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Hubble spots a hidden treasure

Josh Lake's image of LHA 120-N11

Josh Lake’s image of LHA 120-N11, which comprises several adjacent pockets of gas and star formation. It is located in the Large Magellanic Cloud galaxy, roughly 200,000 light-years from Earth.

NEARLY 200,000 LIGHT-YEARS from Earth, the Large Magellanic Cloud, a satellite galaxy of the Milky Way, floats in space, in a long and slow dance around our galaxy.

Vast clouds of gas within it slowly collapse to form new stars. In turn, these light up the gas clouds in a riot of colours, visible in this image from the NASA/ESA Hubble Space Telescope.

The Large Magellanic Cloud (LMC) is ablaze with star-forming regions. From the Tarantula Nebula, the brightest stellar nursery in our cosmic neighbourhood, to LHA 120-N 11, part of which is featured in this Hubble image, the small and irregular galaxy is scattered with glowing nebulae, the most noticeable sign that new stars are being born.

The LMC is in an ideal position for astronomers to study the phenomena surrounding star formation. It lies in a fortuitous location in the sky, far enough from the plane of the Milky Way that it is neither outshone by too many nearby stars, nor obscured by the dust in the Milky Way’s centre.

It is also close enough to study in detail (less than a tenth of the distance of the Andromeda Galaxy, the closest spiral galaxy), and lies almost face-on to us, giving us a bird’s eye view.

Smokey remains of dead stars

LHA 120-N 11 (known as N11 for short) is a particularly bright region of the LMC, consisting of several adjacent pockets of gas and star formation. NGC 1769 (in the centre of this image) and NGC 1763 (to the right) are among the brightest parts.

In the centre of this image, a dark finger of dust blots out much of the light. While nebulae are mostly made of hydrogen, the simplest and most plentiful element in the universe, dust clouds are home to heavier and more complex elements, which go on to form rocky planets like the Earth.

Much finer than household dust (it is more like smoke), this interstellar dust consists of material expelled from previous generations of stars as they died.

The data in this image were identified by Josh Lake, an astronomy teacher at Pomfret School in Connecticut, USA, in the Hubble’s Hidden Treasures image processing competition. The competition invited members of the public to dig out unreleased scientific data from Hubble’s vast archive, and to process them into stunning images.

Josh Lake won first prize in the competition with an image (below) contrasting the light from glowing hydrogen and nitrogen in N 11. The image at the top of the page combines the data he identified with additional exposures taken in blue, green and near infrared light.

Josh Lake's image of NGC 1763

Josh Lake’s image of the NGC 1763 region of nebulosity and stars in the Large Magellanic Cloud galaxy. The image won him first prize in Hubble’s Hidden Treasures Image Processing Competition

More information: Hidden Treasures

Adapted from information issued by ESA / Hubble Information Centre. Images: NASA, ESA and J. Lake.

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Hubble’s deepest view of the cosmos

The Hubble eXtreme Deep Field

This image, called the Hubble eXtreme Deep Field (XDF), combines Hubble observations taken over the past decade. With a total of over two million seconds of exposure time, it is the deepest image of the Universe ever made.

ASTRONOMERS HAVE ASSEMBLED a new, improved portrait of our deepest-ever view of the Universe. Called the eXtreme Deep Field, or XDF, the image was assembled by combining ten years of NASA/ESA Hubble Space Telescope observations taken of a patch of sky within the original Hubble Ultra Deep Field. The XDF is a small fraction of the angular diameter of the full Moon.

The Hubble Ultra Deep Field (UDF) is an image of a small area of space in the constellation of Fornax (The Furnace), created using Hubble data from 2003 and 2004. By collecting faint light over one million seconds of observation, the resulting image revealed thousands of galaxies, both nearby and very distant, making it the deepest image of the Universe ever taken at that time.

The new full-colour XDF image is even more sensitive than the original UDF image, thanks to the additional observations, and contains about 5,500 galaxies, even within its smaller field of view. The faintest galaxies are one ten-billionth the brightness that the unaided human eye can see.

The Hubble eXtreme Deep Field with interesting objects labelled

This view of the XDF image contains shows of the most distant objects ever identified. Among these are: UDFj-39546284, at a redshift of 10.3, is a candidate for the most distant galaxy yet discovered (awaiting confirmation); Supernova Primo, at a redshift of 1.55, the most distant type Ia supernova ever observed; UDFy-38135539, at a redshift of 8.6, is the most distant galaxy to have had its distance independently corroborated; UDFy-33436598, at a redshift of 8.6.

Magnificent spiral galaxies similar in shape to the Milky Way and its neighbour the Andromeda galaxy appear in this image, as do large, fuzzy red galaxies in which the formation of new stars has ceased. These red galaxies are the remnants of dramatic collisions between galaxies and are in their declining years as the stars within them age.

Peppered across the field are tiny, faint, and yet more distant galaxies that are like the seedlings from which today’s magnificent galaxies grew. The history of galaxies — from soon after the first galaxies were born to the great galaxies of today, like the Milky Way — is laid out in this one remarkable image.Diagram showing distances of galaxies in the XDF

Hubble pointed at a tiny patch of southern sky in repeat visits made over the past decade with a total exposure time of two million seconds. More than 2,000 images of the same field were taken with Hubble’s two primary cameras: the Advanced Camera for Surveys and the Wide Field Camera 3, which extends Hubble’s vision into near-infrared light. These were then combined to form the XDF.

The Universe is 13.7 billion years old, and the XDF reveals galaxies that span back 13.2 billion years in time. Most of the galaxies in the XDF are seen when they were young, small, and growing, often violently as they collided and merged together.

Graphic comparing the size of the XDF compared to the full Moon

This image from the Digitsed Sky Survey shows the area of the Hubble eXtreme Deep Field (XDF), with the full Moon shown to scale for comparison.

The early Universe was a time of dramatic birth for galaxies containing brilliant blue stars far brighter than our Sun. The light from those past events is just arriving at Earth now, and so the XDF is a time tunnel into the distant past when the Universe was just a fraction of its current age.

The youngest galaxy found in the XDF existed just 450 million years after the Universe’s birth in the Big Bang.

Download wallpapers of the eXtreme Deep Field:

1024 x 768 (436.0 KB)

1280 x 1024 (722.2 KB)

1600 x 1200 (1.1 MB)

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2048 x 1536 (1.8 MB)

Adapted from information issued by NASA/ESA. Images courtesy NASA, ESA, Z. Levay (STScI), T. Rector, I. Dell’Antonio/NOAO/AURA/NSF, G. Illingworth, D. Magee, and P. Oesch (University of California, Santa Cruz), R. Bouwens (Leiden University) and the HUDF09 Team

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Hubble’s successor passes milestone

NASA engineer looks at first six flight ready James Webb Space Telescope's primary mirror segments

NASA engineer Ernie Wright looks on as the first six flight-ready James Webb Space Telescope's primary mirror segments are prepped to begin final freeze testing at NASA's Marshall Space Flight Centre.

MIRRORS ARE THE MOST CRITICAL PART of a telescope. Quality is crucial, so completion of mirror polishing represents a major milestone. All of the mirrors that will fly aboard NASA’s James Webb Space Telescope have now been polished so the observatory can see objects as far away as the first galaxies in the universe.

The Webb telescope has four types of mirrors. The primary one has an area of approximately 25 square metres, made up of 18 separate mirrors, which will enable scientists to capture light from faint, distant objects in the universe faster than any previous space observatory.

The mirrors are made of the light metal Beryllium and will work together to relay images of the sky to the telescope’s science cameras.

“Webb’s mirror polishing always was considered the most challenging and important technological milestone in the manufacture of the telescope, so this is a hugely significant accomplishment,” said Lee Feinberg, Webb Optical Telescope manager at NASA’s Goddard Space Flight Centre.

The mirrors were polished at the L3 Integrated Optical Systems–Tinsley in Richmond, California to accuracies of less than one millionth of an inch. That accuracy is important for forming the sharpest images when the mirrors cool to minus 240°C in the cold of space.

Artist's impression of the James Webb Space Telescope

Artist's impression of the James Webb Space Telescope, due for launch later this decade.

New technology invented

“The completion of the mirror polishing shows that the strategy of doing the hardest things first has really paid off,” said Nobel Prize Winner John C. Mather, Webb’s senior project scientist at Goddard. “Some astronomers doubted we could make these mirrors.”

After polishing, the mirrors are being coated with a microscopically thin layer of gold to enable them to efficiently reflect infrared light. NASA has completed coating 13 of 18 primary mirror segments and will complete the rest by early next year. The 18 segments fit together to make one large mirror 6.5 metres across.

“This milestone is the culmination of a decade-long process,” said Scott Willoughby, vice president and Webb Telescope Program manager for Northrop Grumman Aerospace Systems. “We had to invent an entire new mirror technology to give Webb the ability to see back in time.”

As the successor to the Hubble Space Telescope, the Webb telescope is the world’s next-generation space observatory. It is the most powerful space telescope ever built.

More than 75 percent of its hardware is either in production or undergoing testing—the observatory will be launched later this decade.

The telescope will observe the most distant objects in the universe, provide images of the first galaxies ever formed and study planets around distant stars. NASA, the European Space Agency and the Canadian Space Agency are collaborating on this project.

The following video shows what it takes to get the Webb Telescope’s mirrors ready for flight:

Adapted from information issued by Rob Gutro, NASA Goddard Space Flight Centre. Images courtesy NASA / Ball Aerospace / Tinsley; NASA / MSFC / David Higginbotham; STScI / Mary Estacion.

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Hubble’s one-millionth observation

Artist's concept of the planet HAT-P-7b

Artist's concept of the planet HAT-P-7b, a "hot Jupiter"-class planet orbiting a star that is much hotter than our Sun. Hubble's millionth science observation was trained on this planet to look for the presence of water vapour and to study it atmospheric structure via spectroscopy.

A LITTLE OVER 21 YEARS SINCE IT WAS LAUNCHED, NASA’s Hubble Space Telescope crossed another milestone in its space odyssey of exploration and discovery. On Monday, July 4, the Earth-orbiting observatory logged its one-millionth science observation during a search for water in the atmosphere of a planet 1,000 light-years away.

“For 21 years Hubble has been the premier space science observatory, astounding us with deeply beautiful imagery and enabling ground-breaking science across a wide spectrum of astronomical disciplines,” said NASA Administrator Charles Bolden. He piloted the space shuttle mission that carried Hubble to orbit.

“The fact that Hubble met this milestone while studying a faraway planet is a remarkable reminder of its strength and legacy.”

At the time Hubble was launched, scientists had yet to detect planets circling other stars.

Hubble Space Telescope

Hubble has spent 21 years in space studying the cosmos, and has just made it's one-millionth observation.

Hubble ideally suited to the task

Although Hubble is best known for its stunning imagery of the cosmos, the millionth observation is a spectroscopic measurement, where light is divided into its component colours. These colour patterns can reveal the chemical composition of cosmic sources.

Hubble’s millionth exposure is of the planet HAT-P-7b, a gas giant planet larger than Jupiter orbiting a star hotter than our Sun. HAT-P-7b, also known as Kepler 2b, has been studied by NASA’s planet-hunting Kepler observatory after it was discovered by ground-based observations.

Hubble now is being used to analyse the chemical composition of the planet’s atmosphere.

“We are looking for the spectral signature of water vapour. This is an extremely precise observation and it will take months of analysis before we have an answer,” said Drake Deming of the University of Maryland and NASA’s Goddard Space Flight Centre.

“Hubble demonstrated it is ideally suited for characterising the atmospheres of exoplanets, and we are excited to see what this latest targeted world will reveal,” he added.

Image from a Hubble Space Telescope servicing mission

Astronauts have conducted five servicing missions to Hubble.

Groundbreaking science

Hubble was launched April 24, 1990, aboard space shuttle’s Discovery’s STS-31 mission. Its discoveries revolutionised nearly all areas of astronomical research from planetary science to cosmology. The observatory has collected more than 50 terabytes of data to-date. The archive of that data is available to scientists and the public at http://hla.stsci.edu/

Hubble’s odometer reading includes every observation of astronomical targets since its launch and observations used to calibrate its suite of instruments. Hubble made the millionth observation using its Wide Field Camera 3, a visible and infrared light imager with an on-board spectrometer. It was installed by astronauts during the Hubble Servicing Mission 4 in May 2009.

“The Hubble keeps amazing us with groundbreaking science,” said Sen. Barbara A. Mikulski, the chairwoman of the Senate Commerce, Justice, Science and Related Agencies Appropriations Subcommittee that funds NASA.

“I championed the mission to repair and renew Hubble not just to get one million science observations, but also to inspire millions of children across the planet to become our next generation of stargazers, scientists, astronauts and engineers.”

Adapted from information issued by NASA / ESA / G. Bacon, STScI.

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Star that changed the universe

Andromeda Galaxy with insets of star V1

Observations of a star in the Andromeda Galaxy that changes its brightness in a regular pattern, convinced astronomers that our cosmos was huge. Edwin Hubble's further studies of such stars showed that the universe is expanding.

THOUGH THE UNIVERSE IS FILLED with billions upon billions of stars, observations of a single star in 1923 altered the course of modern astronomy. And, at least one famous astronomer of the time lamented that the discovery had shattered his worldview.

The star goes by the inauspicious name of Hubble variable number one, or V1, and resides two million light-years away in the outer regions of the Andromeda Galaxy. V1 belongs to a special class of pulsating star called Cepheid variables, which can be used to make reliable measurements of large cosmic distances.

The star helped Edwin Hubble show that Andromeda lies beyond our galaxy. Prior to the discovery of V1 many astronomers, including Harlow Shapley, thought ‘spiral nebulae’, such as Andromeda, were part of our Milky Way Galaxy.

Others weren’t so sure. In fact, Shapley and Heber Curtis held a public debate in 1920 over the nature of these nebulae. But it took Edwin Hubble’s discovery just a few years later to settle the debate.

Hubble sent a letter, along with a light curve of V1, to Shapley telling him of his discovery. After reading the note, Shapley reportedly told a colleague, “Here is the letter that destroyed my universe.”

The universe became a much bigger place after Edwin Hubble’s discovery.

Andromeda Galaxy with an overlay of a Cepheid star light curve

Cepheid variable stars like V1 change their brightness with a regular pattern. This characteristic enables astronomers to use them to measure distances in the cosmos, by comparing their apparent brightness with their calculated theoretical brightness. Courtesy NASA, ESA, and Z. Levay (STScI), HHT (STScI/AURA), AAVSO. Acknowledgment: T. Rector (University of Alaska, Anchorage).

Cosmic distance ladder

In commemoration of this landmark observation, astronomers with the Space Telescope Science Institute’s Hubble Heritage Project partnered with the American Association of Variable Star Observers (AAVSO) to study the star.

AAVSO observers followed V1 for six months, producing a plot, or light curve, of the rhythmic rise and fall of the star’s light. Based on this data, the Hubble Heritage team scheduled Hubble Space Telescope time to capture Wide Field Camera 3 images of the star at its dimmest and brightest light levels.

“This observation is a reminder that Cepheid variables are still relevant today,” explains Max Mutchler of the Heritage team. “Astronomers are using them to measure distances to galaxies much farther away than Andromeda. They are the first rung on what astronomers call the cosmic distance ladder.”

Edwin Hubble's original photo of Andromeda

Edwin Hubble's original photo of Andromeda, showing three stars of interest marked 'N'. The one at the top became even more interesting when it was recognised as being variable (hence 'VAR'). This is Hubble's V1 star.

Copies of the photograph Edwin Hubble made in 1923 flew onboard space shuttle Discovery in 1990 on the mission that deployed Hubble. Two of the remaining five copies were part of space shuttle Atlantis’s cargo in 2009 for NASA’s fifth servicing mission to Hubble.

The most important star

Edwin Hubble’s observations of V1 became the critical first step in uncovering a larger, grander universe. He went on to measure the distances to many galaxies beyond the Milky Way by finding Cepheid variables within them. The velocities of those galaxies, in turn, allowed him to determine that the universe is expanding.

“V1 is the most important star in the history of cosmology,” says astronomer Dave Soderblom of the Space Telescope Science Institute, who proposed the V1 observations.

The space telescope that bears his name continues using Cepheids to refine the expansion rate of the universe and probe galaxies that were far beyond Edwin Hubble’s reach.

Adapted from information issued by STScI. Images courtesy NASA, ESA, and the Hubble Heritage Team (STScI/AURA). Acknowledgment: R. Gendler.

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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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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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Hubble bursts dark energy bubble

Galaxy NGC 5584

Galaxy NGC 5584 was one of eight galaxies astronomers studied to measure the universe's expansion rate. Two special kinds of stars—Type Ia supernovae and Cepheid variable stars—were used as "cosmic yardsticks", due to their predictable brightnesses.

  • Our universe seems to be expanding faster and faster with time
  • ‘Dark energy’ proposed as an explanation, but its nature remains a mystery
  • Hubble observations have ruled out one dark energy hypothesis

ASTRONOMERS USING NASA’s Hubble Space Telescope have ruled out one explanation for the nature of dark energy after recalculating the expansion rate of the universe to unprecedented accuracy.

The universe appears to be expanding at an increasing rate. Some think this is because it is filled with a ‘dark energy’ that works in the opposite way to gravity.

An alternative to that hypothesis is that an enormous ‘bubble’ of relatively empty space eight billion light-years wide surrounds our galactic neighbourhood.

If we lived near the centre of this void, observations of galaxies being pushed away from each other at accelerating speeds would be an illusion.

This hypothesis has now been invalidated because astronomers have refined their understanding of the universe’s present expansion rate.

“We are using the new camera on Hubble like a policeman’s radar gun to catch the universe speeding,” said Adam Riess of the Space Telescope Science Institute (STScI) and Johns Hopkins University, and leader of the science team. “It looks more like it’s dark energy that’s pressing the [accelerator] pedal.”

Portion of NGC 5584 with Cepheid locations marked

A portion of galaxy NGC 5584 with the location of Cepheid variable stars marked.

The observations helped determine a figure for the universe’s current expansion rate to an uncertainty of just 3.3 percent. The new measurement reduces the error margin by 30 percent over Hubble’s previous best measurement in 2009.

Cosmic yardsticks

Riess’ team first had to determine accurate distances to galaxies near and far from Earth, and then compare those distances with the speed at which the galaxies are apparently receding because of the expansion of space.

They used those two values to calculate the Hubble constant, the number that relates the speed at which a galaxy appears to recede to its distance from the Milky Way.

Because we cannot physically measure the distances to galaxies, astronomers have to find stars or other objects that serve as reliable cosmic yardsticks. These are objects with known intrinsic brightness—brightness that hasn’t been dimmed by distance, an atmosphere or interstellar dust. Their distances, therefore, can be inferred by comparing their intrinsic brightness with their apparent brightness as seen from Earth.

To calculate long distances, Riess’ team chose a special class of exploding star called Type Ia supernovae. These stellar blasts all have similar luminosity and are brilliant enough to be seen far across the universe.

By cross-correlating the apparent brightness of Type Ia supernovae with pulsating Cepheid stars (another class of stars whose intrinsic brightness is known), the team could accurately gauge the distances to Type Ia supernovae in far-flung galaxies.

WFC3

Hubble's latest camera, the Wide Field Camera 3, was instrumental in the research.

Bubble is burst

By using the sharpness of Hubble’s new Wide Field Camera 3 (WFC3) to study more stars in visible and near-infrared light, the team eliminated systematic errors introduced by comparing measurements from different telescopes.

“WFC3 is the best camera ever flown on Hubble for making these measurements, improving the precision of prior measurements in a small fraction of the time it previously took,” said Lucas Macri, a collaborator on the Supernova Ho for the Equation of State (SHOES) Team from Texas A&M in College Station.

Knowing the precise value of the universe’s expansion rate further restricts the range of dark energy’s strength and helps astronomers tighten up their estimates of other cosmic properties, including the universe’s shape and its roster of neutrinos, or ghostly particles, that filled the early cosmos.

“Thomas Edison once said ‘every wrong attempt discarded is a step forward,’ and this principle still governs how scientists approach the mysteries of the cosmos,” said Jon Morse, astrophysics division director at NASA Headquarters in Washington.

“By falsifying the bubble hypothesis of the accelerating expansion, NASA missions like Hubble bring us closer to the ultimate goal of understanding this remarkable property of our universe.”

Adapted from information issued by STScI. NGC 5584 image credit: NASA / ESA / A. Riess (STScI/JHU), L. Macri (Texas A&M University) / Hubble Heritage Team (STScI/AURA). NGC 5584 illustrations credit: NASA / ESA / L. Frattare (STScI) / Z. Levay (STScI).

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Galaxy at the edge of time

Portion of the Hubble Ultra Deep Field

The farthest and one of the very earliest galaxies ever seen in the universe appears as a faint red blob in this ultra-deep–field exposure taken with NASA's Hubble Space Telescope. This is the deepest infrared image taken of the universe. Based on the object's colour, astronomers believe it is 13.2 billion light-years away.

  • Using Hubble data, team spots galaxy with redshift of 10.3
  • We’re seeing it as it was 13.2 billion years ago

Astronomers studying ultra-deep imaging data from the Hubble Space Telescope have found what may be the most distant galaxy ever seen, about 13.2 billion light-years away.

The study pushed the limits of Hubble’s capabilities, extending its reach back to about 480 million years after the Big Bang, when the universe was just 4 percent of its current age.

“We’re getting back very close to the first galaxies, which we think formed around 200 to 300 million years after the Big Bang,” said Garth Illingworth, professor of astronomy and astrophysics at the University of California, Santa Cruz.

Illingworth and UCSC astronomer Rychard Bouwens (now at Leiden University in the Netherlands) led the study, which has been published in the January 27 issue of Nature.

Rapid build-up of galaxies

Using infrared data gathered by Hubble’s Wide Field Planetary Camera 3 (WFC3), they were able to see dramatic changes in galaxies over a period from about 480 to 650 million years after the Big Bang.

The rate of star birth in the universe increased by ten times during this 170-million-year period, Illingworth said.

“This is an astonishing increase in such a short period, just 1 percent of the current age of the universe,” he said.

There were also striking changes in the numbers of galaxies detected.

“Our previous searches had found 47 galaxies at somewhat later times when the universe was about 650 million years old. However, we could only find one galaxy candidate just 170 million years earlier,” Illingworth said. “The universe was changing very quickly in a short amount of time.”

According to Bouwens, these findings are consistent with the hierarchical picture of galaxy formation, in which galaxies grew and merged under the gravitational influence of dark matter.

“We see a very rapid build-up of galaxies around this time,” he said. “For the first time now, we can make realistic statements about how the galaxy population changed during this period and provide meaningful constraints for models of galaxy formation.”

Here’s a NASA video with some comments from Garth Illingworth:

Remarkable redshift

Astronomers gauge the distance of an object from its redshift, a measure of how much the expansion of space has stretched the light from an object to longer (“redder”) wavelengths.

The newly detected galaxy has a likely redshift value (“z”) of 10.3, which corresponds to an object that emitted the light we now see 13.2 billion years ago, just 480 million years after the birth of the universe.

“This result is on the edge of our capabilities, but we spent months doing tests to confirm it, so we now feel pretty confident,” Illingworth said.

The galaxy, a faint smudge of starlight in the Hubble images, is tiny compared to the massive galaxies seen in the local universe. Our own Milky Way, for example, is more than 100 times larger.

The researchers also described three other galaxies with redshifts greater than 8.3. The study involved a thorough search of data collected from deep imaging of the Hubble Ultra Deep Field (HUDF), a small patch of sky about one-tenth the size of the Moon.

During two four-day stretches in summer 2009 and summer 2010, Hubble focused on one tiny spot in the HUDF for a total exposure of 87 hours with the WFC3 infrared camera.

Graph showing ability of different telescopes to look increasingly deeper back into time

Timeline of time: Over the years, improvements in technology have enabled astronomers to use their telescopes to peer further and further back into time. The forthcoming James Webb Space Telescope will be able to see even further.

Next step? Hubble’s successor

To go beyond redshift 10, astronomers will have to wait for Hubble’s successor, the James Webb Space Telescope (JWST), which NASA plans to launch later this decade. JWST will also be able to perform the spectroscopic measurements needed to confirm the reported galaxy at redshift 10.

“It’s going to take JWST to do more work at higher redshifts. This study at least tells us that there are objects around at redshift 10 and that the first galaxies must have formed earlier than that,” Illingworth said.

Illingworth’s team maintains the First Galaxies website, with information about the latest research on distant galaxies: http://firstgalaxies.org/

In addition to Bouwens and Illingworth, the co-authors of the Nature paper include Ivo Labbe of Carnegie Observatories; Pascal Oesch of UCSC and the Institute for Astronomy in Zurich; Michele Trenti of the University of Colorado; Marcella Carollo of the Institute for Astronomy; Pieter van Dokkum of Yale University; Marijn Franx of Leiden University; Massimo Stiavelli and Larry Bradley of the Space Telescope Science Institute; and Valentino Gonzalez and Daniel Magee of UC Santa Cruz.

The research was supported by NASA and the Swiss National Science Foundation.

Adapted from information issued by UCSC. Images credit: NASA, ESA, Garth Illingworth (UC Santa Cruz), Rychard Bouwens (UC Santa Cruz and Leiden University) and the HUDF09 Team / A. Feild (STScI).

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Hubble sees a mini-Milky Way

Galaxy NGC 3982

Hubble Space Telescope image of galaxy NGC 3892. It is 30,000 light-years wide and 68 million light-years from Earth.

Though the universe is chock full of spiral-shaped galaxies, no two look exactly the same.

This face-on spiral galaxy, called NGC 3982, is striking for its rich tapestry of star birth, along with its winding arms. It’s like a smaller version of our Milky Way.

The arms are lined with pink star-forming regions of glowing hydrogen, newborn blue star clusters, and obscuring dust lanes that provide the raw material for future generations of stars.

The bright nucleus is home to an older population of stars, which grow ever more densely packed toward the centre.

NGC 3982 is located about 68 million light-years away in the direction of the constellation Ursa Major. The galaxy spans about 30,000 light-years, one-third of the size of our Milky Way galaxy.

See the full-size, high-resolution image here (new window).

This colour image is composed of exposures taken by the Hubble Space Telescope’s Wide Field Planetary Camera 2 (WFPC2), the Advanced Camera for Surveys (ACS), and the Wide Field Camera 3 (WFC3). The observations were taken between March 2000 and August 2009.

The rich colour range comes from the fact that the galaxy was photographed in visible and near-infrared light. Also used was a filter that isolates hydrogen emission that emanates from bright star-forming regions dotting the spiral arms.

Adapted from information issued by NASA / ESA / HHT (STScI/AURA) / A. Riess (STScI).

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