Record discovery in Einstein ring: Universe's smallest dark matter clump found

Astronomers have discovered a surprisingly small "dark object" hidden in a ring of light around a distant galaxy. The record-breaking find could shed light on the mysterious nature of dark matter, which is thought to make up most of the universe.

The hidden object in question was detected in an "Einstein ring" called B1938+666. This structure, approximately 10 billion light-years away, is formed when light from a distant galaxy is bent by another foreground galaxy. This effect is called gravitational lensing. It is named after Albert Einstein because it was predicted in his Theory of General Relativity.

Gravitational lenses typically both bend and magnify light. If the background galaxy aligns with the lensing galaxy, the light forms a ring. Small misalignments can sometimes create crosses, zigzags, or even question-mark patterns.

B1938+666 was first discovered in the 1990s. But in two new studies published October 9 in the journals Nature Astronomy and Monthly Notices of the Royal Astronomical Society, researchers examined the ring in more detail.

MYSTERIOUS SWING

A slight "oscillation" in radio waves caught the attention of scientists , who upon examination determined that it was caused by the gravitational influence of an unseen object.

Astronomer John McKean of the University of Groningen, Netherlands, and the University of Pretoria, South Africa, described the discovery:

"In the first high-resolution image, we noticed a contraction in the gravitational arc. This was a clear indication that a small mass was intervening. Only another lump of mass between us and the distant galaxy could have created this effect."

While the object has a mass roughly a million times that of the Sun, this actually makes it the smallest object ever detected using gravitational lensing, and it's about 100 times smaller than the previous record.

The research was conducted by combining data from telescopes around the world. The Green Bank Telescope (USA), the Very Long Baseline Array (New Mexico), and the European VLBI Network were used in the discovery. This provided the extraordinary observational power of a telescope the size of Earth. However, the amount of data was so vast that scientists had to develop an entirely new computational method.

DARK MATTER BLOCK

While researchers aren't sure if this hidden object is a dark matter clump, they think it's likely.

Dark matter makes up about 27 percent of the universe and cannot be observed directly because it doesn't interact with light. Gravitational lensing is one of the most effective ways to detect dark matter indirectly.

Such discoveries are also important for testing the theory of "cold dark matter," which posits that dark matter can only clump together when it can move at low speeds, meaning it releases less energy.

And according to researchers, such small clumps of dark matter may be much more common in the universe than previously thought. Vegetti says:

"We think every galaxy—including the Milky Way—is filled with clumps of dark matter. But finding them and proving their existence requires significant computing power."

Only three similar dark matter clumps of this size have been detected to date. However, thanks to the newly developed method, more are expected to be discovered within the existing Einstein rings. The James Webb Space Telescope, in particular, has been extremely successful in detecting these rings, and this is expected to accelerate the search.