The Hubble Space Telescope might be a grandparent when it comes to orbital observatories, but it still delivers incredible discoveries. The latest is the observation of a single star or a star system whose light is coming from just 900 million years after the Big Bang.
As reported in the journal Nature, that’s the most distant of such observations, which requires the peculiar phenomenon of gravitational lensing to be achieved. The light from the galaxy that hosts the star has been warped by the exceptional gravity of a foreground galaxy cluster. The galaxy appears as a thin strip of light so it gained the nickname the “Sunrise Arc”.
Studies of the “Sunrise Arc” have revealed a single star or maybe a binary system, that can be isolated from the rest of the galaxy. Thanks to the warping of the galaxy, the light of the star is magnified by a factor of thousands. The magnified light stayed consistent for 3.5 years, suggesting that this is not a transient event.
The team have named the star "Earendel" from the Old English poem of Crist meaning Morning Star or Rising Star. Its root is Proto-Germanic and fantasy aficionados might also recognize it as the name given by Tolkien to the half-elven mariner that carried the light of one of the Silmaril across the sky. Earendel is estimated to weigh about 50 times our Sun.
“It’s the most distant star that has been discovered thus far, which is very exciting just for the superlative of it,” lead author Brian Welch told IFLScience. “It’s also within the first billion years of the Universe so at a time when we know that galaxies look very different and we expect that stars would look very different as well.”
If we wound back the clock to the time of this galaxy, the Universe had only been forming stars for a few hundred million years. While a generation of stars was already born and gone by that time, their evolution had not spread out the heavy elements that make things like planets (and us) just yet. The stars forming and shining at this time are a window into this still mysterious past. So Earendel is a really cool finding.
“It’s a really exciting way to get a detailed study of this one individual star at a time when things look very different than they do in the Universe today,” Welch told IFLScience.
The observations from Hubble are truly record-breaking but the uncertainties are significant. Luckily JWST, NASA’s brand-new observatory, is ready to push the observations further. Welch and his team have already got time scheduled on JWST to follow up on the first cycle of observations.
The team expects some deeper images and the light spectrum of the star. It might not provide the most complete composition of the star but they hope it would allow them to better constrain the mass and the temperature of Earendel.