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In early 2009, a team of astronauts visited Hubble to repair

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 the wear and tear of twenty years of operating in a hostile environment — 

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and to install two new instruments, the Cosmic Origins Spectrograph, 

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and Wide Field Camera 3 — better known as WFC3.

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WFC3 is a combined ultraviolet, visible and infrared camera that dramatically extends  

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Hubble’s ability to image astronomical objects.

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With these new capabilities, Hubble is still pushing the boundaries of science after two decades in orbit.

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This is the Hubblecast, news and images from the NASA/ESA Hubble Space Telescope.

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Travelling through time and space with our host Dr J, aka Dr Joe Liske.

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In episode 30 of the Hubblecast, we saw some of the very first 

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pictures to come back from Wide Field Camera 3

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Hubble’s newest and most advanced instrument. 

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Today we’re going to look at some of the science behind these pictures. 

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We’ll find out how this remarkable new camera 

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is helping Hubble to see the invisible, 

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look far back in time and spot objects further away from us than ever before.

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WFC3 was installed on Hubble as replacement of WFPC2, 

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the Wide Field and Planetary Camera 2, 

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which for many years had been the main workhorse instrument on Hubble. 

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Not only do the two instruments have very similar names, and look virtually identical,

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the capabilities of WFC3 are also in some respects 

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just a tweaked version of those of its predecessor — 

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although with sharper images and more sensitive light detectors. 

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But on top of these incremental improvements, WFC3 also brings a whole  

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battery of new functions to Hubble that are getting us astronomers really excited. 

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WFC3 is actually two instruments in one: 

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the ultraviolet and visible-light channel is WFPC2’s replacement, 

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cramming six times as many pixels into a similar field of view. 

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As well as providing scientists with higher resolution observations than ever before, 

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the pictures from this part of WFC3 are also Hubble’s prettiest yet 

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revealing details never seen before through any telescope.

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But it is WFC3’s infrared channel that is the real breakthrough. 

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Infrared astronomy is getting a lot of attention right now.

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 It’s not just Hubble’s new functions:

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ESA’s Herschel Space Observatory, NASA’s Spitzer Space Telescope 

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and the forthcoming NASA/ESA/CSA James Webb Space Telescope 

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were all designed to work in the infrared.

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One of the reasons for this is that studying the sky in the infrared allows astronomers 

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to look at relatively cool objects which emit little or no visible light. 

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An example of these are so-called protoplanetary nebulae, a cool gas 

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envelope which gets thrown off by a certain type of star 

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when its nuclear fuel supply runs low. 

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Looking at these nebulae through an optical telescope is hard, 

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as they barely emit any visible light, 

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forcing astronomers to rely instead on faint reflected starlight to see anything at all. 

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But protoplanetary nebulae shine far more brightly in the infrared part of the spectrum.

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Infrared imaging is also extremely useful for peering through huge  

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interstellar dust clouds, which are impenetrable to visible light. 

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The reason for this is similar to why sunsets are red. 

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Just as particles in the atmosphere scatter blue light more than red, 

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interstellar dust clouds block visible light more than infrared.

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Hubble has become famous for its striking visible-light pictures 

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of huge clouds of interstellar dust and gas. 

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But sometimes scientists want to know what’s happening behind

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or inside, the cloud of dust. 

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Making infrared observations pulls away the veil and reveals the hidden stars. 

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Until now, infrared imaging was challenging with Hubble. 

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The Near Infrared Camera and Multi-object Spectrometer, or NICMOS

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did allow astronomers to study objects in infrared light 

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in ways not possible from the ground, but it forced them to make a difficult choice. 

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Because its images were small: only about 65 000 pixels

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similar to a mobile phone screen

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NICMOS  produced the sharpest images 

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only if it concentrated on a very narrow field of view.

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Taking in a wider view came at the cost of losing much of the detail.

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Along with a much wider field of view and better sensitivity, 

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WFC3’s infrared channel has a million pixels, 

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15 times better than NICMOS, and similar to what you get on a computer screen. 

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This means astronomers no longer have to compromise 

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between how much of the sky they can observe,

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and how much detail they can study it in.

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These improvements mean Hubble is now far better 

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at observing large areas of sky as well as very faint and very distant objects.

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These are key for the science of cosmology

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the study of the origins and development of the Universe.

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Because the Universe expands, light waves coming from distant objects 

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are stretched as they travel through space, and the wavelengths become longer. 

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The further an object is away, the more its light is stretched on its journey to us, 

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and the redder the light appears. Hence the effect is known as redshift.

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For really distant objects, their ultraviolet and visible light 

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is redshifted so much that it goes infrared, literally “below red”

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and that is the reason that infrared imaging is so important for spotting 

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these very distant galaxies. 

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This is the Hubble Ultra Deep Field, a visible light image  

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taken in 2003 and 4 with Hubble’s Advanced Camera for Surveys.

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The picture is of a little patch of sky almost a hundred times smaller 

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than the area of the full moon.

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It contains no stars visible with the naked eye — but taking a million second exposure 

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of this little black speck of space reveals these vanishingly faint faraway galaxies. 

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Studying the same region with WFC3’s infrared imaging 

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reveals galaxies more distant still: 

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some of these are so far away that 

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they have been redshifted out of the visible spectrum altogether.

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We see galaxies here as they were many billions of years ago. 

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When the light from some of these galaxies started its long journey towards us, 

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our Sun and Earth had not even begun to form. 

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But what is really exciting cosmologists about WFC3’s infrared imaging 

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of the Hubble Ultra Deep Field 

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is not just what’s in the foreground so to speak, amazing as that is

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but the scatter of tiny, faint specks that are just visible 

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in the background, beyond these already faraway galaxies. 

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Some of the flecks of light in this fuzzy image 

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are just anomalies within the light detectors, 

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but among them are faint impressions of early galaxies. 

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In this photo we are looking at some of the most remote objects ever seen. 

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They are so distant, and their light has travelled so far to reach us

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that we see these galaxies as they were 13 billion years ago

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when the Universe was only about 5% of its current age.

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Discovering and studying these galaxies can tell us a lot 

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about the prevailing conditions 

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in the earliest years of the Universe,

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and confirm — or perhaps refute — our theories of early galaxy formation. 

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Whatever the case may be, observations like these 

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certainly take us a few steps closer

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 to understanding the history of our Universe.

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This is Dr J signing off for the Hubblecast. 

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Once again, nature has surprised us beyond our wildest imagination.

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Hubblecast is produced by ESA/Hubble at the European Southern Observatory in Germany.

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The Hubble mission is a project of international cooperation between NASA and the European Space Agency. 

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Transcribed by ESA/Hubble