NASA / ESA / AURA / STScI

The Horsehead Nebula shines in a Hubble Space Telescope image that marks this month's 23rd anniversary of the orbiting observatory's launch.

Astronomers have come out with a Horsehead Nebula of a different color to celebrate the Hubble Space Telescope's 23rd birthday.

The iconic nebula in the constellation Orion, about 1,500 light-years away, can be seen even through small telescopes. In visible light, it's a dark dust cloud in the shape of a horse's head, silhouetted against a backdrop of glowing hydrogen gas. But the Horsehead takes on a completely different look in the new view released Friday.

"This image was taken in the infrared," Joe Liske, an astronomer from the European Southern Observatory, explains in a video introducing the picture. "In infrared light, we can pierce right through some of the bulky plumes of dusty material which usually mask and obscure the inner regions of the Horsehead. The result is this rather fragile-looking structure, made of delicate, wispy folds of gas — very different to the nebula's appearance in the visible."

The infrared glow, captured by Hubble's Wide Field Camera 3, lights up the nebula's clouds from within. Liske says it's "a fitting celebration of an incredible 23 years of the NASA/ESA Hubble Space Telescope."

The Hubble team traditionally releases an eye-popping shot to celebrate the anniversary of the space telescope's launch on April 24, 1990. As part of this year's celebration, the Hubble Heritage Project asked astronomers around the world to send in their own Horsehead Nebula photos, and you can see the collection via Flickr and Tumblr.

Like a veteran racehorse, Hubble is hitting its stride — but that hasn't always been the case. The first couple of years of operation were hampered by a flaw in the telescope's main mirror. Equipment to compensate for the problem was installed during a crucial series of spacewalks 20 years ago, in 1993. The shuttle Atlantis paid a final servicing visit to Hubble in 2009, and the telescope has been working just fine since then.

Hubble operations have been extended through 2016 — and if the telescope remains in good working order, it's likely to continue being funded at least until 2018, when the $8.8 billion James Webb Space Telescope is scheduled for launch. Eventually, Hubble will have to be sent down to a fiery doom. But who knows? Maybe the old telescope will hang around to experience life after 30.

Slideshow: Classic Hubble Hits

NASA / ESA / STSI via Reuters

See the Hubble Space Telescope's best-known images.

Launch slideshow

More Hubble birthday gifts:

• 22 years: Panorama of the Tarantula Nebula
• 21 years: Raise your glass for Hubble's birthday
• Cosmic Log archive on Hubble Space Telescope

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

STScI

NASA and the Space Telescope Science Institute are offering free e-books about space telescopes.

Free books from NASA, the Hubble Space Telescope's science team and the European Space Agency bring Earth and the heavens to life — as long as you have an iPad, and the patience to wait for a longish download.

Even if you have a regular old computer, you can still download the books about Hubble and its successor, the James Webb Space Telescope, as PDF files. But you'll miss out on all the interactive features.

Those two books were unveiled today by the Baltimore-based Space Telescope Science Institute, which takes care of the science programming for the two NASA-funded telescopes. They're joining the ESA's first iBook, "Earth From Space: The Living Beauty," on my iPad bookshelf.

The Hubble book guides you through scores of pictures from the world's most famous space telescope, organized into categories ranging from cosmology to planetary science. There's also a chapter on the telescope itself, with a 3-D model and a diagram you can tap on to learn about all the components. (Our Flash interactive about Hubble takes a similar approach.) When you tally up all the interactives, videos and picture galleries, the content adds up to a lot more than the 84 pages on the screen.

NASA / STScI

The iBooks are crammed with cosmic images.

The 74-page e-book about the Webb telescope uses a similar approach to explain the science behind the $8.8 billion observatory, which is currently scheduled for launch in 2018. There aren't any pictures from the Webb, of course, but the book's interactives, videos and photo galleries explain how the telescope will observe the cosmic frontiers in infrared wavelengths.

"These new e-books from NASA will allow people to discover Hubble and Webb in a whole new way — both the science and the technology behind building them," Amber Straughn, an astrophysicist on the Webb telescope project at NASA's Goddard Space Flight Center, said in today's news release. "They collect all of the amazing resources about these two observatories in an excellent product that I think people will really enjoy."

While the NASA iBooks look outward, ESA's iBook looks back toward Earth, incorporating stunning images from Europe's Earth-observing satellites. The 104 pages cover our planet from the core to the cryosphere, from the oceans to the wilderness. You can set color-coded virtual globes spinning with a brush of your fingertip.

ESA

"Earth From Space" is the European Space Agency's first iBook.

"By turning the virtual pages of this iBook you will discover how some of the latest technology has changed the way we see Earth," Volker Liebig, director of ESA's Earth observation programs, said in the space agency's publication announcement. "So, it was time to bring these ‘scientific voyages’ to you in a dynamic way. I believe that electronic media hold a huge potential, just like satellite technology. They help you to discover the scientific world of spaceflight."

While the Hubble and Webb e-books are downloadable via Apple's iBookstore, you download "Earth From Space" directly from ESA's website and follow the instructions. You'll need to be patient: Each book packs in hundreds of megabytes' worth of data, so the download can take as long as 20 minutes over a home broadband connection. There were times when I wondered whether it'd ever finish. But if you're a fan of space imagery, these books are well worth the wait — especially when you consider that they're free.

More space imagery:

• 2012: The Year in Space
• Space slideshow gallery
• App lets you take the planet's pulse
• 2012 Cosmic Log Space Advent Calendar

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

NASA / JPL-Caltech / SSI

Saturn and its rings glow in a backlit, enhanced-color image from the Cassini orbiter. The picture combines images that were acquired using infrared, red and violet filters on Oct. 17. Two of Saturn's moons, Enceladus and Tethys, sparkle on the left side of the planet.

The holiday season is bringing beautiful baubles from outer space, including an unconventional view of Saturn from the Cassini orbiter, a gaudy nebula from the Hubble Space Telescope and a loopy picture of a supernova's leftovers. You can even send your own celestial season's greetings.

The Saturn picture, released today, marks the first time Cassini captured a backlit view of the ringed planet since 2006. That earlier photo made a huge splash, in part because the planet Earth could just barely be seen as a pale blue dot off to the side. This time, Earth is hidden behind Saturn, but you can spot two moons just to the left and below the planet: The closer speck is Enceladus, and Tethys is farther down and to the left.

This isn't the view that human eyes would see: Cassini's wide-angle camera snagged this picture in infrared, red and violet wavelengths from a distance of 500,000 miles (800,000 kilometers) behind Saturn on Oct. 17. The various views were assigned different colors in the visible-light spectrum to produce this eerie, otherworldly picture. Here's what Carolyn Porco, leader of the Cassini imaging team at the Colorado-based Space Science Institute, says about the image in today's "Captain's Log":

"Of all the many glorious images we have received from Saturn, none are more strikingly unusual than those we have taken from Saturn's shadow. They unveil a rare splendor seldom seen anywhere else in our solar system.

"This one is our special gift to you, the people of the world, in this holiday season that brings to a close the year 2012. We fervently hope it serves as a reminder that we humans, though troubled and warlike, are also the dreamers, thinkers, and explorers inhabiting one achingly beautiful planet, yearning for the sublime, and capable of the magnificent. We hope it reminds you to protect our planet with all your might and cherish the life it so naturally sustains.

"From all of us on Cassini, the happiest of holidays to everyone."

The Hubble Space Telescope's science team is also rolling out the holiday goodies, with a twisty planetary nebula known as NGC 5189 serving as the centerpiece. "The intricate structure of this bright gaseous nebula resembles a glass-blown holiday ornament with a glowing ribbon entwined," the Hubble team says in today's photo advisory.

NASA / ESA / Hubble Heritage

A holiday image from the Hubble Space Telescope shows the planetary nebula NGC 5189. The image was captured by Hubble's Wide Field Camera 3 on Oct. 8.

Planetary nebulae like NGC 5189 are formed when a medium-sized star like our sun enters the last stages of its life, and puffs away its outer shells of glowing gas. This nebula's swirly structure is thought to be due to the influence of an unseen companion star that's stirring the pot, gravitationally speaking.

The picture was taken by Hubble's Wide Field Camera 3, one of the instruments that was installed during the telescope's final servicing mission in 2009. The camera's filters were tuned to the specific wavelengths of fluorescing sulfur, hydrogen and oxygen atoms, plus broad filters in visible and near-infrared wavelengths to capture the star colors.

The National Optical Astronomy Observatory and WIYN Consortium are also putting out a glittery end-of-the-year picture of the Cygnus Loop, a giant supernova remnant that glows 1,500 light-years away in the constellation Cygnus. The observations were made in 2003 by astronomer Richard Cool, using the NOAO Mosaic 1 camera on the WIYN 0.9-meter telescope on Kitt Peak, Ariz.

The Cygnus Loop shines in a picture released by the National Optical Astronomy Observatory and the WIYN Consortium.

Back then, the computing power wasn't sufficient to process the picture's 600 million pixels into a single, full-resolution color image. Now the telescope observations have been re-reduced and reprocessed by Travis Rector at the University of Alaska at Anchorage to produce the version released today. "Images like this are amazing, because they can remind you of the big picture and beauty that surrounds us," Cool said in NOAO's image advisory.

These pictures are cool enough for Christmas cards, but if you need a little inspiration for your last-minute mailing list, the teams behind NASA's Great Observatories can help: The Space Telescope Science Institute's Hubble Web site offers printable holiday cards. The team behind the Chandra X-Ray Observatory has e-cards suitable for a variety of occasions. You can turn to Zazzle or CafePress to order greeting cards featuring imagery from the Spitzer Space Telescope.

The European Space Agency, meanwhile is offering a selection of space-themed e-cards as well as a printable 2013 Hubble calendar.

More holiday treats:

• 2012 Cosmic Log Space Advent Calendar
• Stocking stuffers for stargazers
• The Atlantic: 2012 Hubble Advent Calendar
• 2012 Zooniverse Advent Calendar

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

The team behind the Hubble Space Telescope has transformed our view of the universe through iconic images such as the Pillars of Creation and the Cat's Eye, but even the professionals can miss some gems — as demonstrated by today's winners of the "Hubble's Hidden Treasures" contest.

The contest, which had its kickoff in March, invited members of the public to sort through more than 700,000 archived images from the space telescope and come up with pictures that have never before been put in the spotlight. The results illustrate how today's software is making it easier for amateur astronomers to do professional-level work.

The Hidden Treasures contest is sponsored by the folks at the European Space Agency's Hubble headquarters in Garching, Germany. Nearly 3,000 photo submissions were received, in two categories. One category was reserved for folks who used color compositing and other image-processing techniques to bring out the best in the Hubble imagery. The other was for folks who spotted great pictures in the archive, but didn't fully process the images themselves.

Ten winners were selected in each category and will receive prizes ranging from Hubble posters to Apple gadgets and autographs from "Hubble-hugging" astronaut John Grunsfeld.

Double-winner
The top winner in the image-processing category, as well as the "People's Choice" competition, is Josh Lake, a 34-year-old physics and astronomy teacher (and volleyball coach) at Pomfret School in Connecticut. Lake told me he was "really surprised and happy" to learn that he was a winner.

"We have our own observatory here, so I've been teaching students to do processing for the past five years or so," he said.

The fact that he won the People's Choice online contest might not have been so surprising, considering that he could enlist students and alumni, family and friends to vote for his picture of the star-forming region NGC 1763. "I was totally blown away to find out that I had won the jury prize, too" Lake said.

Lake said that image processing is "something that I love doing," but it sounds as if he won't be giving up his teaching job for a career in astronomical image processing anytime soon. "I think I would really miss the students and this community," he said. "It'd be a tough lifestyle to break out of, and just go to a 9-to-5 job sitting in front of a computer. ... The work here is hard, but it's life-changing."

Here's hoping that Lake's image-building feat will be life-changing as well. To get a sense of how he did it, check out this three-minute time-lapse video of the process, and then feast your eyes on the finished product:

NASA / ESA / Josh Lake

Josh Lake submitted a stunning image of NGC 1763, part of the N11 star-forming region in the Large Magellanic Cloud. ESA/Hubble had previously published an image of an area just adjacent to this, based on observations by the same team. Josh took a different approach, producing a bold two-color image that contrasts the light from glowing hydrogen and nitrogen. The image is not in natural colors — hydrogen and nitrogen produce almost indistinguishable shades of red light that our eyes would struggle to tell apart — but Josh's processing separates them out into blue and red, dramatically highlighting the structure of the region. As well as narrowly topping the jury's vote, Josh Lake also won the public vote.

Here are a few more of the contest winners, with comments from the European Hubble team. For links to all 20 images, check out the European Hubble site's "Hidden Treasures" announcement.

NASA / ESA / Andre van der Hoeven

Andre van der Hoeven of the Netherlands came a close second in the jury vote. His image of the spiral galaxy Messier 77 is highly attractive, and is also an impressive piece of image processing, combining a number of datasets from separate instruments into one amazing picture.

NASA / ESA / Judy Schmidt

Judy Schmidt of the United States entered several highly accomplished images into the competition. Her picture of XZ Tauri, a newborn star spraying out gas into its surroundings and lighting up a nearby cloud of dust, was the jury's favorite - and won third place in the image-processing contest. This was a challenging dataset to process, as Hubble only captured two colors in this area. Nevertheless, the end result is an attractive image, and an unusual object that we would never have found without her help

NASA / ESA / Brian Campbell

Brian Campbell's picture of NGC 6300 won first prize in the basic image-searching category.

NASA / ESA / Budeanu Cosmin Mirel

Budeanu Cosmin Mirel won the public vote in the basic image-searching category with a picture of NGC 4100.

More winners in astrophotography:

• 'World at Night' finds beauty in darkness and light
• All-time top 10 from Astronomy Picture of the Day
• The Year in Space Pictures: 2011

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the dwarf planet and the search for new worlds.

M. Showalter / SETI Institute / NASA / ESA

This photo from the Hubble Space Telescope shows Pluto and its five known moons, including a newly discovered satellite indicated as P5. Its provisional name is S/2012 (134340) 1.

Astronomers using the Hubble Space Telescope have discovered Pluto's fifth moon, a little more than three years before a NASA space probe is due to sail past the dwarf planet and its tribe of satellites.

The irregular moon, estimated to be 6 to 15 miles (10 to 25 kilometers) across, was found in the course of checking out the potential collision hazards facing NASA's New Horizons spacecraft for the Bastille Day flyby on July 14, 2015. "The inventory of the Pluto system we're taking now with Hubble will help the New Horizons team design a safer trajectory for the spacecraft," the mission's principal investigator, Alan Stern of the Southwest Research Institute, said in a Hubble news release.

Stern and his colleagues suspect this fifth moon won't be the stuff they find in Pluto's neighborhood. "The discovery of so many small moons indirectly tells us that there must be lots of small particles lurking unseen in the Pluto system," said Harold Weaver of the Johns Hopkins University Applied Physics Laboratory.

Call it P5 ... for now
The fifth moon is currently known only by its provisional names: S/2012 (134340) 1, or P5 for short. It'll be up to the discoverers to propose a more lyrical name to the International Astronomical Union, which classified Pluto as a dwarf planet in 2006.

P5 was detected in 14 separate sets of images taken by Hubble's Wide Field Camera 3 on June 26, 27 and 29 plus July 7 and 9. The Hubble team says it's in a 58,000-mile-diameter circular orbit around Pluto that steers clear of the dwarf planet's four other satellites — including the biggest moon, Charon. Two other moons, Nix and Hydra, were discovered in 2006, and the fourth moon (P4) was found in Hubble data last year.

"The moons form a series of neatly nested orbits, a bit like Russian dolls," team leader Mark Showalter of the SETI Institute said in today's news release. He told me that small moons have now been found in the Pluto-Charon system at close to a 1-to-3 orbital resonance with Charon (P5), a 1-to-4 resonance (Nix), 1-to-5 (P4) and 1-to-6 (Hydra). This suggests that the moons were formed from debris blasted away by the collision that led to the coalescence of Pluto and Charon as we know them today.

"This is a very tidy system, and what that means is, it's an orbitally evolved system," Showalter said. "Literally there are shells where the orbits are stable."

Pluto's moons are traditionally named after Greek mythological characters associated with the underworld. Nix, for example, is an alternate spelling for Nyx, the name of the Greek goddess of the night and the mother of the Fates. (The more typical spelling, Nyx, was used previously in the name of an asteroid.) Hydra is the serpentine monster that guarded the gates of the underworld. "It's a very colorful cast of characters," Showalter told me.

For P4 and P5, the team members are holding off on proposing names for now, just in case a P6 comes along. "It's still a moving target, because we don't know what might come along," Showalter said. "I expect that in a month or two, we'll have finished everything we're going to find until New Horizons gets close." Only then will the team seriously consider what the two (or more) moons will be named. If things stay as they are, P4 and P5 will probably be named after a pair of characters with Greek underworld connections, such as Orpheus and Eurydice. (The name Orpheus is already taken, but they could go with a variant, such as Orfeo.)

As of today, Showalter says there are no other Plutonian moon candidates in sight. "Of all the things that we have looked at, that we thought might be moons, none of them has ever been convincing until this came along," he said of P5. "There is no P6 in our back pocket at this time."

The detection ... and the debate
Finding P5 was hard enough. Showalter told me that he first spotted the moon in the data on Saturday, the 7th. He and his colleagues then went back and found signs of the moon in the data gathered earlier, as well as the follow-up imagery captured on Monday. The object is just 0.001 percent as bright as Pluto, and 4 percent as bright as Nix, Showalter said. "We're really at the edge of what we can accomplish with Hubble," he said. "I don't know of any instrument that's going to be better than that."

In an IAU circular issued today, the team reports that P5's brightness is about magnitude 27, which makes it half as bright as P4. The brightness was used to estimate P5's size.

Today's announcement revived the debate over whether Pluto should be counted as a planet, period, rather than a dwarf planet. The difference, as outlined by the IAU almost six years ago, has to do with how much a celestial body has "cleared out the neighborhood of its orbit." In my book, "The Case for Pluto," I set out the argument for counting Pluto and other worlds that have a basically roundish shape as types of planets, even if they're put in the dwarf category.

"The name 'dwarf planet' really doesn't bother me," Showalter said. "When you think of a bonsai tree, it's still a tree, and what's interesting about it is that it's really, really small. I think of Pluto the same way. ... It only gets more interesting with each one of these discoveries that comes along. If you don't like the term 'dwarf planet,' call it a 'bonsai planet.'"

I like that approach. But what about you? Feel free to weigh in below with your comments on Pluto, P5, or your suggestions for the names of the bonsai planet's newest moons.

More about Pluto:

• Final push for Pluto's postage stamp
• Scientists spot Pluto's fourth moon
• Carbon monoxide found in Pluto's air
• Pluto debate is about more than one little world
• Cosmic Log archive on Pluto 

Last updated 4:30 p.m. ET.

In addition to Showalter, Weaver and Stern, members of the discovery team include A.J. Steffl and M.W. Buie.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

H. Olofsson / ESA / NASA

The bright star U Camelopardalis, or U Cam for short, is surrounded by a tenuous shell of gas in an image from the Hubble Space Telescope.

The flash of an earthly fireworks display can be over in an instant — sometimes literally — but the show is longer lasting in outer space. The dying red-giant star known as U Camelopardalis, 1,500 light-years away in a region of sky near the north celestial pole, is in the midst of a fireworks blast that lasts for centuries.

By human standards, U Cam's blast may seem like an eternity. The star's shining shell of glowing gas, documented in this picture from the Hubble Space Telescope, has been traveling outward for something like 700 years, as Bad Astronomy's Phil Plait points out. When the outward explosion began, Europe was suffering through famines and plagues, and the mainstream view was that our planet was the center of the universe.

But in the astronomical scheme of things, centuries are mere blinks of the eye — and it won't be long before U Cam gives up the ghost.

U Cam is a carbon-rich star that's running low on its fusion fuel and becoming unstable. Every few thousand years, it coughs away stellar material as a thin, faintly glowing shell. The star itself is actually much smaller than it looks. The brightness dial has been turned way up to emphasize the delicate structure of the shell, and that means U Cam's glare is turned up as well.

Plait notes that our own sun is destined to run low on fuel billions of years from now, turn into a red giant and start blasting away shells of material — just as U Cam is doing now. "What we're seeing here is a glimpse of our own future," he writes. That's certainly a sobering thought, but 7 billion years or so should give us plenty of time to look around for other places where we can hang out.

NASA / JPL-Caltech

The Flame Nebula flares in this color-coded view from NASA's Wide-field Infrared Survey Explorer. The famous Horsehead Nebula can be seenas a small bump poking out from the edge of the cloud, below the bright star of the flame.

Who knows? One of those places might be in the neighborhood of the Flame Nebula. The star-forming nebula is situated about as far away from us as U Cam — but in the direction of the constellation Orion, near the celestial equator. NASA's Wide-field Infrared Survey Explorer captured this view of the vast cloud and dust, lit up by a bright star that's 20 times as massive as our sun.

This view also shows two other familiar nebulae. The knot of light just beneath the brightest part of the image is a nebula known as NGC 2023. The Horsehead Nebula is poking out from the greenish-colored cloud, just to the right of NGC 2023 and down a bit. In visible light, the Horsehead is a dark cloud silhouetted by glowing gas, but in infrared light, we see the glow of the cloud instead.

This image is color-coded to reflect different infrared wavelengths. Hot stars are seen in shades of blue and bluish green, while relatively cool objects, such as the dust of the nebulae, show up in shades of green and red. The color combination makes for a fireworks display well-suited for the week of the Fourth of July.

Where in the Cosmos
The picture of the Flame Nebula served as this week's puzzle picture for the "Where in the Cosmos" contest on the Cosmic Log Facebook page. It only took a few minutes for Matt Gunn to identify the picture as the Flame Nebula, and Michael Vacirca and David Frambo were right behind him. All three are eligible to receive 3-D glasses, wrapped up in a 3-D picture of yours truly.

To put those red-blue glasses to use, check out Cosmic Log's 3-D archive, as well as the 3-D images available through the Planetary Society blog. And to get in position for next week's "Where in the Cosmos" contest, be sure to hit the "like" button for the Cosmic Log Facebook page.

Weekly Space Hangout
Cosmic sights were among the topics addressed during this week's Space Hangout, orchestrated by Universe Today's Fraser Cain, but we also addressed developments closer to home, such as the discovery of a new boson at the Large Hadron Collider and the untimely death of former astronaut Alan Poindexter. Check out the YouTube video for the whole Hangout.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Thierry Legault / Astrophoto.fr

French astrophotographer Thierry Legault captured this view of the Hubble Space Telescope passing over the sun's disk during this week's transit of Venus. The circles highlight the Hubble on multiple exposures taken every tenth of a second during the telescope's 0.9-second transit.

Over the past few days, we've seen lots of amazing photos showing Venus' last-in-a-lifetime crossing of the sun, but this shot of the Hubble Space Telescope zooming past Venus may be the only picture of its kind.

It's actually a combination of photographs, snapped every tenth of a second by master astrophotographer Thierry Legault. Nine speck-sized images of Hubble are highlighted with circles in the image. Legault, who is famed for his pictures of spacecraft transits across the sun, traveled from his home base in France to northern Australia for the shot.

After conducting the calculations with CalSky software, Legault made sure he was in Queensland at 01:42:25 UTC June 6, pointing his Takahashi FSQ-106ED telescope at the sun with the proper filters attached. "Thanks to the continuous shooting mode of the Nikon D4 DSLR running at 10 fps [frames per second], nine images of the HST were recorded during its 0.9s transit (1/8000s, 100 iso, raw mode). Turbulence was moderate to high," Legault reported on his website.

You read that right: While it took Venus more than six hours to inch its way in front of the solar disk, the Hubble Space Telescope zipped across in just nine-tenths of a second. Imagine how disappointing it would have been to have a cloud in the way at that moment!

Legault is promising more pictures of Venus, taken during the transit and afterward. But it'll be hard to match this one. The next transit of Venus won't occur until the year 2117, and even though Hubble has long outlasted its projected lifetime, the space telescope will surely be sent down to its fiery doom by then. So chances are this is the only picture that will ever be taken of Hubble and Venus simultaneously silhouetted by the sun.

By the way, Hubble was conducting its own transit tasks during Venus' crossing. Hubble focused on the moon and analyzed  the reflected sunlight to find out how easy it will be for future telescopes to pick out the spectral signature of Earthlike planets passing over alien suns. Stay tuned for more about the results of that experiment.

Where in the Cosmos
This picture served as today's photo puzzle for our "Where in the Cosmos" contest, open to Cosmic Log Facebook followers. It took just a couple of minutes for Ollie Nanyes to tell me what those little specks represented. For being so quick on the draw, I'm sending Nanyes a pair of 3-D glasses donated by Microsoft Research's WorldWide Telescope project. Kent Avery, the runner-up in the guessing game, is getting 3-D specs as well. (Microsoft is a partner along with NBC Universal in the msnbc.com joint venture.)

The cardboard-and-cellophane glasses I'm sending Nanyes and Avery will be wrapped up in a 3-D picture of yours truly, but there are other, more interesting 3-D space pictures online. This Cosmic Log 3-D archive points you to some stunners. Click the "like" button on the Cosmic Log Facebook page, and you too may be eligible for some 3-D glasses goodness in the weeks to come. Just for fun, go full-screen on this simulated 3-D view of the transit from the National Solar Observatory Integrated Synoptic Program:

More wonders from Thierry Legault:

• Falling satellite seen from Earth
• Last looks at the shuttle in orbit
• Spaceships get their day in the sun
• Sun gets double-crossed
• Still more from Legault's website

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

NASA

This artwork shows one of the concepts for the Wide-Field Infrared Survey Telescope, also known as WFIRST. NASA officials say that the telescopes being made available by the National Reconnaissance Office could address some of the questions to be resolved by the WFIRST mission, including the nature of dark energy and characteristics of extrasolar planets.

A gift of space telescope hardware from America's spy agency could knock $250 million off the billion-dollar-plus cost of a mission to study dark energy and extrasolar planets, NASA says. But scientists and space agency officials say the super-Hubble telescope won't replace the multibillion-dollar James Webb Space Telescope.

After more than a year of deliberation, NASA today revealed that it's taken possession of two optical mirror assemblies that had been built for the National Reconnaissance Office but were rendered surplus when the NRO decided they were unneeded. Although the spy agency has declined to say what the hardware would have been used for, it almost certainly was designed for next-generation spy satellites.

The assemblies fit inside a barrel that's about half the length of the Hubble Space Telescope, sparking the nickname "Stubby Hubble." The size of each primary mirror is the same as Hubble's: 94 inches or 2.4 meters in diameter. But the focal length is shorter, which would give the telescopes "about 100 times bigger area that you can image well," said Alan Dressler, an astronomer at the Carnegie Institution for Science.

That would make the mirrors perfectly suited for a wide-field telescope that could survey the cosmos to gauge the effect of dark energy, a mysterious factor that is speeding up the acceleration of the universe, Dressler and NASA officials told journalists today. Such a telescope could also detect Earthlike planets beyond the solar system by looking for an effect known as microlensing, and study supernovae and other astronomical phenomena as well.

"It's perfectly useful for astronomy in the infrared," Dressler said.

Such a telescope was rated as one of the highest priorities for astronomical research over the next decade in a report prepared for the National Academy of Science, titled "New Worlds, New Horizons." In the report, the mission concept was known as the Wide-Field Infrared Survey Telescope, or WFIRST. Mission cost was estimated at $1.6 billion.

"Depending on the instruments chosen to go with the new telescopes, NASA could address many of the science goals of the WFIRST mission," said Paul Hertz, NASA Headquarters' director of astrophysics.

Hertz's acting deputy director, Michael Moore, declined to put a price tag on the telescope that could be built using the NRO's surplus hardware. But Moore told me that building the kind of mirror assembly that the NRO has now provided would cost somewhere along the lines of $250 million. He said the optical hardware was space-qualified and "completely ready to be integrated into a spacecraft."

However, the transferred hardware doesn't include camera equipment or other key components that are needed to turn the optical assembly into a true space telescope. "There's still a lot of investment work and coordination that's required," Moore said.

Right now, the assemblies look like "cylinders with shiny foil wrapped around them," he said. Moore, an engineer, said he thought they were "gorgeous" pieces of hardware. But a non-technical person might not be as impressed, he said: "I gotta admit, they're not all that glamorous."

Moore said the project began in January 2011, when he took the phone call from NRO officials who were offering the surplus hardware. For months, NASA officials have been considering whether it'd be worth trying to use the equipment. After discussions with Dressler and other astronomers, they finally decided to go ahead with the transfer.

The hardware is currently in storage at ITT Exelis' manufacturing facility in Rochester, N.Y., Moore said. He estimated that it was costing about $75,000 to $100,000 a year for "care and feeding" of the equipment.

Hertz emphasized that NASA did not yet have the funding to go ahead with space telescope assembly. For now, NASA and outside astronomers are merely assessing what it would take to build a complete telescope, and contemplating exactly what the telescope could do. He said the super-Hubble could conceivably be launched in 2024 "with a plausible budget."

The telescope could be finished even earlier, in the 2019-2020 time frame, "if money is no object," Hertz said. However, he added, "We have no reason to believe that that would happen."

He made clear that there was no thought of using the theoretical super-Hubble as a cheaper substitute for the controversial James Webb Space Telescope, which is now slated to launch in 2018 with a mission cost of $8.8 billion. The JWST, which has been portrayed as Hubble's successor, is a much larger telescope with a much narrower field of view than the super-Hubble would have. Hertz said he could imagine an eventual scenario in which the super-Hubble spots something in a wide-field image that would merit follow-up with observations using the narrow-field, deep-viewing JWST'.

Hertz said NASA was considering the development of only one space mission using the transferred hardware, even though the NRO gave the space agency two virtually identical sets of space telescope parts. 

"We don't, at this point in time, anticipate ever being rich enough to use both of them," he told reporters. "But it sure would be fun to think about, wouldn't it?"

Correction for 4 p.m. ET June 5: And speaking of "fun," Dressler included a joke picture in his presentation that purported to show a "heavily redacted" view of the NRO telescope assemblies. You could tell from the image that the object was a "cylinder with shiny foil wrapped around it," but that's about it. The picture was actually a mostly blacked-out file photograph of the Hubble Space Telescope, taken during preparation for launch, but I totally fell for the joke and passed it along as a picture of the real thing. NASA's Bob Jacobs set me straight today. I should have double-checked the circumstances surrounding the photo — and I'm sorry for leading folks astray.

Just for fun, here's the picture again:

A. Dressler via National Academies

As a joke, astronomer Alan Dressler included what he called a "heavily redacted" picture of the NRO-1 telescope in his presentation to the National Academies' Committee on Astronomy and Astrophysics. It's actually a heavily doctored picture of the Hubble Space Telescope from before its launch.

More about future space telescopes:

• NASA plans to 'repurpose' unused spy telescopes
• $1.6 billion telescope would seek out alien planets
• Nobel laureates say we must fund dark energy research
• Webb Space Telescope needs 'big science' support to succeed

Dressler discussed what he called the "NRO-1 2.4-meter telescope" today during a meeting of the National Academies' Committee on Astronomy and Astrophysics. Here are the PDF slides that he presented during his talk.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

This composite image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell 520, formed from a violent collision of massive galaxy clusters. Starlight from galaxies is indicated in orange. Green indicates hot gas, and blue indicates mass, most of which is dark matter.

Astronomers using the Hubble Space Telescope are mystified by a merging galaxy cluster known as Abell 520 in which concentrations of visible matter and dark matter have apparently come unglued.

A report on the Hubble observations, published in the Astrophysical Journal, raises more questions than answers about a cosmic pile-up that's occurring 2.4 billion light-years away.

"We were not expecting this," the study team's senior theorist, Arif Babul of the University of Victoria, said in a news release. "According to our current theory, galaxies and dark matter are expected to stay together, even through a collision. But that's not what's happening in Abell 520. Here, the dark matter appears to have pooled to form the dark core, but most of the associated galaxies seem to have moved on."

The dark core was first detected in 2007 during a survey aimed at measuring the masses of 50 galaxy clusters using data from the Canada-France-Hawaii Telescope at Mauna Kea in Hawaii.

The discovery presented the perfect opportunity to map the distribution of visible vs. dark matter in the cosmic mess. Studies have shown that we can see only about 15 percent of the matter in the universe. Most of the matter that exists around us can't be seen directly, but can be detected only by its gravitational effect. Scientists don't know what dark matter is, but they suspect it's an exotic class of subatomic particles that can interact only weakly with the kinds of matter we can see.

Dark matter is thought to provide the invisible "scaffolding" for structure in the universe, gravitationally binding galaxy clusters into a cosmic web. Those clusters get so massive that they bend the light of distant galaxies like a lens. By analyzing those subtle deflections of light, it's possible to come up with a map showing where the dark matter lies. That's what astronomers did with Abell 520 — first with the telescope in Hawaii, and then with the Hubble Space Telescope's Wide Field Planetary Camera 2.

The results contradict what scientists thought they knew about dark matter. In a previous study of the Bullet Cluster, 3 billion light-years from Earth, astronomers found that concentrations of dark matter blasted through the scene of a collision, with their associated galaxies tagging along. Meanwhile, waves of hot, X-ray-emitting gas clumped up in the middle.

In the case of Abell 520, the situation is completely different: The galaxies sailed through the collision, but the dark matter piled up in the middle, along with the hot gas.

Researchers were hoping that Hubble would resolve the mystery first posed by the detection of the dark core in 2007. No such luck.

"We know of maybe six examples of high-speed galaxy cluster collisions where the dark matter has been mapped. But the Bullet Cluster and Abell 520 are the two that show the clearest evidence of recent mergers, and they are inconsistent with each other," James Jee, an astronomer at the University of California at Davis who is the lead author of the Astrophysical Journal paper, said in a news release from the Space Telescope Science Institute. "No single theory explains the different behavior of dark matter in those two collisions. We need more examples."

Jee, Babul and their colleagues propose several possible explanations for the discrepancy. One explanation might be that the dynamics of the Abell 520 collision are more complex than the Bullet Cluster's crash. Maybe multiple collisions, involving three or four galaxy clusters, have led to the dark matter pile-up.

Another possibility is that there's actually lots of ordinary galactic material in the core, but it's just too dim to be seen, even by Hubble. That would suggest that the super-dim galaxies in the core have somehow formed far fewer stars than normal galaxies.

The most unsettling scenario proposes that there are different kinds of dark matter, and some of those kinds are "stickier" than others. Abell 520 might have a particularly sticky kind of dark matter that interacts with itself and clumps up like a wet snowball.

The astronomers behind the Abell 520 observations are now planning to run computer simulations of cluster crashes to find out whether there's an unusual set of conditions that could produce those observations and still fit current theory. "My colleagues tell me the likelihood is nil," Andisheh Mahdavi, a member of the study team from San Francisco State University, said in a news release, "but now we have the responsibility to go and do the hard work to check the simulations."

If the simulations aren't successful, the mystery might have to be left for particle physicists to mull over. Some hope that experiments such as Europe's Large Hadron Collider and the Alpha Magnetic Spectrometer, installed last year on the International Space Station, will eventually shed additional light on the dark matter mystery.

"I'm just as perplexed as I was back in 2007," Mahdavi said. "It's a pretty disturbing observation to have out there."

Update for 5:40 p.m. ET March 2: The picture of Abell 520 served as this week's "Where in the Cosmos" picture puzzle on the Cosmic Log Facebook page this morning, and it took only a few minutes for Ryan Marquis to figure out what the image was all about. "It appears the dark matter and galaxies aren't anchored as previously believed," he wrote.

I'm sending Ryan a pair of 3-D glasses as a token of my appreciation. It turns out Ryan's a fellow space blogger who posts his items on 46BLYZ. We're glad to have him as a Cosmic Log correspondent, and hope that more of you will join our Facebook community. That's where you'll find the next "Where in the Cosmos" puzzle, a week from now.

Correction for 9 p.m. ET March 5: The original version of this item had the wrong first name for SFSU's Andisheh Mahdavi. I regret the error and extend apologies to the professor.

More about dark matter:

• Crazy cosmic lens focuses on dark matter
• The darkest mystery of them all
• Dark matter mapped in 3-D detail
• Gallery: Dark matter revealed!
• Search for dark matter on msnbc.com
• ... And what about dark energy?

In addition to Jee, Mahdavi and Babul, the authors of "A Study of the Dark Core in A520 With Hubble Space Telescope: The Mystery Deepens" include H. Hoekstra, J.J. Dalanton, P. Carroll and P. Capak.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.

Analysis of the galaxy ESO 243-49 in multiple wavelengths has detected the signature of hot stars swirling around a midsize black hole, highlighted by the white circle on this Hubble Space Telescope image. Astronomers say the readings suggest that the black hole is actually part of the leftovers from a dwarf galaxy that crashed into the bigger galaxy and disintegrated.

Astronomers have reconstructed what they think is a galactic crash scene, with a rare breed of black hole left behind amid a dwarf galaxy's wreckage. The Hubble Space Telescope played a key role in the accident investigation.

The black hole was detected three years ago in the edge-on spiral galaxy ESO 243-49, about 290 million light-years from Earth, and raised a question that's been bugging astronomers ever since.

The theoretical scenario for creating black holes through the collapse of stars is well-known. But scientists are just beginning to figure out how galaxy formation can lead to the creation of supermassive black holes that are millions or billions of times heavier than the sun. This particular black hole, designated HLX-1, was even more of a puzzler: It's about 20,000 times as massive as our sun, a kind of midsize monster that's rarely seen in our celestial neighborhood.

The astronomer who led the HLX-1 search effort, Sean Farrell of the University of Leicester and the Sydney Institute for Astronomy, took a closer look at the black hole with the aid of imagery in ultraviolet, visible and infrared wavelengths from Hubble, as well as X-ray imagery from NASA's Swift satellite. Now he and his colleagues are suggesting that the midsize black hole is a leftover from a dwarf galaxy's unfortunate encounter with the much bigger galaxy less than 200 million years earlier.

They came to that conclusion based on observations of light toward the reddish side of the spectrum — so much red light that it can't be explained just by the blaze of material falling into the black hole. Farrell and his colleagues think the light is coming from a cluster of hot stars surrounding the black hole.

"The fact that there’s a very young cluster of stars indicates that the intermediate-mass black hole may have originated as the central black hole in a very low-mass dwarf galaxy," Farrell said in a news release from the European Space Agency's Hubble team. "The dwarf galaxy was then swallowed by the more massive galaxy."

As the dwarf galaxy was ripped apart, the black hole and some of its surrounding material would have survived.

The researchers say it's not yet clear what will happen to the black hole. It might spiral into the center of ESO 243-49, merging with the supermassive black hole that's already there. Or it might settle into a stable orbit in the bigger galaxy's outer environs. Either way, the X-ray emissions that brought the black hole to light in the first place will eventually fade away.

The findings from Farrell and his colleagues were published today by The Astrophysical Journal, and the team will continue watching HLX-1 for more clues.

Looking beyond just one intermediate-mass black hole, the astronomers say the case of HLX-1 sheds light on the bigger mysteries surrounding the formation of those supermassive, galaxy-scale black holes. Most theorists surmise that big galaxies — and the big black holes at their centers — are built up gradually through the merger of smaller galaxies. This research supports that view.

Our own Milky Way galaxy might well go through the next phase of the merger process in a few billion years, when it's due to mix it up with Andromeda and create a bigger behemoth nicknamed "Milkomeda."

More about galaxy mergers:

• Twisted galaxy warped by 'stealth merger'
• Almost every galaxy has had a major collision
• Galactic merger could boot our solar system
• NASA spots most crowded space collision ever
• Black hole knocked off its axis by galaxy collision
• Cosmic Log archive on galaxies | black holes

In addition to Farrell, authors of "A Young Stellar Population Around the Intermediate Mass Black Hole ESO 243-49 HLX-1" include M. Servillat, J. Pforr, T.J. Maccarone, C. Knigge, O. Godet, C. Maraston, N.A. Webb, D. Barret, A. Gosling, R. Belmont and K. Wiersema.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.