Last December, a team of astronomers discovered the most distant black hole in the universe, ULAS J1342+0928. The black hole is a star-swallowing behemoth that weighs in at some 800 million times the mass of the sun, located at the center of a dusty galaxy about 13.1 billion light-years from Earth.
Looking at the distant cosmos is equivalent to looking back in time, so this black hole discovery also marks the oldest known black hole, noted Sky & Telescope, dating back to a mere 690 million years after the Big Bang. The black hole discovery promises to give us new answers about the early age of the universe. However, as is often the case in science, the answers come in the form of new questions.
A Lantern Glimpsed Through Primordial Fog
The earliest age of the universe was filled with light from the Big Bang. Within a few hundred thousand years, the universe expanded and cooled enough that the initial “hot soup” of ions and electrons combined to form ordinary hydrogen atoms, according to Space.com, and the universe became dark.
The era that followed is known as the “dark ages” of the universe, which ended when the first stars were born. Bright, hot stars poured out ultraviolet light, reionizing the surrounding hydrogen gas. This period is called the epoch of reionization, and the effect was like morning sunlight burning through fog. The universe began to take the form we know — filled with stars, galaxies and eventually life.
When Black Holes Illuminate
Thanks to the new black hole discovery, we now know that stars weren’t the only light sources burning through the fog. The age of the black hole found in December, per Space.com, puts it squarely in the midst of the epoch of reionization.
Black holes, despite their name, can be prodigious sources of light. According to NASA, while no light can escape from the black hole itself, matter falling into the black hole can emit a high-energy light invisible to the human eye. A supermassive black hole like ULAS J1342+0928 can thus be observed as a quasar, one of the most luminous objects in the universe, according to an article in Nature. And it now seems that early quasars like this one may have been major contributors to the epoch of reionization.
ULAS J1342+0928 also tells us something else — that a black hole equivalent to the mass of 800 million suns was able to form and light up at this very early date, only 690 million years after the Big Bang. A lot was going on back then, and we are only just beginning to understand it.
The Future of Black Holes
As bright and massive as it is, ULAS J1342+0928 is probably not the oldest black hole. Astronomers are busy looking for more to fill in their understanding of why and how the epoch of reionization saw the universe turn bright.
Researchers have enlisted a whole family of powerful telescopes for this task, as Space.com reports, including the Magellan Telescopes in Chile, the Large Binocular Telescope in Arizona and the Gemini North telescope in Hawaii. What these telescopes have in common is their sheer deep-sky penetrating power: they are ultimate “light buckets,” able to capture and detect light even after a journey of more than 13 billion light-years.
The epoch of reionization may have ended some 13 billion years ago, but we are still shining new light onto the formative age of the universe.