Newswise — NASA’s James Webb Space Telescope has followed up on observations by the Hubble Space Telescope of the farthest star ever detected in the very distant universe, within the first billion years after the big bang. Webb’s NIRCam (Near-Infrared Camera) instrument reveals the star to be a massive B-type star more than twice as hot as our Sun, and about a million times more luminous.

The star, which the research team has dubbed Earendel, is located in the Sunrise Arc galaxy and is detectable only due to the combined power of human technology and nature via an effect called gravitational lensing. Both Hubble and Webb were able to detect Earendel due to its lucky alignment behind a wrinkle in space-time created by the massive galaxy cluster WHL0137-08. The galaxy cluster, located between us and Earendel, is so massive that it warps the fabric of space itself, which produces a magnifying effect, allowing astronomers to look through the cluster like a magnifying glass.  

While other features in the galaxy appear multiple times due to the gravitational lensing, Earendel only appears as a single point of light even in Webb’s high-resolution infrared imaging. Based on this, astronomers determine the object is magnified by a factor of at least 4,000, and thus is extremely small – the most distant star ever detected, observed 1 billion years after the big bang. The previous record-holder for most distant star was detected by Hubble and observed around 4 billion years after the big bang. Another research team using Webb recently identified a gravitationally lensed star they nicknamed Quyllur, a red giant star observed 3 billion years after the big bang.

Stars as massive as Earendel often have companions. Astronomers did not expect Webb to reveal any companions of Earendel since they would be so close together and indistinguishable on the sky. However, based solely on the colors of Earendel, astronomers think they see hints of a cooler companion star. This light has been stretched by the expansion of the universe to wavelengths longer than Hubble’s instruments can detect, and so was only detectable with Webb. 

Webb’s NIRCam also shows other notable details in the Sunrise Arc, which is the most highly magnified galaxy yet detected in the universe’s first billion years. Features include both young star-forming regions and older established star clusters. On either side of the wrinkle of maximum magnification, which runs right through Earendel, these features are mirrored by the distortion of the gravitational lens. The region forming stars appears elongated, and is estimated to be at least 10 million years old. Smaller dots on either side of Earendel are two images of one older, more established star cluster, estimated to be 10 million years or older. Astronomers determined this star cluster is gravitationally bound and likely to persist until the present day. This shows us how the globular clusters in our own Milky Way might have looked when they formed 13 billion years ago.

Astronomers are currently analyzing data from Webb’s NIRSpec (Near-Infrared Spectrograph) instrument observations of the Sunrise Arc galaxy and Earendel, which will provide precise composition and distance measurements for the galaxy.

Since Hubble’s discovery of Earendel, Webb has detected other very distant stars using this technique, though none quite as far as Earendel. The discoveries have opened a new realm of the universe to stellar physics, and new subject matter to scientists studying the early universe, where once galaxies were the smallest detectable cosmic objects. The research team has cautious hope that this could be a step toward the eventual detection of one of the very first generation of stars, composed only of the raw ingredients of the universe created in the big bang – hydrogen and helium. 

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

For more information or to download full-resolution images, visit https://webbtelescope.org/contents/news-releases/2023/news-2023-132.

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Newswise: Webb Reveals Colors of Earendel, Most Distant Star Ever Detected

Credit: Image: NASA, ESA, CSA, (STScI/AURA for ESA; Johns Hopkins University), B. Welch (NASA’s Goddard Spaceflight Center; University of Maryland, College Park). Image processing: Z. Levay

Caption: This image from NASA’s James Webb Space Telescope of a massive galaxy cluster called WHL0137-08 contains the most strongly magnified galaxy known in the universe’s first billion years: the Sunrise Arc, and within that galaxy, the most distant star ever detected. The star, nicknamed Earendel, was first discovered by the Hubble Space Telescope. Follow-up observations using Webb’s NIRCam (Near-Infrared Camera) reveals the star to be a massive B-type star more than twice as hot as our Sun, and about a million times more luminous. Earendel is positioned along a wrinkle in spacetime that gives it extreme magnification, allowing it to emerge into view from its host galaxy, which appears as a red smear across the sky. The star is detectable only due to the combined power of human technology and nature via an effect called gravitational lensing. In this image, the Sunrise Arc appears just below the diffraction spike at the 5 o’clock position. The fuzzier, white galaxies at the center of the image are part of the galaxy cluster bound together by gravity. The various redder, curved galaxies are background galaxies picked up by Webb’s sensitive mirror.

Newswise: Webb Reveals Colors of Earendel, Most Distant Star Ever Detected

Credit: Image: NASA, ESA, CSA, (STScI/AURA for ESA; Johns Hopkins University), B. Welch (NASA’s Goddard Spaceflight Center; University of Maryland, College Park). Image processing: Z. Levay

Caption: This image from NASA’s James Webb Space Telescope shows a massive galaxy cluster called WHL0137-08, and at the right, an inset of the most strongly magnified galaxy known in the universe’s first billion years: the Sunrise Arc. Within that galaxy is the most distant star ever detected, first discovered by the Hubble Space Telescope. Webb’s NIRCam (Near-Infrared Camera) instrument reveals the star, nicknamed Earendel, to be a massive B-type star more than twice as hot as our Sun, and about a million times more luminous. Stars of this mass often have companions. Astronomers did not expect Webb to reveal any companions of Earendel since they would be so close together and indistinguishable on the sky. However, based solely on the colors of Earendel detected by Webb, astronomers think they see hints of a cooler companion star.