In March 2022, astronomers announced an exciting discovery – the most distant known star in an image taken by the Hubble Space Telescope. This star was named Earendel, after the old English name for “morning star.” But what else is behind this mysterious celestial body?
Earendel appears to be a massive B-type star that is on the Main Evolutionary Sequence. This means that it is a hydrogen-burning star. Compared to our Sun, it is twice as hot and a million times brighter. Astronomers speculate that Earendel may have a companion like many other similar massive stars. However, because of their close proximity and great distance (about 13 billion light years), they are difficult to distinguish.
But Earendel’s light spectra hint that a companion does exist. Further studies using a gravitational lens and more detailed observations with the JWST Near-Infrared Camera (NIRCam) should help astronomers discover this mysterious companion.
Earendel emits light that was first observed about 900 million years after the Big Bang. A gravitational lens magnifies its image 4,000 times. Astronomers are now wondering if Earendel is part of the first generations of stars that ever shone. If it is, its spectra would show that its chemical composition consists mostly of hydrogen and helium. If it is a second-generation star, then the properties of its light would indicate the presence of other elements.
It is interesting to note that Earendel’s host galaxy is a long crescent-shaped blur of light. This blur is caused by gravitational lensing from a massive galaxy cluster called WHL0137-08. The NIRCam observations reveal many details about this distant galaxy, including the nursery where the next generations of stars are born. Some of these stars are younger than five million years old.
The galaxy also contains star clusters that have undergone a long evolution. One of these clusters is about 10 million years old and still exists today. These clusters provide astronomers with interesting information about the globular clusters that surround our Milky Way galaxy. Some of them may have formed around the same time as the distant clusters in galaxy WHL0137-08.
The use of gravitational lensing has become an important tool for studying more distant stars. JWST has already discovered other distant stars using its infrared instruments. But the farthest one remains Earendel. Astronomers hope that in the future they will be able to detect the very first stars to shine – one of the Holy Grails of astronomy.