Yohkoh Solar Observatory

This animation shows the multi-layered nature of the solar atmosphere. It was built from three images, a white-light image of the photosphere, a red-light image of the chromosphere, and an X-Ray image of the corona, the outermost layer. These images were captured on the same day by the telescope aboard the Yohkoh Solar Observatory satellite. The satellite was launched from Japan in August of 1991 and is used to investigate X-Rays and Gamma rays from the Sun. Yohkoh is Japanese for sunbeam.

Layers of the Solar Atmosphere

The Sun is a giant ball of gas; there is no hard surface on the Sun to stand on. However, there is a surface through which we cannot see called the photosphere. The location of the photosphere is defined to be where the gas is so dense that it becomes opaque. The photosphere is about 330 kilometers thick and lies 696,000 kilometers from the center of the Sun. Above the photosphere is the chromosphere, about 2,000 kilometers thick, where the temperature rises from the 5,800-Kelvin-photosphere to tens of thousands of Kelvin. Beyond the chromosphere is the corona, where the density of the gas is very low and tenuous. The corona is difficult to observe and is only seen on Earth during a total solar eclipse.

Ellen Cohen

NASA/JPL/University of Arizona

This brief animation shows the motion of the clouds in the Jovian atmosphere. Most notable is the dark, oval-shaped Great Red Spot. The animation was compiled from blue filter images taken using the narrow-angle camera on NASA's Cassini spacecraft during seven rotations of Jupiter between October 1 and October 5, 2000. The images reveal an area on Jupiter centered on the equator that extends about 50° north and south and covers 100° east-west (about a quarter of Jupiter's circumference).

Video: 428 kB, Animated GIF

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The dynamics of the Jovian atmosphere

Jupiter's atmosphere is driven by strong zonal winds, analogous to the jet stream on Earth. However, unlike Earth, the atmosphere is made up of an array of belts and zones which rotate in an east-west direction. The light zones are regions of upwelling air, forming ammonia cirrus clouds. The dark belts are regions where the cooler the circulation moves downward. Because there are no ammonia clouds, we can see deeper into the atmosphere in these regions. The speed of the main equatorial jet is about 300 km/hr and these speeds have not changed for hundreds of years.

The Great Red Spot

Jupiter's Great Red Spot is a storm that has been present for centuries, first observed by Galileo 400 years ago. The storm lies in the southern hemisphere and is about 30,000 kilometers by 14,000 kilometers, much larger than the planet Earth! It is an anticyclonic storm and has a high-pressure center (unlike storms on Earth that have low-pressure centers). Its winds rotate counterclockwise and have a period of about 6 days. Scientists do not know what drives the storm or if the storm will ever dissipate. One theory suggests the Great Red Spot is continually fueled by the smaller storms that merge with the giant storm.

Ellen Cohen

Kevin Zahnle (NASA Ames Research Center) and Mordecai-Mark Mac Low (American Museum of Natural History)

Motivated by the Comet P/Shoemaker-Levy 9 impact with Jupiter in the summer of 1994, scientists began to calculate the effects of such an impact on the comet as well as on Jupiter. Once the comet had traveled deep into the atmosphere, it was ultimately destroyed in a powerful explosion. This explosion sent a plume of material shooting hundreds, even thousands, of kilometers above the cloud tops. The material eventually fell back into the Jovian atmosphere where it produced the scars or spots seen on Jupiter after the collision.

The simulation

Using a complex computer code to calculate the structure and density of the gas, scientists are able to predict what would happen to the gas in the Jovian atmosphere during the collision. In this movie, the comet explodes sending material ballooning out into the atmosphere. After exploding from the upper cloud deck, the material will soon fall back to the atmosphere and come to equilibrium with the surrounding gas in the atmosphere.

The Great Red Spot

Jupiter's Great Red Spot is a storm that has been present for centuries, first observed by Galileo 400 years ago. The storm lies in the southern hemisphere and is about 30,000 kilometers by 14,000 kilometers, much larger than the planet Earth! It is an anticyclonic storm and has a high-pressure center (unlike storms on Earth that have low-pressure centers). Its winds rotate counterclockwise and have a period of about 6 days. Scientists do not know what drives the storm or if the storm will ever dissipate. One theory suggests the Great Red Spot is continually fueled by the smaller storms that merge with the giant storm.

Brian Abbott