A lucky discovery has allowed astronomers to probe the very early universe. The collision between light from the cosmic microwave background and the jet from a supermassive black hole has made the jet 150 times brighter, revealing some of its features from when it was emitted over 11 billion years ago.

The jet is found in an active galaxy called B3 0727+409, and it is believed to be at least 300,000 light-years long. The findings, published in The Astrophysical Journal Letters, provide an insight into a time when the universe was still very young.

How jets emit X-rays has been a matter for debate, but the astronomers appear to have have found an explanation for this occurance. The cosmic microwave background (CMB) is the light produced after the Big Bang. As the universe expands photons lose energy, so they were more powerful in the early universe. These photons interacted with the electrons in the supermassive black hole jets and stole some of their energy, turning the microwave photons into X-rays.

"Because we’re seeing this jet when the universe was less than three billion years old, the jet is about 150 times brighter in X-rays than it would be in the nearby universe," said Aurora Simionescu, who led the study using data from NASA’s Chandra X-ray Observatory, in a statement.

The discovery is very fortuitous as X-ray sources are difficult to detect. Supermassive black holes tend to emit an abundance of both X-rays and radio waves, but astronomers usually rely on radio signals to spot the active objects. Observing B3 was serendipitous.

"We essentially stumbled onto this remarkable jet because it happened to be in Chandra’s field of view while we were observing something else," said coauthor Lukasz Stawarz, of Jagiellonian University in Poland, in the statement.

"If bright X-ray jets can exist with very faint or undetected radio counterparts, it means that there could be many more of them out there because we haven’t been systematically looking for them.”

The properties of supermassive black holes might have changed over time, and a discovery such as this will help us better understand how they have evolved over billions of years. 

^{Composite optical-X-ray image of B3 0727+409 NASA/CXC/ISAS/A.Simionescu et al, Optical: DSS}