Hubble spots the farthest star ever seen, whose light took 12.9 billion years to reach Earth

 

 

Earlier this week, NASA announced that the Hubble Space Telescope had spotted the farthest star ever seen. The ESA writes, 'NASA's Hubble Space Telescope has established an extraordinary new benchmark: detecting the light of a star that existed within the first billion years after the universe's birth in the big bang – the farthest individual star ever seen to date.' To put that into perspective, the light from the newly-spotted star took 12.9 billion years to reach Earth. When the light that reached Hubble left the star, the universe was only seven percent of its current age.

The newly-detected star, nicknamed Earendel, which means 'morning star' in Old English, was spotted at redshift 6.2. As the universe expands, light from distant objects is stretched, or 'shifted' to longer (redder) wavelengths, hence the term 'redshift.' You can learn more about redshift here.

Seeing the star is quite the feat. While Hubble has spotted galaxies from further away, 13.4 billion light-years away, in fact, this is the first time a single star has been seen from so far away. Even though astronomers estimate that the star is massive – at least 50 times the mass of our Sun – it is only visible to Hubble thanks to natural magnification. Between Hubble and Earendel is a huge galaxy cluster, WHL0137-08. This galaxy cluster is so massive that it warps the fabric of space, which creates a magnifying glass of sorts. The warping effect of the galaxy amplifies the light from distant objects behind it, in this case, that includes Earendel. Earendel appears on, or very close to, a ripple in the fabric of space. ESA writes, 'This ripple, which is defined in optics as a 'caustic,' provides maximum magnification and brightening. The effect is analogous to the rippled surface of a swimming pool creating patterns of bright light on the bottom of the pool on a sunny day. The ripples on the surface act as lenses and focus sunlight to maximum brightness on the pool floor.'

Astronomer Brian Welch of Johns Hopkins University, lead author of a new paper in Nature on the discovery, said of Earendel, 'We almost didn't believe it at first, it was so much farther than the previous most-distant, highest redshift star. Normally at these distances, entire galaxies look like small smudges, with the light from millions of stars blending together. 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 old that it made be made from different raw materials than the stars around us today. Welch added, '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.'

 

'This detailed view highlights the star Earendel's position along a ripple in space-time (dotted line) that magnifies it and makes it possible for the star to be detected over such a great distance—nearly 13 billion light-years. Also indicated is a cluster of stars that is mirrored on either side of the line of magnification. The distortion and magnification are created by the mass of a huge galaxy cluster located in between Hubble and Earendel. The mass of the galaxy cluster is so great that it warps the fabric of space, and looking through that space is like looking through a magnifying glass—along the edge of the glass or lens, the appearance of things on the other side are warped as well as magnified.'

Credits: Science: NASA, ESA, Brian Welch (JHU), Dan Coe (STScI); Image processing: NASA, ESA, Alyssa Pagan (STScI)

The discovery was made using data collected by Hubble's RELICS (Reionization Lensing Cluster Survey) program, which paper co-author Dan Coe leads at the Space Telescope Science Institute (STScI). Earendel will remain highly magnified for years, meaning that it can be observed by NASA's new James Webb Space Telescope, which is currently in the later stages of its preparatory work in space and should begin scientific operations this summer. '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,' Coe said.

The composition of Earendel is of great interest to astronomers. The star formed when the universe was filled with heavy elements. ESA writes, '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 be able to spot stars even further away than Earendel. Its new record may not last long, but the star is fascinating and further study could shed critical light on the early days of the universe.

(Via The Verge)