The farthest astronomical object in the universe has been identified: a galaxy called Hd1 that is about 13.5 billion light-years away from us. Born only 300 million years after the Big Bang, it could host the oldest stars in the universe or a black hole 100 million times the mass of the Sun. The discovery was published in The Astrophysical Journal and Monthly Notices of the Royal Journal Astronomical Society Letters by an international group of astronomers from the Harvard and Smithsonian Center for Astrophysics, including the Italian Fabio Paccucci with the contribution of three ground-based telescopes and one in space: the Japanese Subaru and the British Ukirt at Hawaii, European Vista in Chile and NASA Spitzer.
“It’s hard to answer questions about the nature of such a distant object,” explains Fabio Paccucci on MediaInaf. “It’s like trying to guess the nationality of a boat by watching the flag fly while we’re on land and the ship is in the middle of a storm and under thick fog.”
Galaxy Hd1 appears very bright in ultraviolet light: this means that strong energy processes are underway. Astronomers initially assumed it was a star galaxy, a galaxy that creates stars at a high rate, but after counting the number of stars Hd1 produces, they get an “incredible rate: Hd1 was supposed to have more than 100 stars each year.” It is at least 10 times higher than what we would expect for these galaxies,” Pascucci confirms. This is how researchers began to think that Hd1 could form certain stars. “The first stars in the universe were much more massive, brighter, and warmer than modern stars,” the astronomer explains. “If we assume that the stars formed in Hd1 are the first, then their properties can be explained more easily.”
However, even a supermassive black hole can explain the extreme luminosity of Hd1: if so, it would be the first supermassive black hole known to mankind, observed much closer to the Big Bang than the current record holder. “HD1 represents a giant baby in the delivery room of the early universe,” says Avi Loeb, an astronomer at the Harvard-Smithsonian Center for Astrophysics.
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