UFO'S of UAP'S, ASTRONOMIE, RUIMTEVAART, ARCHEOLOGIE, OUDHEIDKUNDE, SF-SNUFJES EN ANDERE ESOTERISCHE WETENSCHAPPEN

As NASA's Saturn-orbiting Cassini spacecraft begins its final eight months of operation, scientists are looking back at one of the mission's most dramatic moments: the landing of the piggyback Huygens probe on the huge moon Titan.

Huygens touched down on Titan's frigid surface on Jan. 14, 2005, three weeks after separating from the Cassini mothership. It was a landmark moment in planetary science, mission team members said.

"The Huygens descent and landing represented a major breakthrough in our exploration of Titan as well as the first soft landing on an outer-planet moon," Cassini project scientist Linda Spilker, of NASA's Jet Propulsion Laboratory in Pasadena, California, said in a statement. "It completely changed our understanding of this haze-covered ocean world." [Huygens Probe's Titan Landing Revisited 12 Years Later (Video)]

Cassini and Huygens launched together in October 1997 and reached the Saturn system in July 2004. On Dec. 24 of that year, Huygens separated from the Cassini orbiter to begin a 20-day voyage toward the lander's final destination.

The Huygens lander revealed a never-before-seen world in the landscape of Saturn's moon Titan. This view was created using images taken during the probe's descent, from an altitude of about 6 miles (10 kilometers).
**Credit: ESA/NASA/JPL/University of Arizona**

Titan, the mysterious cloud-covered moon of Saturn, is the ringed planet's largest moon. Find out the facts about Titan's heavy atmosphere, lakes of hydrocarbons and the possibility of life in this Space.com infographic.
**Credit: Karl Tate, SPACE.com contributor**

At the time, little was known about the 3,200-mile-wide (5,150 kilometers) Titan; dense atmospheric haze kept the moon's surface features shrouded in mystery. To an extent, the Cassini mothership has been able to use radar to peer through the haze from orbit, but Huygens' up-close photographic views were a revelation, mission scientists said.

During its 2.5-hour descent, the lander captured hundreds of images of the moon's surface, revealing bright highlands cut by steep ravines and channels. Huygens also took photos of its surroundings after touching down, on a dark granulated surface that resembled a dry lake bed. (The lander operated for a few hours before ending its mission.)

"The Huygens images were everything our images from orbit were not," Carolyn Porco, Cassini imaging team lead at the Space Science Institute in Boulder, Colorado, said in the same statement.

"Instead of hazy, sinuous features that we could only guess were streams and drainage channels, here was incontrovertible evidence [that] at some point in Titan's history — and perhaps even now — there were flowing liquid hydrocarbons on the surface," Porco added. "Huygens' images became a Rosetta Stone for helping us interpret out subsequent findings on Titan."

Titan is the only solar system object aside from Earth known to harbor stable bodies of liquid on its surface. But Titan's seas contain liquid ethane and methane, not water.

Huygens also sampled the atmosphere of the huge moon while passing through, measuring winds and analyzing the organic chemistry of the unusual world.

In the dozen years since Huygens touched down on Titan, Cassini has continued studying the moon from Saturn orbit during a series of flybys. The spacecraft has examined the clouds in the moon's atmosphere and analyzed the satellite's climate and seasonal changes. Cassini has probed the variation in surface features, including lakes, rivers, channels and reservoirs. Bizarre "magic islands" have been observed appearing and disappearing over time in one of Titan's northern lakes. The moon also shows signs of potential cryovolcanism, low peaks that may permit cold lava flows on the surface.

"Cassini and Huygens have shown us that Titan is an amazing world with a landscape that mimics Earth in many ways," said Cassini scientist Alex Hayes, of Cornell University in New York.

"During its descent, the Huygens probe captured views that demonstrated an entirely new dimension to that comparison and highlighted that there is so much more we have yet to discover," Hayes added. "For me, Huygens has emphasized why it is so important that we continue to explore Titan."

The $3.2 billion Cassini-Huygens mission is a collaboration involving NASA, the European Space Agency and the Italian Space Agency.

The venerable mission is nearing its end. In April, the Cassini mothership will begin its "Grand Finale" phase, a series of 22 dives between Saturn's cloud tops and the planet's innermost ring. Then, on Sept. 15, the probe will perform an intentional death plunge into Saturn's atmosphere, to ensure that microbes from the craft don't contaminate Titan or the icy moon Enceladus, two worlds that may be capable of supporting life.

Follow Nola Taylor Redd on Twitter @NolaTRedd or Google+. Follow us at @Spacedotcom, Facebook or Google+. Originally published on Space.com.

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Green Glow from Ancient Galaxies Surprises Scientists — This image shows the results of a deep field survey by the Subaru Telescope. A new analysis used a Subaru deep field image to identify the location of nearly 1,300 distant galaxies. The analysis then combined the UV radiation from those galaxies to learn about their composition. A few bright supernovas can also be seen in the image.
**Credit: Subaru Telescope, NAOJ**

GRAPEVINE, Texas — The galaxies are greener on the other side of the universe, it seems: A new analysis reveals that some of the most distant galaxies ever observed are radiating green light, a finding that could deeply affect developing models of those early galaxies.

"It’s a very distinctive, intense green light that these galaxies are just pouring out," Matt Malkin, a professor of physics at the University of California, Los Angeles, who led the new research, said on Dec. 8 during a news conference at the 229th American Astronomical Society meeting.

Researchers have seen this same kind of green light coming from a few galaxies in the nearby universe, but, according to Malkin, the "shocking" part of the new analysis is in the number of galaxies involved: The green light that researchers observed in the new study appears to be coming from most or all of the galaxies that formed in the first 1 billion or 2 billion years of the universe. The finding is further evidence that scientists don't fully understand many of the characteristics of stars and galaxies that existed in this early period of the universe's lifetime. Thankfully, that's an era that a few upcoming telescopes are going to illuminate. [The History & Structure of the Universe (Infographic)]

Being green

Green is a not a typical color for a galaxy. Most galaxies that scientists observe tend to be whitish in color, with a few subtle deviations — some may have a red, orange or yellow hue if they contain a lot of cool, red stars; others appear bluish-white if they contain a lot of hot, short-lived blue stars. Regions with a lot of hot gas can have strong, distinct colors, as well. For example, regions of recent heavy star formation, like the Orion Nebula, may radiate a pinkish glow created by the presence of hydrogen. (Thanks to a technique called spectroscopy, scientists can look at the light from an object and figure out what chemicals are present.)

**A Hubble Space Telescope image of the compact green pea galaxy J0925+1403. The diameter of the galaxy is approximately 6,000 light years, and it is about twenty times smaller than the Milky Way.**
**Credit: NASA**

But there are a few exceptions in the relatively nearby universe: a sprinkling of dwarf galaxies with high rates of star formation known as "green pea galaxies" that were identified through the citizen scientist project Galaxy Zoo. The greenish tint comes specifically from oxygen atoms that have had two of their electrons ripped away (the symbol for this type of oxygen atom is O++).

For a star to produce enough energy to doubly ionize oxygen atoms, it would have to have a temperature of around 50,000 Kelvin, according to Malkin; the hottest known stars in the universe reach temperatures of 50,000 or 60,000 Kelvin. It could be that these green peas have an unusually high number of very hot stars that send their energy through oxygen-rich gas clouds and deliver a solid wallop to the oxygen atoms therein, removing two electrons from the atoms. But a full explanation for how green-pea galaxies produce such a large amount of these specific types of oxygen atoms is still a matter of debate, according to a statement from UCLA about the new work.

Green peas make up less than one hundredth of 1 percent of known galaxies. The galaxies that Malkin and colleagues studied are all very, very far away, and because light takes time to travel through space, that means that astronomers are seeing those galaxies the way they were a long, long time ago. The light from the galaxies that Malkin and his team are studying was emitted about 11 billion years ago, when the universe was only about 2 billion or 3 billion years old.

Those early galaxies were a little less chemically cluttered than modern ones. The furnace at the heart of a star fuses atoms together, creating stuff like carbon, iron and oxygen. When massive stars die, they explode and spread those elements out into space, and those explosions can also compress and heat material to create more heavy elements. After more than 10 billion years of star formation and star death, modern galaxies are a rich stew of heavy elements (astronomers characterize these stars as having "high metallicity") — a condition that wasn't present in those young galaxies.

When those heavy elements are inside a star, they tend to absorb the energy coming from the star's internal furnace, so stars in the modern universe (where there are more heavy elements) tend to be cooler than stars in the early universe. In other words, lower metallicity stars tend to be hotter and release more high energy radiation, Daniel Stark, an assistant professor of astrophysics at the University of Arizona who was not involved in the new analysis, told Space.com. Modern galaxies may certainly display a little bit of the green light indicative of O++ atoms, according to Malkin, but that light doesn't dominate the color of the galaxy.

If early galaxies didn't contain quite so many heavy elements, then there should be more of those very hot stars. That energy could pass through oxygen-rich interstellar gas clouds, and potentially create a stronger O++ green glow. Models of those early, massive stars indicate that this is likely the case, but the new finding shows that the green light is a factor of two more intense than what the models predict. Malkin said the models "depend on a lot of unknown parameters" and are currently fairly simplistic, but he estimates that the light from the O++ atoms is "four or more times stronger" than the pink light from gaseous hydrogen; most models predict that the signature of hydrogen should be equal or stronger than O++. (A study released earlier this year confirmed the presence of oxygen in one equally distant galaxy).

Malkin's new results highlight how underdeveloped those models are, Stark said.

"We can study the massive stellar populations in the Milky Way in great detail. But stars that are present in the early universe are likely to have much lower metal content," Stark said. "The massive stars in such low metallicity systems remain very poorly understood."

It's possible that the stars are actually "somehow much hotter, more energetic than even the hottest energetic stars we're familiar with today," Malkin said during his presentation at AAS. "So they're not just emitting UV photons, they're emitting extreme, high-energy UV photons. They're practically X-rays, coming out of these stars."

For comparison, the surface temperature of the sun is around 5,000 or 6,000 Kelvin and thus the central body of our nearest star is not hot enough to produce X-rays or knock two electrons off an oxygen atom. (The surrounding corona reaches temperatures of up to a million Kelvin, and can produce X-rays.)

**This image shows a planetary nebula — a very hot star near the end of its life. The greenish tint arises from the presence of oxygen atoms with two electrons removed.**
Credit: Bruce Balick (University of Washington), Jason Alexander (University of Washington), Arsen Hajian (U.S. Naval Observatory), Yervant Terzian (Cornell University), Mario Perinotto (University of Florence, Italy), Patrizio Patriarchi (Arcetri Observatory, It

Greenlighting new telescopes

One of the reasons models of ancient galaxies aren't very robust is because those galaxies are incredibly far away, and thus they're incredibly difficult to study; there's simply not a lot of observational data to go on. Malkin and his colleagues could not see the green glow from the individual galaxies they studied; by themselves, the galaxies are too faint. But by combining the observations from the Subaru Deep Field of 1,294 galaxies (a technique called "stacking"), Malkin and his colleagues were able to see the general characteristics of these galaxies. They were shocked when they saw that the green light they observed was so much stronger than what their models anticipated; in fact, it's the strongest emission line emitted by these galaxies, which means that even though hydrogen should be the most common element in these galaxies, the light they're emitting is dominated by this doubly ionized oxygen.

According to Malkin, the signal is so strong that it can't easily be explained by a few outliers; it appears that most of the young galaxies that existed at that particular point in the universe's evolution were emitting this green light.

A new generation of telescopes will be needed to answer major questions about these stars and galaxies, both Malkin and Stark said. Right now, scientists can't see the very high-energy UV light that these galaxies might be emitting. But the James Webb Space Telescope will be sensitive to the green light that Malkin and his colleagues detected; the instrument will also very quickly provide a resolution that's high enough to study those distant galaxies individually.

If that strong O++ green glow is truly characteristic of most galaxies from that time, then scientists could use that doubly ionized oxygen signal to help date the age of distant galaxies, and confirm the detection of new galaxies from that period in the universe's history.

The results of the new analysis by Malkin and his colleagues are currently undergoing review for publication.

Follow Calla Cofield @callacofield. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.