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MAP OF THE EDGEA map of neutral atoms, generated by NASA's Interstellar Boundary Explorer, shows a ribbonlike structure near the edge of the heliosphere, the boundary between the solar system and interstellar space. The ribbon is not predicted by any model. Blue denotes the lowest intensity of atoms, red the highest. Image from Southwest Research Institute

The edge of the solar system is tied up with a ribbon, astronomers have discovered. The first global map of the solar system reveals that its edge is nothing like what had been predicted. Neutral atoms, which are the only way to image the fringes of the solar system, are densely packed into a narrow ribbon rather than evenly distributed.

“Our maps show structure and energy spectra that are completely different from what any model has predicted,” says study coauthor Herbert Funsten of the Los Alamos National Laboratory in New Mexico.

NASA’s Interstellar Boundary Explorer satellite, or IBEX, discovered the narrow ribbon, which completes nearly a full circle across the sky. The density of neutral atoms in the band is two to three times that in adjacent regions.

These and related findings, reported in six papers posted online October 15 in Science, will not only send theorists back to the drawing board, researchers say, but may ultimately provide new insight on the interaction between the heliosphere — the vast bubble in which the solar system resides — and surrounding space.

The bubble is inflated by solar wind, the high-speed stream of charged particles blowing out from the sun to the solar system’s very edge. For 48 years, researchers have assumed that the solar wind sculpted the structure at the heliosphere’s boundary with interstellar space, says Tom Krimigis of Johns Hopkins University’s Applied Physics Laboratory in Laurel, Md.. But the newly found ribbon’s orientation suggests that the galaxy’s magnetic field, just outside the heliosphere, seems to be the chief organizer of structure in this region, says theorist Nathan Schwadron of Boston University, a lead author of one of the studies.

It’s not known whether the ribbon lasts for just a few years or is a permanent feature.

Equally puzzling are observations of the same boundary region with an instrument on the Cassini spacecraft, which recorded the density of atoms at higher energies, above 6,000 electron volts. From its vantage point at Saturn, Cassini sees a belt rather than a ribbonlike structure, a team led by Krimigis also reports in Science. The belt is substantially broader than the ribbon seen by IBEX but is in the same general area.

The heliosphere shields the solar system from 90 percent of energetic cosmic rays — high-speed charged particles that would otherwise bombard the planets and harm life. Understanding more about the heliosphere and its ability to filter out galactic cosmic rays could be critical for assessing the safety of human space travel, Schwadron notes. The new findings may also help predict how the heliosphere varies in shape and size as it moves through the galaxy and encounters regions of space having different densities and magnetic field strengths.

The ribbon found by IBEX, recorded at energies between 200 and 6,000 electron volts, is brightest at about 1,000 electron volts and lies between about 100 and 125 astronomical units from the sun, notes David McComas of the Southwest Research Institute in San Antonio. One astronomical unit is the distance between the Earth and the sun. The atoms recorded by IBEX, which orbits Earth, took a year or two, depending on their energies, to reach the craft from the outer edge of the heliosphere.

The IBEX ribbon runs perpendicular to the direction of the galaxy’s magnetic field at the interstellar boundary, an indication that the field has a much stronger than expected influence on the sun’s environs, report Schwadron and his colleagues. One possibility is that pressure from this external magnetic field has forced particles just inside the heliosphere to bunch together into a ribbon.

“First and foremost, this is a big surprise because we thought we know a lot about this region, the edge of the heliosphere,” McComas says. The Voyager 1 craft in 2004 (SN: 1/3/04, p. 7) and the Voyager 2 craft in 2007 (SN: 8/2/08, p. 7) journeyed to opposite sides of this fringe region of the solar system and crossed the termination shock — where the solar wind encounters a shock that precedes the influx of particles drifting into the solar system from interstellar space. Both craft recorded the density of particles and the strength of the magnetic fields.

Both Voyager 1 and 2 missed seeing the newly found ribbon because it spans a region between their flight paths, says McComas. No existing model can explain the ribbon, he adds, which was found independently by two instruments on IBEX.

Researchers had assumed that the pressure from the solar wind would compress in the heliosphere in the direction that the solar system was moving through space and create a cometlike tail in the opposite direction, notes Krimigis. “Now we know that’s wrong,” he says.

IBEX has also generated the first maps of neutral hydrogen and oxygen atoms entering the solar system from interstellar space. Previous observations had traced only incoming helium atoms. The sensitivity of the IBEX instruments allowed researchers to record the relatively small number of oxygen atoms that travel from beyond the termination shock, about 16 billion kilometers from Earth, to the spacecraft, notes study coauthor Stephen Fuselier of the Lockheed Martin Advanced Technology Center in Palo Alto, Calif..

Hydrogen atoms are more abundant than either helium or oxygen but their low mass means they are easily swept aside by the high-speed solar wind and can’t readily be detected. The sun’s unusually low activity during the current minimum in the solar cycle allowed more of the hydrogen atoms from the outer heliosphere to travel unimpeded to the inner solar system, enabling IBEX to record those atoms, Fuselier says.

How Do Space Pictures Get So Pretty?Photoshop, of course.

A picture taken by the Spitzer Space Telescope was released on Monday; the image, which depicts the birth of 100,000 stars in a far-away gas cloud, shows a splotchy shape in light red, set against a background of speckled blue-white stars and olive mist. How do these photographs get to be so pretty?

Teams of specialists on the ground gussy them up for public consumption. Here's how it works: Telescopes like the Spitzer and the Hubble take black-and-white pictures using different filters to capture particular wavelengths of light. (The image released this week is a composite created from four shots of the same thing.) Then these pictures are sent back to Earth via the Deep Space Network, a set of large antennae set up around the world.

For the Hubble telescope, the image files can be up to 70MB in size, with a resolution of 16.7 megapixels. Data is downloaded from the telescope at a speed comparable to that of a good Internet connection.

Once the images are on the ground, scientists can look at them in the FITS ("Flexible Image Transport System") file format, a standard protocol used among astronomers. For analysis, most scientists use the data in this form-as grey-scale images representing light at different wavelengths.

To create an image suitable for public viewing, the scientists send the FITS files over to a public outreach team. Specialists on the team-who tend to be astronomers with graduate degrees and a passion for graphics and photography-begin the process of converting the information into the images sent out in press releases.

First, they put the image into a file format appropriate for media. That means that the data from the FITS files, which show a range of about 65,000 shades of grey, must be squeezed into a standard JPEG or TIFF file, with only 256 shades. This process is counterintuitively called "stretching" the data and must be done carefully to preserve important features and enhance details in the finished product.

Then each grey-scale image is assigned a color. In reality, each shot already represents a color-the wavelength of light captured by the filter when that picture was taken. But in some cases the images represent colors that we wouldn't be able to see. (The Spitzer, for example, registers the infrared spectrum.) To create a composite image that has the full range of colors seen by the human eye, an astronomer picks one image and makes it red, picks another and makes it blue, and completes the set by coloring a third image green. When he overlays the three images, one on top of the other, they produce a full-color picture. (Televisions and computer monitors create color in the same way.)

Sometimes the team assigns new colors even when the original pictures were taken in the visible spectrum. An object that would in real life comprise several indistinguishable shades of red might be represented to the public as the composite of three pictures in red, green, and blue. As a general rule, professional "visualizers" try to assign red to the image showing the longest wavelengths of light and blue to the one showing the shortest. (This parallels the relationship among the colors in the visible spectrum.)

Finally, the colorized images are cropped, rotated to the most dramatic orientation, and cleaned of instrument errors and other unsightly blemishes. Most of this work is done in Photoshop, using a freely downloaded plug-in that allows users to convert from the FITS format. (The original telescope images are also available, so you can create your own color gas cloud picture at home.)

Space pictures weren't always so pretty. David Malin, a scientist at a telescope facility in Australia, did the pioneering work in color visualization more than 20 years ago. He figured out how to use black-and-white photographic film and color filters to create full-color visualizations. The modern master of the field is Zoltan Levay, who works on images sent down from the Hubble.

LONDON - The tiny tangled threads of the world's oldest spider web have been found encased in a prehistoric piece of amber, a British scientist said Monday.

Oxford University paleobiologist Martin Brasier said the 140-million-year-old webbing provides evidence that arachnids had been ensnaring their prey in silky nets since the dinosaur age. He also said the strands were linked to each other in the roughly circular pattern familiar to gardeners the world over.

"You can match the details of the spider's web with the spider's web in my garden," Brasier said.

The web was found in a small piece of amber picked up by an amateur fossil-hunter scouring the beaches on England's south coast about two years ago, Brasier said. A microscope revealed the existence of tiny threads about 1 millimeter (1/20th of an inch) long amid bits of burnt sap and fossilized vegetable matter.

While not as dramatic as a fully preserved net of spider silk, the minuscule strands show that spiders had been spinning circle-shaped webs well into prehistory, according to Simon Braddy, a University of Bristol paleobiologist uninvolved with the find.

"It's not a striking, perfect web," Braddy said. "(But) this seems to confirm that spiders were building orb webs back in the early Cretaceous" - the geological term for the period of time between 145.5 and 65.5 million years ago when dinosaurs and small mammals shared the earth.

Spider experts believe that webs were developed even earlier, but the delicate gossamer threads rarely leave any trace. Amber, or fossilized tree resin, can occasionally conserve bits of web - an earlier find in Lebanon was dated to 130 million years ago, according to Brasier.