Astronomers were making observations with the Atacama Large Millimeter Array , when some light appeared in the cosmos. The signal came from so far that it took 12.5 billion years to reach Earth: they were the footprints of an old and monstrous galaxy that had never been seen before. As a cosmic Yeti, the scientific community generally regarded these galaxies as folklore, given the lack of evidence for their existence, but astronomers in the United States and Australia have managed to capture a photo of this cosmic beast for the first time.
What we see in the image is an artistic representation of what a massive galaxy in the early universe would look like.
The discovery, published in the Astrophysical Journal, provides new insights into the first steps of some of the largest galaxies in the universe.
Astronomer Christina Williams of the University of Arizona, lead author of the study, was the one who found a faint spot of light in new observations from the ALMA telescope , a collection of 66 radio telescopes located high in the mountains of Chile. Oddly enough, the glow seemed to be coming out of nowhere, like a ghostly passage in a vast dark desert.
Hidden galaxies, the tip of the iceberg
“It was very mysterious because the light seemed not to be linked to any known galaxy”said Williams of the Steward Observatory. “When I saw that this galaxy was invisible at any other wavelength, I was very excited because it meant it was probably very far away and hidden by dust clouds.
The researchers estimate thatthe signal came from so far away that it took 12.5 billion years to reach Earth,therefore, it gives us a glimpse of the universe in its infancy. The observed emission has been caused by the warm glow of star-heated dust particles that form inside a young galaxy. Giant dust clouds hide starlight, rendering the galaxy completely invisible.
“We discovered that the galaxy is actually a massive monster galaxy with as many stars as our Milky Way, but full of activity,forming new stars at 100 times the speed of our own galaxy“, clarified Ivo Labbé, of the Technological University of Swinburne, Melbourne (Australia) and co-author of the work.
Recent studies found that some of the largest galaxies in the young universe grew up and came of age rapidly, a result that is not theoretically understood. Furthermore, it is even more puzzling that these mature galaxies appear to come out of nowhere:astronomers never see them while they are forming.
Smaller galaxies have been seen in the early universe with the Hubble Space Telescope, but such creatures are not growing fast enough to solve this puzzle. Other monstrous galaxies have also been previously observed, but those sightings have been too rare to offer a satisfactory explanation.
“Our hidden monstrous galaxy has precisely the right ingredients to be that missing link,” explains Williams,“because they are probably much more common.”
How many galaxies like this will there be?
The observations for the current study were made in a small part of the sky, less than 1/100 of the disk of the full moon. Like the Yeti, finding footprints of the mythical creature in a small area would be a sign of incredible luck or that monsters are literally lurking everywhere.
Williams said scientists are eagerly awaiting the scheduled March 2021 launch of NASA’s James Webb Space Telescope to investigate these objects in more detail.
“JWST will be able to look through the veil of dust so we can learn how big these galaxies really are and how fast they are growing, to better understand why models can’t explain them.
But for now, the monsters are out there, wrapped in dust and, how could it be otherwise, a lot of mystery.
Referencia: Christina C. Williams, Ivo Labbe, Justin Spilker, Mauro Stefanon, Joel Leja, Katherine Whitaker, Rachel Bezanson, Desika Narayanan, Pascal Oesch, Benjamin Weiner. Discovery of a Dark, Massive, ALMA-only Galaxy at z ∼ 5–6 in a Tiny 3 mm Survey. The Astrophysical Journal, 2019; 884 (2): 154 DOI: 10.3847/1538-4357/ab44aa
