A new view of one of the oldest stars

Scientists using the Hubble Space Telescope have spied a distant single star, or star system, dating back to just 900 million years after the universe began with the Big Bang.

Their observations were reported in Nature this week. The ancient star has been named Earendel, from an Old English word meaning “morning star” or “rising light”, though researchers believe that it’s more likely that they have identified one or more individual stars, as opposed to a star cluster.

Earendel is far more distant than similar systems that have been observed, leading researchers to conclude that it comes from an early stage in the evolution of the universe. It is estimated to be around 50 times the size of the Sun. Scientists were able to posit the distance and the age of the star system using calculations of the redshift – that is, by making observations of the way light stretches as it travels.

Other properties, such as information about its mass and temperature, are yet to be determined. The research team hopes that more studies, especially utilising the recently launched James Webb Space Telescope – which has infrared astronomy as its focus – will uncover more details.

The very first stars contained only hydrogen and helium, and were formed just a few million years after the Big Bang sparked the creation of matter, an estimated 13.8 billion years ago. These are commonly known as Population III stars, and they are only known hypothetically. The dating of Earendel puts it into the next-oldest category, Population II, which have some (low) traces of elements other than hydrogen and helium. More recent stars (known as Population I) contain heavy elements. For example, our Sun, which is 4.6 billion years old, contains a small percentage of iron, neon and magnesium.