The James Webb Space Telescope is hailed as the successor of the Hubble Telescope, but Hubble, the "old-timer", still has a certain vitality. Now, the two iconic instruments have teamed up to capture a deep view of the colorful "Christmas Tree Cluster" of stars.
The Hubble Space Telescope has been taking stunning images since its launch in 1990, but it won't be abandoned just because another powerful new member takes to the sky. Hubble primarily observes the universe using visible light wavelengths, which are the wavelengths that the human eye can see. The Webb telescope focuses on infrared light, which is more suitable for observing objects farther away in space and time.
Now, astronomers have combined these two unique views of the universe to image a region of space in greater detail. The object of the photo is a galaxy cluster called MACS0416, which is about 4.3 billion light-years away from Earth. In fact, two galaxy clusters are currently merging, eventually forming one giant galaxy cluster. Some of the objects in the image are actually farther away from Earth, but their light is magnified or distorted due to a phenomenon called gravitational lensing.
The Hubble image was originally taken in 2014 and required approximately 122 hours of exposure time. The Webb images, taken earlier this year over a period of about 22 hours, bring an entirely new group of galaxies into focus.
In the resulting composite image, different colors of light indicate the distance of the galaxies and which telescope captured them. Blue galaxies have the shortest wavelengths, are easiest for Hubble to see, and are typically galaxies closer to our Earth. The green and yellow are in the middle, while the red galaxies are Webb's work—they're often farther away from Hubble or so shrouded in dust that they're largely invisible to Hubble.
Rogier Windhorst, author of the Webb study, said: "We are building on Hubble's legacy and pushing toward farther distances and dimmer objects. Only by combining Webb data with Hubble data will the whole picture become clear."
The images taken by the Webb telescope are not purely aesthetic. The team was looking for "transients" - objects whose brightness changes over time - so they made multiple observations separated by several weeks to see how the objects changed. Within this field of view, they found 14 transients, 12 of which were concentrated in three galaxies that were highly magnified by gravitational lensing. This suggests that they are individual stars or star systems that briefly entered a specific alignment that dramatically amplified their brightness. The other two were likely supernovae, the team said.
"We call MACS0416 the Christmas Tree Galaxy Cluster, both because of its colorful colors and because of these twinkling lights we found in it," said Yan Haojing, lead author of one of the studies. "We see transients everywhere."
One of the studies was published in the journal Astronomy & Astrophysics, and the other has been accepted for publication in The Astrophysical Journal.