Sun less active compared to similar stars, scientists find

James Marshall
May 4, 2020

"Compared to the entire lifespan of the sun, 9,000 years is like the blink of an eye", Timo Reinhold, lead author of the new study and an astrophysicist at the Max Planck Institute for Solar System Research, said in the same statement.

The researchers compared data on similar stars to historical records of the sun's activity.

In many stars, the observed variation in brightness is driven by their internal magnetic field. Be that as it may, contrasted with these stars, our sun's brilliance changes essentially less, recommending that it is quieter than different stars of about a similar size. "A direct measure of solar activity is the number of sunspots on the surface".

To understand what the sun was doing before those records begin, scientists can interpret a host of data types, like levels of specific elements in tree rings and ancient ice. Because all stars rotate, sunspots are carried around the star, causing its brightness to fluctuate - and scientists know very well how to track variations in brightness of a star over time. "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".

The sun seems to be much less active than similar stars in terms of brightness fluctuations caused by sunspots and other phenomena - scientists say a "boring" personality that is not necessarily a bad thing for us compatriots.

Be thankful that the sun is truly freakish, as researchers have learned by contrasting its action and that of comparable stars. Its surface temperature is about 5,500 degrees Celsius.

"The speed at which a star rotates around its own axis is a crucial variable". Dr. Sami Solanki, director at MPS and co-author of the new publication.

Bright spots and illuminated arcs of solar material hovering in the sun's atmosphere highlight what's known as active regions on the sun, in this image from NASA's Solar Dynamics Observatory, captured on April 20, 2015.

A comprehensive catalogue containing the rotation periods of thousands of stars has been available only for the last few years. The researchers were able to further narrow down this sample by using data from the European Gaia Space Telescope. In the end, they came up with 369 Sun-like stars to study. By taking random four-year segments of the Sun's light curve, they found the typical variability of the Sun's brightness was only 0.07% - and even at its greatest was no more than 0.20%. It was surprising to find stars with very similar parameters to our sun, but we are five times more variable, "Reinhold said". Viewed through the Kepler telescope, even the Sun would not reveal its rotation period. But compared to these stars, our sun's brightness varies significantly less, suggesting that it is calmer than other stars of about the same size.

These results allow two interpretations.

"A much more active sun might have also affected Earth on geological time scales - palaeoclimatology".

There is, however, no cause for concern. Understanding the Sun's magnetic field is critical for predicting the star's future, but scientists debate whether the Sun's activity will diminish or may still become more magnetically active.

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