The most distant known star is called Earendel. First seen by Hubble thanks to a phenomenon known as gravitational lensing, the light of this object has traveled for almost 13 billion years to reach Earth. JWST observations have previously hinted at a possible companion and have now gone even further in establishing the color of the star. This allows researchers to classify it.
Earendel is a type B star. These stars are very bright and blue. It is in fact twice as hot as our Sun and about a million times more luminous. The light of Earendel comes from 900 million years after the Big Bang and it has been stretched out by the expansion of the universe. This means that it looks redder to Hubble than if it was in our galaxy.
But JWST can see into redder wavelengths better than the veteran space telescope. It not only could establish the star’s true color, but it was also able to see a hint of a much redder and cooler companion. Bright, massive stars like Earendel often have companions but being so far away it would be beyond the range of Hubble.
Still, the only reason that either telescope has been able to see this star system is thanks to the massive star cluster WHL0137-08. This collection of galaxies is so dense that it warps space-time around it in such a way that it magnifies the background. And in the background of this cluster, there is Earendel.
The gravitational lens produces an arc of light, called the Sunrise Arc, that included Earendel. The star and its companion are magnified an incredible 4,000 times by the effect of gravity, providing a unique view into the distant past. The research team is still analyzing the data from the observations and more will come out about Earendel and its host galaxy.
Astronomers hope that this is a stepping stone to even further away stars, hoping to see one of the first-ever stars – the so-called population III stars. They have never been seen before and JWST could be the first observatory to spot them. They are made exclusively of hydrogen and helium created in the Big Bang and some of them are expected to be truly enormous.
The new observations are shared on the Space Telescope Science Institute website.