In March 2022, astronomers announced the discovery A distant known star Image courtesy of the Hubble Space Telescope. They named it Arendelle, after the Old English name for „morning star”.
Now, JWST’s Near-infrared Camera (NIRCam) and its NIRSpec spectrometer have looked at the same star and revealed more details about it.
Earendel appears to be a large B-type star. This puts it evolutionarily on the main sequence, meaning it is a hydrogen-burning star.
Compared to the Sun, it is twice as hot and a million times more luminous. What astronomers suspect is that this star, like many such massive stars, may have a companion. However, they are so close, and we see them at such a great distance (about 13 billion light years), that it is difficult to make them out individually.
However, this star’s spectrum (i.e. the colors of its light) indicates the presence of a companion. Further studies using the magnification provided by gravitational lensing and detailed observations using NIRCam on JWST should help them tease out the companion.
The light we see from Erental was first emitted from that star 900 million years after the Big Bang. The gravitational lens that exposed it magnifies Erendel by 4,000 times.
Now, astronomers want to know if it is among the first generation of stars to ever shine. If so, its spectrum would reveal its chemical composition to be mainly hydrogen and helium.
If it is a second-generation star, the properties of its light will show other elements as well. Other examples of this type of blue supergiant star are Rigel and Beta Centauri.
Arendal’s home at Sunrise Bend
This star’s host appears to us as a long crescent-shaped smear of interstellar light.
The smear is caused by gravitational lensing from a massive galaxy cluster called WHL0137-08. The NIRCam view shows some of the details of this distant galaxy. There are places where the next generation of stars are born. Some of those stars are very young, less than five million years old.
The galaxy also contains star clusters well in their evolution. One of them is about 10 million years old. It may still exist in the modern universe.
The cluster provides astronomers with some interesting clues about the globular clusters clustered in our own Milky Way today. Some of them may have formed at the same time as the distant clusters in WHL0137-08.
Interestingly, JWST’s image shows more detail about the lensing effect on the distant galaxy. Erendel lies in the „ripple” produced by lensing.
It appears separate from its host galaxy. In addition to the NIRCam view of this scene, JWST’s Infrared Spectroscopy (NIRSpec) captured data. This gives astronomers more details about the exact distance to Arendal and its home galaxy.
Applying gravitational lensing to more distant stars
JWST has detected other distant stars using its infrared sensing instruments. So far, Earendel is the far-reaching record holder. But, there are many more observations.
Eventually, astronomers hope to discover one of astronomy’s holy grails: the first stars to shine.
Those early objects could have formed only 100 million years after the Big Bang.
They can be very large and very luminous. As they began to emerge from the dimness of the cosmic dark ages, they heated up and ionized the gas around them. As they evolved and died, they formed heavy chemical elements in hydrogen-burning cores.
When they died, they spread the material into space, seeding new generations of stars and eventually planets.
Evidence of their lives and lifestyles will tell us a lot about all the conditions in the infant universe, the distribution of matter (including dark matter) and the eventual formation of galaxies in the early ages of the cosmos.
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