The new study focuses on JWST-ER1g, a huge ancient galaxy discovered by the James Webb Space Telescope (JWST) in September, which formed when the Universe was only a quarter of its current age.
Surprisingly, JWST-ER1g is associated with an Einstein ring, a phenomenon predicted by Einstein's theory of general relativity. Essentially, this galaxy acts like a lens, deflecting light from a distant source, which then appears in the shape of a ring.
The phenomenon, known as strong gravitational lensing, allowed the researchers to calculate the total mass enclosed in the ring, which consisted of two types of components: stellar and dark matter.
"If we subtract the stellar mass from the total mass, we get the mass of the dark matter inside the ring," explained Professor Yu, Professor of Physics and Astronomy at the University of California, quoted by EurekAlert. "However, the value of the dark matter mass seems higher than expected. This is intriguing. In our scientific paper, we provide an explanation."
The team proposes that the high density of dark matter present in JWST-ER1g may be due to the compression of the dark matter halo surrounding the galaxy.
As ordinary matter, such as primitive gas and stars, collapses and condenses in the dark matter halo, it can compress the halo, leading to a higher density of dark matter.
JWST-ER1g, formed 3.4 billion years after the Big Bang, is seen by scientists as a unique opportunity to study dark matter, which makes up 85% of the matter in the Universe, even though it has never been detected in laboratories.
"This strong lensing object is unique because it has a perfect Einstein ring, from which we can obtain valuable information about the total mass inside the ring, a critical step in testing the properties of dark matter," reacted the co-author of the scientific article, published in The Astrophysical Journal Letters, Daneng Yang.
