An area seen as a dark patch on the Sun's surface. Sunspots appear dark because they are cooler (of about 4000 °C) than the surrounding photosphere (about 6000 °C). They range in size from a few hundr
ed kilometers to several times the Earth's diameter and last from a few hours to a few months. Very small sunspots are called pores. The number of sunspots varies from maximum to minimum in about 11 years, the sunspot cycle. Their appearance during a cycle follows the Sporer law. A typical spot has a central umbra surrounded by a penumbra, although either features can exist without the other. Sunspots are associated with strong magnetic fields of 0.2 to 0.4 tesla. A given sunspot has a single magnetic polarity. The opposite polarity may be found in other sunspots or in the bright and diffuse facular region adjacent to the sunspot. The first recorded naked-eye sightings of sunspots were by Chinese astronomers in the first century B.C. Johannes Fabricius (1587-1617) was the first to argue that sunspots are areas on the solar surface.
Dark areas on the solar surface that contain constantly shifting strong magnetic fields. An average sunspot is about as large as Earth and it moves along with the sun's rotation, lasting for days or e
ven weeks. The magnetic activity in sunspots can give rise to various solar eruptive events such as flares and coronal mass ejections (CMEs). The number of sunspots on the sun wax and wane over approximately an 11-year cycle, thus defining what is called the solar cycle. They appear dark since they are cooler than the surrounding solar material.
A cavity hundreds of light-years across filled with a hot gas blown into the interstellar medium by multiple supernovae and stellar winds. Examples are the Local Bubble in the Orion Arm of the Milky W
ay and the N44 Superbubble in the Large Magellanic Cloud.
An aggregation of clusters of galaxies. Superclusters are typically about one hundred million (10^8) light-years in diameter and contain tens of thousands of galaxies. Some examples are the Local Supe
rcluster, Centaurus supercluster, Laniakea supercluster, Perseus-Pisces supercluster, Shapley supercluster, Virgo supercluster.
In geology, a supercontinent is a land mass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.