Astronomers have combined observations from the James Webb and Hubble Space Telescopes to better understand how interstellar dust obscures views of distant galaxies.
The newly released image capturing two galaxies which appear close together combines the infrared measurements of the James Webb Space Telescope with visible and ultraviolet imaging performed by the Hubble Space Telescope.
In the image, the two galaxies known by the collective name VV 191 appear to be interacting, but they are actually quite distant. Light from the simple elliptical galaxy visible in the image at left shines through the complex spiral galaxy on the right, which is closer Earth. The light from the background galaxy must pass through the outer portions of the front galaxy’s spiral arms, which Webb’s infrared vision can distinguish in the image. Features detected by Webb are represented by green, yellow, and reddish hues in this image, while Hubble’s observations are represented by shades of blue.
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“By combining data from NASA’s James Webb Space Telescope and NASA’s Hubble Space Telescope, we have achieved more than we anticipated!” Rogier Windhorst, an astronomer at Arizona State University and lead author of the new research, said in a NASA statement (opens in new tab). “Webb’s new data allowed us to trace the light emitted by the bright white elliptical galaxy on the left through the twisting spiral galaxy on the right and identify the effects of interstellar dust in the spiral galaxy.”
Tracking the distribution of dust in galaxies helps astronomers understand how this dust changes the brightness and color of background objects, Windhorst added. In addition, regions with high dust and gas concentrations are likely new areas Stars and planets form, making them particularly attractive targets for astronomers.
In analyzing this image, astronomers made a bonus discovery: they found an unknown and very distant galaxy, made visible thanks to the combination of Webb’s observational superpowers and an effect known as gravitational lensesextremely massive foreground objects refract the light and act like a magnifying glass for faint bodies in the background
The unknown galaxy, which has not yet been named, can be seen to the left of the white elliptical galaxy as an arcing streak of orange light. In fact, the lensed galaxy is visible twice in this image thanks to the duplication effect that accompanies gravitational lensing. However, the second phenomenon is much more difficult to recognize. The galaxy shines as a small, faint dot at 4 o’clock in the enlarged inset.
“These images of the lens galaxy are so faint and so red that they were not detected in Hubble data, but are unmistakable in Webb’s near-infrared image,” Windhorst said in the statement. “Simulations of galaxies with gravitational lenses like this one help us to reconstruct how much mass individual stars have and how much dark matter is in the core of this galaxy.”
VV 191 was chosen as the target for Webb’s observations from about 2,000 galaxies included in Webb’s imagery by citizen scientists as part of the Galaxy Zoo Project. There’s more to this image that warrants in-depth study, Windhorst said. Spiral galaxies of various sizes and colors are scattered in the background, requiring astronomers to do more work to understand how far away they are and how much dust they contain.
The observations were described in two still unpublished papers available through the Arxiv online repository.
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