How the Hubble Space Telescope spotted the oldest, furthest star known so far

Earendel, a name from the world that J.R.R. Tolkien created in his novels such as The Lord of The Ri

Earendel, a name from the world that J.R.R. Tolkien created in his novels such as The Lord of The Rings, means ‘morning star’ or ‘rising light’ in old English. In an engaging symbolism, astronomers have given this nickname to a newly spotted star that happens to be the most distant one to be seen until now. It is believed to be a whopping 12.9 billion light years away from us.

The finding, published in the journal Nature, was the result of careful observations over nearly four years, made possible by a phenomenon known as ‘gravitational lensing’.

Light from a star that is one light year away would take one year to reach us. Hence, the astronomers are seeing the star Earendel as it existed 12.9 billion years ago. If confirmed by further studies and by the James Webb Space Telescope, it would be the discovery of one of the earliest stars, formed less than a billion years after the Big Bang. It may be made up of raw materials quite unlike those making up the stars that formed much later — say, our Sun, which is only 4.5 billion years old.

Astronomer Brian Welch from Johns Hopkins University, Baltimore, the corresponding author of the Nature paper, said in a press release posted on NASA’s Hubble site that studying Earendel would be like opening a window into the era of the universe that we are unfamiliar with but which led to everything we know. “It’s like we have been reading a really interesting book, but we started with the second chapter, and now we will have a chance to see how it all got started,” Welch says.

It was possible to see this particular star only because of a phenomenon called gravitational lensing. It is known that when light from a star or galaxy passes close to a massive object such as another galaxy, a black hole or any massive entity, it gets bent by gravity. Thus the image of the source of the light may appear distorted from the original. This phenomenon is called gravitational lensing. Just like the optical lens in a magnifying glass magnifies the letters on a page, the distortion due to a gravitational effect may magnify the object.

There are multiple effects of gravitational lensing: If the original object, say a huge star or galaxy, is directly behind a massive galaxy, there will be four images on four sides of the intervening galaxy. This produces four luminous spots in the image, which are collectively called Einstein’s cross.

If the original object is not exactly behind the intervening galaxy, but is slightly off-centre, the image produced will be like a curve or arc.