Webb, Hubble space telescopes capture an intriguing galactic pair

By Ashley Strickland, CNN

When astronomers combine the observational powers of James Webb Space Telescope and Hubble Space Telescope, they capture more detailed portraits of the cosmos.

A new image showcasing a galactic pair, shared by NASA on Wednesday, is the striking result of using data from both space observatories.

The telescopes each contributed observations across different wavelengths of light. Webb can detect infrared light, which is invisible to the human eye, while Hubble has the capability to observe the two galaxies in visible light as well as ultraviolet light. The duo of the elliptical galaxy and the spiral galaxy is known as VV 191, and it’s located about 700 million light-years away from Earth.

“We got more than we bargained for by combining data from NASA’s James Webb Space Telescope and NASA’s Hubble Space Telescope!” wrote Webb interdisciplinary scientist and Arizona State University Regents Professor Rogier Windhorst for NASA’s Webb blog.

“Webb’s new data allowed us to trace the light that was emitted by the bright white elliptical galaxy, at left, through the winding spiral galaxy at right — and identify the effects of interstellar dust in the spiral galaxy. … Webb’s near-infrared data also show us the galaxy’s longer, extremely dusty spiral arms in far more detail, giving the arms an appearance of overlapping with the central bulge of the bright white elliptical galaxy on the left.”

The image is an early result from the observation program called the Prime Extragalactic Areas for Reionization and Lensing Science, or PEARLS, through the Webb Telescope, which has not yet been through the peer-review process. The study has been submitted to The Astrophysical Journal.

Scientists selected the galactic pair from nearly 2,000 candidates identified by Galaxy Zoo citizen science volunteers. These small galaxies, which appear to be very close together, aren’t actually interacting with one another, but they allow researchers to trace and compare galactic dust.

“Understanding where dust is present in galaxies is important, because dust changes the brightness and colors that appear in images of the galaxies,” Windhorst wrote. “Dust grains are partially responsible for the formation of new stars and planets, so we are always seeking to identify their presence for further studies.”

But a closer look at this galactic pair isn’t the only celestial wonder this composite image revealed. Other galaxies are also visible behind the pair, and one of these points of light led to a second discovery within the new image. This phenomenon, called gravitational lensing, occurs when foreground galaxies act as a magnifying glass for the objects behind them.

Scientists used the same technique for Webb’s first image released in July. The space telescope “delivered the deepest and sharpest infrared image of the distant universe to date,” according to NASA.

Above the white elliptical galaxy to the left is a faint red arc, which is actually a very distant galaxy. The gravity of the elliptical galaxy in the foreground has bent the more distant galaxy’s light. The warping of the distant galaxy also causes it to reappear as a red dot to the lower right of the elliptical galaxy.

The images of the distant galaxy are so faint that they weren’t recognized in the Hubble data, but they appear clearly in Webb’s near-infrared observation.

“Simulations of gravitationally lensed galaxies like this help us reconstruct how much mass is in individual stars, along with how much dark matter is in the core of this galaxy,” Windhorst wrote.

Beyond the insights astronomers are gleaning about VV 191, the background of this Webb image hints at more mysteries deeper in the universe yet to be revealed, he added. “Two patchy spirals to the upper left of the elliptical galaxy have similar apparent sizes, but show up in very different colors. One is likely very dusty and the other very far away, but we — or other astronomers — need to obtain data known as spectra to determine which is which.”

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