The sun is 'unusually quiet', say scientists

Our sun is "unusually quiet", according to scientists.

The star in our solar system is very inactive when compared to its galactic counterparts, new research shows.

The latest research used data from the Kepler Space Telescope to compare the brightness of our sun with other similar stars elsewhere in the universe.

According to new research, the sun appears to be less active than those hundreds of similar stars based on brightness variations.

When matched up to 369 solar-like stars, scientists found they typically fluctuated about five times stronger than the Sun over the last 140 years.

However, researchers also studied more than 2,500 Sun-like stars with unknown rotation periods, which showed that their brightness fluctuated much less than that of the other group.

"We were very surprised that most of the Sun-like stars are so much more active than the Sun," said Dr Alexander Shapiro, from the Max Planck Institute for Solar System Research (MPS).

Scientists narrowed down the first batch of comparable candidates from a vast catalogue of measurement data recorded by Nasa's Kepler Space Telescope, selecting stars with a similar surface temperature, age and rotation period.

They chose to look at stars that rotate once around their own axis within 20 to 30 days, though it does not determine the rotation period of all the stars, so the team had to consider other factors such as re-appearing dips in the star's lightcurve.

Previously, scientists have largely relied on recent histories of out star to understand its brightness. Through a range of techniques, we have been able to understand more about its history over the past 9,000 years – but that is a relatively tiny period when compared with the nearly 4.6 billion years the sun has been around.

The new study allowed the reserchers to instead compare our star with its other counterparts, helping give a better picture of how normal its behaviour is. And scientists are still unclear about why exactly it is so unusual.

"It is conceivable that the Sun has been going through a quiet phase for thousands of years and that we therefore have a distorted picture of our star," explained Dr Timo Reinhold, first author of the new study, who published the findings in the Science journal.

The scientists behind the research note that it is possible that the Sun can have higher variability over long timescales, or differs from similar stars in ways that haven't yet been recognised.

Additional reporting by Press Association