Astro Bob: Hubble spots 'Earendel,' the farthest star ever seen
Hubble sets a new distance record and sees a single star 12.9 billion light-years away. We're also expecting more aurora Thursday night, March 31.
Astronomers using the Hubble Space Telescope announced the discovery this week of the most distant star ever found. Dubbed Earendel, it's so far away its light takes 12.9 billion years to get here. Brian Welch at Johns Hopkins University led the team that found the object, which formed just 900 million years after the Big Bang, when the cosmos was only about 7% of its current age.
A big fan of "Lord of the Rings" author J.R.R. Tolkien, Welch chose the name Earendel after the half-elven mariner Earendil from Tolkien's "The Silmarillion." Earendil wore a brilliant jewel on his brow that's associated with the "morning star," a reference to the planet Venus. Welch dug a little deeper and discovered it was also the Old English word for "morning star," cementing his choice. It seems a good fit for an object that formed at the dawn of the universe.
Icarus , the previous single-star record holder from 2018, formed when the universe was 4 billion years old, its light taking some 9 billion years to reach the Earth. Normally, no telescope, not even Hubble, would be able to detect a individual star so far away, but thanks to a fortuitous alignment of a massive foreground galaxy cluster, astronomers got lucky. The cluster, called WHL0137-08 and located in the constellation Cetus the Sea Monster , is packed with galaxies. Together they exert a powerful gravitational force, enough to warp the fabric of space and time.
Similar to how a lens bends light to magnify and brighten a distant object, the cluster acted as a colossal magnifying glass, focusing and amplifying the light of a much more distant galaxy that would otherwise be invisible. Within that galaxy, one particular star — Earendil — was so precisely aligned with a particular wrinkle of space-time that it popped into view, along with a double image of one of the galaxy's star clusters. Astronomers call the effect gravitational lensing, and it's been used to mine some of the most distant objects in the universe.
Lensing also distorts the light of more distant objects, stretching Earendel's host galaxy into a narrow arc and producing multiple images of a single star cluster. Gravitational lenses typically magnify by a factor of a few to ten times, but the alignment was so tight in this instance, the star's light was boosted by a factor of thousands.
“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.”
It helps that Earendel is also an exceptional star. The team estimates it's about 50 times more massive than the sun and millions of times brighter. Although likely not a member of the first generation of stars, it formed long before its descendants enriched the cosmos with heavier elements via supernovae and stellar winds, so its composition should be distinctively different from the sun.
To find out, astronomers will observe Earendel with NASA's James Webb Space Telescope to learn more about its brightness, temperature and makeup. The Webb is sensitive to infrared light (light beyond the red end of the rainbow), so it should be able to spot even more remote stars. Expansion of the universe causes light from objects at great distances to stretch and "redden," making them undetectable in visible light.
Massive stars like Earendel use up their nuclear fuel quickly and typically live for just millions of years compared to the sun, which has been around for almost 5 billion years. For this reason the star likely exploded and dissipated long ago. All that remains is its old light, which set on its way nearly 13 billion years ago and through ingenuity and dint of good fortune, finally found us.
The aurora arrived as forecast Wednesday, March 3), but it turned into only a minor G1 storm. On Thursday night, March 31, NOAA is still predicting a G2 moderate storm between the hours of 10 p.m. and 1 a.m. CDT. If it's clear, find a dark place with a view to the north and allow your eyes about 10 minutes to dark-adapt. Good luck!
"Astro" Bob King is a freelance writer for the Duluth News Tribune.