A Black Hole Twice The Size of Our Galaxy

Written by: Keya Gambhir

Astronomers have recently discovered the oldest and largest black hole jet ever observed, stretching an incredible 200,000 light-years, which is twice the diameter of our Milky Way galaxy. This jet comes from a distant cosmic object called a quasar named J1601+3102, which existed when the universe was just 1.2 billion years old, or less than 10 percent of its current age.

What is a quasar? A quasar is an extremely bright and energetic region at the center of a distant galaxy, powered by a supermassive black hole. As the black hole pulls in gas and dust, it heats up this material, causing it to shine brilliantly across many types of light, from radio waves to visible light. Quasars are among the brightest objects in the universe and can be seen across vast distances.

Jets like the one from J1601+3102 are streams of charged particles shot out from the area near a black hole, often at nearly the speed of light. These jets help scientists understand how black holes interact with and influence their galaxies. However, detecting such jets from very far away is difficult because the universe itself produces a background glow called the cosmic microwave background, which is leftover light from the Big Bang and can drown out faint signals.

The recent discovery was made possible by the Low Frequency Array (LOFAR), a network of over 50 radio telescope stations spread across Europe. LOFAR is specially designed to detect low-frequency radio waves, allowing it to see long, faint jets that other telescopes might miss. The two lobes of this jet stretch roughly 66,000 light-years each, combining to an enormous length of 200,000 light-years.

Interestingly, the black hole powering this jet has a mass about 450 million times that of our sun, which is surprisingly modest compared to other black holes known to produce huge jets. This challenges the earlier idea that only the largest black holes could create such powerful jets. Instead, it shows that even smaller black holes in the early universe could generate massive jets that influenced galaxy formation.

The jets form because gas and dust fall toward the black hole and create a swirling disk around it called an accretion disk. While most of this material spirals into the black hole, strong magnetic fields near the black hole’s poles shoot some particles outward in narrow streams, creating the jets.

To better understand the jet’s size and structure, astronomers used additional telescopes like the Gemini Near-Infrared Spectrograph in Hawaii and the Hobby Eberly Telescope in Texas. These instruments helped measure how fast gas moves near the black hole and how quickly the entire galaxy is moving away from us due to the universe’s expansion, a phenomenon known as redshift.

One notable feature of this jet is its asymmetry. One lobe is brighter and larger, while the other is smaller and fainter. Scientists think this happens because the jet interacts with uneven amounts of gas or magnetic fields in its surrounding space, which slows or weakens one side.

Detecting jets this old is difficult because cosmic microwave background radiation steals energy from them, making weaker jets invisible. Only unusually powerful jets like this one can be seen, which explains why so few were found until now.

This discovery is important because it shows that powerful jets were active in the early universe and played a big role in shaping galaxies. By pushing gas out or stirring it up, jets can either slow down or encourage star formation, influencing how galaxies grow over billions of years.

With more sensitive telescopes coming online soon, astronomers expect to find many more jets like this one, each helping to tell the story of how black holes shaped the young universe. The study detailing this discovery was published in The Astrophysical Journal Letters, marking a major step forward in our understanding of cosmic history.