All We Are Is Dust in the Interstellar Wind

Radio/optical composite of the Orion Molecular Cloud Complex, which includes the Orion Nebula (bottom), featuring a dust-rich star-forming filament called OMC-2/3. Orange: Green Bank Telescope data. Credit: S. Schnee, et al.; B. Saxton, B. Kent (NRAO/AUI/NSF)

Cosmic dust is not simply something to sweep under the rug and forget about.

Instead, National Science Foundation (NSF)-funded astronomers are studying and even mapping it to learn more about what it might be hiding from us, where it comes from and what it's turning into.

Some researchers are delving deep down to see how dust comes together at the atomic level, while others are looking at the big picture to see where stars and planets might be forming in dusty stellar nurseries. Recent discoveries, such as that of a very young galaxy containing much more dust than expected, have shown us that we still have much to learn about where exactly all this dust comes from.

A little bit of dust makes a very large problem

Although dust only makes up about 1 percent of the interstellar medium (the stuff between the stars), it can have big effects on astronomical observations. Dust has a bad reputation because it gets in the way by absorbing and scattering the visible light from objects such as far-off galaxies and stars, making them difficult or impossible to observe with optical telescopes.

The scattering effect dust has is known as "reddening" -- dust scatters the blue light coming from an object, making it appear redder. This occurs because dust has a greater effect on light with short wavelengths, such as blue. A similar effect is what causes sunsets to appear red.

Astronomers can tell a lot about a star simply by its color, so this reddening effect can trick us into thinking a star is cooler and dimmer than it actually is. However, thanks to NSF-funded astronomers like Doug Finkbeiner of the Harvard-Smithsonian Center for Astrophysics, we can now correct for dust reddening and recover a star's intrinsic color.

Finkbeiner first began studying cosmic dust as a graduate student at the University of California, Berkeley in the late 1990s. Dust may seem like an odd thing to dedicate an astronomical career to but "dust is not as obscure as it sounds," Finkbeiner said. "Objects like the Orion Nebula, the Horsehead Nebula, and the Pillars of Creation are dense, dusty clouds intermingled with bright stars, making a beautiful scene. But every part of the sky has at least some dust, and even a tiny amount of dust can interfere with astronomical measurements, so we need a way to correct for it."

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Source:  Harvard-Smithsonian Center for Astrophysics (CfA)

Star formation and magnetic turbulence in the Orion Molecular Cloud

Star formation and magnetic turbulence in the Orion Molecular Cloud

Copyright: ESA and the Planck Collaboration. Hi-res JPG

An annotated version of the image can be found here

With blue hues suggestive of marine paradises and a texture evoking the tranquil flow of sea waves, this image might make us daydream of sandy beaches and exotic holiday destinations. Instead, the subject of the scene is intense and powerful, because it depicts the formation of stars in the turbulent billows of gas and dust of the Orion Molecular Cloud.

The image is based on data from ESA’s Planck satellite, which scanned the sky between 2009 and 2013 to study the cosmic microwave background, the most ancient light in the Universe’s history. While doing so, Planck also detected foreground emission from material in the Milky Way, as well as from other galaxies.

Our Galaxy is pervaded by a diffuse mixture of gas and dust that occasionally becomes denser, creating giant gas clouds where stars can form. While present only in traces, dust is a crucial ingredient in these interstellar clouds. It also shines brightly at some of the wavelengths that were probed by Planck, so astronomers can use these data to learn more about the cradles of star formation.

In addition, dust grains have elongated shapes and tend to align their longest axis at right angles to the direction of the Galaxy’s magnetic field. This makes their emission partly ‘polarised’ – it vibrates in a preferred direction. Since Planck was equipped with polarisation-sensitive detectors, its scans also contain information about the direction of the magnetic field threading the Milky Way.

This image combines a visualisation of the total intensity of dust emission, shown in the colour scale, with an indication of the magnetic field’s orientation, represented by the texture. Blue hues correspond to regions with little dust, while the yellow and red areas reflect denser (and mostly hotter) clouds containing larger amounts of dust, as well as gas.

The red clumps at the centre of the image are part of the Orion Molecular Cloud Complex, one of the closest large regions of star formation, only about 1300 light-years from the Sun. The most prominent of the red clumps, to the lower left of centre, is the famous Orion Nebula, also known as M42. This is visible to the naked eye in the constellation Orion, just below the three stars forming the ‘belt’ of the mythological hunter. 

The magnetic field appears regular and organised in almost parallel lines in the upper part of the image: this is a result of the large-scale arrangement of the magnetic field along the Galactic plane, which is located above the top of this image. However, the field becomes less regular in the central and lower parts of the image, in the region of the Orion Molecular Cloud. Astronomers believe that the turbulent structure of the magnetic field observed in this and other star-forming clouds is related to the powerful processes taking place when stars are being born.

The emission from dust is computed from a combination of Planck observations at 353, 545 and 857 GHz, whereas the direction of the magnetic field is based on Planck polarisation data at 353 GHz. The image spans about 40º across.

Source: ESA

Horsehead of a Different Color

The famous Horsehead nebula of visible-light images (inset) looks quite different when viewed in infrared light, as seen in this newly released image from NASA's Spitzer Space Telescope. Image credit: NASA/JPL-Caltech/ESO.  › Full image and caption

Sometimes a horse of a different color hardly seems to be a horse at all, as, for example, in this newly released image from NASA's Spitzer Space Telescope. The famous Horsehead nebula makes a ghostly appearance on the far right side of the image, but is almost unrecognizable in this infrared view. In visible-light images, the nebula has a distinctively dark and dusty horse-shaped silhouette, but when viewed in infrared light, dust becomes transparent and the nebula appears as a wispy arc.

The Horsehead is only one small feature in the Orion Molecular Cloud Complex, dominated in the center of this view by the brilliant Flame nebula (NGC 2024). The smaller, glowing cavity falling between the Flame nebula and the Horsehead is called NGC 2023. These regions are about 1,200 light-years away.

The two carved-out cavities of the Flame nebula and NGC 2023 were created by the destructive glare of recently formed massive stars within their confines. They can be seen tracing a spine of glowing dust that runs through the image.

The Flame nebula sits adjacent to the star Alnitak, the westernmost star in Orion's belt, seen here as the bright blue dot near the top of the nebula.

In this infrared image from Spitzer, blue represents light emitted at a wavelength of 3.6-microns, and cyan (blue-green) represents 4.5-microns, both of which come mainly from hot stars. Green represents 8-micron light and red represents 24-micron light. Relatively cooler objects, such as the dust of the nebulae, appear green and red. Some regions along the top and bottom of the image extending beyond Spitzer's observations were filled in using data from NASA's Wide-field Infrared Survey Explorer, or WISE, which covered similar wavelengths across the whole sky.

NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. 

For more information about Spitzer, visit: http://spitzer.caltech.edu - http://www.nasa.gov/spitzer

Media Contact

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Jet Propulsion Laboratory, Pasadena, Calif.
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Source: JPL-Caltech