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After circling the Earth for over two decades, Hubble has been responsible  

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for many fascinating scientific discoveries.

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Following the visit by astronauts in 2009 to service the spacecraft and to install new instruments, 

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the telescope is now at the height of its powers.

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As the observatory has matured, 

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attention has turned to some ambitious projects on a scale 

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that would not have even been considered a few years ago.

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Between them, these projects could help answer some of the biggest questions in astronomy today,

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and will contribute to science for many years to come.

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Hubblecast Episode 45: Building a treasure trove of observations

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Presented by Dr J, aka Dr Joe Liske

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Hello and welcome to the Hubblecast.

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Now, observing time on Hubble is a very precious commodity and it’s hugely sought after. 

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That means that when astronomers want to use Hubble, they have to apply for observing time.

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And in their application, 

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they have to be very detailed about what it is exactly that they want to study, 

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and how they are going to do it.

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Now this process works just fine for the vast majority of projects 

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which usually have very focused scientific goals.

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However, once in a while, Hubble gets used for something much bigger, 

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with much broader scientific goals. 

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And in these cases, the normal way of handing out time just isn’t quite enough.

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Three such big projects, called multicycle treasury programs, are underway right now, 

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and they are the most ambitious projects to have ever been carried out with Hubble.

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The Hubble multicycle treasury programs are on a completely different scale 

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from the telescope’s usual work, 

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featuring thousands of hours of observations split over several years. 

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And rather than being tied to the research question of individual scientists, 

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as Hubble observations usually are, the multicycle treasury programs are designed

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to create a treasure trove of data which can be used by as many people as possible in their work. 

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For example, the Panchromatic Hubble Andromeda Treasury program is working 

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on a detailed map of part of the nearby Andromeda Galaxy,  

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going from its bright core all the way to the wispy ends of one of its spiral arms.

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Andromeda is actually the closest spiral galaxy to the Milky Way 

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and it gives us an unparalleled view of the structure of a galaxy 

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that is somewhat similar to our own.

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It’s actually quite big in the sky — several times the size of the full moon, 

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but it’s so faint that it’s barely visible with the naked eye, even on a very dark night. 

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For Hubble, though, it’s ablaze with stars — 

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and an estimated 100 million of them will have been mapped by the time the survey is complete. 

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The survey won’t just be plotting their position, but taking detailed colour information in visible, 

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near infrared and ultraviolet light — something no other telescope can do. 

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Accurately measuring the colours of stars is vital for studying many of their properties,

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 for example their surface temperature.

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With this abundance of data, scientists will be making discoveries 

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in the Andromeda Galaxy for a long time.

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Another of these Hubble treasury programs is looking far back into the evolution of our Universe. 

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And that’s the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey…

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or CANDELS for short.

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By scanning large, dark areas of sky with very few foreground stars in them, 

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this survey is is looking beyond the confines of our cosmic neighbourhood 

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and into the farthest reaches of the Universe.

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They’re observing galaxies that are so far away that their light has taken billions of years to reach us. 

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This allows astronomers to study the distant past of our cosmos

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and how galaxies have evolved over time. 

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Like the Andromeda Galaxy survey, 

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CANDELS is using Hubble’s ability to make detailed maps of the sky across the visible spectrum 

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and into near-infrared and ultraviolet.

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From the early galaxies forming, 

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to the emergence of galaxy clusters to the age of quasars half way back through cosmic history, 

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CANDELS is going to give us a wealth of information to study some of the biggest questions in cosmology.

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The third of these multicycle treasury programs is the Cluster Lensing

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 and Supernova survey with Hubble, 

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or CLASH for short. CLASH is looking into huge clusters of elliptical galaxies. 

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These have so much mass that their gravity noticeably bends the path of light, 

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a bit like a huge magnifying glass. 

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The lenses can actually help astronomers see distant galaxies

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that would otherwise be too faint by amplifying the light we receive from them. 

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What’s more, studying these clusters is key to explaining two of the big mysteries of modern astronomy, 

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dark matter and dark energy.

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Studying normal matter in the Universe, like stars or gas clouds, 

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is relatively easy because it emits or absorbs light. 

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However, it turns out that most of the matter in the Universe is not in fact normal 

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but rather so-called dark matter, which doesn’t give off any radiation whatsoever.

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Now, astronomers don’t really know what dark matter is. 

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But by looking at how these clusters bend light from distant galaxies in the background 

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allows us to reconstruct a map of how the dark matter is distributed inside these clusters.

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The CLASH survey is also going to study distant supernovae. 

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This is going to probe the expansion rate of the Universe

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and help us understand the mystery why this expansion is accelerating.

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In fact there are already discoveries being made with the first data released from this survey.

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In April of this year,  

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a new study identified a faraway galaxy imaged by the gravitational lens in Abell 383 —

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the first of 25 to be mapped by this survey.

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Thanks to the cluster amplifying the light from this distant galaxy, 

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astronomers were able to make much more detailed observations than would otherwise have been possible. 

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And they discovered that the stars in this galaxy were surprisingly old:

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they must have been born just a few hundred million years after the Big Bang, 

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much earlier than expected.

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So although Hubble is more than 20 years old, 

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it’s actually doing some of its most ambitious work right now, 

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building a library of data that will serve astronomers far into the future.

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And this means that despite its age 

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Hubble won’t be eclipsed by the next big thing in space-based astronomy, 

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the James Webb Space Telescope, or JWST.

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JWST, which launches later this decade, 

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has been designed to answer some of the fascinating questions that Hubble asked:

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how do stars form? When did the first galaxies appear? What hides in huge dusty nebulae?

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To answer these profound questions, the JWST is designed to observe mainly in infrared light.  

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That means that Hubble’s ability to see across the spectrum from ultraviolet through the visible, 

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all the way into the near infrared is a unique capability

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that no other telescope will have for decades to come. 

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These multicycle treasury programs are taking full advantage of this,

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building up a legacy of data that will help scientists to unravel 

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the secrets of the cosmos for many years to come. 

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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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Transcribed by ESA/Hubble.