Astronomy Picture of the Day 09-17-04

Explanation: Sprawling across hundreds of light-years, emission nebula IC 1805 is a mix of glowing interstellar gas and dark dust clouds. Only about 7,500 light-years away, stars were born in this region whose nickname - the Heart Nebula - derives from its suggestive shape (seen here sideways). This gorgeous, deep telescopic image of the nebula is very colorful, but if you could travel there and gaze across these cosmic clouds with your own eyes, are those the colors you would really see? The short answer is no, even though the image was made with light visible to the human eye. Light from this and other glowing gas clouds surrounding hot, young stars comes in very narrow bands of emission characteristic of energized atoms within the clouds. In fact, the nebular glow is often dominated by hydrogen atoms emitting light in only a small fraction of that broad region of the spectrum that we see as the color red. Adopting an artificial color scheme commonly used for narrow band images of emission nebulae, this beautifully detailed view shows the light from sulfur atoms in red hues, with hydrogen in green, and oxygen atoms in blue.

Colorful threads and shadows of Saturn
CASSINI NEWS RELEASE
Posted: September 16, 2004

Saturn's faintly banded atmosphere is delicately colored and its threadbare rings cross their own shadows in this marvelous natural color view from Cassini.

Credit: NASA/JPL/Space Science Institute
Download larger image version here

The planet and its rings would nearly fill the space between Earth and the Moon. Yet, despite their great breadth, the rings are a few meters thick and in some places, very translucent. In this image, we can see through the C ring, which is closest to Saturn, and through the Cassini division, the 4,800-kilometer- (2,980-mile-) wide gap that arcs across the top of the image and separates the optically thick B ring from the A ring. The part of the atmosphere seen through the gap appears darker and more bluish due to scattering at blue wavelengths by the cloud-free upper atmosphere.

The different colors in Saturn's atmosphere are due to particles whose composition is yet to be determined.

The image was obtained with the Cassini spacecraft narrow angle camera at a distance of 7.6 million kilometers (4.7 million miles) from Saturn. Images taken with red, green and blue filters were combined to create this color view. The image scale is 46 kilometers (28 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras, were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

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