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.

R. Soummer / STScI / NASA / ESA

The left image shows Hubble's view of HR 8799p as seen in 1998, while the right image shows the view after state-of-the-art reprocessing, with three planets indicated within white circles.

New techniques for analyzing decade-old images from the Hubble Space Telescope are helping astronomers track planets that went undiscovered at the time. So far, the techniques have confirmed the existence of planets that were found in the meantime using other methods — but astronomers will be checking hundreds of stars in hopes of making brand-new discoveries.

Remi Soummer, an astronomer at the Space Telescope Science Institute in Baltimore who led the new study, compared the technique to a "time machine" for seeking out planets beyond our solar system.

The key to the time machine is a huge database of observations made in the '90s by the Hubble Space Telescope's Near Infrared Camera and Multi-Oblect Spectrometer, or NICMOS. The instrument was used back then to look for dusty planetary disks and brown dwarfs. NICMOS focused on the regions around hundreds of stars, using a coronagraphic disc to block out the glare of the stars themselves.

The images were then processed to remove any remaining glare and bring out dim details. But back then, astronomers "did not have the cleanup techniques that we have now," Soummer told me today. Now Soummer and other astronomers are taking a second look at the NICMOS targets with improved image-processing software, and they're finding objects that were missed the first time around.

The star HR 8799, which is 130 light-years away in the constellation Pegasus, serves a classic example. NICMOS took a look at the star in 1998, but the imaging software available at the time didn't pick up any planets. In 2008 and 2009, a team led by Christian Marois of Canada's National Research Council analyzed ground-based imagery of the star and spotted three planets. The same team detected a fourth planet in 2010.

R. Soummer / STScI / NASA / ESA

This is an illustration of the HR 8799 exoplanet system based on the reanalysis of Hubble NICMOS data and ground-based observations. The positions of the star and the orbits of the four known planets are shown schematically. The sizes of the dots are not to scale with the planet's true sizes. The three outermost planets, b, c and d, are detected in both the NICMOS and ground-based data. A fourth, inner planet, e, was detected in ground-based observations. The orbits appear elongated because of a slight tilt of the plane of the orbits relative to our line of sight. The size of the HR 8799 planetary system is comparable to our solar system, as indicated by the orbit of Neptune, shown to scale.

Spurred by the planet discoveries, the University of Montreal's David Lafrenière and his colleagues used upgraded software to find one of those four planets in the old NICMOS picture. Soummer, Marois and others followed up by locating two more of the planets. The fourth, innermost planet can't be seen in the NICMOS image because it's on the edge of the coronagraphic disc.

"From the Hubble images, we can determine the shape of their orbits, which brings insight into the system stability, planet masses and eccentricities, and also the inclination of the system," Soummer said in a Hubblesite news release. The results from his team are to be published in the Astrophysical Journal.

The three outermost planets make one orbit around HR 8799 roughly every 100, 200 and 400 years — so being able to see where the planets were a decade ago will give astronomers an extra data point for calculating the orbits more precisely. That's why the technique works like a time machine: It's as if you could go back to 1998 and see where the planets were back then. "It's 10 years of science for free," Soummer said.

But that's just the beginning. "What's really exciting now is that we're going to apply the same method to a bunch of other stars, and hopefully we'll make some discoveries of our own," said Brendan Hagan, a member of the research team who recently graduated from Goucher College in Baltimore.

Soummer said his team plans to analyze about 400 other stars in the NICMOS archive with upgraded image-processing software, which should improve image quality by a factor of 10.

"Once the code is ready, it's going to be a very intensive computing process," he told me. "It's going to take a few weeks to go through everything." Soummer plans to make several passes through the data, then compare the NICMOS results with other imagery to confirm the existence of new extrasolar planets.

The Extrasolar Planets Encyclopaedia currently lists 690 worlds that orbit other stars, and Soummer can hardly wait to add to the tally. "We have this huge wealth of data," he said, "and it's ready to be analyzed."

More about exoplanets:

• Real-life 'Star Wars' planet seen
• Fifty new alien worlds revealed
• 'Super-Earth' just might support life
• Interactive: How scientists search for other worlds
• Looking for alien Earths? Here they come

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

NASA / ESA / STScI / OSU / SRON

is image of Markarian 509 was taken in April 2007 with the Hubble Space Telescope's Wide Field Camera 2. Observations reveal bullets of gas being driven away from the galaxy's supermassive black hole, and a corona of hot gas hovering above the disk of in-falling matter.

Astronomers have taken an unprecedented look at the tumult surrounding a supermassive black hole, using a quintet of space telescopes. And they're finding out that it's a horribly messy eater.

The black hole in question is at the center of the galaxy Markarian 509, which is nearly 500 million light-years away. Unlike the black hole at the center of our own Milky Way galaxy, Markarian 509's colossal black hole is sucking huge amounts of dust and gas into its gravitational maw. Its mass is 300 million times that of the sun, or roughly 75 times the mass of the Milky Way's central black hole.

Five space telescopes focused on Markarian 509: the European Space Agency's XMM-Newton telescope and Integral gamma-ray observatory, NASA's Chandra X-Ray Observatory and Swift gamma-ray probe, and the Hubble Space Telescope. The ground-based William Herschel Telescope and PARITEL telescope were also put on the case.

The telescopes couldn't see the black hole itself, but they could see the strong emissions of radiation in various wavelengths from the wreckage that's swirling around it. The X-ray observatories — XMM-Newton and Chandra — were particularly useful.

Markarian 509's gravitational monster is known for its variability. During the 100-day observing campaign, its brightness in the soft X-ray band jumped up by 60 percent, signaling a cosmic feeding frenzy. In a news release, the European Space Agency said giant, blobby bullets of gas were stripped away from the whirlpool and ejected at speeds of millions of miles per hour.

The astronomers were surprised to find that the bullets were coming from a dusty reservoir of matter waiting to fall into the black hole, situated more than 15 light-years away. That's farther away than some astronomers thought was possible.

"There has been a debate in astronomy for some time about the origin of the outflowing gas," said Jelle Kaastra of the SRON Netherlands Institute for Space Research. Kaastra coordinated the international black-hole research team of 26 astronomers from 21 institutes.

M. Weiss / CXC / NASA

In this artist's illustration, turbulent winds of gas swirl around a black hole. Some of the gas is spiraling inward toward the black hole, but another part is blown away.

The dusty reservoir forms a doughnut-shaped torus around the black hole. Material spirals in toward the black hole, creating a whirling accretion disk. The disk appears to give rise to a "corona" that hovers above it.

"This corona absorbs and reprocesses the ultraviolet light from the disk, energizing it and converting it into X-ray light," Kaastra said in a SRON news release. "It must have a temperature of a few million degrees. ... This discovery allows us to make sense of some of the observations of active galaxies that have been hard to explain so far."

The researchers said the corona appears to be the source of the X-rays and gamma rays that drive the bullets outward.

The initial results are being published as a series of seven papers in the journal Astronomy and Astrophysics, titled "Multiwavelength Campaign on Mrk 509." SRON said still more results are in preparation.

More about black holes:

• Snapshot reveals a black hole's jets
• Inside a celestial super-volcano
• Scientists size up a monster black hole
• PlayStation 3 tackles black-hole vibrations

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

Astronomers are using movies created from Hubble Space Telescope imagery to track the gassy burps belched out by young stars.

They say the moving pictures have already unraveled some of the mysteries surrounding Herbig-Haro objects, which are stars that send out colorful, blobby jets of glowing gas at supersonic speeds. The phenomenon is named after astronomers George Herbig and Guillermo Haro, who studied the outflows in the 1950s. Researchers still don't fully understand how the stars unleash such jets, but the new imagery has given them a better sense of the mechanism behind them.

The time-lapse movies were assembled from high-resolution still images collected by Hubble over the course of 14 years.

"For the first time, we can actually observe how these jets interact with their surroundings by watching these time-lapse movies," Rice University's Patrick Hartigan said today in a news release. "Those interactions tell us how young stars influence the environments out of which they form. With movies like these, we can now compare observations of jets with those produced by computer simulations and laboratory experiments to see which aspects of the interactions we understand and which we don't understand."

Hartigan is the leader of a research team that published an analysis of the time-lapse imagery in the July 20 issue of the Astrophysical Journal.

How the jets work
Herbig-Haro jets occur during a relatively brief phase of star formation, lasting about 100,000 years. When a star is born, its gravity pulls in still more material from the disk of gas and dust that swirls around it. That's when the stuff really hits the fan: As the star spins, it flings blobs of the in-falling gas back out into space. At first, those blobs may zoom outward in a tightly focused beam due to the star's strong magnetic field. But eventually they collide with each other, creating a cosmic traffic jam.

The process stops when the disk is emptied of its excess gas and dust, leaving behind planets and bits of cosmic flotsam and jetsam. Such a scenario may well have unfolded in our own solar system 4.5 billion years ago.

Hartigan and his colleagues focused on three stars where the Herbig-Haro jets are in full swing. One star, near the Orion Nebula, has opposing jets known as HH 1 and HH 2. Another star in the southern constellation Vela expels jets that are designated HH 46 and HH 47. The third star, in Orion, has a jet called HH 34. All three stars are about 1,350 light-years from Earth.

For each star, the astronomers collected Hubble imagery at three data points between 1994 and 2008. Then they fed the still pictures into a computer program that turned the pictures into smooth animations. That made it easier to analyze how different parts of the jets interacted as they were expelled. (Check out this webpage for the animated images.)

The movies confirm that blobs of material are not ejected in a continuous stream, but are belched out sporadically — apparently as the result of material falling onto the stars. The blobs move at different speeds, and when one blob plows into another, that creates a bow shock that heats up the gas. Bow shocks also occur when the blobs slam into concentrations of interstellar gas. Regions of the jets brighten and fade as the clumps of gas warm up and cool down.

Lessons from virtual nuclear blasts
"Taken together, our results paint a picture of jets as remarkably diverse objects that undergo highly structured interactions between material within the outflow, and between the jet and the surrounding gas," Hartigan said. "This contrasts with the bulk of the existing simulations, which depict jets as smooth systems."

To improve the fidelity of the simulations, Hartigan's team turned to experts in fluid dynamics from Los Alamos National Laboratory in New Mexico, the UK Atomic Weapons Establishment in Britain and General Atomics in San Diego, Calif., as well as computer specialists from the University of Rochester in New York. Those experts on simulated thermonuclear blasts helped the astronomers understand the interactions powered by Mother Nature's thermonuclear furnaces.

The astronomers are now conducting experiments at the Omega Laser Facility, which is housed at the University of Rochester.

"Our collaboration has exploited not just large laser facilities such as Omega, but also computer simulations that were developed for research into nuclear fusion," said Paula Rosen of the UK Atomic Weapons Establishment, a co-author of the paper. "Using these experimental methods has enabled us to identify aspects of the physics that the astronomers overlooked — it is exditing to know that what we do in the laboratory here on Earth can shed light on complex phenomena in stellar jets over 1,000 light-years away."

More oddities in the cosmic menagerie: 

• Space tornado whirls for trillions of miles
• Lose yourself in a celestial lagoon
• Stellar jets spiral in 'reverse whirlpool'
• Powerful laser simulates stellar jet

In addition to Hartigan and Rosen, the authors of "Fluid Dynamics of Stellar Jets in Real Time: Third Epoch Hubble Space Telescope Images of HH 1, HH 34 and HH 37" include Adam Frank, John Foster, Bernie Wilde, Rob Coker, Melissa Douglas, Brent Blue and Freddy Hansen.

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

M. Showalter / SETI Inst. / NASA / ESA

Hubble imagery from June 28 and July 3 show the changing positions of Pluto's four known moons, including a newly discovered satellite temporarily designated P4.

Astronomers looking for rings around Pluto have instead made an unexpected find: a fourth moon circling the dwarf planet.

The object, temporarily designated P4, is probably the most dwarvish of Pluto's moons: It's estimated to be just 8 to 21 miles (13 to 34 kilometers) in diameter. In comparison, Pluto's diameter is about 1,400 miles, and its other three moons range in diameter from 648 miles (for Charon) to between 20 and 70 miles (for Nix and Hydra, discovered in 2005). The newfound moon orbits in a region between Nix and Hydra, and makes a complete circuit roughly every 31 Earth days.

P4 was detected in June, during a round of Hubble Space Telescope observations aimed at looking for rings or other potential hazards for NASA's New Horizons probe, which is due to zoom through the Pluto system in 2015. Alan Stern, a planetary scientist at the Southwest Regional Institute who heads the $700 million New Horizons mission, told me in an email that the discovery was a testament to the dwarf planet's continuing ability to surprise.

"Pluto's satellite system is truly knocking our socks off with surprises — it's magnificently complex, and getting more crowded all the time. I can't wait till we get there to see what other surprises this planet and its moons have in store for us!" he said.

The find is also a testament to Hubble's amazing vision. The object was spotted on June 28 using the space telescope's Wide Field Camera 3, and its existence was confirmed through follow-up observations this month as well as a search through archived imagery. The moon was not spotted in earlier imagery because the exposure times were shorter.

"I find it remarkable that Hubble's cameras enabled us to see such a tiny object so clearly from a distance of more than 3 billion miles (5 billion km)," Mark Showalter of the California-based SETI Institute, who led the Hubble observing program, said in today's announcement from the Space Telescope Science Institute.

P4 and Pluto's other moons are thought to be the result of a cosmic collision between the dwarf planet and another celestial body early in the solar system's history. Astronomers believe a similar smash-up gave rise to Earth's moon.

Pluto has gotten a bad rap in the past few years, due to its reclassification by the International Astronomical Union in 2006 as a dwarf planet rather than one of the solar system's major planets. Stern sees Pluto as just a different kind of planet rather than an also-ran, and I tend to agree with him. In any case, the fact that the world has a thin atmosphere, changing seasons and more known moons than Mercury, Venus, Earth and Mars combined demonstrates conclusively that you don't have to be one of the big planets to be fascinating. And there may be more to come as New Horizons closes in for its 2015 rendezvous.

"Pluto can retain moons out to almost 100 times the distance of Charon," Stern pointed out.

Update for 10:30 a.m. ET: Although having moons is certainly cool, that doesn't automatically qualify a celestial body to be a planet. A fair number of craggy asteroids possess a moon, or even two. The way the IAU sees it, a "planet" is a roundish celestial body that circles the sun and has "cleared the neighborhood of its orbit," which is widely seen as a deficient definition. A "dwarf planet" is a sun-orbiting celestial body that's big enough to crush itself into a roundish shape, but hasn't cleared out its neighborhood. The way I see it, dwarf planets are planets, too. But I realize a lot of smart folks see it differently. 

Connect with the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter. You can also add me to your Google+ circle, and check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.