The earliest known drawings of solar activity appeared many years later, in 1128, in John of Worcester's chronicle. ![]() However, there are no known early illustrations of such observations. Chinese and Korean astronomers frequently observed sunspots, according to the Chandra X-ray Center. According to the Chandra X-ray Center (opens in new tab), the earliest records of solar activity are from Chinese astronomers around 800 B.C. There is some debate about who discovered sunspots. To see what sunspots look like today, check out this observing page (opens in new tab) from the Solar and Heliospheric Observatory (SOHO). The sun is experiencing solar cycle 25, in which solar activity is currently on the rise, resulting in a greater emergence of sunspots. This period of severely reduced solar activity came to be known as the "Maunder minimum," after British astronomer Edward Walter Maunder, who - along with his wife, Annie - discovered the lack of activity from the records in 1890, according to The Times (opens in new tab). For comparison, during a "normal" solar minimum there are usually 12 to more than 100 sunspots per year. Between 16, fewer than 50 sunspots were recorded, according to Physics World (opens in new tab). Though the 11-year solar cycle is fairly consistent, between 16, very few sunspots were observed. (Image credit: Future) (opens in new tab) Sunspots and the solar cycleĭuring solar maximum a large number of sunspots are visible at mid-latitudes and during solar minimum a very small number (sometimes zero) of sunspots are visible at the equator. According to the University Corporation for Atmospheric Research (opens in new tab) (UCAR), if you could cut out a standard sunspot from the sun and place it in the night sky, it would appear as bright as a full moon. The strong magnetic field inhibits the influx of hot, new gas from the sun's interior, causing sunspots to be cooler and appear darker than their surroundings, relatively speaking. The magnetic field in active sunspot regions can be some 2,500 times stronger than Earth's, according to the NWS. A group of sunspots is known as an active region. This disturbance in the sun's magnetic field forms pores that can grow and join together to form larger pores, or proto-spots, that eventually become sunspots. Eventually, the magnetic fields "snap," rise and break the surface. They may also travel at relative speeds ("proper motions") of a few hundred m/s when they first emerge onto the solar photosphere.Sunspots are, on average, about the same size as Earth, though they can vary from hundreds to tens of thousands of miles across, according to Cool Cosmos (opens in new tab).Īs the sun rotates, these magnetic loop "rubber bands" get more wound up (both tighter and more complicated). Sunspots expand and contract as they move across the surface of the Sun and can be as large as 80,000 kilometers (50,000 mi) in diameter, making the larger ones visible from Earth without the aid of a telescope. If the sunspot were isolated from the surrounding photosphere it would be brighter than an electric arc. Although they are at temperatures of roughly 3000-4500 K (2727-4227 ☌), the contrast with the surrounding material at about 5,780 K leaves them clearly visible as dark spots, as the luminous intensity of a heated black body (closely approximated by the photosphere) is a function of temperature to the fourth power. They are caused by intense magnetic activity, which inhibits convection by an effect comparable to the eddy current brake, forming areas of reduced surface temperature. Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. ![]() This is called granulation, as seen in the picture below. This process repeats, creating convection currents and the visual effect of boiling on the Sun's surface. As it falls down to the top of the radiative zone, it heats up and starts to rise. As the gas rises, it cools and begins to sink again. It can do this because the convective zone is cooler than the radiative zone and therefore less dense. Hotter gas coming from the radiative zone expands and rises through the convective zone. This is because it is transferred through the process of convection. In the convective zone, the energy is transferred much faster than it is in the radiative zone. Atoms with electrons are able to absorb and emit radiation, making this region more opaque, like a thick fog. The atoms in this layer of the Sun have electrons because the temperature is not hot enough to strip them away like it is in the core (15.6X 106 K as opposed to 2 million K). This is the area that we consider to form the outer shell of the Sun.
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