NASA has announced that Hubble has ‘established an extraordinary new benchmark’ by spotting the farthest star ever seen. The star, named Earendel, existed within the first billion years following the big bang. The light from the previous record holder, Icarus, took 9 billion years to reach Earth. The light from Earendel took 12.8 billion years to reach Hubble. It’s worth noting that Earendel isn’t the oldest known star. That honor belongs to Methuselah, which Hubble discovered in 2013.
Earendel appears to us now as it appeared when the universe was a mere 7 percent of its current age. This corresponds to a 6.2 redshift. As the universe expands, light from distant objects is stretched, or shifted, toward longer (redder) wavelengths as it travels toward us. Observed objects as far away as Earendel have previously been clusters of stars rather than a single star.
‘We almost didn’t believe it at first, it was so much farther than the previous most-distant, highest redshift star,’ said astronomer Brian Welch of the Johns Hopkins University in Baltimore, MD, and lead author of the research paper that outlines the momentous discovery. The paper is published in Nature. NASA points out that the discovery was made from data collected during Hubble’s RELICS (Reionization Lensing Cluster Survey) program, which is led by co-author Dan Coe at the Space Telescope Science Institute (STScI), which is also located in Baltimore. ‘Normally at these distances, entire galaxies look like small smudges, with the light from millions of stars blending together,’ said Welch. ‘The galaxy hosting this star has been magnified and distorted by gravitational lensing into a long crescent that we named the Sunrise Arc.’
Earendel is so far away and so old that it may not have included the same type of composition as newer stars. ‘Earendel existed so long ago that it may not have had all the same raw materials as the stars around us today,’ explained Welch. ‘Studying Earendel will be a window into an era of the universe that we are unfamiliar with, but that led to everything we do know. It’s like we’ve been reading a really interesting book, but we started with the second chapter, and now we will have a chance to see how it all got started.’
The research team, led by Welch and Coe, estimate that Earendel is ‘at least 50 times the mass of our Sun and millions of times as bright.’ It may even rival the most massive known stars. Despite its mass and brightness, Earendel wouldn’t have been visible if not for the natural magnification provided by a huge galaxy cluster, WHL0137-08, that’s located between Earth and Earendel. WHL0137-08’s mass ‘warps the fabric of space, creating a powerful natural magnifying glass that distorts and greatly amplifies the light from distant objects behind it.’ The distortion magnified Earendel’s brightness by a thousandfold, or perhaps even more. Scientists can’t tell yet if Earendel is a binary star. Generally, massive stars, like Earendel, have at least one companion star.
|Credits: Science: NASA, ESA, Brian Welch (JHU), Dan Coe (STScI); Image processing: NASA, ESA, Alyssa Pagan (STScI)|
The good news is that we won’t have to wait long to learn more about Earendel. Astronomers think that the star will remain magnified for years, allowing the James Webb Space Telescope (https://jwst.nasa.gov) to turn its attention toward Earendel. ‘With Webb we expect to confirm Earendel is indeed a star, as well as measure its brightness and temperature,’ Coe said. ‘We also expect to find the Sunrise Arc galaxy is lacking in heavy elements that form in subsequent generations of stars. This would suggest Earendel is a rare, massive metal-poor star.’ By measuring brightness and temperature, scientists will better understand Earendel’s type and stage in its lifecycle.
NASA adds, ‘Earendel’s composition will be of great interest for astronomers, because it formed before the universe was filled with the heavy elements produced by successive generations of massive stars. If follow-up studies find that Earendel is only made up of primordial hydrogen and helium, it would be the first evidence for the legendary Population III stars, which are hypothesized to be the very first stars born after the big bang. While the probability is small, Welch admits it is enticing all the same.’ Webb may also be able to see stars even further away than Earendel. ‘I would love to see Webb break Earendel’s distance record,’ Welch added.