Readers discuss colors and spikes in the James Webb Space Telescope’s images and more

Space palettes

The stunning first pictures from the James Webb Space Telescope provide the deepest and clearest look yet into outer space, Lisa Grossman reported in “Postcards from a new space telescope” (SN: 8/13/22, p. 30).

JWST observes space using infrared, a form of light not visible to the human eye. To visualize the images, scientists colorize them. Reader John Dohrmann wondered how that colorizing is done.

JWST’s images are colorized by senior data imaging developer Joseph DePasquale and science visuals developer Alyssa Pagan, both of the Space Telescope Science Institute in Baltimore, Grossman says. Their basic rule of thumb is to paint the pictures using wavelengths of light as a guide. The light emitted in the longest wavelength in an image is assigned the color red, and the shortest blue, she says. Wavelengths in between are assigned a spectrum of greens and yellows (SN: 3/17/18, p. 4). But there are also other considerations, such as data on the chemical compositions of stuff in the image. How to colorize those elements can be more of an art than a science, Grossman says. “There’s a subjective artistry to it too.”

Reader Stu Kantor asked why some stars in the JWST images appear to have eight spikes — six large ones and two smaller ones (see “Out of this world,” below).

Those are called diffraction spikes, Grossman says, and they’re an artifact of the telescope’s optical setup. JWST has two mirrors: a primary hexagonal mirror and a smaller secondary mirror that sits in front of the primary mirror and is held up by three support beams. When it hits the telescope, light bends at the two edges of each of the secondary mirror’s supports, producing six diffraction spikes. The six edges of the primary mirror also create six spikes. Scientists designed the telescope so that four of the spikes from the secondary supports overlap with four of the primary mirror’s spikes, Grossman says, so though there are 12 spikes, we see only eight.

Diffraction spikes are not unique to JWST. “Images from the Hubble Space Telescope have these too, but they only have four,” Grossman says. “The eight points are a distinctive feature of JWST, like an artist’s signature.”

On the nose

Scientists discovered a neural link in the dog brain that connects the olfactory system to vision, which may help explain why humankind’s best friend is such a good sniffer, Laura Sanders reported in “New nose-to-brain link ID’d in dogs” (SN: 8/13/22, p. 9).

The story inspired several readers to reflect on the behavior of their own furry friends.

“I now know why my German shepherd could not play the simplest version of the shell game,” Ed Hughes wrote. “Using a small piece of dog food and two Dixie cups … one shift in the location of the cup hiding the dog food completely confused her. I could watch her eyes follow the cup, but she never picked the cup with the dog food. She had prelocated it with her nose, and anything her eyes detected was completely ignored.”

Reader Roy R. Ferguson shared his fascination with dogs’ sniffing abilities, having worked with the animals in search and rescue efforts for the last 20 years with his wife.

“We have learned to allow the K-9s to do their work with as little super​vision as possible,” Ferguson wrote. “They constantly make decisions that seem unusual at the time but make sense once the full story is known.”

“Our K-9s have located drops of blood in light rain and human decomposition in various vehicles. Live finds include one man who wandered over 10 miles after a head wound and a 6-year-old who had been out all night …. The child find was notable due to the large amount of scent contamination in the area,” Ferguson added.

“We have no idea how these amazing creatures do such marvelous feats. They work their hearts out for nothing more than praise and a toy reward,” Ferguson wrote. “It has occurred to [us] that we are there to provide them support, drive and work the radio. In return, they make us look as though we know what we’re doing.”