Japanese researchers have discovered perhaps the most distant of the galaxies known today. Named HD1, this ultra-remote object is a staggering 13.5 billion light-years away.
This makes the HD1 100 million years older than its previous record holder, the GN-z11. Researchers suggest that the galaxy may be home to some of the earliest stars (population III). They arose as a result of reionization after the “dark ages” of the universe and have never been observed. This is a higher-order journey in time. HD1 no longer exists, but its light is still moving in our direction.
A team of astronomers discovered the HD1 using about 1,200 hours of observations with the help of Subaru, VISTA, UK Infrared Telescope and Spitzer Space Telescopes. They checked the distance using a large millimeter / submillimeter Atacama array.
“It was very hard work to find HD1 out of more than 700,000 objects,” said Yuichi Harikane, the astronomer who discovered HD1. “HD1’s red color matched the expected characteristics of a galaxy 13.5 billion light-years away surprisingly well, giving me a little bit of goosebumps when I found it”
Galaxy HD1 has red light because very old light stretches in time, traveling in space. The red light has the longest wavelength. As the universe expands, very distant galaxies appear to be moving away from us at a faster rate than nearby galaxies. Therefore, their light is even redder.
What is strange about HD1 is its extreme luminosity. It is extremely bright in ultraviolet light and therefore most likely it was a very active galaxy with star formation. It is estimated that more than 100 stars could form in it every year.
“The first population of stars to form in the universe were more massive, brighter, and hotter than modern stars, “said Fabio Pacucci, an astronomer at the Center for Astrophysics. “If we assume the stars produced in HD1 are these first, or Population III, stars, then its properties could be explained more easily. In fact, Population III stars are capable of producing more UV light than normal stars, which could clarify the extreme ultraviolet luminosity of HD1.”
However, astronomers want to test their results again. The HD1 signal has a significance of 99.9%, but observers will not be sure until it receives a significance of 99.999% or higher. Researchers may be able to do so when the James Webb Space Telescope looks at the galaxy using its infrared-focused sensors.