Scientists believe that one in five galaxies distant could be hiding behind cosmic dust. They discovered two systems previously unknown at 29 billion light-years away.

  • Two galaxies found to be heavily dusty 29 billion light-years from Earth, experts have discovered
  • With Chile’s ALMA radio telescopes, ‘REBELS-12-2’ and ‘REBELS-2-9-2’ were discovered.
  • These galaxies suggest that about a fifth are hidden behind space dust

Two ‘previously inaccessible’ galaxies were discovered by scientists around 29 billion light-years from Earth. 

The two ‘heavily dust-obscured’ galaxies – called REBELS-12-2 and REBELS-29-2 – were found during observations with the ALMA radio telescopes in Chile’s Atacama Desert. 

Both were previously undetectable to the optical lens of NASA’s Hubble Space Telescope, because they were hidden behind curtains of cosmic dust. 

According to the astronomers, up to 20% of all galaxies within the universe have been found.    

With the help of the giant ALMA radio telescopes (Atacama Large Milimeter Array) in Chile’s Atacama Desert the two invisible galaxies 'suddenly appeared'. ALMA has a spatial resolution five times better than the Hubble Space Telescope, as this graphic shows, which was key to the discovery

With the help of the giant ALMA radio telescopes (Atacama Large Milimeter Array) in Chile’s Atacama Desert the two invisible galaxies ‘suddenly appeared’. As this graphic shows ALMA offers a five-fold spatial resolution than Hubble Space Telescope. This was crucial to their discovery


These hidden galaxies have been called REBELS-12-2 & REBELS-29-2.

– We have reached the light of two invisible galaxies after it has traveled 13 billion years.

– The galaxies are now located 29 billion light years away due the universe’s expansion.

The ALMA telescope was used by researchers to study radio waves.

ALMA blends the light of its 66 antennae into a high resolution image of the sky. 

However, many of these “missing” galaxies can be discovered by equipment like the James Webb Space Telescope. 

This new study was done by scientists at University of Copenhagen’s Niels Bohr Institute. 

Pascal Oesch (associate professor at the Niels Bohr institute) said, “We were looking, a sample, of very distant galaxies which we already knew existed through the Hubble Space Telescope,” 

“Then, we realized that one of the two had a neighbor that we hadn’t expected to be there.” 

Hubble is unable to see these two galaxies because they are both surrounded by dust. 

Hubble was launched into low Earth orbit in 1990, while the ground-based ALMA (Atacama Large Milimeter Array) radio telescopes began scientific observations in 2011.  

ALMA, which is five times more precise than Hubble Space Telescope’s spatial resolution, was the key to its discovery.

ALMA uses the combined light from all its 66 antennae in order to produce a high-resolution image and spectrum of the sky. It can also capture radio waves that are emitted by the darkest and coldest parts of the universe.   

Antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, set against the splendour of the Milky Way

Antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, set against the splendour of the Milky Way

Team says that the light of both REBELS-12-2 & REBELS-2-9-2 has traveled about 13 billion year to reach Earth.  

REBELS-12-2 was compared to REBELS-229-2, and the results showed that between 10 and 20% of the early universe’s sources (about 13 Billion years ago) may be still hidden behind cosmic debris.

‘Our discovery demonstrates that up to one in five of the earliest galaxies may have been missing from our map of the heavens,’ said Professor Oesch.  

The James Webb Space Telescope, which is expected to be launched into orbit on December 22 this year after 25 years in development, will help experts better understand when and how galaxies formed.  

The general consensus is that the oldest galaxies were formed in the first 100 million years following the Big Bang. However, astronomers are still not sure how they got there.  

Hubble Space Telescope is more than 30 years old. This NASA image shows Hubble drifting over Earth on May 19, 2009

Hubble Space telescope is over 30 years old. NASA captured Hubble’s drift over Earth in this NASA photo on May 19, 2009.

NASA's James Webb Space Telescope is the largest, most powerful, and most complex space science telescope ever built

NASA’s James Webb Space Telescope (NASA) is the biggest, most powerful and complex space science telescope ever made.

James Webb is one of many things that help scientists see through cosmic dust better than Hubble and ALMA. 

Professor Oesch stated that the next step was to find galaxies not yet identified. There are many more than we think.’That’s where the James Webb Telescope will be a huge step forward. 

“It will be more sensitive than Hubble. It can also investigate longer wavelengths. This should enable us to find these hidden galaxies easily.   

Nature has published this new study. 


On November 22, NASA delayed the launch of the James Webb Space Telescope yet again to allow for additional testing following a ‘recent incident’.

The $10 billion telescope is now due to launch on December 22 on an Arianespace Ariane 5 rocket from Kourou, a town in French Guiana, South America.  

Although originally scheduled for launch December 18, the launch was delayed by a’recent incident’ in launch preparations. 

In 1996, the James Webb Space Telescope was developed and originally planned to be launched in 2007. 

Testing work was already delayed by the Covid-19 pandemic in 2020, by which time the estimated total cost of developing the telescope had increased to over $10 billion (£7.4 billion). 

James Webb, who will be studying the history and origins of the universe’s first stars when it launches eventually, will also participate in the launch.