Since the James Webb Space Telescope began operating two years ago, astronomers have used it to look back millions of years into the past, to the moment when the first stars and galaxies formed, a time known as the cosmic dawn.
Last month, an international team working on a mission known as the JWST Advanced Deep Extragalactic Survey (JADES) announced they had identified the oldest and most distant galaxy ever discovered: a banana-shaped blob of color 1,600 light-years across. Astronomers say the galaxy was already glowing with intense starlight when the universe was still in its relatively young stages, just 290 million years old.
The new galaxy, known as JADES-GS-z14-0, is one in a series of discoveries from the Webb Study that call into question conventional models of the formation of the first stars and galaxies, including early galaxies and black holes.
“This discovery proves that luminous galaxies were already in existence 300 million years after the Big Bang and are more common than expected,” the researchers wrote in their paper posted to the online Archives of Physics.
“Models of galaxy formation need to deal with the fact that such large and luminous galaxies existed very early in the history of the universe,” said the study authors, led by Professor Stefano Carniani of the École Normale Supérieure in Pisa, Italy.
The galaxy was first discovered during a deep-space survey with the Webb Telescope's near-infrared camera, one of its flagship instruments. In a region of the southern sky called the Jade Origin Field, an area roughly the size of a quarter of the full moon, scientists found 11 galaxies that appear to date back to when the universe was less than 400 million years old — far more than scientists had expected.
Subsequent work by Dr. Carniani and his colleagues using the telescope's infrared spectrograph revealed that the wavelength of the light from JADES-GS-z14-0 has been stretched by more than 15 times (a redshift of 14 in astronomical terms) by the expansion of the universe, similar to a siren's tone getting lower as it moves away, meaning that the light has been coming towards us for 13.5 billion years, since shortly after the universe began (cosmological calculations put the universe at about 13.8 billion years old).
The light from the galaxy is spread out in a diffuse field, indicating that its glow comes from a star rather than the cleft of a black hole, and its brightness is equivalent to the emission of hundreds of millions of suns, an astounding number to have formed and come together in just 290 million years.
The starlight also contained the spectral signature of oxygen, which was not present when the universe was first created, meaning that the galaxy's stars had already undergone several cycles of birth, death and rebirth, enriching the universe with the heavy elements needed for evolution and survival.
How that happened in such a short time is a mystery, one of many in the sky. Some astronomers suggest that the galaxy could have been seeded by a supermassive black hole formed by the collapse of a primordial gas cloud.
Dr. Carniani and Kevin Hainline from the University of Arizona, another member of the JADES team, wrote in a blog post: “Together with Webb, astronomers will discover many more such bright galaxies over the next decade, and perhaps sooner. We are excited to see the extraordinary diversity of galaxies that were present in Cosmic Dawn.”
