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Today’s telescopes study the sky across the electromagnetic spectrum.

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Each part of the spectrum tells us different things about the Universe,

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giving us more pieces of the cosmic jigsaw puzzle. 

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The most powerful telescopes on the ground and in space 

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have joined forces over the last decade

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in a unique observing campaign, known as GOODS, 

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which reaches across the spectrum and deep back into cosmic time.

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This is the ESOcast! 

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Cutting-edge science and life behind the scenes of ESO,

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the European Southern Observatory.

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Exploring the ultimate frontier with our host Dr J, a.k.a. Dr Joe Liske.

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Hello and welcome to this very special “multicast”.

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We’ll be exploring a unique collaboration 

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between some of the world’s most powerful telescopes both

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on the ground and in space.

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Now, to do this, we’ve set up a similar collaboration between 

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the ESOcast, the Hubblecast, 

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the Spitzer Space Telescope’s “Hidden Universe” and

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the Chandra X-Ray Observatory’s “Beautiful Universe”.

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I’m Megan Watzke for the Beautiful Universe from the Chandra X-ray Center

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And I’m Dr Robert Hurt for Hidden Universe from NASA Spitzer Science Center

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It’s the combination of deep observations from many different telescopes 

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that makes this project so important.

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The longer a telescope spends looking at a target, 

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the more sensitive the observations become, and the deeper we can look into space. 

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But to get the full picture of what’s happening in the Universe, 

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astronomers also need observations at a range of different wavelengths, 

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requiring different telescopes. 

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These are the key ideas behind the Great Observatories Origins Deep Survey, 

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or GOODS for short.

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The GOODS project unites the world’s most advanced observatories,

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these include ESO’s Very Large Telescope, 

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the NASA/ESA Hubble Space Telescope,

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the Spitzer Space Telescope, 

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the Chandra X-ray Observatory and many more, 

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each making extremely deep observations 

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of the distant Universe, across the electromagnetic spectrum.

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By combining their powers and observing the same piece of sky, 

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the GOODS observatories are giving us a unique view of the formation 

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and evolution of galaxies across cosmic time, 

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and mapping the history of the expansion of the Universe.

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Now, this is not the first time that telescopes 

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have been used to give us extremely deep views of the cosmos.

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For example, the Hubble Deep Field is a very deep image 

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of a small region of sky in the northern constellation of Ursa Major. 

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This revealed thousands of distant galaxies 

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despite the fact that the whole field is actually only a tiny speck of sky, 

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about the size of a grain of sand held at arm’s length.

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Now, with GOODS, many different observatories 

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have brought their powers to bear on two larger targets, 

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one centred on the original Hubble Deep Field in the northern sky,

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and one centred on a different deep target, 

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the Chandra Deep Field South, in the southern sky.

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The main GOODS fields are each 30 times larger than the Hubble Deep Field, 

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and additional observations cover an area the size of the full Moon.

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These areas of the sky were already some of the most extensively explored,

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and so the combination of existing archival data with the many new, dedicated observations 

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gives us an unprecedented view of the history of galaxies.

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At ESO’s Very Large Telescope on Cerro Paranal, the 8.2-metre-diameter giants 

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were used for a total of almost 100 nights of dedicated observations.

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The telescopes made images of the region both in near-infrared light, 

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and on the boundary between visible light and ultraviolet light. 

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At these short wavelengths, only telescopes on exceptional sites 

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such as the VLT’s Cerro Paranal 

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have a chance to observe through the Earth’s atmosphere.

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The NASA/ESA Hubble Space Telescope observed

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the GOODS regions at optical and near-infrared wavelengths,

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in order to detect distant star-forming galaxies among other things.

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Now, Hubble spent a total of five days observing the fields, 

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spread over five repeat visits. 

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Each of these was separated from the previous one by about 45 days. 

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Now, by spreading out the observations like this, 

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Hubble was able to watch out for new supernovae appearing over the months, 

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providing key information for studying the expansion and the acceleration of the Universe 

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due to the mysterious dark energy.

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But it wasn’t just Hubble making space-based observations for GOODS…

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NASA’s Spitzer Space Telescope imaged the GOODS regions 

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in near- and mid-infrared light for five days, 

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at wavelengths up to 30 times longer than the Hubble observations. 

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These longer wavelengths are important for revealing distant galaxies 

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whose light may be obscured by cosmic dust, 

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or stretched by the expansion of the Universe, making them invisible to Hubble. 

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For these distant galaxies, the Spitzer images also tell astronomers about their age 

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and their total mass of stars — complementary information to the data from Hubble.

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Now, let’s move from the infrared to much shorter wavelengths…

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Also in orbit, the Chandra X-Ray Observatory had already observed the GOODS field 

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in many long observations taken over the course of a year. 

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The Chandra images are the deepest X-ray images ever taken, 

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and detected more than 200 X-ray sources 

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believed to be supermassive black holes in the centres of young galaxies. 

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The X-rays are produced by extremely hot interstellar gases

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falling into the black holes.

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These multiwavelength observations identified tens of thousands of galaxies. 

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To get a full understanding of the history and development of galaxies 

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over the vast stretch of the Universe’s history,

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we need to be able to pin down their distances more precisely, 

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to fix them in cosmic time.

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As these galaxies are so far away, 

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the light waves we see from them today

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started their journey up to about 13 billion years ago,

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and because the Universe has been expanding since the Big Bang, 

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back then the Universe was less than one seventh of its current size.

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During the billions of years of the light’s journey, 

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its wavelength has been stretched as the fabric of space has expanded. 

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This effect is known as “redshift” 

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because, for example, light that was originally blue or ultraviolet in colour 

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is shifted to longer and redder wavelengths.

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Back on the ground, astronomers used spectrographs 

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on ESO’s Very Large Telescope 

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to capture the spectra of galaxies,

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spreading out their light like the colours of the rainbow.

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Now, the spectra allow astronomers to measure 

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the redshifts of the galaxies, and hence, their distances.

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An extensive campaign produced redshifts 

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for almost 3000 galaxies in the GOODS fields.

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Now, with this knowledge, we can place the galaxies 

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at their distances along a vast cone of space, 

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stretching out from our own vantage point 

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like a searchlight beam into the cosmos. 

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We can take an amazing journey

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through kind of a tunnel towards the edge of the Universe. 

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In some places, the galaxies cluster together, 

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forming structures which are up to tens of millions of light years in scale.

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Thanks to GOODS and other surveys of the same region, 

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these areas of the sky are uniquely well studied 

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with high resolution, deep observations 

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across a wide wavelength range, 

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plus there is more to come.

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For example, the Atacama Pathfinder Experiment telescope, or APEX, 

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has spent a total of 300 hours — nearly two full weeks —

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imaging the region at submillimetre wavelengths,

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from its high site on the 5000-metre-altitude plateau of Chajnantor 

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in the Chilean Andes.

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Observations at these wavelengths 

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are ideal for finding the redshifted light 

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of distant dusty galaxies in the very early Universe.

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Because of the longer wavelength of its submillimetre light, 

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the APEX image is not as sharp as the visible light and infrared images.

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However, thanks to the deep Spitzer images, 

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as well as images made at radio wavelengths,

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we can match up and identify the objects found by APEX 

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with galaxies seen at other wavelengths.

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The submillimetre light glow 

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reveals that hundreds of stars are being formed per year in these galaxies. 

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In the next couple of years, 

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ALMA, the Atacama Large Millimeter/submillimeter Array, 

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currently under construction on the same plateau as APEX, 

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will begin its first science observations. 

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Also observing at submillimetre wavelengths,

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it will have much greater sensitivity than APEX, 

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and resolution even better than Hubble. 

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ALMA will revolutionise our understanding of the early Universe 

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by revealing many more distant, dust-obscured galaxies 

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that cannot be seen at all by visible light and infrared telescopes.

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These projects are an excellent example of how great observatories 

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are joining together, across the electromagnetic spectrum, 

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to give us a more complete view of galaxies over the history of the Universe.

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Already, astronomers have written over 400 papers based on these data, 

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with even more in the pipeline! 

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And on top of that, the observations of the GOODS fields will continue in the future.

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These patches of the sky will be prime targets for the next generation of telescopes 

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both on the ground and in space, 

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and astronomers around the world will use these data

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to learn new things about the Universe for many years to come.

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Saying goodbye to our friends at the other observatories, 

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this is Dr J signing off for the ESOcast and the Hubblecast…

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This is Dr Robert Hurt signing off for the Hidden Universe and the Spitzer Science Center, 

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reminding you there’s a hidden Universe just waiting to be discovered.

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And this is Megan Watzke 

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signing off for the Chandra X-ray Observatory and the Beautiful Universe.

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Join me again next time for another cosmic adventure, 

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which I’m sure will surprise us beyond our wildest imagination.

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This was a multicast from: 

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ESOcast, Hubblecast, Hidden Universe, Beautiful Universe 

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ESOcast is produced by ESO, the European Southern Observatory.

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ESO, the European Southern Observatory, is the pre-eminent intergovernmental science and technology organisation in astronomy,

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designing, constructing and operating the world’s most advanced ground-based telescope 

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The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, 

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is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile.

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APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, 

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the European Southern Observatory, and the Onsala Space Observatory.

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Transcription by ESO ; translation by —

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Now that you've caught up with ESO, 

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head 'out of this world' with Hubble. 

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The Hubblecast highlights the latest discoveries of the world´s most recognized and prized space observatory, 

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the NASA/ESA Hubble Space Telescope