These images show two Jupiter-sized sunspot groups on the face of the Sun (left) and an extreme close-up of a different, smaller sunspot group (right). The lefthand image was taken on Oct. 24, 2003 by the SOHO (Solar & Heliospheric Observatory) spacecraft. The righthand image was taken on July 15, 2002 by the Swedish 1-m Solar Telescope on the island of La Palma off the western coast of Africa. The central dark part of the large sunspot in the middle of the righthand image is about 14,000 km (8,700 miles) across... slightly larger than Earth! Click on image for full size (76K JPEG) Images courtesy SOHO (NASA & ESA) and the Royal Swedish Academy of Sciences.

Sunspots are dark, planet-sized regions that appear on the "surface" of the Sun. Sunspots are "dark" because they are cooler than their surroundings. A large sunspot might have a central temperature of 4,000 K (about 3,700° C or 6,700° F), much lower than the 5,800 K (about 5,500° C or 10,000° F) temperature of the adjacent photosphere. Sunspots are only dark in contrast to the bright face of the Sun. If you could cut an average sunspot out of the Sun and place it elsewhere in the night sky, it would be about as bright as a full moon. Sunspots have a lighter outer section called the penumbra, and a darker central region named the umbra.

Sunspots are caused by disturbances in the Sun's magnetic field welling up to the photosphere, the Sun's visible "surface". The powerful magnetic fields in the vicinity of sunspots produce active regions on the Sun, which in turn frequently spawn disturbances such as solar flares and Coronal Mass Ejections (CMEs). Because sunspots are associated with solar activity, space weather forecasters track these features in order to help predict outbursts of "solar storms".

Sunspots form over periods lasting from days to weeks, and can persist for weeks or even months before dissipating. The average number of spots visible on the face of the Sun is not constant, but varies in a multi-year cycle. Historical records of sunspot counts, which go back hundreds of years, verify that this sunspot cycle has an average period of roughly eleven years.

Our Sun isn't the only star with spots. In recent years, astronomers have been able to detect "starspots" - "sunspots" on other stars.

These are two pictures of different sunspots. The picture on the left shows the whole Sun with some large sunspot groups on it. The sunspot groups in that picture are as big as the giant planet Jupiter. The picture on the right is a closeup of some other sunspots. The large sunspot near the middle of the righthand picture is bigger than Earth! Click on image for full size (76K JPEG) Images courtesy SOHO (NASA & ESA) and the Royal Swedish Academy of Sciences.

Sunspots are dark, planet-sized regions that appear on the "surface" of the Sun. Sunspots are "dark" because they are colder than the areas around them. A large sunspot might have a temperature of about 4,000 K (about 3,700° C or 6,700° F). This is much lower than the 5,800 K (about 5,500° C or 10,000° F) temperature of the bright photosphere that surrounds the sunspots.

Sunspots are only dark in contrast to the bright face of the Sun. If you could cut an average sunspot out of the Sun and place it in the night sky, it would be about as bright as a full moon. Sunspots have a lighter outer section called the penumbra, and a darker middle region named the umbra.

Sunspots are caused by the Sun's magnetic field welling up to the photosphere, the Sun's visible "surface". The powerful magnetic fields around sunspots produce active regions on the Sun, which often lead to solar flares and Coronal Mass Ejections (CMEs). The solar activity of flares and CMEs are called "solar storms".

Sunspots form over periods lasting from days to weeks, and can last for weeks or even months. The average number of spots that can be seen on the face of the Sun is not always the same, but goes up and down in a cycle. Historical records of sunspot counts show that this sunspot cycle has an average period of about eleven years.

Our Sun isn't the only star with spots. Just recently, astronomers have been able to detect "starspots" - "sunspots" on other stars.

These are pictures of sunspots. The picture on the left shows the whole Sun. There are two groups of sunspots on the Sun. The picture on the right is a close-up look at a sunspot. Click on image for full size (76K JPEG) Images courtesy SOHO (NASA & ESA) and the Royal Swedish Academy of Sciences.

Sunspots are dark spots on the Sun. They may look small, but they are actually as big as a planet like Earth or Mars!

Sunspots are "dark" because they are colder than the areas around them. Of course, they are not really cold like we think of cold! A large sunspot might have a temperature of about 3,700° C or 6,700° F!

Areas around sunspots called active regions on the Sun can lead to solar flares and Coronal Mass Ejections (CMEs for short). The solar activity of flares and CMEs are called "solar storms".

Sunspots can last for weeks or even months. The number of spots on the face of the Sun is not always the same, but goes up and down in a cycle. Over time, astronomers have used different instruments to look at how many sunspots are on the Sun, but remember that you should NEVER LOOK directly at the Sun!

Other stars have spots too. They are called "starspots".