A galaxy born just after the cosmic dark ages, when the universe was only about 330 million years old, may be the farthest cosmic object ever spotted, but the true nature of the object remains very much a mystery.
Two new studies, published on April 7, present the case that an astronomical object -- a galaxy -- could be up to 13.5 billion light-years away. They've dubbed it HD1 and, if confirmed, it would overtake the current record holder: GN-z11, a galaxy that sits about 13.39 billion light-years away.
HD1 was discovered with the help of a number of space- and ground-based telescopes, including NASA's Spitzer and Japan's Subaru telescope, situated at Hawaii's Mauna Kea Observatory. Yuichi Harikane, an astronomer at the University of Tokyo and lead author on one of the new studies, said the team searched among more than 700,000 objects to find HD1. He noted it was a surprising find that gave him goosebumps.
The galaxy appears super bright in UV and gives astronomers some clues about what is happening. The teams present two theories.
The first is that HD1 is a superpowered starburst galaxy. It could be so bright because it's producing stars at about 10 times the rate than expected for a traditional starburst galaxy and those stars might even be some of the earliest stars in the universe. They're known to shine brightly compared to other stars.
"If we assume the stars produced in HD1 are these first, or Population III, stars, then its properties could be explained more easily," said Fabio Pacucci, an astronomer at the Center for Astrophysics | Harvard & Smithsonian and lead author on one of the studies.
Alternatively, it might be a supermassive black hole feasting on gas and dust -- a violent process that creates a huge amount of light.
The paper also describes another very distant galaxy, HD2, but because it's not quite as far away it doesn't get as much of the limelight.
Michael Brown, an astronomer at Monash University in Australia not affiliated with the research, noted the team have done a "perfectly reasonable job at identifying these galaxies and trying to confirm their distances," but said, "there are reasons for caution."
Brown noted the method used to calculate the distance to the galaxy, known as redshift, can sometimes through up more than one solution. In this instance, the redshift for HD1 could be 13, which is what the team suggests, or it could be 4 -- which would mean the object is billions of light-years closer.
Confirmation of the galaxy's distance will provide the motivation to explore new physical processes in the early universe, Harikane noted, because "the existence of HD1 is not expected with the current theoretical models."
So how can we confirm, exactly, what HD1 is? More data, of course. Brown said NASA's, which is in the next few months, will be capable of examining HD1 and revealing just how far away it might be. Another NASA telescope, the Nancy Grace Roman Telescope, will also help elucidate the nature of HD1 but that's not due to launch until 2027 at the earliest.
And if you're looking for other distant space objects, why not try Earendel? NASA's Hubble recently spotted that star, the farthest star ever observed, at a distance of 12.9 billion light-years away.