Category: esa

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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

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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

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

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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

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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

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 1996 to April 1998.

The ability of the Hubble Space Telescope to be serviced by astronauts, using a space shuttle as a platform, is one of its design features. This proved its worth very early, with the first servicing mission installing COSTAR. The second such mission – a ten day effort with Discovery as the workhorse – took place in February 1997; two new instruments were installed (and two removed), the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and the Space Telescope Imaging Spectrograph (STIS), and many other, smaller, upgrades and repairs made.

Yesterday’s article featured the Pillars of Creation; today’s captures the beauty of a star’s death.
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How does the Hubble work? Who runs it? The Space Telescope Science Institute (STScI) is responsible for the scientific operation of Hubble as an international observatory; it has a combined staff of approximately 500, of whom approximately 100 are PhDs. Among the prime tasks of the STScI are the selection of the Hubble observing proposals, their execution, the scientific monitoring of the telescope and its instruments and the archiving and distribution of the Hubble observations.

The Space Telescope-European Coordinating Facility (ST-ECF) offers support for the preparation of Hubble observing proposals and the scientific analysis of observations. It also operates the Hubble Science Archive, which makes data available to the astronomical community via the Internet.

With the exception of observations like the Hubble Deep Field – which are available for immediate release – the data from Hubble observations are the exclusive property of the observers for one year, after which all scientific data are made available to anyone and everyone, via the internet. And guess what? Thousands of papers have been published, using such freely available data!

One example of the tremendous value of the Hubble archive is all the asteroids it inadvertently images; because of the Hubble’s sensitivity, motion, and resolution, the orbits of many of these can be determined from just the serendipitous images (discoveries made by ground-based telescopes usually require follow-up images days apart). And yes, many papers have been written, based on these images, “Asteroid Trails in Hubble Space Telescope” for example.

Sometimes something happens in the sky and you want to point powerful telescopes at it, quickly, before it disappears. By far the most interesting yet fleeting ‘something’ is gamma-ray bursts (GRBs). Although known for decades, none had been seen in any other electromagnetic waveband … until February 28, 1997. Right after its servicing mission, Hubble caught the afterglow of GRB 970228, located in very distant galaxy. A milestone in astronomy.

Volcanoes, active ones, were discovered on Io, by accident, in 1979, as volcanic plumes rising above the limb. Who could have imagined that such plumes would be imaged not twenty years later, from low-Earth orbit, with Jupiter as the backdrop?

In 1920 Betelgeuse’s diameter was estimated, using a 6 meter interferometer mounted on the front of the 100-inch Mount Wilson telescope. In 1996, the Hubble made a direct observation of Betelgeuse, resolving it; only the second star to have ever been seen as anything but a point of light (what was the first?).

The Antennae galaxies, NGC 4038/NGC 4039, are not only highly photogenic (how many amateurs count their snaps of these among their most prized?), but great natural laboratories for studying galaxy collisions, star formation, etc. Hubble’s 1997 images provided the basis for hundreds of papers.

Tomorrow: 1998 and 1999.

Previous articles:
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

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 1994 to April 1996.

After the famous Apollo 8 “Earthrise” image, comet Shoemaker-Levy 9’s impact with Jupiter, in July 1994, strikes us as the most stark reminder of the fragility of our home. And the Hubble gave us the clearest pictures of just how destructive that collision was; those dark blotches are bigger than the Earth.

Equally memorable, from Hubble’s early childhood years – ages five and six – is the “Pillars of Creation” image.
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Much of the Hubble’s time in the first few years was devoted to the Hubble Space Telescope Key Projects, two of which I mentioned yesterday, “on the Extragalactic Distance Scale”, and the “Quasar Absorption Line” Key Project. There is a third, the Medium-Deep Survey (MDS), lead by Richard Griffiths, who is now at Carnegie Mellon University. Here’s a nice bit of trivia: astronomers spend an inordinate, a humongous amount of time doing surveys; they even build entire observatories devoted exclusively to them (think Sloan Digital Sky Survey, of Galaxy Zoo fame)! And here’s a question for you: why? Why are surveys soooo important to astronomers?

Anyway, MDS is interesting for another reason too; it’s a “parallel mode” project … while the Hubble is pointed at its main target, a nearby field is also observed, using WF/PC or the Faint Object Camera (or, later, WFPC2); two results for the price of one! However, perhaps more than any other observations, the MDS ones before the Hubble had its vision fixed (see yesterday’s article) suffered from the mis-figuring of the primary mirror. And it’s a tribute to the ingenuity and perseverance of Griffiths and his colleages that they were, eventually, to wring so much good science from the data (you guessed it, hundreds and hundreds of papers).

Jupiter wasn’t the only solar system object of interest to Hubble; Uranus, its rings and inner moons captured on film (well, CCD); the first surface features on Pluto were snapped; Saturn’s Aurorae imaged; the Galilean moons of Jupiter mapped; etc, etc, etc.

My own favorite Hubble recollection from these two years is (another!) paper by John Bahcall, “M dwarfs, microlensing, and the mass budget of the Galaxy“, which basically proved that the Milky Way’s halo is composed principally of non-baryonic dark matter. I remember reading it and thinking, “nah, that can’t be right, you guys can’t conclude that from that data!”, but the more I gnawed at it, the more it struck me just how simple, yet profound, this work was (pay attention you fans of Universe Puzzle, there’s a clue to a future puzzle here).

Finally, towards the end of the time I’m covering in this article, Hubble took the famous Hubble Deep Field. The version posted here you may not have seen before, because it uses a different color transform, by Robert Lupton (more images using this technique here).

Tomorrow: 1996 and 1997.

Previous articles:
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

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 1992 to April 1994.

“And we have liftoff, liftoff of the Space Shuttle Endeavor, on an ambitious mission to service the Hubble Space Telescope”

Without a doubt, Servicing Mission 1 in early December 1993 was the high point of the Hubble Space Telescope’s third and fourth years in space.

For starters, it successfully replaced the high speed photometer instrument with COSTAR (Corrective Optics Space Telescope Axial Replacement), which, as its name implies, corrected for the mis-figured primary mirror and so permitted the three instruments not replaced to make the high quality images intended (they were the Faint Object Camera, the Faint Object Spectrograph, and the Goddard High Resolution Spectrograph).

It also replaced the WF/PC (Wide Field Planetary Camera) with an upgraded WF/PC (called WFPC2), and made several other repairs and replacements which considerably improved the Hubble’s performance and robustness.
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Well before the Hubble was launched much of its observing time was pre-allocated, especially to two Hubble Key Projects, “on the Extragalactic Distance Scale”, and the “Quasar Absorption Line” Key Project. The former is well-known (and I’ll cover it in a later Hubble 20th birthday article); the latter hardly known at all outside the astrophysics community. It was the brainchild of the remarkable John Bahcall, and much of the Hubble’s time in its first four years was devoted to it. There are 13 main papers on its results, with hundreds more based on them. In a word, this project revolutionized our understanding of the space between galaxies and galaxy clusters, all the way from just beyond the Milky Way to billions of light-years distant.

It wasn’t only professional astronomers who used the Hubble in these two years; 16 amateurs did too! Do you know what they found? If you had the chance, what would you use the Hubble to observe?

Perhaps the most captivating images the Hubble took in these two years are the ones of Comet Shoemaker-Levy 9 on its way to a collision with Jupiter (I’ll cover the collision itself tomorrow). Do you remember, back then, that asteroid and comet threats to life on Earth just became a whole lot more believable?

Hubble sent back images of many more objects in these two years, including a much better one of eta Carinae (compare this one with the one in yesterday’s article) and the optical jet of the iconic quasar 3C273.

Tomorrow: 1994 and 1995.

Previous article:
Hubble: It Was Twenty Years Ago Today

Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System

That NASA sent the Hubble into space, to stay.

The date was 24 April, 1990; “Liftoff of the Space Shuttle Discovery, with the Hubble Space Telescope, our window on the universe”.

Over the next ten days I’ll be reviewing these twenty years, starting with the first two today; I hope you will enjoy the show.

Of course, the Hubble’s history goes back many years before 1990; astrophysicist Lyman Spitzer is credited with the first paper proposing a space-based optical observatory, in 1946! He spent a good half century working on the idea (Trivia fact: Spitzer really knew his plasma physics; among other things he founded the Princeton Plasma Physics Laboratory, in 1951; the PPPL is home to some exciting magnetic reconnection experiments). Not so well-known, in the US at least, is that European involvement in the Hubble – via the European Space Agency (ESA) – dates from 1975, 15 years before its launch (Trivia fact: ESA’s Space Telescope European Coordinating Facility (ST-ECF) issued its first newsletter in March 1985).

For all the brilliant engineering, the best money could buy, the Hubble’s primary mirror was ground to exquisite precision and accuracy … but precisely and accurately wrong; the “presence of significant spherical aberration” was announced by NASA at the end of June, 1990. (Trivia fact: the cause of the mis-grinding was a field lens in the reflective null corrector used to test the figure of the primary mirror; it was “mis-located by about 1.3mm” Did heads roll as a result?)

However, because the primary mirror was ground so precisely and accurately, if wrongly, images sent back from the Hubble could be processed to largely remove the unintended blur, and so after a half year or so of rather intense work, the scientific show did go on.

And what a show it was!

Take a trip down memory lane, check out Hubble’s image of Saturn’s North Polar Hood; it’s zoomable!

But a faulty mirror and image processing are not quite the real thing; sometimes there are image processing artifacts, as this 1991 image of a nearby supernova-to-be shows:

Of course it wasn’t only pretty pictures that the Hubble returned to Earth; a great many papers based on the astronomical data from the Hubble were published in its first two years of operation, covering a wide range of topics (perhaps I’ll base a future Universe Puzzle on this, maybe ‘what was the first such paper?’). And it wasn’t only images; the Hubble carried an instrument called the Faint Object Spectrograph, which worked in a part of the electromagnetic spectrum accessible only from space, the far ultraviolet (click on this link to read about limits on He I emission, the He I Gunn-Peterson effect, and Ly-alpha absorption spectrum “at z roughly 0.5”).

What’s your favorite from the first two years?

Mine’s The Ultraviolet Absorption Spectrum of 3C 273; not only is about the iconic quasar 3C 273, not only is it a classic John Bahcall paper (he writes so well!), not only does it illustrate well the scientific power of spectroscopy, but shines a light on composition of the intracluster medium.

Tomorrow: 1992 and 1993, including COSTAR and the first servicing mission.

Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System