.”

Meanwhile, ground-based observations will be used to follow up on CoRoT's observations of HD 49933 when it re-emerges from behind the Sun next month.