In a corner of the universe, when the universe was less than 1 billion years old, a star that was then 4 billion light-years away from the primordial Milky Way glowed brightly. These rays of light travel in the direction of the structure of space in deep space, passing through the bends of countless massive celestial bodies, which lasted for 12.9 billion years and finally reached Earth at the age of 13.8 billion in the universe. Because these lights were amplified just right by the accidental arrangement of a massive galaxy cluster, they were successfully captured by the Hubble Space Telescope. At this time, because of the amazing expansion of the universe itself, the star has been taken 28 billion light-years away.
The story sounds like a sci-fi product of some kind of space-time machine behind it, but it's exactly what Hubble has released in its latest observations. The star discovered by astronomers is the most distant single star ever observed. Its mass may even reach 500 times the mass of the Sun. The study has been published in the journal Nature.
Einstein's predicted cosmic telescope
When you look up at the stars in the middle of the night, all the stars you can see are located in our Milky Way. Even with the help of the most powerful telescopes, typically, the individual stars found are mostly located in our neighboring galactic neighbors.
In general, when we look at distant galaxies, many of them are mixed rays of light from billions of stars. In 2016, for example, Hubble broke the record for the most distant cosmic observation distance, a young nascent galaxy whose light came from 13.4 billion years ago, just 400 million years after the Big Bang.
Hubble broke the record for the universe's most distant observation in 2016, when scientists found a young galaxy called GN-z11 whose light came from 13.4 billion years ago. | Image credit: NASA
But a wonderful natural phenomenon called gravitational lensing opens us up even more opportunities. One of the miracles predicted by Einstein's theory of relativity is that mass bends space itself. When light approaches a massive object, its path also changes direction with curved space.
If a massive object happens to be between us and a distant background light source, the object may act like a lens, deflecting and focusing the light, thereby amplifying the light source. In this way, galaxies that are magnified several times are often discovered.
Gravitational lensing. | Image source: L. Hustak, STScI
In an incredible cosmic coincidence, the galaxies in the WHL0137-08 cluster happen to be arranged in a special way that focuses the light from one star, magnifying the light from that star thousands of times.
Due to its rare alignment with an enlarged galaxy cluster, the star appears directly on a "ripple" in the structure of space, or extremely close to it. This ripple is optically defined as a caustic line that provides maximum amplification and brightening. This effect is like a pattern of bright light formed at the bottom of the pool on a clear day by the ripples on the surface of the pool. The ripples on the surface act like lenses, allowing sunlight to focus to its maximum brightness and reflect it underwater.
This very coincidental gravitational lensing effect, coupled with Hubble's 9-hour exposure, allowed an international team of astronomers to finally discover the star. This is the first time we have observed such a distant and so small object.
Morningstar "Elandir"
Astronomers nicknamed the star Earendel. It is a very poetic name, derived from Old English, meaning "morning star" or "rising light", and there are stories about Elandir in myths in Northern Europe and other places, and the famous literary artist Tolkien also borrowed this name in his novels.
This detailed view highlights the position of Elandir's star in a ripple (dotted line) in space-time, which magnifies the star, making it possible to detect it at a distance of nearly 13 billion light-years. In addition, a mirrored group of stars is shown on either side of the enlargement line. The deformation and amplification is caused by the mass of a massive galaxy cluster located between Hubble and Elandir. The mass of the galaxy cluster is so great that it distorts the structure of space, and along the edge of the lens, the object on the other side is magnified. | Image credit: Science: NASA, ESA, Brian Welch (JHU), Dan Coe (STScI); Image processing: NASA, ESA, Alyssa Pagan (STScI)
Astronomers have calculated that the star has at least 50 times the mass of our Sun, and may even reach 500 times, and that it is millions of times brighter than the Sun.
The observation of this star is an astonishing achievement in itself, and in addition to that, it offers a unique possibility for studying the early universe. We all know that when we look into the deep space of the universe, we are also going back in time. These extremely high-resolution observations give us the opportunity to understand the constituent elements of some of the oldest galaxies.
The oldest known star, also from Hubble's observations, was discovered in 2013 and is about 190 light-years from Earth. | Image credit: Digitized Sky Survey (DSS), STScI/AURA, Palomar/Caltech, and UKSTU/AAO
It took 12.9 billion years for the light from Elandir to finally come to us. When we see these lights emanating from Elandir, the universe is less than 1 billion years old, only about 6 percent of the current age of the universe, in more scientific terms as "redshift 6.2." Scientists use the term redshift because as the universe expands, light from distant objects moves toward us, stretched into longer, more "red" wavelengths. This is the most distant and redshifted single star ever detected by humans.
The previous record holder came from Hubble's 2018 discovery of a star called Icarus whose light came from the universe, about a third of the current age (redshift 1.5), when much of Icarus's structure had formed and evolved. In contrast, Elandir is indeed a more groundbreaking record.
Previous records come from a blue star nicknamed Icarus, and light from Icarus took about 9 billion years to reach Earth. | Image credit: NASA, ESA, and P. Kelly (University of Minnesota)
Target of the Webb Space Telescope
To measure Elandir's brightness, astronomers built a physical model of a gravitational lens. The exact nature of the light source depends on the model, but many different models give roughly the same answer, allowing astronomers to be pretty sure that this little bright spot is actually a star.
Nevertheless, in principle, it is possible that Elandir has more than one star, such as a very close binary star or other situations. To this end, the team has applied for and obtained the observation time of the Webb Space Telescope, pending final confirmation.
In the future, Webb will help confirm whether Erandir is just a star and quantify what type of star it is. Webb even expected to measure its chemical composition.
The researchers say hopefully that there is a good chance that Elandir will become one of the earliest generations of stars in the universe as we know it.
#创作团队:
Written by: Takeko
Typography: Wenwen
#参考来源:
https://phys.org/news/2022-03-hubble-distant-star-distance-billion.html
https://www.nasa.gov/feature/goddard/2022/record-broken-hubble-spots-farthest-star-ever-seen
#图片来源:
封面图：NASA/ESA/Brian Welch (JHU)/Dan Coe (STScI)/Alyssa Pagan (STScI)
First image: L. Hustak, STScI