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Study shows sun to be less active than other similar stars

The scientists compared the sun with other stars that have similar rotation periods and other fundamental properties. As a result, most of the stars displayed much stronger variations in comparison to our sun.

May 1, 2020 17:18 IST
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As per the new study by the researchers, solar brightness variations have become extremely weak and by cosmic standards, the sun has become extraordinarily monotonous. The study was done through an analysis of 369 solar-like stars.

The result was shown by the researchers under the leadership of the Max Planck Institute for Solar System Research in Germany.

The scientists compared the sun with other stars that have similar rotation periods and other fundamental properties. As a result, most of the stars displayed much stronger variations in comparison to our sun.

Is sun going through an unusually quiet phase?

While comparing other stars to the sun which showed much stronger variations, the question arises that whether the feebleness of the sun is a basic trait or whether it has been going through an unusually quiet phase. There are various methods through which the extent to which solar activities varies can be reconstructed, at least for a definite period of time.

There have been reliable records of sunspots covering the sun since 1610. It allowed in drawing conclusions about the level of solar activities over the past 9000 years. For this period of time, scientists have found regularly recurring fluctuations comparable strengths as during the recent decades.

As per the scientist Dr. Timo Reinhold who is also the first author of the new study, as the star is almost 4.6 billion years old, it can be conceived that the sun has been going through thousands of years and that why we only have a distorted picture.

To find out how active the sun was in its primeval times, the only option is resorting to the stars.

Study to find whether the sun has been behaving normally:

The MPS researchers along with colleagues from the University of South Wales in Australia and School of Space Research in South Korea collaborated to study whether the sun has been behaving normally in comparison to other stars.

For this, researchers started picking stars that resembled sun its properties such as age, surface temperature, and researchers also looked above all the rotation period as the speed at which star rotates is a crucial variable. The rotation of the star contributes to the creation of a magnetic field which is a driving force for all the fluctuations activity.

The state of the magnetic field helps in determining how often the sun emits energetic radiation and thus how brightly the sun shines.

With the help of a comprehensive catalog that contained the rotation period of thousand of stars, it has been based on the measurement data from NASA’s Kepler Space telescope. From this, the researchers took the sample and selected those stars that rotate around their axis within 20 to 30 days while our sun needs around 24.5 days.

By further narrowing down the sample data, 396 stars remained that was also familiar with the sun in other properties.

What the analysis of the brightness variation of the sample stars indicates?

The analysis of the brightness variations of the sample stars from 2009 to 2013 revealed a clear picture. Between inactive and active phases, the sun’s irradiance fluctuated on an average by 0.7 percent, the other stars revealed much larger variation.

As per the scientists, it was surprising to see that most of the sun-like stars were much more active than the Sun.

However, since it is not possible to determine the rotational period of all the stars observed with the help of the Kepler Telescope, the researchers also studied more than 2,500 sun-like stars with unknown rotation periods and their brightness fluctuated much less than the other group.  

The Result gives us two interpretations:

There can still be unexplained fundamental differences between stars with unknown and known rotation periods.

It can also be conceived that stars with known and sun-like rotation periods showed the fundamental fluctuations inactivity that the sun is capable of. This would also mean that the sun has been unusually feeble over the past 9000 years and much greater fluctuations on very large time scales are also possible.

However, there is no cause of concern as for the foreseeable future, there has been no indication of such solar hyperactivity. The sun, on the contrary, has been showing itself to be rather weakly active and predictions of the next 11 years activity show that this will not change soon.  

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