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Scientists find the most distant object ever seen from Earth
A galaxy that could be giving birth to the earliest stars may have been spotted for the first time.
Dating back to over 13 billion years ago, HD1 could have formed shortly after the Big Bang, with properties unlike any modern galaxy.
The most distant object ever seen from Earth may have just been discovered.
HD1 is an object estimated to lie around 13.3 billion light years away from our planet, placing it in an era when many chemical elements were yet to form. If confirmed, it is more than two billion light years beyond the current record holder.
Despite being so far away it is extremely bright, suggesting high energy processes taking place billions of years ago. Astronomers have suggested it could either be the earliest supermassive black hole ever discovered, or more intriguingly, a galaxy giving birth to one of the 'Holy Grails' of astronomy – Population III stars, the first to form in the universe.
Dr Fabio Pacucci, the lead author of one of two new papers discussing the find, says, 'If HD1 is producing stars, it is doing so at an incredible rate - forming more than 100 stars every single year. This is at least 10 times higher than what we expect for these galaxies.
'As the very first population of stars that formed in the universe were more massive, more luminous and hotter than modern stars, then its properties could be explained more easily if we assume the stars produced in HD1 are these first, or Population III, stars.
'In fact, Population III stars are capable of producing more UV light than normal stars, which could clarify the extreme ultraviolet luminosity of HD1.'
The team behind the discovery intend to use the newly-launched James Webb telescope to verify their findings, and find out more about its identity.
HD1 formed within a few hundred million years of the Big Bang. Image © Harikane et al., NASA, EST and P. Oesch/Yale
How did the first stars form?
In the beginning, the first elements formed rapidly after the Big Bang. Only minutes after the creation of matter itself, the lightest three elements (hydrogen, helium and lithium) would have come into being as the density and temperature of the early universe forced subatomic particles together.
About 20 minutes after the Big Bang, the universe was no longer hot or dense enough to keep forming new elements. The elements that remained formed part of an opaque plasma of different particles, which persisted for around 380,000 years.
Once the universe cooled to just over 2700⁰C, this plasma condensed to form the first atoms and the universe became transparent. The energy released by this process, known as recombination, can still be detected today as cosmic microwave background radiation.
With the early elements now clouds of gas, different patches of density of the early universe would have caused them to collapse together under the weight of gravity. Eventually, the heat and pressure would build up so much that nuclear fusion would begin, forming the first stars.
These first stars are the Population III stars, which are given their name due to being the third group to be considered by astronomers. Because of the sheer amount of light elements available, these stars may have been up to 1000 times the size of the Sun as they began the process of converting hydrogen and helium into heavier elements.
The amount of fuel available meant Population III stars were probably some of the brightest stars ever, but they rapidly ate through their reserves. Within a few million years, they would have started to burn iron, which releases less energy after fusing its atoms together than is needed to perform the reaction.
As a result, the stars would have subsequently collapsed into supernovae or to form black holes as they ran out of fuel. It is believed no Population III stars exist today, as the conditions for their formation no longer exist.
However, the light from these distant stars continues travelling. By looking further and further away from Earth, the images we see come from deeper into the past. Look far enough, and the Population III stars should be visible.
We may now have seen the home of the first.
The Nancy Grace Roman telescope, once launched, may be used to help confirm the age and identity of HD1. Image © NASA's Goddard Space Flight Center
How was the oldest-known galaxy discovered?
Astronomers used a range of different infrared telescopes to examine some of the furthest reaches of space, looking for a specific shade of red. As the universe continues to expand, light travelling vast distances is stretched in a process known as red-shifting and becomes more red.
The amount of red-shifting can be used to estimate how far away the light's source is. After thousands of hours scanning the skies, the team discovered HD1.
Yuichi Harikane, an astronomer at the University of Tokyo who discovered the galaxy, says, 'It was very hard work to find HD1 out of more than 700,000 objects. Its red colour matched the expected characteristics of a galaxy 13.5 billion light-years away surprisingly well, giving me goosebumps when I found it.'
Their observations of HD1 suggest that it has unusual properties compared to modern galaxies. It is extremely bright and productive, suggesting that it contains Population III stars, or that early galaxies were up to 24 times more efficient at forming stars than today.
On the other hand, the brightness could be explained by a supermassive black hole around 100 million times the mass of the Sun consuming gas and becoming red hot. The discovery of such an object would also be a landmark discovery, being much closer to the Big Bang than any other known black hole.
This current work was done using ground-based telescopes which suffer from interference from Earth's atmosphere, but the researchers hope to make use of the next generation of space telescopes. This includes the James Webb telescope, which the team intend to use to observe HD1 and confirm their theories.
Planned new satellites, such as the Nancy Grace Roman space telescope, may also be used in future to continue improving our knowledge of the oldest galaxy.
'Answering questions about the nature of a source so far away can be challenging,' says Fabio. 'It's like guessing the nationality of a ship from the flag it flies, while being faraway from shore, with the vessel in the middle of a gale and dense fog. One can maybe see some of the colours and shapes of the flag, but it can't be seen in its entirety.
