The satellite observations are as yet of insufficient length to answer the question whether the sun is varying in luminosity on timescales longer than the 11 year sunspot cycle. – Douglas V. Hoyt
The Sun has been seen by human beings since the emergence of our species, wondered at and worshiped for ages, and has been studied within the framework and with the instruments of science in recent centuries.
Ever bright and shining, always orange or red or white hot from where we stand, the Sun’s apparent disc has such brilliant perfection that no one can imagine blemishes on its spotless face. And yet, even as the greatest of human beings are never without a fault, the Sun too displays dark patches now and then. One of the first features of the sun that came to be recognized in the era of modern science is that we can sometimes detect black blurs on an otherwise unblemished solar surface. But it is said that already in 28 BCE some Chinese observers reported spots on the Sun.
It must be noted that when the planet Venus or Mercury happens to orbit in front of the Sun on the plane on which we see it, the planet in question seems like a dark spot on the Sun. But it was only in the first decade of the seventeenth century that telescopic astronomy clearly uncovered sunspots. In fact, the Dutch astronomer Johannes Fabricius was one of the first to have observed sunspots, on March 9, 1611 to be exact. He was certainly the first to write a book on the phenomenon: De Maculis in Sole Observatis: On the Spots observed in the Sun. In the diagram below Jupiter and earth are indicated as relative sizes with respect to the sun’s surface.
Some others also claimed priority in spotting the spots. They were not aware of the much earlier Chinese observation in the fourth century BCE, or even of the ninth century report by a Benedictine monk to the effect that he had seen the transit of Mercury across the Sun which looked like a moving dark spot. Be that as it may, most modern historians of science assert that Thomas Harriot was the first to observe sunspots using a telescope in 1610, and Christoph Scheiner in 1611, though they did not publish their discovery before Fabricius. Galileo, noting their movement across the solar disc, stated that this was proof that the sun was spinning on its axis.
In the nineteenth century it was discovered that intense sunspots showed up periodically, roughly every 11 years. The largest number of patches observed thus far, some seven thousand in all, were the Great Sun Spots of 8 April 1947, exactly 69 years ago. The most recent one was in 2014.
We have come a long way since those patches were regarded as mysterious blots that revealed the rotation of the sun. Today solar physicists know (strongly suspect) that they are regions of enormous magnetic fields, appearing as pairs of north and south polarity, dark only because they are regions of much lower temperature than their surrounding areas. They are of stupendous surface area. The spots recorded in 1947 covered seven billion square miles. But that was only a 6000th part of the Sun’s total surface.
The 1947 flare-up instigated great interest and further study of the sun by astronomers. In the 1960s and 70s, interplanetary probes to Venus and Mercury got pretty close to the sun. In the 1990s one of these revealed that, unlike the earth, the sun does not have any magnetic pole: What this means is that if one gets lost on the sun’s surface, no magnetic compass would point the errant traveler to the way 🙂
Associated with sunspot activity are solar flares: ejection of massive quantities of highly energetic electrically charged particles: essentially protons and electrons. They are huge superhot emanations from the normal sun: like gigantic fireballs from a mammoth dragon’s tongue. During sunspot season they become thousands of times more intense. When they gush forth every which way and arrive in our vicinity, they wreak havoc on earth’s more stable magnetic fields. Their arrival in the geomagnetic polar regions at speeds of millions of miles an hour give rise to spectacular auroras, revealing that there can be magnificent aesthetic grandeur even in (what may strike us as) the Sun’s horrendous belching.
It used to be said that when America catches a cold, Europe sneezes. It is even more true that when there are spots on the sun, wild magnetic storms are created here on earth. These are known to affect some birds in their egg-laying habits. But they meant little for us until the advent of electro-technical civilization. To give but one example of how we can be affected, when there was a sunspot-triggered geomagnetic storm in 1989, it drastically upset the hydroelectric generators in Quebec and caused a huge blackout. There was also significant disruption of communication systems, including transmission of TV signals. What can be more disastrous!
While we earthlings live our fleeting years in all the gore and glory of our cultures and civilizations, pursuing our sciences and religions in great and grotesque ways, the Sun and stars do their routines up there in the sky dancing to the music of the laws of physics, but on much, much grander scales. They may sometimes have detectable impact on us: that of sunspots has been well established by science. As to the astrologically proclaimed effects like Venus affecting Romeos and Juliets or Jupiter rocking the stock market, these are only as true as comets foretelling the demise of kings or full moon causing hyperactivity in asylums, i.e. not in the least valid on the basis of scientific data. Nevertheless statements like the following by William S. Jevons have received wide publicity and credence: “Periods of higher solar activity (reflected also in the sunspot cycle) are associated with a stronger appetite for risk, more bullish equity markets, and stronger growth.” And they don’t diminish human proclivity for believing in pseudoscience, one might add.
Yet, we know not how happenings way out there affect and have affected things here on earth. Only a couple of weeks ago, some astrophysicists announced that perhaps the blasting of a supernova up there in a distant niche in the Milky Way ejected certain isotopes of iron which found their way to here below God alone knows how or with what subtle consequences.
April 8, 2016