The Euclid space telescope has found the two oldest quasars ever observed, pushing the boundary of known cosmic history and adding to a growing puzzle about how the early universe produced such enormous objects so quickly. The discovery was announced in a study published Monday in Astronomy & Astrophysics.
Quasars are powered by supermassive black holes at the center of early galaxies consuming surrounding matter at enormous rates. That process releases energy that can shine trillions of times brighter than the sun, making quasars visible across vast stretches of space and time. Because looking deep into space also means looking back in time, scientists have been hunting for the oldest quasars they can find.
According to Phys.org, the international team of astronomers found 31 quasars in total. The two oldest ones emit light from when the universe was roughly 670 million years old, just 5 percent of its current age of 13.8 billion years. That beats the same team's previous record, set in 2021, by around 20 million years.
The Euclid telescope has been operating from a stable position about 1.5 million kilometers from Earth since its launch in 2023. Previous quasar searches relied mostly on ground-based telescopes. The launch of Euclid "has transformed this field," said Daming Yang, the study's lead author and a Ph.D. student at Leiden University in the Netherlands. In just two years, Euclid has doubled the number of ancient quasars known to science.
The newly discovered quasars come from the epoch of reionization, the period when the first stars and galaxies began to form, ending what scientists call the cosmic dark ages. Yang said researchers can use quasars as a kind of lighthouse: "We can use quasars as a lighthouse to study the gas between us and them, so that we can trace how the universe was reionized through this cosmic history."
The findings add to a problem that has been growing more difficult to explain as telescopes become more powerful. Across the universe, galaxies and other large structures observed in the early universe are turning out to be far bigger than current models predict was possible at such an early age. Study co-author Joseph Hennawi described the situation directly in a statement. "Every step further back in time makes the puzzle more perplexing," he said. "These monsters — weighing billions of times the mass of our sun — somehow already existed when the universe was in its infancy. We don't yet have a good understanding of how they grew so massive, so fast."
The team is now searching for even older quasars. The James Webb Space Telescope recently observed the newly announced quasars as well, and researchers said they will soon begin analyzing that data. The team's long-term goal is to build what Hennawi described as "a quasar chronicle of the first billion years."
