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Luckily for us, our Sun is a fairly constant star. It doesn’t vary its brightness too much, leaving us to either singe or to freeze. Surprisingly, on May 1st scientists announced in Science magazine that our Sun may be far less active than other comparable stars. Why? We don’t really know. But it’s possible that our Sun will not always be so constant, and may amp up its activity in the future.
Luckily, the brightness of our Sun doesn’t vary greatly. But this might not always be the case.
All stars “flicker” – change their brightness slightly from one moment to the next. This may originate from the star’s magnetic field, created as the star rotates. When this magnetic field becomes unstable near the surface of the star, it can form “starspots” (dark regions on the star) or bright spots called faculae on the star – changing the overall brightness of the star. These events create a more active star. It seems that stars with high rotation rates have high magnetic fields, and hence, a lot of activity.
We have fairly accurate observations of sunspots since 1610, and thanks to carbon and beryllium in tree rings and ice cores, we can determine that, at least within the last 9,000 years, our Sun doesn’t flicker very often. In fact, our Sun only changes its irradiance (or its power per area) only 0.07%.
Dr. Timo Reinhold and his team decided to look at how active stars similar to our Sun behave. They took a sample of more than 34,000 stars with rotation periods and 99,000 with unknown periods. From these, they selected stars with similar temperatures and surface gravity to our Sun. These stars are like the Sun in every way we can constrain.
Stars with known periods ranged from about 20 to 30 days. Our own Sun rotates once every 25 days. They found that stars in the sample with known rotation rates had 5 times more variability than our Sun.
“How can this mystery be solved?” asks Dr. Reinhold. “The fact that these stars are more active (although there are very similar to the Sun in all parameters that we could constrain) lead us to conclude that these stars are either different from the Sun, or that also the Sun could potentially become that active at some point in its life.”
If this is the case, our Sun may have gone through periods of strong activity in the past and may continue to do so in the future.
Every 11 years, the Sun goes through a solar cycle – moving from a period of strong activity to quietness. These times of activity on the Sun affect the Earth – having an influence on the power grid, satellites, and even weather. It can even be dangerous for astronauts. A more active Sun? It would change life and technology on Earth. For now, we can enjoy the quiet.
Dr. Elizabeth Fernandez is the host of SparkDialog Podcasts (sparkdialog.com), which covers the intersection of science and society. She has a PhD in astrophysics from
Dr. Elizabeth Fernandez is the host of SparkDialog Podcasts (sparkdialog.com), which covers the intersection of science and society. She has a PhD in astrophysics from the University of Texas at Austin and has worked around the world in both astronomy and in science and society. She currently specializes in how science and technology are impacting our lives.
World news – CA – Think Our Sun Is A Nice, Constant Star? Changes Might Be Coming.