Astronomers spot missing link from the early universe
Scientists have discovered a new object in space that could help explain how quasars and supermassive black holes originated in the early years after the Big Bang.
In the search for the early universe, attention is currently on the data coming from the new James Webb Space Telescope. But data from the Hubble telescope still has plenty to offer scientists delving into the past.
For example, it has long been a mystery to astrophysicists how supermassive black holes originated and grew over the first million years of the universe’s life, and also how active galaxies, or quasars, formed. They seem to have originated at an speed that is difficult to explain.
Now an international team of scientists from the Niels Bohr Institute and DTU Space in Denmark have observed a new type of cosmic object that could provide an explanation. The new object is a missing link in the transition from a dust-laden and intense starforming galaxy to a bright quasar, and so is the preliminary stage of what later becomes a quasar with a supermassive black hole at the centre. Named GNz7q, the object was born 750 million years after the Big Bang that took place 13.8 billion years ago, so in what astronomers know as the universe’s cosmic dawn.
“The object is a link between two rare objects – dusty star-forming galaxies and bright quasars,” says Seiji Fujimoto from the Niels Bohr Institute. “So the find might provide us with a new understanding of how supermassive black holes formed at great speeds in the early universe.”
Ordinary galaxies are full of gas, dust and stars, and at their centres, there is a supermassive black hole that consumes the matter of the galaxy. Quasars are galaxies that emit much more energy in the shape of radiation than ‘normal’ galaxies such as the Milky Way. So, quasars
are the brightest objects in the universe and among the remotest we can observe. Like ‘ordinary’ galaxies, quasars hence also have a huge black hole at the centre, which is surrounded by a disc of gas that slowly disappears into the black hole. As black holes do not emit any light, the bright light in a quasar originates in intense friction between the gas particles that are on their way into the black hole. The heat from the friction makes the gas in the disc shine extremely brightly.
The object scientists have found is also turning into a quasar, but is still veiled in dust and gas and hence not as bright as a quasar. In the galaxy in which GNz7q has been observed, new stars are formed at an incredible speed – 1600 times faster than in our own galaxy. The new stars produce cosmic dust that is heated and makes the dust glow and shine brightly. At the centre of the observed galaxy there is already a black hole, and because it is in an early galaxy stage, where stars are formed at a very high speed, it will later become a supermassive black hole as it swallows huge quantities of matter.
The discovery of GNz7q was based on data from the Hubble space telescope covering one of the most intensively-explored regions of the universe, known as the GOODS North field. So the object was hiding right under the scientists’ noses, only retrieved by combining data of many different wavelengths.
With the newly-launched and higher-resolution James Webb Space tTelescope, the team hopes to find more objects reminiscent of GNz7q, and in the future to be able to describe the new objects and their development in greater detail.