NASA scientists have discovered a remnant of the ancient universe in the form of an outermost supermassive black hole, with its mass almost 800 million times that of the Sun, which is startling since it's relatively young.

"This black hole grew far larger than we expected in only 690 million years after the Big Bang, which challenges our theories about how black holes form," said the study's co-author Daniel Stern from NASA's Jet Propulsion Laboratory in Pasadena, according to a report published in Nature.

The astronomers gathered all the data from NASA's Wide-field Infrared Survey Explorer (WISE), along with all the ground-based surveys in order to spot the distant objects. Then, they conducted a follow-up study, using Chile's Carnegie Observatories' Magellan telescopes.

Astronomer Eduardo Bañados from Carnegie, who led the initiative of identifying the possible options among the millions discovered by WISE.

Astronomers hypothesize that for normal blackholes to grow as large as the recently found supermassive one, special conditions must have there but perplexed to point them out exactly.

The supermassive black hole is rapidly consuming matter at the galaxy's center, known as a quasar, which astronomers believe could have belonged to a time when the universe had just started to "emerge from its dark ages." It will now provide scientists with insights into the galaxy "when it was only 5% of its current age," said NASA experts.

"Quasars are among the brightest and most distant known celestial objects and are crucial to understanding the early universe," said co-author of the study Bram Venemans from the Max Planck Institute for Astronomy in Germany.

Scientists also found out that most of the hydrogen that surrounds this black hole is neutral in nature. This means that the quasar is not only the farthest but also the one and only example that humans have, which "can be seen before the universe became reionized."

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As per the experts, the universe only has around 20 to 100 such bright and distant quasars like this one.