The Hubble Space Telescope is one of the greatest technological achievements in our history, and for two decades has astonished us with dynamic images of our solar system and the world beyond. To celebrate this important twenty-year milestone, NASA looks back at the contributions of this extraordinary scientific tool, and the scientists who created it, in a documentary entitled “Hubble: Twenty Years of Discovery.” The movie is narrated by Brent Spiner, Data from Star Trek.
GOODS, Under Astronomers’ AEGIS, Produce GEMS
No, not really (but I got all three key words into the title in a way that sorta makes sense).
Astronomers, like most scientists, just love acronyms; unfortunately, like most acronyms, on their own the ones astronomers use make no sense to non-astronomers.
And sometimes not even when written in full:
GOODS = Great Observatories Origins Deep Survey; OK that’s vaguely comprehensible (but what ‘origins’ is it about?)
AEGIS = All-wavelength Extended Groth strip International Survey; hmm, what’s a ‘Groth’?
GEMS = Galaxy Evolution from Morphology and SEDs; is Morphology the study of Morpheus’ behavior? And did you guess that the ‘S’ stood for ‘SEDs’ (not ‘Survey’)?
But, given that these all involve a ginormous amount of the ‘telescope time’ of the world’s truly great observatories, to produce such visually stunning images as the one below (NOT!), why do astronomers do it?
Astronomy has made tremendous progress in the last century, when it comes to understanding the nature of the universe in which we live.
As late as the 1920s there was still debate about the (mostly faint) fuzzy patches that seemed to be everywhere in the sky; were the spiral-shaped ones separate ‘island universes’, or just funny blobs of gas and dust like the Orion nebula (‘galaxy’ hadn’t been invented then)?
Today we have a powerful, coherent account of everything we see in the night sky, no matter whether we use x-ray eyes, night vision (infrared), or radio telescopes, an account that incorporates the two fundamental theories of modern physics, general relativity and quantum theory. We say that all the stars, emission and absorption nebulae, planets, galaxies, supermassive black holes (SMBHs), gas and plasma clouds, etc formed, directly or indirectly, from a nearly uniform, tenuous sea of hydrogen and helium gas about 13.4 billion years ago (well, maybe the SMBHs didn’t). This is the ‘concordance LCDM cosmological model’, known popularly as ‘the Big Bang Theory’.
But how? How did the first stars form? How did they come together to form galaxies? Why did some galaxies’ nuclei ‘light up’ to form quasars (and others didn’t)? How did the galaxies come to have the shapes we see? … and a thousand other questions, questions which astronomers hope to answer, with projects like GOODS, AEGIS, and GEMS.
The basic idea is simple: pick a random, representative patch of sky and stare at it, for a very, very long time. And do so with every kind of eye you have (but most especially the very sharp ones).
By staring across as much of the electromagnetic spectrum as possible, you can make a chart (or graph) of the amount of energy is coming to us from each part of that spectrum, for each of the separate objects you see; this is called the spectral energy distribution, or SED for short.
By breaking the light of each object into its rainbow of colors – taking a spectrum, using a spectrograph – you can find the tell-tale lines of various elements (and from this work out a great deal about the physical conditions of the material which emitted, or absorbed, the light); “light” here is shorthand for electromagnetic radiation, though mostly ultraviolet, visible light (which astronomers call ‘optical’), and infrared (near, mid, and far).
By taking really, really sharp images of the objects you can classify, categorize, and count them by their shape, morphology in astronomer-speak.
And because the Hubble relationship gives you an object’s distance once you know its redshift, and as distance = time, sorting everything by redshift gives you a picture of how things have changed over time, ‘evolution’ as astronomers say (not to be confused with the evolution Darwin made famous, which is a very different thing).
GOODS
The great observatories are Chandra, XMM-Newton, Hubble, Spitzer, and Herschel (space-based), ESO-VLT (European Southern Observatory Very Large Telescope), Keck, Gemini, Subaru, APEX (Atacama Pathfinder Experiment), JCMT (James Clerk Maxwell Telescope), and the VLA. Some of the observing commitments are impressive, for example over 2 million seconds using the ISAAC instrument (doubly impressive considering that ground-based facilities, unlike space-based ones, can only observe the sky at night, and only when there is no Moon).
There are two GOODS fields, called GOODS-North and GOODS-South. Each is a mere 150 square arcminutes in size, which is tiny, tiny, tiny (you need five fields this size to completely cover the Moon)! Of course, some of the observations extend beyond the two core 150 square arcminutes fields, but every observatory covered every square arcsecond of either field (or, for space-based observatories, both).
GOODS-N is centered on the Hubble Deep Field (North is understood; this is the first HDF), at 12h 36m 49.4000s +62d 12′ 58.000″ J2000.
GOODS-S is centered on the Chandra Deep Field-South (CDFS), at 3h 32m 28.0s -27d 48′ 30″ J2000.
The Hubble observations were taken using the ACS (Advanced Camera for Surveys), in four wavebands (bandpasses, filters), which are approximately the astronomers’ B, V, i, and z.
AEGIS
The ‘Groth’ refers to Edward J. Groth who is currently at the Physics Department of Princeton University. In 1995 he presented a ‘poster paper’ at the 185th meeting of the American Astronomical Society entitled “A Survey with the HST“. The Groth strip is the 28 pointings of the Hubble’s WFPC2 camera in 1994, centered on 14h 17m +52d 30′. The Extended Groth Strip (EGS) is considerably bigger than the GOODS fields, combined. The observatories which have covered the EGS include Chandra, GALEX, the Hubble (both NICMOS and ACS, in addition to WFPC2), CFHT, MMT, Subaru, Palomar, Spitzer, JCMT, and the VLA. The total area covered is 0.5 to 1 square degree, though the Hubble observations cover only ~0.2 square degrees (and only 0.0128 for the NICMOS ones). Only two filters were used for the ACS observations (approximately V and I).
I guess you, dear reader, can work out why this is called an ‘All wavelength’ and ‘International Survey’, can’t you?
GEMS
GEMS is centered on the CDFS (Chandra Deep Field-South, remember?), but covers a much bigger area than GOODS-S, 900 square arcminutes (the largest contiguous field so far imaged by the Hubble at the time, circa 2004; the COSMOS field is certainly larger, but most of it is monochromatic – I band only – so the GEMS field is the largest contiguous color one, to date). It is a mosaic of 81 ACS pointings, using two filters (approximately V and z).
Its SEDs component comes largely from the results of a previous large project covering the same area, called COMBO-17 (Classifying Objects by Medium-Band Observations – a spectrophotometric 17-band survey).
Sources: GOODS (STScI), GOODS (ESO), AEGIS, GEMS, ADS
Special thanks to reader nedwright for catching the error re GEMS (and thanks to to readers who have emailed me with your comments and suggestions; much appreciated)
Hubble, Renewed, Reinvigorated, Raring to Go
Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today has featured highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the last two years, to April 2010.
The stakes for the fifth, and final, Hubble servicing mission couldn’t have been higher; not only were two new instruments to be installed (a relatively straight-forward task), not only was much of key infrastructure to be replaced (batteries, fine-guidance sensors, thermal blankets), but intricate repairs had to be performed on the two most complicated instruments (ACS and STIS), something not in the design, something difficult enough in a well-appointed lab on Earth much less done by astronauts in bulky space suits. The servicing mission was postponed, as it became clear that the work to be done was more extensive; but in May 2009 STS-125, involving five full days of space walks and 11 days in space, met all the objectives.
And a little under four months later, after extensive testing and calibration, the Hubble was back in the astronomy business.
This image is the Hubble Ultra-Deep Field (HUDF), as seen by WFC3 in the infrared (now that Hubble Zoo is live, you will have a chance to analyze fields like this yourself!)
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MACS J0025.4-1222 is not as well known as the Bullet Cluster, but perhaps it should be. One of the really big, open questions in astronomy today is the nature of dark matter; observations of the Bullet Cluster point to dark matter being a form of matter that does not interact with normal (baryonic) matter, except gravitationally. But perhaps the Bullet Cluster is just an anomaly, or perhaps we don’t really understand what’s going on? In astronomy, as in all science, independent verification is key, and what better way to provide that, for dark matter, than to observe another interacting cluster? “Revealing the Properties of Dark Matter in the Merging Cluster MACS J0025.4-1222” is the paper to read, and Hubble’s ACS provided many of the key observations.
A direct image of an exoplanet, and an estimate of its orbit; the coronagraph on ACS blocked out most of the light of Fomalhaut so its planet – Fomalhaut b – could be seen.
WFPC2 was removed during SM4 (and replaced by WFC3); this was Hubble’s workhorse camera for some 16 years, the camera which just kept on working. It is fitting then that one of its last images is of Arp 194, dubbed ‘the fountain of youth’.
Previous articles:
Hubble’s Late Teen Years: It Was the Best of Times, It Was the Worst of Times
Hubble Turns Sixteen, and Just Keeps on Working
Hubble Enters its Teen Years, More Powerful, More Ambitious
Hubble’s 20th: At Least as Good as Any Human Photographer
Hubble’s 10th Birthday Gift: Measurement of the Hubble Constant
Hubble at 8: So Many Discoveries, So Quickly
Hubble’s 20 Years: Now We Are Six
Hubble’s 20 Years: Time for 20/20 Vision
Hubble: It Was Twenty Years Ago Today
Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System
Hubble’s Birthday Gift to Us: Mystic Mountain
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Happy 20th Birthday to the Hubble Space Telescope! While we should be showering HST with gifts, instead the telescope provides this present to us: an amazing view of what has been nicknamed “Mystic Mountain. ” It is just a small portion of one of the largest known star-birth regions in the galaxy, the Carina Nebula. Three light-year-tall towers of cool hydrogen laced with dust rise from the wall of the nebula. The scene is reminiscent of Hubble’s classic “Pillars of Creation” photo from 1995, but even more striking. “Mystic Mountain has clouds of gas and dust, that have not only baby stars, but also baby solar systems,” said John Grunsfeld, Hubble-hugger, repairman and now the Deputry Director of the Space Telescope Science Institute. “4.5 billion years ago, this may be what our solar system looked like.”
Would you like to wish Hubble a happy birthday?
Hubble fans worldwide are being invited to take an interactive journey with Hubble. They can also visit Hubble Site to share the ways the telescope has affected them. Follow the “Messages to Hubble” link to send an e-mail, post a Facebook message, or send a cell phone text message. Fan messages will be stored in the Hubble data archive along with the telescope’s science data. For those who use Twitter, you can follow @HubbleTelescope or post tweets using the Twitter hashtag #hst20.
Hubble launched on April 24, 1990.
“Hubble is undoubtedly one of the most recognized and successful scientific projects in history,” said Ed Weiler, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. “Last year’s space shuttle servicing mission left the observatory operating at peak capacity, giving it a new beginning for scientific achievements that impact our society.”
This morning during interviews on NASA TV, Grunsfeld and Weiler said they both felt fortunate to work with Hubble, a telescope who’s legacy will live on, no matter how much longer the telescope operates.
“I’m lucky to have worked on a project that will outlive me,” Weiler said.
“The discovery that I think is so incredible, and could not be imaged was that Hubble has now analyzed the constituents of an atmosphere of a planet around another star,” said Grunsfeld. “It is as if we were exploring that planet – and that’s what Hubble does for us, allows us to visit places we’ll never be able to go.”
On that note, take a 3-D trip into the Carina Nebula with the video below:
Click on Hubble: Galaxy Zoo Now Includes HST Images
The Hubble Space Telescope is 20 years old on Saturday and, to mark this anniversary, all the world’s space and astronomy fans have a chance to become part of the Hubble team.
As part of the birthday celebrations NASA’s Space Telescope Science Institute and the online astronomy project Galaxy Zoo are making some 200,000 Hubble images of galaxies available to the public at Galaxy Zoo (www.galaxyzoo.org). They hope that volunteers looking for their own favorite galaxies will join forces to give the venerable telescope a present – classifications of each galaxy which will help astronomers understand how the Universe we see around us formed.
But there’s more to it than that; remember Hanny and the Voorwerp? The Green Peas? Mitch’s mysterious star? For every unexpected Galaxy Zoo discovery there are likely a dozen Hubble Zoo ones.
“The large surveys that Hubble has completed allow us to trace the Universe’s evolution better than ever before,” said University of Nottingham astronomer and Galaxy Zoo team member Dr. Steven Bamford. “The vast majority of these galaxies will never have been viewed by anyone, and yet we need human intuition to make the most of what they are telling us”.
More than 250,000 people have already contributed to Galaxy Zoo since its launch in 2007, but so far they have been looking only at the ‘local’ Universe, up to a hundred million or so light-years away. The galaxies in HubbleZoo are from some of the big surveys, such as GOODS, and the images were processed by the Galaxy Zoo team alongside Roger Griffith at JPL and the Space Telescope Science Institute (see this article, from my Universe Today series on the Hubble, for more details on GOODS).
“Hubble will enable us to look back in time, to the era when many of the galaxies we see today were forming,” said Dr. Chris Lintott of Oxford University, Galaxy Zoo principal investigator. “As a kid I always wanted a time machine for my birthday, but this is the next best thing!”
“We never dreamt that people would find so many fascinating objects in the original Galaxy Zoo,” said Yale University astronomer Dr. Kevin Schawinski. “Who knows what’s hiding in the Hubble images?” Lintott added: “As we recovered from the launch of the original Galaxy Zoo, we knew we’d want to have a look at Hubble. Now we realize the images are better and the galaxies weirder than we ever thought they would be.”
And how will you, dear zooite-to-be, contribute, and find a hidden gem among the Hubble galaxies? Once you log in, you will asked to answer simple questions about what you are seeing, for example, identifying the number of spiral arms visible, or spotting galaxies in the process of merging. And if you spot something odd, you can bring it to the attention of other zooites, and the Zoo astronomers.
“Every galaxy is special in its own way,” said Stuart Lynn of Oxford University, Galaxy Zoo team member, “but some are worthy of individual attention. Anyone combing through the data using our site could make a spectacular discovery, and that would be the best birthday present of all.”
Sources: NASA, HubbleSite, Oxford University, Galaxy Zoo Forum The two images above, of a galaxy called SDSS J100213.52+020645.9, highlight the sharpness and depth of the Hubble’s images (the SDSS telescope and the Hubble have primary mirrors of approximately the same diameter).
Hubble’s Late Teen Years: It Was the Best of Times, It Was the Worst of Times
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Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today will feature highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the period April 2006 to April 2008.
The image of the Antennae galaxies, above, released on October, 17 2006, is bitter-sweet. On the one hand it’s a stunning image, even more spectacular than the one taken nine years earlier with WFPC2; on the other the star instrument which took it, Advanced Camera for Surveys (ACS), failed first in July 2006, and again in January 2007. On top of that, one by one the Hubble’s gyroscopes started to fail, and its batteries too. In October 2006 the new NASA Administrator, Mike Griffin, had given the go-ahead for one last Space Shuttle mission to the Hubble, for a final servicing. With failure following failure, the servicing mission become more and more complex, and it was hard to maintain optimism in the future of Hubble.
The ACS’ failure came after it had completed its part of the Cosmic Evolution Survey (COSMOS), which was a coordinated project involving many of the world’s leading observatories, both on the ground and in space (a bit like GOODS, which I covered in yesterday’s article). Among the successes of COSMOS was this 3D map of the distribution of dark matter.
The way the Hubble keeps its gaze steady, during the sometimes quite long exposures of some of its instruments, is a marvel of modern engineering. Central to this intricate system is a set of sensors, called the Fine Guidance Sensors (FGS), which were designed to do science too, specifically astrometry.
The sensors aim the telescope by locking onto guide stars and measure the position of the telescope relative to the object being viewed. Adjustments based on these constant, minute measurements keep Hubble pointed precisely in the right direction.
One of most interesting results from the FGS is the finding that the main star in the R136 cluster in the 30 Doradus nebula (better known as the Tarantula Nebula in the Large Magellanic Cloud) – R136a – is actually a triple (“Hubble Space Telescope Fine Guidance Sensor interferometric observations of the core of 30 Doradus“). Once upon a time the entire cluster was thought to be a single star, the most massive one ever seen; today R136a1 weighs in at ‘merely’ some 30 to 80 sols.
Comet Holmes is certainly one of the most memorable comets of recent times, not so much for its spectacular tail, but for its odd behavior; Hubble observed it several times Finally, Hubble’s View of Comet Holmes is the Universe Today story on this.
One of the most difficult challenges astronomers face, in doing science, is understanding and accounting for biases. For example, how could you tell, just by examining the approximately 6,000 stars you can see with your unaided vision, that none of them are examples of the most common kind of star! The nearest, brightest red dwarfs are far too faint to see without a telescope (do you know what their names are?), and it’s no easy matter to even find these stars. And what about stars that are fainter still, stars that aren’t quite stars, brown dwarfs? The first, certain, brown dwarf was not discovered until 1995, but since then our understanding of them has improved dramatically, and Hubble’s ACS has helped greatly in that understanding (see the Universe Today article on CHXR 73: Giant Planet or Failed Star?).
Cassiopeia A, or Cas A, is undoubtedly a supernova remnant. And it also results from a rather recent supernova; but which? There’s some uncertainty, but it seems it was seen, by the astronomer Flamsteed, in 1680. The ACS image above is the most detailed optical images of Cas A; Hubble’s View of Supernova Remnant Cassiopeia A.
With a galaxy (or cluster) positioned just so in front of a more distant galaxy (or quasar), gravitational lensing will produce an Einstein ring (or a partial ring). Several such rings had been observed prior to 2008, but the one ACS snapped – of SDSSJ0946+1006 – turned out to be a double; three galaxies lined up one behind the other (the right hand image is a highly processed version of the left hand one, with the light of the massive, foreground elliptical galaxy removed). Hubble Sees a Double Einstein Ring.
Tomorrow: 2008 and 2009
Previous articles:
Hubble Turns Sixteen, and Just Keeps on Working
Hubble Enters its Teen Years, More Powerful, More Ambitious
Hubble’s 20th: At Least as Good as Any Human Photographer
Hubble’s 10th Birthday Gift: Measurement of the Hubble Constant
Hubble at 8: So Many Discoveries, So Quickly
Hubble’s 20 Years: Now We Are Six
Hubble’s 20 Years: Time for 20/20 Vision
Hubble: It Was Twenty Years Ago Today
Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System
Hubble Turns Sixteen, and Just Keeps on Working
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Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today will feature highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the period April 2004 to April 2006.
First, in 1995, there was the Hubble Deep Field (HDF). Then, in 1998, the Hubble Deep Field South (HDF-S). With the new Advanced Camera for Surveys (ACS) aboard, and the Near Infrared Camera and Multi-object Spectrometer (NICMOS) continuing to work well, the Hubble took a new, even deeper, image. And what was it called? Why, the Hubble Ultra-Deep Field (HUDF) of course! The total exposure was approximately a million seconds, and the observations were made in late 2003 and early 2004 (Earliest Star Forming Galaxies Found is Universe Today’s first story on it). Hundreds of scientific papers have been published using data from these observations (and others; a lot of time on major ground-based telescopes has also been devoted to these fields).
In its more than a decade of operation, the Hubble’s main astronomical instruments worked well. Sure, they needed various repairs and were upgraded in one way or another during the four servicing missions to date (remember that 3 was split into two, 3A and 3B), but none failed completely. Well, in August 2004 STIS (the Space Telescope Imaging Spectrograph) did.This intensified the gloom created earlier in the year when NASA Director announced that there would be no more Space Shuttle missions to the Hubble, and his announcements about possible robotic missions left space and astronomy fans cold.
In April 2006, Hubble turned 16; would you have chosen M82 as a ‘sweet sixteen’ snap to put in your album? Universe Today did!
One of the biggest challenges in astronomy today is working out how galaxies formed and evolved. In turn this involves understanding the role of star formation (and its rates), how supermassive black holes accrete matter and create jets, and how dark matter structures form. One powerful way to get at least some answers to the many questions is to point the world’s most powerful telescopes at the same, small, patch of sky for a very long time. Choosing the patch of sky to stare at isn’t easy; for example, ideally you want a ‘hole’ in the Milky Way’s hydrogen, to let you see as clearly as possible in the soft x-ray part of the electromagnetic spectrum. The GOODS team, comprising dozens of astronomers from many institutions, chose two fields, one in the north (centered on the Hubble Deep Field) and one in the south (centered on the Chandra Deep Field-South). The image above gives an idea of what one project involved; the red dots are objects whose spectra were taken (by a spectrograph called VIMOS, on one of the European Southern Observatory’s Very Large Telescopes), overlaid on an image from a ground-based telescope; the contours are the Chandra 2Ms (yes, that’s 2 million seconds) region, and the Hubble ACS GOODS-S field. Over 400 GOODS papers have been published so far, with all sorts of interesting results established. For more information, visit the STScI GOODS website and the ESO one; to get you started, “The Great Observatories Origins Deep Survey: Initial Results from Optical and Near-Infrared Imaging“.
I mentioned earlier – Hubble’s 20th: At Least as Good as Any Human Photographer – that astronomers have their own file format, called FITS, for astronomical data, whether images, spectra, or whatever. Well, FITS is not exactly user friendly (unless you’re an astronomer), so to make the data more accessible, a joint team from the European Space Agency, the European Southern Observatory, and NASA produced the ESA/ESO/NASA Photoshop FITS Liberator, a free plug-in. Why not give it a try?
Even though various space probes visit various planets (and their moons), and undertake intensive research of them, good science is still done from afar. Hubble’s studies of Saturn’s aurorae are a good example (Universe Today’s coverage here).
Hubble had taken many images of the Crab Nebula before (see Hubble at 8: So Many Discoveries, So Quickly for example), but the above was a first, in many ways. It was taken by WFPC2, and is actually 24 separate images; it is the highest resolution image of the Crab, to date (Giant Hubble Mosaic of the Crab Nebula is the Universe Today title).
The Orion nebula is the closest ‘star factory’, so receives intense scrutiny by astronomers. Hubble pointed all its imaging instruments at it, in 2005, for over 100 orbits. This image is an ACS mosaic (do you know what the other imaging instruments were, then? Best Orion Nebula Image Ever Taken has the answer).
The theory of general relativity predicts gravitational lensing, and this prediction was confirmed in 1919 (do you know how?). When a point source, such as a quasar, is lensed by a foreground object such as a galaxy cluster, the resulting image will have quite specific properties; for example, only an odd number of images, but one image is usually very weak and embedded deep within the light of the lensing object itself. Four images produced by SDSS J1004+4112 (the foreground cluster) had been detected before, but Hubble found the fifth (the blue circles are the quasar, the red a lensed galaxy, the yellow a supernova). Hubble’s Best Gravitational Lens is the Universe Today article on this discovery.
Tomorrow: 2006 and 2007.
Previous articles:
Hubble Enters its Teen Years, More Powerful, More Ambitious
Hubble’s 20th: At Least as Good as Any Human Photographer
Hubble’s 10th Birthday Gift: Measurement of the Hubble Constant
Hubble at 8: So Many Discoveries, So Quickly
Hubble’s 20 Years: Now We Are Six
Hubble’s 20 Years: Time for 20/20 Vision
Hubble: It Was Twenty Years Ago Today
Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System
Hubble Enters its Teen Years, More Powerful, More Ambitious
Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today will feature highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the period April 2002 to April 2004.
As I mentioned yesterday, Hubble servicing mission 3B in March 2002 saw the successful replacement of the Faint Object Camera with the Advanced Camera for Surveys (ACS). Surveys, surveys, and yet more surveys; astronomers are forever spending huge amounts of time doing surveys. And from its name you’d not be wrong to guess that a great deal of ACS’ time has been devoted to surveys. Perhaps the best known – to astronomers anyway – is GOODS, which stands for the Great Observatories Origins Deep Survey. It was kicked off in late 2001, and is still on-going; in addition to hundreds of hours of observations by the most powerful ground-based facilities and Hubble’s ACS, an awful lot of time on Spitzer, Chandra, XMM-Newton, and Herschel has been devoted to it (I’ll cover GOODS in more detail later; for now, here’s a link to the project’s website).
Shortly after the ACS went into operation, the world was treated to a sample of stunning images from it. My favorite is ‘the Mice’ (NGC 2676); what’s yours?
Oh, and that galaxy collision?
We imagine that the Space Telescope Science Institute (STScI) is devoted exclusively to the Hubble, both its scientific work and its public outreach and education. Sometimes however the work goes a bit beyond that, and combines both science and outreach.
A good example of this is the video at the top of this article; Dr. Frank Summers, an STScI astrophysicist, took research simulation data from Case Western Reserve University’s Chris Mihos and Harvard University’s Lars Hernqvist and visualized it using the same software that Hollywood uses to produce blockbuster visual effects. Special care was taken so that what appears onscreen accurately reflects what was calculated in the simulation.
How good is ACS? Judge for yourself; the image of Uranus’ moons above is from ACS, compare it to the WFPC2 one, in Hubble’s 20 Years: Now We Are Six article (Universe Today’s story on this is Hubble Finds Two Small Moons Around Uranus).
Hubble’s superb resolution, close to the theoretical best for its new instruments (and old ones, using COSTAR), gives us spectacularly detailed images (and oodles of data) for such transient events as the flare-up on the star V838 Mon, lighting up the surrounding gas and dust and giving us much better understanding of the interstellar medium.
As you’ve no doubt already concluded, the Hubble helped our understanding of planetary nebulae greatly; but, as is always the case in an active field of science, new observations sometimes bring new questions. Such is the case of Henize 3-1475, the ‘garden sprinkler’ nebula (Puzzling Jets Seen Blasting Out from a Nebula is Universe Today’s story on this).
Some gravitational lenses produce images which can be analyzed using observations from ground-based telescopes. Generally, however, the Hubble produced by far the best data … and stunning images (Abell would have been astonished; he died in 1983, only a few years after the first astronomical lens was discovered, the ‘twin QSO’; it looks nothing like this).
Tomorrow: 2004 and 2005.
Previous articles:
Hubble’s 20th: At Least as Good as Any Human Photographer
Hubble’s 10th Birthday Gift: Measurement of the Hubble Constant
Hubble at 8: So Many Discoveries, So Quickly
Hubble’s 20 Years: Now We Are Six
Hubble’s 20 Years: Time for 20/20 Vision
Hubble: It Was Twenty Years Ago Today
Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System, GOODS
Hubble’s 20th: At Least as Good as Any Human Photographer
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Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today will feature highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the period April 2000 to April 2002.
The International Center for Photography gave its 2000 Infinity Award to the Hubble Heritage Project, in the Applied Photography section. And what did that team choose to showcase their award? The above image of NGC 3314! Clearly the Hubble has had a deep impact far beyond the astronomical community and space fans.
Columbia’s last flight, before the one that ended in disaster, was STS-109, or the Hubble servicing mission 3B, in March, 2002. In terms of imaging capability, it was the most dramatic; the Advanced Camera for Surveys (ACS) was installed (replacing the Faint Object Camera), and NICMOS’ cooling system was replaced (giving the Hubble ‘night vision’ again – it could see in the infrared once more). I’ll be covering the cornucopia of science results from ACS in later articles.
My pick for the Hubble image most of you, my readers, would put at the top your ‘what I remember from these two years’ is Stephan’s Quintet.
What we see on a webpage or in a magazine, when we look at a Hubble image, resembles a photograph. What an astronomer sees is data, glorious data, in all its numerical detail (astronomers even invented a special file format for their data, called FITS, short for flexible image transport system; more about it here). And among the most critical aspect of astronomical data is its calibration, e.g. the function which relates pixel values to things like flux (which may be measured in janskys, or ergs per second per square meter per hertz). But how do you calibrate an instrument that’s aboard the Hubble? You turn to the Instrument Physical Modelling Group, part of the Space Telescope European Coordinating Facility! This highly specialist team actually models the Hubble’s instruments, in software, from first (physics) principles, and from those models produces robust software for taking the raw data from a Hubble instrument and producing calibrated, science-grade data. They then make their results public, for anyone and everyone to use; for example the Faint Object Spectrograph Post-Operational Archive (you can read the details of their work in ST-ECF Newsletter 29).
Another behind-the-scenes activity is the production of the Hubble Guide Star Catalog, essential for the Hubble’s smooth operation (and a major boon to amateurs); 2001 saw a major new release (II).
Every now and then a (faint) star will pass close to the line of sight of a more (bright) distant star, and we will see the (distant) star brighten in a characteristic way (due to gravitational lensing). One kind of such lensing is the object of many astronomers’ desire, a MACHO (massive compact halo object); even more desirable is to see both the lensed and lensing stars, as separate points of light, some time after the event. Hubble observed just such a rarity.
Comets are fragile things; their very tails tell tales of constant erosion at the hands of sunlight. And when they die, do they do so with a bang, or merely a whimper? Hubble captured an example of the latter (Comet LINEAR is no more).
But the Hubble isn’t only for astronomers, even amateur astronomers; it’s there for us all, to take pictures that awe and inspire us. And by popular demand, the famous Horsehead nebula, as never seen by anyone using a telescope down here on Earth.
It was during these two years that Universe Today began its coverage of the Hubble (and other astronomy and space topics); for example Hubble Reveals Backward Galaxy (however, I can’t find any Universe Today stories from this period with Hubble images; can you help me out please, dear reader?)
Tomorrow: 2002 and 2003.
Previous articles:
Hubble’s 10th Birthday Gift: Measurement of the Hubble Constant
Hubble at 8: So Many Discoveries, So Quickly
Hubble’s 20 Years: Now We Are Six
Hubble’s 20 Years: Time for 20/20 Vision
Hubble: It Was Twenty Years Ago Today
Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System
Hubble’s 10th Birthday Gift: Measurement of the Hubble Constant
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Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today will feature highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the period April 1998 to April 2000.
In October 1998, Hubble complemented the original Hubble Deep Field with Hubble Deep Field South (HDF-S). Three instruments – NICMOS, STIS, and WFPC2 – stared at a tiny spot in the sky for ten days (more images here).
Hubble got dizzy in November 1999; the fourth (of six) gyroscopes failed, and the observatory was put into safe mode. The third servicing mission, planned for mid-2000, was split in two, with 3A being done in December 1999. Along with replacing all the gyros, Hubble got a computer upgrade … to a 486 model (did you ever own a PC with a 486 CPU?)
I reckon the image which most of us remember best from these two years is this one of M57, yet another planetary nebula.
“Final Results from the Hubble Space Telescope Key Project to Measure the Hubble Constant” is one of the most heavily cited papers in astronomy, perhaps even science, period. It also happens to be one of easiest to read, and is likely to serve as a model for a long time. It is based on a great deal of ‘Hubble time’ (dedicated observations), but should anyone want use all the data from all that time, they are free to do so. Wendy Freedman is the lead author on that paper, and led this Hubble Key Project (HKP) from start to finish.
At its heart, this HKP is a repeat of Edwin Hubble’s work, some seven decades earlier – observing lots of Cepheid variables in some 19 nearby galaxies, with the Hubble, and using the period-luminosity relationship to estimate the distances to them (Of course, there’s a very great deal more to it than that!). No prizes for guessing who the Hubble is named after, and why.
The end of the Key Projects freed up more time for the Hubble to observe other things; some of which may surprise you. For example, many people think the Hubble cannot look at the Moon, much less take pictures of it.
To make some of Hubble’s best eye-candy more accessible, the Hubble Heritage Project was set up, in 1998. And what more appropriate eye candy is there, in a story about the Hubble, than Hubble’s variable nebula?
And one of the things the Hubble Heritage team did was run a competition for the best image; the polar ring galaxy NGC 4650A won (was that your choice?); if you think this looks odd, it is … I rotated it 90 degrees (there’s no up or down in space).
To close, two much less often seen HDF-S results, from NICMOS (above) and STIS (below).
Tomorrow: 2000 and 2001.
Previous articles:
Hubble at 8: So Many Discoveries, So Quickly
Hubble’s 20 Years: Now We Are Six
Hubble’s 20 Years: Time for 20/20 Vision
Hubble: It Was Twenty Years Ago Today
Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System, Hubble Deep Field South