[ad_1]
Our Sun is the source of life on Earth. Its quiet glow for billions of years has allowed life to evolve and flourish in our world. This does not mean that our Sun does not have an active side. We have observed massive solar flares, such as the Carrington event of 1859, which produced northern lights to the southern Caribbean, and conducted electric currents on telegraph lines. If such a flare-up occurred in Earth’s direction today, it would devastate our electrical infrastructure. But fortunately for us, the Sun is mostly calm. Unusually quiet compared to other stars.
Astronomers have recently studied the activity of the sun. The oldest study, carried out since the 17th century, follows the number of points seen on the surface of the Sun. It has shown us that the Sun goes through cycles of active and calm periods. A four-century study is long in human terms, but it is hardly a moment of cosmic time.
Longer studies have looked at carbon isotopes and other elements in ice cores and tree rings. When the Sun is particularly active, high-energy protons can hit atoms in the upper atmosphere, turning them into radioactive isotopes. Then they can get caught in ice and wood. This gives us an idea of solar activity for almost ten millennia.
That is still only a fraction of the Sun’s life. Are the last few thousand years a good sample of solar activity? What if the Sun is going through an unusually quiet period and is generally much more active? To answer this question, a team of astronomers compared our Sun to similar stars, and the results are surprising.
Using data from the Gaia spacecraft, the team searched for stars very similar to the Sun. They found stars of similar mass, age, and surface temperature. From these, they chose stars that not only had a similar metallicity, but also a similar rotational speed. They were left with 369 stars that are almost twins of our Sun.
The team then compared the variation in activity of the Sun over four years with the activity of these other stars. They discovered that the Sun’s activity is much lower than the others. The variability of other stars is five times stronger than our Sun. Solar flares like the Carrington event are much more common in other stars.
This could mean that our Sun has generally been quiet during the period of human civilization. If that is the case, it could become more active in the future, which could have serious consequences for our civilization. It is also possible that there is some unknown factor that keeps our Sun so calm.
At the moment, there is no indication that the Sun may enter a hyperactive period. For now and for the foreseeable future we can continue to enjoy the calm of the sun.
Reference: Reinhold, Timo et al. “The Sun is less active than other solar-like stars.” Science 368.6490 (2020): 518-521.
