THESE NEXT-GEN TELESCOPES WILL PEER INTO THE DEEP HISTORY OF THE UNIVERSE


Astronomers recently held groundbreakings for three huge telescopes in five months, the first of which should begin observations by 2021. The scopes’ light-collecting mirrors—each 80 to 126 feet across—will dwarf those at the W.M. Keck Observatory, whose twin 33-foot mirrors are the benchmark today.

 With telescopes this large, one challenge is to develop a design that swings easily across the sky and minimizes the atmosphere’s blurriness. Overcoming these hurdles, engineers have created observatories that will take pictures of the cosmos at resolutions 100 times higher than the current generation of telescopes. Astronomers will use them to study stars born just after the big bang, detect the expansion of the universe in more detail, and hunt for signs of life on planets around other stars. Even more tantalizing is the prospect of the unknown—the questions astronomers don’t yet know to ask but will inevitably stumble upon with new, more powerful tools.

In some ways, three groundbreakings in five months isn’t as surprising as it may seem: Over the past century, design leaps have occurred roughly every 30 years, so this crop is right on schedule. Gary Sanders, project manager for the new Thirty Meter Telescope, explains that three decades is simply the time it takes technology to advance enough to warrant new facilities. Upgraded capabilities come at a price; the observatories will cost more than $1 billion apiece and likely direct resources away from existing facilities, such as Keck. But Sanders is confident that astronomers will make good use of them. “There are only 365 nights in a year,” he says, “and a lot of questions to answer.”

“With each generation of new telescopes, we open up new things we never anticipated. It’s the serendipity that really drives the science.”

—Debra Elmegreen, astronomy professor at Vassar College and former president of the American Astronomical Society

Eyes On The Skies

The size of a telescope’s primary mirror—the glass that concentrates light from the sky onto the detector—determines its observing power. Bigger mirrors make for finer-detailed images. Here’s how the next generation of mirrors stack up against Keck I and II.

 

From left to right: Keck I and II, 33 feet; Giant Magellan Telescope, 80 feet; Thirty Meter Telescope, 98 feet; European Extremely Large Telescope, 126 feet.

Mirrors That Erase The Atmosphere

Adaptive optics (AO) systems—which compensate for the blurring effects of the atmosphere—were tacked on to the current generation of big telescopes years after they were built. In the new machines, AO is a standard feature. About 800 times per second, actuators adjust the curvature of a mirror in the telescope’s light path by a few microns. Luc Simard, the TMT’s lead instrumentalist, says AO will allow these observatories to take pictures 10 times clearer than Hubble, whose price tag was four times more than these billion-dollar scopes.

Discovered: the galaxy that’s so far away we’re seeing it as it was 13 billion years ago


Scientists detected z8-GND-5296 with help of Hubble Space Telescope and Keck Telescope in Hawaii.

Astronomers have detected the furthest known galaxy in the Universe which is more than 13 billion light years away on the very edge of space.

Because of the time it takes for its light to reach Earth, the galaxy is seen today as it was just 700 million years after the Big Bang – the primordial event that created the Universe some 13.8 billion years ago.

Scientists detected the galaxy – known as z8-GND-5296 – with the help of the Hubble Space Telescope parked in geostationary orbit and the Keck Telescope on the summit of Mauna Kea in Hawaii.

They searched a library of about 100,000 of the most distant galaxies before finding that one of them could be accurately positioned in space by analysing the infrared light it had emitted.

A spectroscopic analysis of the galaxy’s wavelength showed how much it has shifted to the red end of the spectrum. This “redshift”, and the known expansion velocity of the Universe, was used to measure the galaxy’s precise distance from Earth.

“What makes this galaxy unique, compare to other such discoveries, is the spectroscopic confirmation of its distance,” said Bahran Mobasher of the University of California, Riverside and a member of the research team.

“By observing a galaxy that far back in time, we can study the earliest formation of galaxies. By comparing properties of galaxies at different distances, we can explore the evolution of galaxies throughout the age of the Universe,” Dr Mobasher said.

At this particular point in its early history,  the z8-GND-5296 galaxy was producing new stars at a rate of about 300 a year, which is about 100 times faster than our own galaxy, the Milky Way.

There is only one other known object to be further away in space – a massive star that had exploded some 70 million years earlier. The period before this is known as the “cosmic dark ages” because so little is known about it.

Astronomers believe they are close to finding the first galaxies that were probably responsible for the transition from an opaque Universe, when much of its hydrogen was neutral, to a translucent Universe, when the hydrogen became ionised – called the Era of Re-ionisation.

Steven Finkelstein of the University of Texas at Austin, who led the project, said the new galaxy is in the same region of the sky as the previous record holder.

“So we’re learning something about the distant universe. There are way more regions of very high star formation than we previously thought. There must be a decent number of them if we happen to find two in the same area of the sky,” Dr Finkelstein said.

‘Most distant galaxy’ discovered


An international team of astronomers has detected the most distant galaxy yet.

The galaxy is about 30 billion light-years away and is helping scientists shed light on the period that immediately followed the Big Bang.

It was found using the Hubble Space Telescope and its distance was then confirmed with the ground-based Keck Observatory in Hawaii.

The study is published in the journal Nature.

Because it takes light so long to travel from the outer edge of the Universe to us, the galaxy appears as it was 13.1 billion years ago (its distance from Earth of 30 billion light-years is because the Universe is expanding).

Lead researcher Steven Finkelstein, from the University of Texas at Austin, US, said: “This is the most distant galaxy we’ve confirmed. We are seeing this galaxy as it was 700 million years after the Big Bang.”

The far-off galaxy goes by the catchy name of z8_GND_5296.

Astronomers were able to measure how far it was from Earth by analysing its colour.

Because the Universe is expanding and everything is moving away from us, light waves are stretched. This makes objects look redder than they actually are.

Astronomers rate this apparent colour-change on a scale that is called redshift.

They found that this galaxy has a redshift of 7.51, beating the previous record-holder, which had a redshift of 7.21.

This makes it the most distant galaxy ever found.

Galaxy
z8_GND_5296 is churning out stars at a remarkable rate, say astronomers

The system is small: about 1-2% the mass of the Milky Way and is rich in heavier elements.

But it has a surprising feature: it is turning gas and dust into new stars at a remarkable rate, churning them out hundreds of times faster than our own galaxy can.

It is the second far-flung galaxy known that has been found to have a high star-production rate.

Astronomer looking at the Milky Way
  • Human eyes can see long distances, but the further away an object gets the harder it is to see in detail
  • Telescopes make a distant object appear larger by collecting its light and focusing it to a point
  • The large reflecting Hubble Telescope creates images from the Universe’s visible light and can also detect infrared and ultraviolet radiation
  • The optical and infrared Keck Telescopes examine young stars and can look into the centre of galaxies

Prof Finkelstein said: “One very interesting way to learn about the Universe is to study these outliers and that tells us something about what sort of physical processes are dominating galaxy formation and galaxy evolution.

“What was great about this galaxy is not only is it so distant, it is also pretty exceptional.”

He added that in the coming years, astronomers are likely to discover even more distant galaxies when Nasa’s James Webb Space Telescope (JWST) is launched and other ground-based telescopes come online.

Commenting on the research, Dr Marek Kukula, Public Astronomer at the Royal Observatory Greenwich, told BBC News: “This, along with some other evidence, shows that there are already quite surprisingly evolved galaxies in the very early Universe .

“This high star-formation rate maybe is a clue as to why these galaxies can form so quickly.”

Prof Alfonso Aragon-Salamanca, from the University of Nottingham, added: “This is an important step forward, but we need to continue looking for more.

“The further away we go, the closer we will get to discovering the very first stars that ever formed in the Universe. The next generation of telescopes will make this possible.”

But Dr Stephen Serjeant from the Open University said: “Chasing ultra-high redshift galaxies is a very exciting but equally very difficult game, and many claims of extremely distant galaxies have since turned out to be more nearby interlopers.”

Dead star eats water-rich asteroid


Artist's impression of an asteroid being torn apart
The scientists suspect the remains of an icy asteroid have been pulled on to the white dwarf star

Astronomers have detected the tell-tale signs of a shattered asteroid being eaten by a dead star, or white dwarf.

The Hubble telescope spotted the event some 150 light-years from Earth.

The researchers tell Science Magazine that the chemical signatures in the star’s atmosphere indicate the asteroid must contain a lot of water.

This makes it the first time both water and a rocky surface – key components for habitable planets – have been found together beyond our Solar System.

The dead star is called GD 61. It has long since burnt through its nuclear fuel and has shrunk down to a dimly glowing ember.

But its gravity is still intense, and it is shredding rocky objects in its vicinity and pulling the debris into its outermost layers.

Runaway process

Hubble and the Hawaiian Keck observatory record how this inflow of material taints the star’s atmosphere.

They detect elements such as magnesium, silicon, iron, and oxygen – the chemical ingredients of rock minerals.

But what piques the scientists’ interest is the abundance of oxygen.

This is far too high to be explained just from the in-fall of rock, and indicates that whatever is being dragged on to the dwarf must also contain a lot of water.

The team’s calculations point to the source body being an asteroid at least 90km across and composed of perhaps 26% by mass of water.

This water content is very similar to Ceres, the largest asteroid in the main belt of our Solar System and the target of a Nasa probe in 2015.

By way of comparison, the Earth is a very dry object, containing just 0.02% by mass of water, and much of this was probably delivered by comets and asteroids.

The astronomers – from the universities of Cambridge and Warwick, UK, and from Kiel, Germany – speculate that a similar water-delivery system could also have occurred in the GD 61 system, which is very likely to have had rocky planets in its heyday.

Sun’s future

Lead author Dr Jay Farihi told the BBC’s Science In Action programme: “The reason that we can say that is that the planet-formation process starts with things as small as dust grains. They grow into things as big as pebbles and boulders and then as large as asteroids. Once you get to things as big as asteroids, planets are essentially inevitable – it’s a runaway process; you simply cannot stop it.

“Having asteroids and no planets is logically possible but it’s very likely physically implausible. So, we know there were rocky planets [in GD 61] because we can see the rocky building blocks; and we know there was the potential to deliver water to their surfaces because we’ve seen at least one very water-rich and large asteroid.”

Of the 1,000 planets so far identified beyond our Solar System, none has been definitively associated with the presence of water.

For most of these objects, all that is known is a few details such as distance, size, density and the time taken to orbit the host star. The Hubble-Keck observations therefore represent the first time water has definitively been put in immediate contact with a far-off rocky surface, says Dr Farihi.

The GD 61 system also gives us a glimpse of what is likely to occur one day in the vicinity of our own star – the Sun. Billions of years into the future, it too will burn out and shrink into a white dwarf, consuming asteroids and other debris.

“I think alien astronomers would then be getting pretty similar information to what we’re getting on GD 61,” Dr Farihi, from the Cambridge Institute of Astronomy, explained.

“I guess it would depend on what time they looked and which asteroid they were lucky enough to catch. But we know of water-rich asteroids in the outer main belt and I think there would be a good chance that they would see a signature of something like the asteroid Ceres. And in that case, if the alien astronomers speculated about habitable planets – well, if they’re looking back at our system, in that case they’d be correct.”