Study reveals that the sun is calmer than average - Space News

Image of the solar cycle, nasa space news 2020.
By cosmic standards, the Sun is an extraordinarily peaceful star. Space News, 2020.

A survey pointed out that our Sun, unlike the vast majority of stars in its class, has far fewer variations in its brightness, as well as much less active sunspots - which is excellent news for life on Earth. 

Although the same study also revealed that our Astro-King may be going through a period of tranquility and, if it decides to get nervous, the inhabitants of our planet may find themselves in serious trouble.

Calm sun

The sun itself is a yellow dwarf, that is, a star of the main sequence of class G - which includes stars with 0.8 to 1.2 solar masses and temperatures ranging from 5.3 thousand and 6 thousand K on the surface. 

In addition, these star bodies produce energy by converting hydrogen into helium through nuclear fusion and, after about 10 billion years, after burning all the fuel in their nuclei, they expand until they become red giants that, over time, as they lose their outer layers, turn into nebulae and, finally, when only the nucleus remains, it cools and contracts, giving rise to white dwarfs.

The life cycle of a star like the Sun is more or less the one we have described above, but according to the study we have mentioned, the life itself of these stars is much more agitated than the one we observe in our planetary system.

Solar Cycle image.
Solar Cycles.

In the case of the Sun, the intensity of its brightness is related to another cycle, the solar, which lasts approximately 11 years and begins with a period of quiet time in which the magnetic fields of our star are aligned with its polar regions.

However, as the sun's equator rotates faster than its poles, the magnetic fields eventually distort. This, in turn, causes an increase in solar activity, the appearance of sunspots and variations in the intensity of their brightness - which occurs over 11 years, until a reversal of the poles occurs, the magnetic fields line up again and there is a renewed calm.

Through the study of ice cores collected in the polar regions of the Earth, the analysis of tree trunk rings and thanks to the examination of rocks and sediment deposits, for example, today we know that the solar cycle has been behaving in the same way for at least 9,000 years. 

The problem is that we have no information before that, and for a star that totals more than 4.5 billion years of existence, 9,000 are nothing - and it may be that our star has gone through and will go through periods of turbulence.

Solar Cycle Comparisons

To conduct the survey, scientists decided to compare the sun's behavior with that of other stars - and used several years of observations from the Kepler space telescope to select the suns that most closely resemble ours. 

More specifically, of the millions of stars studied by the equipment, the researchers selected those that had rotational periods between 20 and 30 days, since that of the Sun is 24 and a half days, and this aspect has a direct influence on the activity of the stars' magnetic fields.

The scientists also took into consideration characteristics such as composition, age, temperature, color and mass and, after checking a portion of data with surveys conducted by the space satellite Gaia, the astronomers selected 369 stars like ours. So, the next step was to compare the behavior of the Sun with all these stars and the conclusion was that our star is beyond peaceful.

According to the survey, the brightness of the other suns examined showed about 5 times more variations, indicating a much higher level of activity. Curiously, when compared with the behavior of 2.5 thousand stars whose rate of rotation is unknown, the sun's seems much more normal. One explanation for this weirdness is that our star is in transition to a period of lower activity or is already immersed in it.

The problem is whether there are fluctuations between these periods and the Sun becomes much more active - and this can have serious consequences for radar, communications and power supply systems, for example. An aggravating factor is that, if this is indeed the case, there is no way to predict when a period of great solar activity will begin and all that remains is to hope that the current calm will extend over many more thousands of years.