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Galaxy at the dawn of time

Galaxy GN-108036

One of the most distant galaxies known, called GN-108036, is seen 750 million years after the Big Bang. The galaxy's light took 12.9 billion years to reach us. Infrared observations taken by NASA's Spitzer and Hubble space telescopes show it to be surprisingly bright, thought to result from an extreme burst of star formation

  • Galaxy seen as it was 750 million years after the Big Bang
  • Observations suggest it is forming stars at a furious rate

ASTRONOMERS USING NASA’S Spitzer and Hubble space telescopes have discovered that one of the most distant galaxies known is churning out stars at a shockingly high rate. The blob-shaped galaxy, called GN-108036, is the brightest galaxy found to date at such great distances.

The galaxy, which was discovered and confirmed using ground-based telescopes, is 12.9 billion light-years away.

Data from Spitzer and Hubble were used to measure the galaxy’s high star production rate, equivalent to about 100 Suns per year.

For reference, our Milky Way galaxy is about five times larger and 100 times more massive than GN-108036, but makes roughly 30 times fewer stars per year.

“The discovery is surprising because previous surveys had not found galaxies this bright so early in the history of the universe,” said Mark Dickinson of the US National Optical Astronomy Observatory in Arizona. “Perhaps those surveys were just too small to find galaxies like GN-108036.”

“It may be a special, rare object that we just happened to catch during an extreme burst of star formation.”

Seen shortly after the Big Bang

The international team of astronomers, led by Masami Ouchi of the University of Tokyo, Japan, first identified the remote galaxy after scanning a large patch of sky with the Subaru Telescope atop Mauna Kea in Hawaii.

Its great distance was then carefully confirmed with the W.M. Keck Observatory, also on Mauna Kea.

“We checked our results on three different occasions over two years, and each time confirmed the previous measurement,” said Yoshiaki Ono of the University of Tokyo, lead author of a new paper reporting the findings in the Astrophysical Journal.

Spitzer (left) and Hubble space telescopes

The Spitzer (left) and Hubble space telescopes were used to measure the galaxy's redshift, a indication of how far away it is.

GN-108036 lies near the very beginning of time itself, a mere 750 million years after our universe formed 13.7 billion years ago in an explosive “Big Bang.”

Its light has taken 12.9 billion years to reach us, so we are seeing it as it existed in the very distant past.

Remarkable redshift

Astronomers refer to an object’s distance by a number called its “redshift,” which is a measure of how much its light has been stretched to longer, redder wavelengths due to the expansion of the universe.

Objects with larger redshifts are farther away and are seen further back in time.

GN-108036 has a redshift of 7.2. Only a handful of galaxies have confirmed redshifts greater than 7, and only two of these have been reported to be more distant than GN-108036.

Infrared observations from Spitzer and Hubble were crucial for measuring the galaxy’s star-formation activity. Astronomers were surprised to see such a large burst of star formation because the galaxy is so small and from such an early cosmic era.

Back when galaxies were first forming, in the first few hundreds of millions of years after the Big Bang, they were much smaller than they are today, having yet to bulk up in mass.

During this epoch, as the universe expanded and cooled after its explosive start, hydrogen atoms permeating the cosmos formed a thick fog that was opaque to ultraviolet light. This period, before the first stars and galaxies had formed and illuminated the universe, is referred to as the “dark ages.”

The era came to an end when light from the earliest galaxies burned through, or “ionised,” the opaque gas, causing it to become transparent. Galaxies similar to GN-108036 may have played an important role in this event.

Adapted from information issued by NASA / JPL-Caltech / STScI / University of Tokyo.

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Galaxy caught blowing bubbles

Hubble Space Telescope image of Holmberg II

The Hubble Space Telescope captured this image of dwarf irregular galaxy Holmberg II. The main part of the galaxy is the spread of stars in the lower left half of the image. Huge bubbles of glowing gas produced by stellar explosions dominate the galaxy; they are now sites of ongoing star formation.

HUBBLE’S FAMOUS IMAGES OF GALAXIES typically show them to be elegant spirals or soft-edged elliptical shapes.

But these neat forms are only representative of large galaxies. Smaller galaxies like the dwarf irregular galaxy Holmberg II come in many shapes and types that are harder to classify.

Holmberg II’s indistinct shape is punctuated by huge glowing bubbles of gas, captured in this image from the Hubble Space Telescope.

The intricate glowing shells of gas were formed by the energetic life cycles of many generations of stars. High-mass stars form in dense regions of gas, and later in life expel strong stellar winds that blow away the surrounding material.

At the very end of their lives, they explode in as a supernova. Shock waves rip through these less dense regions blowing out and heating the gas, forming the delicate shells we see today.

Holmberg II is a patchwork of dense star-forming regionsand extensive barren areas with less material, which can stretch across thousands of light-years.

Keck Observatory view of Holmberg II

A wider view of Holmberg II. Courtesy B. Mendez / Keck Observatory.

As a dwarf galaxy, it has neither the spiral arms typical of galaxies like the Milky Way nor the dense nucleus of an elliptical galaxy.

This makes Holmberg II, gravitationally speaking, a gentle haven where fragile structures such as these bubbles can hold their shape.

A hidden black hole?

While the galaxy is unremarkable in size, Holmberg II does have some intriguing features. As well as its unusual appearance—which earned it a place in Halton Arp’s Atlas of Peculiar Galaxies, a treasure trove of weird and wonderful objects—the galaxy hosts an ultraluminous X-ray source in the middle of the three gas bubbles in the top right of the image.

There are competing ideas as to what causes this powerful radiation—one intriguing possibility is that an intermediate-mass black hole is pulling in material from its surroundings, with the material giving off energy as it nears the black hole.

The colourful image is a composite of visible and near-infrared exposures taken using the Wide Field Channel of Hubble’s Advanced Camera for Surveys. Hubble is a project of international cooperation between the European Space Agency and NASA.

Download the Hubble wallpapers:

Holmberg II (1024×768, 588.2 KB)

Holmberg II (1280×1024, 1.0 MB)

Holmberg II (1600×1200, 1.5 MB)

Holmberg II (1920×1200, 1.8 MB)

Adapted from information issued by HEIC / NASA / ESA.

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Hubble’s replacement put to the test

THE MANY COMPONENTS of the James Webb Space Telescope undergo testing at their place of construction, as well as at the locations where the individual pieces are assembled into larger parts.

But closer to launch, engineers need to put the fully assembled telescope through environmental testing.

NASA will be using its largest thermal vacuum chamber to accomplish this task. The chamber at Houston’s Johnson Space Centre was used to test Apollo vehicles back in the ’60s and ’70s, and has been used sporadically throughout the following years for other space vehicles.

Changes are being made to the chamber so the James Webb Space Telescope can be tested even more rigorously than the Apollo spacecraft.

Adapted from information issued by Space Telescope Science Institute.

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Pluto has a new moon

Artist's impression of Pluto and Charon

Artist's impression of Pluto and its large moon Charon (diameter 1,043km). Hubble telescope observations have uncovered a previously unseen Plutonian moon, probably only 13 to 34km across.

ASTRONOMERS USING THE Hubble Space Telescope have discovered a fourth moon orbiting the icy dwarf planet Pluto. The tiny, new satellite, temporarily designated P4, was uncovered in a Hubble survey searching for rings around the dwarf planet.

The new moon is the smallest discovered circling Pluto. It has an estimated diameter of 13 to 34 km. By comparison, Charon, Pluto’s largest moon, is 1,043 km across, and the other moons, Nix and Hydra, are in the range of 32 to 113 km in diameter.

“I find it remarkable that Hubble’s cameras enabled us to see such a tiny object so clearly from a distance of more than 5 billion km,” said Mark Showalter of the SETI Institute, who led this observing programme with Hubble.

Hubble image showing motion of Pluto's four moons

This composite of two Hubble images—taken on June 28, 2011 and July 3, 2011—shows Pluto's four satellites in motion. P4 is the as-yet-unnamed new moon.

Mission to Pluto

The finding is a result of ongoing work to support NASA’s New Horizons mission, scheduled to fly through the Pluto system in 2015. The mission is designed to provide new insights about worlds at the edge of our Solar System.

Hubble’s mapping of Pluto’s surface and discovery of its satellites have been invaluable to planning for New Horizons’ close encounter.

“This is a fantastic discovery,” said New Horizons’ principal investigator Alan Stern of the Southwest Research Institute. “Now that we know there’s another moon in the Pluto system, we can plan close-up observations of it during our flyby.”

Moons formed in a smash-up

The new moon is located between the orbits of Nix and Hydra, which Hubble discovered in 2005. Charon was discovered in 1978 at the US Naval Observatory and first resolved using Hubble in 1990 as a separate body from Pluto.

The dwarf planet’s entire moon system is believed to have formed by a collision between Pluto and another planet-sized body early in the history of the Solar System. The smash-up flung material that coalesced into the family of satellites observed around Pluto.

Artist's concept of Pluto's satellite system

An artist's concept of Pluto's satellite system with newly discovered moon P4 highlighted.

Lunar rocks returned to Earth from the Apollo missions led to the theory that our moon was the result of a similar collision between Earth and a Mars-sized body 4.4 billion years ago.

Scientists believe material blasted off Pluto’s moons by micrometeoroid impacts may form rings around the dwarf planet, but the Hubble photographs have not detected any so far.

No sign of rings yet

“This surprising observation is a powerful reminder of Hubble’s ability as a general purpose astronomical observatory to make astounding, unintended discoveries,” said Jon Morse, astrophysics division director at NASA Headquarters in Washington.

P4 was first seen in a photo taken with Hubble’s Wide Field Camera 3 on June 28. It was confirmed in subsequent Hubble pictures taken on July 3 and July 18. The moon was not seen in earlier Hubble images because the exposure times were shorter.

There is a chance it appeared as a very faint smudge in 2006 images, but was overlooked because it was obscured.

Adapted from information issued by NASA. Images and graphics courtesy NASA / A. Feild (STScI) / ESA.

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Hubble sees a southern wonder

Close-up image of the central region of NGC 5128

Resembling looming rain clouds on a stormy day, dark lanes of dust crisscross the heart of the giant elliptical galaxy NGC 5128. Hubble's reveals the vibrant glow of young, blue star clusters and a glimpse into regions normally obscured by the dust.

THE GALAXY KNOWN AS NGC 5128 is a favourite of amateur astronomers in the Southern Hemisphere. Easily visible through a small telescope, it has a rounded shape with a prominent “dark lanes” running through its centre.

Those lanes are composed of interstellar “rivers” of dust encircling the galaxy.

Astronomers have now used the Hubble Space Telescope’s Wide Field Camera 3 to zoom in on this region of NGC 5128 in multi-wavelength observations, resulting in the most detailed view ever of this galaxy.

As well as features in the visible spectrum, the composite shows ultraviolet light from young stars, and near-infrared light, which lets us glimpse some of the detail otherwise obscured by the dust.

The dark dust lane that crosses Centaurus A does not show an absence of stars, but rather a relative lack of starlight, as the opaque clouds block the light of background stars from reaching us.

Hubble’s Wide Field Camera 3 has focused on these dusty regions, which span from corner to corner in this image.

It is thought that at some point in the past, NGC 5128 collided and merged with another galaxy. The shockwaves of this event caused hydrogen gas clouds to coalesce and sparked intense areas of star formation, as seen in its outlying regions and in red patches visible in this Hubble close-up.

Wide-field image of NGC 5128

This wide-field image shows the full extent of galaxy NGC 5128 and its dark, central dust lanes. NGC 5128 is more than 11 million light-years from Earth.

The galaxy’s compact core contains a very active giant black hole. Powerful jets emanating from the vicinity of the black hole are emitting vast amounts of radio and X-ray radiation (although these are invisible here as Hubble’s instruments).

At just over 11 million light-years distant, NGC 5128is relatively nearby in astronomical terms. However, it is not only close, it is also bright. This makes it a very attractive target for amateur astronomers in the Southern Hemisphere, where it is visible. Stargazers can see the galaxy through binoculars, while larger amateur telescopes begin to unveil the distinctive dusty lanes.

Editor’s note: You’ll often see this galaxy called Centaurus A, but this is not strictly correct. Centaurus A is the name given to a region within the galaxy that is emitting large amounts of radio waves. The overall galaxy is called NGC 5128.

Adapted from information issued by NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgment: R. O’Connell (University of Virginia) and the WFC3 Scientific Oversight Committee. Wide-angle NGC 5128 image courtesy ESO.

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Are galaxies ‘see through’?

Galaxy pair AM500-620

Galaxy pair AM500-620 comprises two dusty spiral galaxies, one in front of the other.

THIS HUBBLE SPACE TELESCOPE image shows a galaxy pair known only by its catalogue number, AM0500-620. It comprises consists of a highly symmetrical spiral galaxy seen nearly face-on, partially backlit by a background galaxy.

The Hubble image shows the foreground spiral galaxy to have a number of ‘dust lanes’ between its spiral arms.

The background galaxy had originally been classified as an elliptical galaxy, but Hubble’s observations revealed it to be a dusty spiral arms and bright knots of stars.

The image was taken in order to work out how much dust is held within galaxies, and whether this dust reduces the amount of light we see from the stars within those galaxies.

By finding foreground-background galaxy pairs, astronomers were able to refine their estimates of dust in the foreground galaxies through the backlighting effect of the background galaxies.

AM0500-620 is 350 million light-years away from Earth in the direction of the constellation Dorado, the Swordfish.

Download a 1280 x 1280-pixel wallpaper image of AM0500-620.

Adapted from information issued by NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and W. Keel (University of Alabama, Tuscaloosa) / UA News Bureau.

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Rocky horror show in deep space

LATE LAST YEAR, ASTRONOMERS noticed an asteroid named Scheila had unexpectedly brightened, and it was sporting short-lived plumes. Data from NASA’s Swift satellite and Hubble Space Telescope showed these changes likely occurred after Scheila was struck by a much smaller asteroid.

“Collisions between asteroids create rock fragments, from fine dust to huge boulders, that impact planets and their moons,” said Dennis Bodewits, an astronomer at the University of Maryland in College Park and lead author of the Swift study.

“Yet this is the first time we’ve been able to catch one just weeks after the smash-up, long before the evidence fades away.”

Asteroids are rocky fragments thought to be debris from the formation and evolution of the solar system approximately 4.6 billion years ago. Millions of them orbit the Sun between Mars and Jupiter in the main asteroid belt. Scheila is approximately 110 kilometres wide and orbits the Sun every five years.

Astronomers have known for decades that comets contain icy material that erupts when warmed by the Sun. They regarded asteroids as inactive rocks whose destinies, surfaces, shapes and sizes were determined by mutual impacts.

However, this simple picture has grown more complex over the past few years.

During certain parts of their orbits, some objects, once categorised as asteroids, clearly develop comet-like clouds that can last for many months. Others display much shorter outbursts. Icy materials may be occasionally exposed, either by internal geological processes or by an external one, such as an impact.

HST image of asteroid Scheila

The Hubble Space Telescope imaged asteroid Scheila on December 27, 2010, when it was about 350 million kilometres away. The C-shaped cloud of particles and dust tail suggest the asteroid was struck by another object.

Asteroid or comet?

On December 11, 2010, images from the University of Arizona’s Catalina Sky Survey, a project of NASA’s Near Earth Object Observations Program, revealed Scheila to be twice as bright as expected and immersed in a faint comet-like glow. Looking through the survey’s archived images, astronomers inferred the outburst began between November 11 and December 3.

Three days after the outburst was announced, Swift’s Ultraviolet/Optical Telescope (UVOT) captured multiple images and a spectrum of the asteroid. Ultraviolet sunlight breaks up the gas molecules surrounding comets—water, for example, is transformed into hydroxyl (OH) and hydrogen.

But none of the emissions most commonly identified in comets, such as hydroxyl or cyanogen, show up in the UVOT spectrum. The absence of gas around Scheila led the Swift team to reject scenarios where exposed ice accounted for the activity.

Images show the asteroid was flanked by dual plumes formed as small dust particles excavated by the impact were pushed away from the asteroid by sunlight.

The teams found the observations were best explained by a small asteroid hitting Scheila’s surface at an angle of less than 30 degrees, leaving a crater 300 metres across. The researchers estimate the crash ejected more than 660,000 tons of dust.

Adapted from information issued by NASA’s Goddard Space Flight Centre. Images courtesy NASA / ESA / D. Jewitt (UCLA) / Goddard Space Flight Centre /Conceptual Image Lab.

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Latest Hubble video report

THE HUBBLE SPACE TELESCOPE is working on three of the most ambitious projects in its history just now. These programs are using Hubble’s unique ability to observe across the spectrum from ultraviolet, through visible, to infrared light, to build up a library of data that will serve astronomers for many years.

In this podcast episode, presenter Dr J (aka Joe Liske) looks at these projects, and how they will complement the capabilities of the next great thing in space-based astronomy, the James Webb Space Telescope.

Adapted from information issued by ESA / Hubble.

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The outer limits

Hubble image of distant galaxy

Earlier this year, the Hubble Space Telescope spotted what could be the farthest and one of the very earliest galaxies ever seen in the universe so far. This is the deepest infrared image taken of the universe (deeper even than the Hubble Deep Field; see image below). Based on the galaxy's colour, astronomers believe it is a staggering 13.2 billion light-years away.

HOW FAR CAN WE SEE into the cosmos? And what lies beyond what we can see? Will we ever know what exists beyond the ‘edge of space’?

These questions were posed recently by SpaceInfo readers in response to our story on what astronomers will see one trillion years from now.

They’re very interesting questions indeed. The answers require a bit of thought, and especially they require someone who knows what they’re talking about and can provide them in an understandable manner.

Dr Tamara Davis

Dr Tamara Davis

Introducing Dr Tamara Davis, a cosmologist and Research Fellow in the Physics Department at the University of Queensland. Tamara is involved in some of the most exciting cosmological research going at the moment, and her achievements were recognised a couple of years ago when she was honoured with the 2009 L’Oréal Women in Science Award.

We’re grateful to Tamara for taking the time to give us the following brief explanation of how far we can see, how far we might be able to see in the future, and why there are some things we’ll never see.

Our cosmic Horizons

by Dr Tamara Davis, University of Queensland

SpaceInfo readers have asked about what lies beyond the reach of our view of the cosmos. This is a great question, and I hope the following explanation will help everyone to understand the situation.

There are actually two types of ‘cosmic horizon’. There’s a limit to how far we can see right now, and a different limit to how far we’ll be able to see in the far future.

The limit to how far we can see right now is called our “particle horizon” because it is the distance to the most far-away “particle” (eg. galaxy) that we can currently see.

The particle horizon arises because light has been able to travel only a finite distance since the Big Bang. If we had been around to shine a light from our position at the time of the Big Bang, then the distance that light could have travelled by now is the distance to our particle horizon.

This kind of horizon is getting bigger as time goes on (as light has more time to travel), and we’re continually able to see things further and further away (and further and further back in time).

Practically speaking, we can’t actually see all the way to our theoretical particle horizon because to do so we’d have to see light that was emitted right at the moment of the Big Bang. The universe was so dense back then that light couldn’t travel very far before getting scattered. It was unable to ‘break out’ from the dense cosmic ‘soup’.

In practical terms the most distant thing we can see is what cosmologists call the “last scattering surface”. This was the state of play about 100,000 years after the Big Bang, when the universe’s density dropped to the point that light could break out and travel relatively unimpeded.

These days we perceive that light as a uniform glow of microwave radiation from all directions, known as the cosmic microwave background. Some of the static picked up by old analogue TVs came from this radiation … so, funnily enough, when you saw fuzz on your TV screen you were actually detecting light from our effective particle horizon!

Hubble Deep Field

The Hubble Deep Field is one of the iconic images of space, showing us galaxies into the far distant universe. And the further away a galaxy is, the further back in time we're seeing it.

Edge of the great unknown

The other type of horizon, probably more relevant to the discussion in the original article, is our “event horizon”, which is the limit to how far we will be able to see in the infinite future.

If we were to shine a light outwards from our position now, then the distance it can travel in the future is our event horizon.

Now, you might think that, unless the cosmos were to somehow end, a light beam could travel an infinite distance into an infinite future. But in a universe whose rate of expansion is accelerating (like ours) that isn’t true, so there’s a limit to how far we will be able to see, even given infinite time.

This is because there are distant parts of the universe expanding away from us faster than the speed of light… the only way light from galaxies in the most distant reaches of the universe can reach us is if the universe’s expansion slows down.

It’s a bit like a swimmer caught in a rip, trying to swim back to shore…she can’t swim faster than the rip, so she’ll never make it. Unless the rip slows down she hasn’t got a chance.

But our universe is not slowing down, the expansion is actually speeding up, so light from some distant galaxies will forever be out of view.

This limit is called our “event horizon” because it separates events we will be able to see from events we will never be able to see.

The event horizon is actually a more stringent limit than the particle horizon, because not only do you have to ask whether you can see the particle, but also if you can see it for its entire life.

Many galaxies that we can currently see are actually, by now, well beyond our event horizon—because although we can see them as they were in the past, we will never be able to see them as they are today.

Our current event horizon is at a redshift of 1.8…that’s about 5 giga-parsecs away. (A giga-parsec is one billion parsecs, with a parsec being 3.26 light-years.)

You might have seen the Hubble Deep Field (see image above)—one of the ‘deepest,’ most detailed photos of the universe ever taken. The most distant galaxy in that image is beyond a redshift of 6 (more than 8 giga-parsecs away).

That means that a huge number of the galaxies we can see in that image are now actually beyond our event horizon. The Hubble Deep Field shows us a snapshot of them as they were in the past, but we’ll never be able to communicate with them.

More information

For more information about this subject, and for some scientific diagrams of how far we can see in the universe, you can download a fascinating PDF-format article by Tamara from http://www.physics.uq.edu.au/download/tamarad/astro/scienceimages/Spacetime_diagrams.pdf

She’s also written another great article that helps straighten out this wide topic, “Misconceptions about the Big Bang” (Scientific American, March 2005). And for even more information you can visit her website at http://www.physics.uq.edu.au/download/tamarad/astro/index.html

Distant galaxy image courtesy NASA, ESA, Garth Illingworth (UC Santa Cruz), Rychard Bouwens (UC Santa Cruz and Leiden University) and the HUDF09 Team / A. Feild (STScI). HDF image courtesy R. Williams (STScI), the Hubble Deep Field Team and NASA. Tamara Davis image courtesy timothyburgess.net / Science in Public.

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First galaxies older than expected

Abell 383 and a distorted background galaxy

The gravity of this giant cluster of galaxies, including the huge one in the middle, acts as a sort of magnifying glass, distorting and concentrating the light of a distant background galaxy. Visible as two tiny dots (labelled), the galaxy is seen as it was less than a billion years after the Big Bang.

ASTRONOMERS HAVE DISCOVERED a distant galaxy whose stars were born unexpectedly early in cosmic history.

“We have discovered a distant galaxy that began forming stars just 200 million years after the Big Bang,” says Johan Richard, the lead author of a new study. “This challenges theories of how soon galaxies formed and evolved in the first years of the Universe.”

Richard’s team spotted the galaxy in recent observations from the NASA/ESA Hubble Space Telescope, verified it with observations from the NASA Spitzer Space Telescope and measured its distance using W.M. Keck Observatory in Hawaii.

The distant galaxy is far beyond a cluster of galaxies called Abell 383, whose powerful gravity bends passing rays of light almost like a magnifying glass.

The chance alignment of the galaxy, the cluster and the Earth amplifies the light reaching us from the distant galaxy, enabling the astronomers to make detailed observations.

Without this gravitational lens, the galaxy would have been too faint to be seen even with today’s largest telescopes.

A young galaxy of old stars

After spotting the galaxy in Hubble and Spitzer images, the team carried out spectroscopic observations with the Keck-II telescope in Hawaii. Spectroscopy is the technique of breaking up light into its component colours.

By analysing the spectra, the team was able to make detailed measurements of the galaxy’s redshift and infer information about the properties of its component stars.

The redshift is 6.027, which means we’re seeing the galaxy as it was when the Universe was around 950 million years old.

Diagram explaining gravitational lensing

The gravity of huge galaxy clusters acts as a magnifying glass, amplifying the light of galaxies in the distant background and making them easier to see.

This doesn’t make it the most remote galaxy ever detected—several have been confirmed at redshifts of more than 8, and one has an estimated redshift of around 10, placing it 400 million years earlier.

However the newly discovered galaxy is very different to other distant ones, which generally shine brightly with only young stars.

“When we looked at the spectra, two things were clear,” explains co-author Eiichi Egami. “The redshift placed it very early in cosmic history, as we expected. But the Spitzer infrared detection also indicated that the galaxy was made up of surprisingly old and relatively faint stars.”

“This told us that the galaxy was made up of stars already nearly 750 million years old—pushing back the epoch of its formation to about 200 million years after the Big Bang, much further than we had expected,” adds Egami.

“This suggests that the first galaxies have been around for a lot longer than previously thought,” says Dan Stark, another co-author of the study.

Artist's impression of the James Webb Space Telescope

When operational, the James Webb Space Telescope will be able to see even further back in time.

Unseen army may solve the mystery

The discovery has implications beyond the question of when galaxies first formed. It might also help explain how the Universe became transparent to ultraviolet light in the first billion years after the Big Bang.

In the early years of the cosmos, a diffuse fog of neutral hydrogen gas blocked ultraviolet light in the Universe. Some source of radiation must have progressively ionised the diffuse gas, clearing the fog and making it transparent to ultraviolet rays as it is today—a process known as reionisation.

Astronomers believe that the radiation that powered this reionisation must have come from galaxies. But, so far, nowhere near enough of them have been found to provide the necessary radiation.

The new discovery may help solve this enigma.

“It seems probable that there are in fact far more galaxies out there in the early Universe than we previously estimated—it’s just that many galaxies are older and fainter, like the one we have just discovered,” says co-author Jean-Paul Kneib.

“If this unseen army of faint, elderly galaxies is indeed out there, they could provide the missing radiation that made the Universe transparent to ultraviolet light.”

As of today, astronomers can discover these galaxies only by seeing them through gravitational lenses. But the NASA/ESA/CSA James Webb Space Telescope, scheduled for launch later this decade, will be able to make high-resolution observations of the distant, highly redshifted bodies.

Astronomers hope then to be in a position to solve this mystery once and for all.

Adapted from information issued by the ESA Hubble Information Centre. Abell 383 image courtesy of NASA, ESA, J. Richard (CRAL) and J.-P. Kneib (LAM) (acknowledgement: Marc Postman (STScI)). Gravitational lensing diagram courtesy NASA, ESA & L. Calçada.

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