When the universe was a fledgling billion years old, a galaxy spewed a ginormous, fast-moving jet of radiation and plasma into the cosmos. Nearly 13 billion years later, that jet is visible to humans in the form of a blazar. The jet was recently imaged and analysed by a team of Italian astronomers. Their findings, which give a sense of the jet’s length and speed, were recently published in the journal Astronomy & Astrophysics.
Viewed through the Very Long Baseline Array — a formation of 10 radio telescope antennas stretching from St. Croix in the Atlantic Ocean to Hawai’i’s Mauna Kea in the Pacific — the blazar looks like a galactic smear of tomato sauce on the cosmic lens. What’s actually captured in the false-colour image, though, is a bright-orange jet of plasma, pointed roughly at us and stretching about 1,600 light-years long, a distance that defies any terrestrial analogy.
According to Cristiana Spingola, an astronomer at the University of Bologna and lead author of the recent paper, scientists don’t see as many blazars as would be expected in the early universe.
“Among different scenarios, this mismatch could be due to the distant blazars having different properties as the local blazar population, such as the jet is moving slower than what happens locally,” Spingola wrote in an email. “This is what our findings suggest. If confirmed, we would have found that the local and distant blazars are different beasts.”
Such jets are emitted from the centres of galaxies by supermassive black holes. The black holes accrete disks of matter around them, sometimes ejecting jets of material outward at extraordinary speed. These galactic centres, called active galactic nuclei, are all known as quasars; when the beams they eject are oriented toward us, they’re called blazars.
A couple of years ago, blazars were found to be the sources of ultra-high-energy cosmic rays, transforming them from an object of intrigue into a compelling source of information about the early universe. First detected in March 2020, the recently described blazar, named PSO J030947.49+271757.31 (mercifully shortened to PSO J0309+27), is located in the constellation Aries, about 12.8 billion light-years away from Earth. The blazar is the brightest in radio waves and second brightest in X-rays among those from when the Universe was younger than a billion years old. It’s also the farthest galaxy from us ever seen ejecting such a jet, which also makes it the oldest blazar yet observed.
“These properties make it an ideal object to study [active galactic nuclei] at cosmological distances,” Spingola wrote. “We know very little of the young Universe, so any new information is crucial to better understand that era.”
The team found the blazar jet was moving at three-quarters the speed of light; an extraordinary pace, though not the fastest, as other blazars have been recorded at over 90% the speed of light.
The pretty streak you see is actually an image made by integrating three different observations of the jet, taken at different radio frequencies, to elicit structures of the jet invisible on the other ones. All told, the image shows a blazar jet extending upward into the empty black, with its brightest section toward the bottom, where the core of the blazar lies.