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Did Life Start With A Cosmic Splash

October 30, 2017 by  
Filed under Around The Net

A new study bolsters the theory that the chemical origins of life on Earth were midwifed by meteorites that delivered essential building blocks from space.

Meteorites slamming into warm, small ponds on the planet’s rising land surfaces more than 4 billion years ago could have delivered those building blocks into an environment where they could grow and combine into ribonucleic acid, or RNA, said Ben K.D. Pearce, an astrobiologist at Canada’s McMaster University.

The study, produced by researchers at McMaster and Germany’s Max Planck Institute for Astronomy and published in the journal Proceedings of the National Academy of Sciences, is the latest in a debate over the origins of life. Did it come from Earth itself — forming around hot undersea vents in the crust — or from small ponds on land, as Darwin theorized, with material deposited from the cosmos around it? Pearce and his colleagues come down on the “warm little pond” side, arguing that the oceans were too harsh an environment for the building blocks of life.

RNA can reproduce itself and evolve. In its current form, it takes the genetic code contained in DNA and forms proteins.

“At one time, it was the dominant life form on Earth, and likely the first life form on Earth,” Pearce told Seeker. But it’s made up of a family of molecules known as nucleobases, which stem from a reactive type of nitrogen that wouldn’t have formed on a lifeless early Earth.

Nitrogen compounds like ammonia and hydrogen cyanide likely collected on bits of dust and rock floating around the sun, snowballing into larger bodies where they could react to produce nucleobases.

“You have get these molecules from space,” he said. And when those space rocks fell to Earth, the nucleobases they held could have landed in ponds of water and reacted with other chemicals that produced RNA.

Previous studies have put forth that theory, but what Pearce and his colleagues have done is to use computer models to gauge how probable that would have been. Nucleotides would have to survive in an environment bombarded with ultraviolet light, since there was no protective ozone layer at the time, and in water that could have broken them up.

While other scientists, including the famous astronomer Carl Sagan, have theorized that cosmic dust may have delivered those precursors, Pearce said any nucleotides riding in on dust particles were likely to have been too small to survive in their new home.

But by entering data “from all facets of science,” including biology, geophysics, and astrophysics, they’ve calculated that meteorites would have been a frequent and durable enough vehicle to deliver the building blocks of life, and wet and dry cycles could have helped them bond into larger chains that formed RNA.

“There were thousands of opportunities for this to emerge from thousands of different pond environments,” Pearce said.

Pearce said the next step will be to try to test that theory in a laboratory. Researchers at McMaster, located at the western end of Lake Ontario, are building a “planet simulator” in which they hope to reproduce the conditions of a primeval Earth and see whether they can get the same results.

Courtesy-Space

Is Planet 9 The Missing Super-Earth

October 19, 2017 by  
Filed under Around The Net

Planet Nine is out there, and astronomers are determined to find it, according to a new statement from NASA. In fact, mounting evidence suggests it’s hard to imagine our solar system without the unseen world. 

The hypothetical planet is believed to be about 10 times more massive than Earth and located in the dark, outer reaches of the solar system, approximately 20 times farther from the sun than Neptune is. While the mysterious world still has yet to be found, astronomers have discovered a number of strange features of our solar system that are best explained by the presence of a ninth planet, according to the NASA statement. 

“There are now five different lines of observational evidence pointing to the existence of Planet Nine,” Konstantin Batygin, a planetary astrophysicist at the California Institute of Technology (Caltech) in Pasadena, said in the statement. “If you were to remove this explanation and imagine Planet Nine does not exist, then you generate more problems than you solve. All of a sudden, you have five different puzzles, and you must come up with five different theories to explain them.”

In 2016, Batygin and co-author Mike Brown, an astronomer at Caltech, published a study that examined the elliptical orbits of six known objects in the Kuiper Belt, a distant region of icy bodies stretching from Neptune outward toward interstellar space. Their findings revealed that all of those Kuiper Belt objects have elliptical orbits that point in the same direction and are tilted about 30 degrees “downward” compared to the plane in which the eight official planets circle the sun, according to the statement. 

Using computer simulations of the solar system with a Planet Nine, Batygin and Brown also showed that there should be even more objects tilted a whopping 90 degrees with respect to the solar plane. Further investigation revealed that five such objects were already known to fit these parameters, the researchers said. 

Since then, the astronomers have found new evidence that further supports the existence of Planet Nine. With help from Elizabeth Bailey, an astrophysicist and planetary scientist at Caltech, the team showed that Planet Nine’s influence might have tilted the planets of our solar system, which would explain why the zone in which the eight major planets orbit the sun is tilted by about 6 degrees compared to the sun’s equator.

“Over long periods of time, Planet Nine will make the entire solar-system plane precess, or wobble, just like a top on a table,” Batygin said in the statement. 

Finally, the researchers demonstrate how Planet Nine’s presence could explain why Kuiper Belt objects orbit in the opposite direction from everything else in the solar system. 

“No other model can explain the weirdness of these high-inclination orbits,” Batygin said in the statement. “It turns out that Planet Nine provides a natural avenue for their generation. These things have been twisted out of the solar system plane with help from Planet Nine and then scattered inward by Neptune.”

Going forward, the researchers plan to use the Subaru Telescope at Mauna Kea Observatory in Hawaii to find Planet Nine, and then deduce where the mysterious world came from. 

The most common type of planets discovered around other stars in our galaxy has been what astronomers call “super Earths” — rocky worlds that are larger than Earth but smaller than Neptune. However, no such planet has yet been discovered in our solar system, meaning that Planet Nine could be our missing “super Earth,” the researchers said. 

Follow Samantha Mathewson @Sam_Ashley13. Follow us @Spacedotcom, Facebook

 

Courtesy-Space

Is NASA Planning Another Mission To Saturn

September 26, 2017 by  
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Humanity’s light at Saturn has gone out.

NASA’s robotic Cassini spacecraft burned up in the ringed planet’s atmosphere Friday morning (Sept. 15), ending a remarkable 13-year run at Saturn that has revolutionized scientists’ understanding of the outer solar system and its potential to host life.

For example, Cassini discovered methane seas on Saturn’s huge moon Titan and geysers of water vapor blasting from fellow moon Enceladus. Both of these moons are worthy of much further study, as is the ringed planet itself and the diverse Saturn system as a whole, Cassini team members said. 

“We left the world informed, but still wondering, and I couldn’t ask for more,” Cassini project manager Earl Maize, of NASA’s Jet Propulsion Laboratory in Pasadena, California, said during a news conference Wednesday (Sept. 13). “We’ve got to go back — we know it.”

And various research teams are indeed working on plans to return to Saturn. In fact, five such concepts are in the running for NASA’s next New Frontiers mission — the same type flown by the agency’s New Horizons Pluto probe, Juno Jupiter orbiter and OSIRIS-REx asteroid sample-return craft.

During its intentional death dive Friday, Cassini briefly became the first-ever Saturn atmospheric probe. One of the proposed New Frontiers missions would pick up on, and greatly extend, the last measurements Cassini ever made.

The SPRITE (Saturn Probe Interior and Atmosphere Explorer) spacecraft would plunge into Saturn’s thick atmosphere, characterizing its composition and structure for about 90 minutes before breaking apart and burning up. (Cassini, which was not built for such work, lasted just a minute or two during its dive.)

“Fundamental measurements of the interior structure and noble-gas abundances of Saturn are needed to better constrain models of solar system formation, as well as to provide an improved context for exoplanet systems,” principal investigator Amy Simon, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and her colleagues wrote in a mission description last year.

SPRITE would make such measurements, and its data would help “ground-truth” data Cassini gathered about Saturn from afar over the years, the scientists added

Cassini studied Titan closely over the course of 127 targeted flybys. The Saturn orbiter also carried a piggyback European lander called Huygens, which touched down on the 3,200-mile-wide (5,150 kilometers) moon in January 2005. In the process, it became the first probe ever to pull off a soft landing on a body in the outer solar system.

Observations by both Cassini and Huygens revealed Titan in all its otherworldly glory. Hydrocarbon rain falls from the huge moon’s sky, pooling in lakes and seas of methane, some of which are as big as Earth’s Black Sea. Complex organic chemicals — the carbon-containing building blocks of life as we know it — waft about in Titan’s thick, nitrogen-dominated atmosphere and eventually drift down to the moon’s surface.

It’s possible that this bizarre landscape could harbor life, astrobiologists say. And Cassini’s work suggests that the big moon may have another potentially habitable environment as well: a salty ocean of liquid water buried beneath the crust. (Indeed, Cassini was directed to its doom primarily to ensure that it would never contaminate Titan or Enceladus with microbes from Earth.)

A proposed New Frontiers mission called Oceanus would investigate both of these environments, taking a variety of measurements from its perch in orbit around Titan. For example, the probe would characterize the organics in the moon’s atmosphere and help researchers determine how thick and rigid Titan’s crust is, and whether it is convecting internal heat to the surface.

Oceanus “would follow up on Cassini’s amazing discoveries and assess Titan’s habitability by following the organics through the methanologic cycle and assessing exchange processes between the atmosphere, surface and subsurface,” the concept mission’s planners wrote in a description of the project, which they presented earlier this year at the 48th Lunar and Planetary Science Conference in The Woodlands, Texas.

Also in the New Frontiers running is Titan Dragonfly, which would send a drone to study the moon from the air and the ground.

“Heavier-than-air flight is substantially easier [on Titan]” than on Earth, Dragonfly principal investigator Elizabeth Turtle, a planetary scientist at the Johns Hopkins University Applied Research Laboratory in Maryland, told Space.com earlier this year. (Titan’s atmosphere is considerably thicker than that of Earth, but the moon’s gravity is just 14 percent as strong as our planet’s.)

“That means we can take a really capable lander and move it by a few tens of kilometers in a single flight, and hundreds of kilometers over the time of the mission,” Turtle added.

The drone would study the composition of Titan’s organics in detail, at a variety of different locations.

“Dragonflyis a truly revolutionary concept providing the capability to explore diverse locations to characterize the habitability of Titan’s environment, investigate how far prebiotic chemistry has progressed, and search for chemical signatures indicative of water-based and/or hydrocarbon-based life,” Turtle and her colleagues wrote about the potential mission in their presentation at the 48th Lunar and Planetary Science Conference.

The other two Saturn-oriented New Frontiers proposals target 313-mile-wide (504 km) Enceladus, whose geysers were a revelation to the Cassini team, NASA officials and space scientists in general.

“When we observed the southern hemisphere [of Enceladus] and geysers of water spewing out into the Saturn system, it amazed us and began changing the way we view the habitability — or potential habitability — of moons in the outer part of our solar system,” Jim Green, chief of NASA’s Planetary Science Division at the agency’s headquarters in Washington, D.C., said at Wednesday’s news conference.

That’s because the water in Enceladus’ geysers is apparently coming from an ocean of liquid water that sloshes beneath the frigid moon’s icy crust. Cassini observations suggest that this ocean may even have a chemical energy source that could support life as we know it.

But researchers want to learn more about the ocean, and the geysers’ plume provides a great way of doing so. One of the New Frontiers candidates, known as Enceladus Life Finder (ELF), would zoom through this plume repeatedly, collecting and analyzing molecules. ELF would look for complex organic compounds that could be a sign of prebiotic chemistry — or perhaps even of life itself.

“It’s free samples,” principal investigator Jonathan Lunine, of Cornell University, told Space.com in 2015, when ELF was competing for a slot in NASA’s Discovery program of low-cost, extremely focused missions. (In January of this year, NASA chose the asteroid-studying Lucy and Psyche missions as its next Discovery projects.) “We don’t need to land, drill, melt or do anything like that.” 

Cassini did some plume sampling of its own, but ELF would sport more-sensitive mass spectrometers than its predecessor did, ELF team members have said. (Cassini’s handlers didn’t know about Enceladus’ geysers before launch, so they didn’t put any life-hunting gear aboard the craft.)

Not much has been publicly revealed about the final Saturn-oriented New Frontiers proposal. But its name — Enceladus Life Signatures and Habitability — suggests that it would also be a plume-sampling mission.

You can learn more about all 12 New Frontiers candidates — the other seven of which would target Venus, a comet or Earth’s moon — in this excellent synopsis by The Planetary Society’s Van Kane.

NASA is expected to cull the New Frontiers proposals to a handful of finalists before the end of the year and announce the selected mission sometime in 2019. (That mission will have a cost cap of $850 million, excluding launch, and will lift off by 2025.)

So, it’s too soon to say if any of the Saturn-centric missions will ever get off the ground. But fans of the ringed planet may be heartened by one of Green’s comments at Wednesday’s news conference.

Cassini’s discoveries “will live on for many decades afterwards, and already they’re beckoning us to go back,” Green said. Between NASA’s Voyager mission, which visited Saturn with back-to-back flybys in 1980 and 1981, “and Cassini was 30 years,” he said, “and I believe that will be much shorter the next time around.”   

 

Courtesy-Space

Cassini Captures On Saturn’s Rings

September 19, 2017 by  
Filed under Around The Net

NASA’s Cassini spacecraft has captured a spectacular photo of a perplexing wave structure in one of Saturn’s rings as the probe heads into its final days at the gas giant. 

The rings of Saturn are embedded with billions of water-ice particles ranging in size from grains of sand to monstrous chunks. Saturn’s rings also feature waves that propagate outward in spiral patterns. 

The new image from Cassini captures an up-close view of a spiral density wave visible in Saturn’s B ring. The wave structure is a buildup of material that has formed from the gravitational pull of Saturn’s moons, NASA officials said.

The density wave visible in Saturn’s B ring originates 59,796 miles (96,233 kilometers) from the planet, where the “ring particles orbit Saturn twice for every time the moon Janus orbits

In the new image, the wave structure — aptly named the Janus 2:1 spiral density wave — appears to ricochet outward, away from Saturn and toward the upper-left corner of the photo, creating hundreds of bright wave crests. 

The density wave is generated by the gravitational pull of Saturn’s moon Janus. However, Janus and one of Saturn’s other moons, Epimetheus, share practically the same orbit and swap places every four years, creating a new crest in the wave, according to the statement. 

As a result, the distance between any pair of crests corresponds to four years’ worth of wave oscillations. This pattern represents the orbital history of Janus and Epimetheus, much like the rings of a tree reveal information about its growth. 

Based on this idea, the crests of the wave at the very upper left of the new Cassini image correspond to the positions of Janus and Epimetheus during the Saturn flybys of NASA’s twin Voyager probes in 1980 and 1981, according to the statement.

The recent images of Saturn’s B ring were taken on June 4, 2017, using Cassini’s narrow-angle camera. After 20 historic years in space, the Cassini mission will come to a close on Sept. 15, when the spacecraft will intentionally dive into Saturn’s atmosphere. 

 

Courtesy-Space

NASA Researching The Stripes On Venus

September 8, 2017 by  
Filed under Around The Net

A proposed NASA mission could solve the mystery of how Venus got its stripes.  

To the human eye, the cloud tops of Venus may look smooth and monochrome, but in ultraviolet light, dark and light streaks decorate Earth’s sister planet. The cause of these stripes is unknown, and Venus’ thick, blistering atmosphere (which is hot enough to melt lead) has made the world a difficult planet to study.

Now, NASA has invested money in a proposed mission that could help researchers figure out what causes the Venusian bands, according to a statement from the agency. The mission would use a very small space probe, equipped with cutting-edge technology, the statement said. 

The CubeSat UV Experiment, or CUVE, would orbit Venus over the poles and study the planet’s atmosphere in ultraviolet and visible wavelengths of light. Venus’ cloud tops scatter visible light, which makes the planet look like a smooth, featureless globe. But some of the material in the clouds absorbs ultraviolet light, creating the dark stripes, according to the statement. 

“The exact nature of the cloud-top absorber has not been established,” Valeria Cottini, CUVE principal investigator and a researcher at the University of Maryland, said in the statement. “This is one of the unanswered questions, and it’s an important one.”

One hypothesis that could explain how Venus gets its stripes posits that material from
“deep within Venus’ thick cloud cover” could rise into the cloud tops via convection (in which hot material in a fluid naturally rises above cold material). Winds would then disperse the material along breezy pathways, creating streaks. 

The CUVE team has now received additional funding from NASA’s Planetary Science Deep Space SmallSat Studies, or PSDS3, to further develop the mission concept. 

The spacecraft would be a cubesat, or a miniature satellite that typically consists of single unites that are about 10 inches (25.4 centimeters) cubed. CUVE would include a miniaturized ultraviolet camera “to add contextual information and capture the contrast features,” according to the statement, and a spectrometer to study the UV and visible light in detail.  

CUVE could also carry a “lightweight telescope equipped with a mirror made of carbon nanotubes in an epoxy resin,” officials said in the statement. “To date, no one has been able to make a mirror using this resin.” 

Planet Venus is often likened to Earth but with a runaway greenhouse problem. The 2nd planet from the sun is hot shrouded with deadly clouds. Those are hints. Now test your knowledge of Venus facts.

The nanotubes and epoxy would be poured into a mold, heated to harden the epoxy and then coated with a reflective material. This telescope would be lightweight and easy to reproduce, and would not require polishing, which is typically time-consuming and expensive, according to the statement.

“This is a highly focused mission — perfect for a cubesat application,” Cottini said in the statement. She later added, “CUVE would complement past, current and future Venus missions and provide great science return at lower cost.”

Courtesy-Space

The Voyage Of Cassini-Huygens

August 29, 2017 by  
Filed under Around The Net

The Cassini spacecraft has been orbiting Saturn since 2004. The mission is known for discoveries such as finding jets of water erupting from Enceladus, and tracking down a few new moons for Saturn. Now low on fuel, the spacecraft will make a suicidal plunge into the ringed planet in 2017 and capture some data about Saturn’s interior on the way. (This will avoid the possibility of Cassini crashing someday onto a potentially habitable icy moon, such as Enceladus or Rhea.)

The ambitious mission is a joint project among several space agencies, which is a contrast from the large NASA probes of the past such as Pioneer and Voyager. In this case, the main participants are NASA, the European Space Agency and Agenzia Spaziale Italiana (the Italian space agency).

Cassini is the first dedicated spacecraft to look at Saturn and its system. It was named for Giovanni Cassini, a 17th-century astronomer who was the first to observe four of Saturn’s moons — Iapetus (1671), Rhea (1672), Tethys (1684) and Dione (1684). 

Before this spacecraft came several flybys of Saturn by Pioneer 11 (1979), Voyager 1 (1980) and Voyager 2 (1981). Some of the discoveries that came out of these missions included finding out that Titan’s surface can’t be seen in visible wavelengths (due to its thick atmosphere), and spotting several rings of Saturn that were not visible with ground-based telescopes.

It was shortly after the last flyby, in 1982, that scientific committees in both the United States and Europe formed a working group to discuss possible future collaborations. The group suggested a flagship mission that would orbit Saturn, and would send an atmospheric probe into Titan. However, there was a difficult “fiscal climate” in the early 1980s, NASA’s Jet Propulsion Laboratory noted in a brief history of the mission, which pushed approval of Cassini to 1989.

The Europeans and the Americans each considered either working together, or working solo. A 1987 report by former astronaut Sally Ride, for example, advocated for a solo mission to Saturn. Called “NASA’s Leadership and America’s Future in Space,” the report said that studying the outer gas giant planets (such as Saturn) help scientists learn about their atmospheres and internal structure. (Today, we also know that this kind of study helps us predict the structure of exoplanets, but the first exoplanets were not discovered until the early 1990s.) 

“Titan is an especially interesting target for exploration because the organic chemistry now taking place there provides the only planetary-scale laboratory for studying processes that may have been important in the prebiotic terrestrial atmosphere,” the report added, meaning that on Titan is chemistry that could have been similar to what was present on Earth before life arose.

Cassini’s development came with at least two major challenges to proceeding. By 1993 and 1994, the mission had a $3.3 billion price tag (roughly $5 billion in 2017 dollars, or about half the cost of the James Webb Space Telescope.) Some critics perceived this as overly high for the mission. In response, NASA pointed out that the European Space Agency was also contributing funds, and added that the technologies from Cassini were helping to fund lower-cost NASA missions such as the Mars Global Surveyor, Mars Pathfinder and the Spitzer Space Telescope, according to JPL. 

Cassini also received flak from environmental groups who were concerned that when the spacecraft flew by Earth, its radioisotope thermoelectric generator (nuclear power) could pose a threat to our planet, JPL added. These groups filed a legal challenge in Hawaii shortly before launch in 1997, but the challenge was rejected by the federal district court in Hawaii and the Ninth Circuit Court of Appeals.

To address concerns about the spacecraft’s radioisotope thermoelectric generators, which are commonly used for NASA missions, NASA responded by issuing a supplementary document about the flyby and detailing the agency’s methodology for protecting the planet, saying there was less than a one-in-a-million chance of an impact occurring.

Cassini didn’t head straight to Saturn. Rather, its mission involved complicated orbital mechanics. It went past several planets — including Venus (twice), Earth and Jupiter — to get a speed boost by taking advantage of each planet’s gravity.

The nearly 12,600-lb. (about 5,700 kilograms) spacecraft was hefted off Earth on Oct. 15, 1997. It went by Venus in April 1998 and June 1999, Earth in August 1999 and Jupiter in December 2000.

Cassini settled into orbit around Saturn on July 1, 2004. Among its prime objectives were to look for more moons, to figure out what caused Saturn’s rings and the colors in the rings, and understanding more about the planet’s moons.

Perhaps Cassini’s most detailed look came after releasing the Huygens lander toward Titan, Saturn’s largest moon. The lander was named for Dutch scientist Christiaan Huygens, who in 1654 turned a telescope toward Saturn and observed that its odd blob-like shape — Galileo Galilei had first seen the shape in a telescope and drew it in his notebook as something like ears on the planet — was in fact caused by rings. 

The Huygens lander descended through the mysterious haze surrounding the moon and landed on Jan. 14, 2005. It beamed information back to Earth for nearly 2.5 hours during its descent, and then continued to relay what it was seeing from the surface for 1 hour 12 minutes.

In that brief window of time, researchers saw pictures of a rock field and got information back about the moon’s wind and gases on the atmosphere and the surface.

One of the defining features of Saturn is its number of moons. Excluding the trillions of tons of little rocks that make up its rings, Saturn has 62 discovered moons as of September 2012. NASA lists 53 named moons on one of its websites.

In fact, Cassini discovered two new moons almost immediately after arriving (Methone and Pallene) and before 2004 had ended, it detected Polydeuces.

As the probe wandered past Saturn’s moons, the findings it brought back to Earth revealed new things about their environments and appearances. Some of the more notable findings include:

Saturn has not gone ignored, either. For example, in 2012, a NASA study postulated that Saturn’s jet streams in the atmosphere may be powered by internal heat, instead of energy from the sun. Scientists believe that heat brings up water vapor from the inside of the planet, which condenses as it rises and produces heat. That heat is believed to be behind jet stream formation, as well as that of storms.

Mission extension and end

Cassini was originally slated to last four years at Saturn, until 2008, but its mission has been extended multiple times. Its last and final leg was called the Cassini Solstice Mission, named because the planet and its moons reached the solstice again toward the mission end. Saturn orbits the sun every 29 Earth-years. With Cassini’s mission lasting 13 years, this meant that the spacecraft observed almost half of Saturn’s seasonal change as the planet went around its orbit.

In 2016, the spacecraft was set on a series of final maneuvers to provide close-up views of the rings, with the ultimate goal of plunging Cassini into Saturn on Sept. 15, 2017. This protected Enceladus and other potentially habitable moons from the (small) chance of Cassini colliding with the surface, spreading Earth microbe.

Major milestones of the finale included:

Ring-grazing orbits: Every week between Nov. 30, 2016, and April 22, 2017, Cassini did loops around Saturn’s poles to look at the outer edge of the rings, to learn more about their particles, gases and structure. It also observed small moons in this region, including Atlas, Daphnis, Pan and Pandora.

On April 22, 2017, Cassini made the final flyby of Titan. The flyby was done in such a way to change Cassini’s orbit so that it began 22 dives (once a week) between the planet and its rings. This was the first time any spacecraft explored this zone, and it entailed some risk because the orbit brought it between the outer part of the atmosphere and the inner zone of the rings (where it is at risk of striking particles or gas molecules). 

On Sept. 15, 2017, Cassini will make a suicidal plunge into Saturn, taking measurements for as long as its instruments can make communications back to Earth.

Some of the science Cassini performed during this period included creating maps of the planet’s gravity and magnetic fields, estimating how much material is in the rings, and taking high-resolution images of Saturn and its rings from close-up. 

The spacecraft made an interesting discovery from its new vantage point. It found that Saturn’s magnetic field is closely aligned with the planet’s axis of rotation, which baffled scientists because of how they think magnetic fields are generated — through a difference of tilt between the magnetic field and a planet’s rotation. As of late July 2017, however, scientists planned to gather more data to see if perhaps Saturn’s internal processes confused their measurements.

 

Courtesy-Space

 

Can A Supernova Form In A Heavy Metal Galaxy

August 8, 2017 by  
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The most powerful exploding stars are popping up in unexpected places, new research indicates. It turns out that these superbright “rebel” supernovas can form in “heavy metal” areas, using elements heavier than hydrogen and helium, scientists said in the new study.

Supernovas happen when huge stars run out of fuel and collapse, creating an explosion that can briefly outshine their host galaxy. Thousands of supernovas have happened in the past decade, but only about 50 of them were “superluminous,” meaning they were 100 times brighter than usual supernovas.

New research zeroes in on one supernova, called SN 2017egm, which exploded May 23 within view of the European Space Agency’s Gaia satellite, which monitors star positions. If it had exploded in the Milky Way, it would have appeared as bright as the full moon does from Earth, researchers said in a statement.

In fact, SN 2017egm was not only superluminous, but superclose: At just 420 million light-years away, it was three times closer than any other observed supernova of its type.

More strangely, the supernova exploded in a spiral galaxy with a high concentration of elements heavier than hydrogen and helium. (These elements are called “metals” in astronomy.) Before this, researchers had found superluminous supernovas in dwarf galaxies, which have low metal content, according to the statement. 

This work marks the first time astronomers have identified a superluminous supernova that exploded in a large spiral galaxy, and in a metal-rich area. So when it comes to forming these explosions, a lack of metals may not be as important as astronomers had thought.

“Superluminous supernovas were already the rock stars of the supernova world,” Matt Nicholl, lead author of the study and an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, said in the statement. “We now know that some of them like heavy metal, so to speak, and explode in galaxies like our own Milky Way.”

The researchers also investigated what makes SN 2017egm so bright. They concluded that the supernova may be powered by a rapidly spinning dead star called a magnetar. Such ultradense, spinning neutron stars created by supernovas could continue to generate magnetic power that would heat up the expanding gas left over from the supernova.

SN 2017egm shares magnetar properties with other superluminous supernovas, but the researchers noted that the newly discovered supernova does have some differences.

For example, SN 2017egm might have ejected less mass than its supernova counterparts because its massive star might have shed mass before exploding. Also, the spin rate of SN 2017egm’s magnetar may be slower than usual.

The supernova is currently invisible to astronomers because it is too close to the sun, but it will re-emerge on Sept. 16 after more than two months of obscurity.

“This should break all records for how long a superluminous supernova can be followed,” Raffaella Margutti, study co-author and an astronomer at Northwestern University, said in the statement. “I’m excited to see what other surprises this object has in store for us.”

The research was accepted for publication in The Astrophysical Journal Letters, and it is available online at arXiv.org. Nicholl’s team studied the supernova on June 18 with the 60-inch (152 centimeters) telescope at the Smithsonian Astrophysical Observatory’s Fred Lawrence Whipple Observatory in Arizona.

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Astronomers Gain Insight Into Black Hole With Powerful Space Explosion

August 2, 2017 by  
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An ultrapowerful, superfast explosion in space is providing new insight into how dying stars turn into black holes.

An international team of researchers looked at a gamma-ray explosion called GRB 160625B that brightened the sky in June 2016. Gamma-ray bursts are among the most powerful explosions in the universe, but they are typically tough to track because they are very short-lived (sometimes lasting just a few milliseconds). 

“Gamma-ray bursts are catastrophic events, related to the explosion of massive stars 50 times the size of our sun,” said Eleonora Troja, lead author of the new study and an assistant research scientist in astronomy at University of Maryland. “If you ranked all the explosions in the universe based on their power, gamma-ray bursts would be right behind the Big Bang.” [Record Breaking Gamma-Ray Burst Captured By Fermi (Video)]

“In a matter of seconds, the process can emit as much energy as a star the size of our sun would in its entire lifetime,” Troja said in a statement. “We are very interested to learn how this is possible.”

Two key findings emerged from the observations, gathered using several ground- and space-based telescopes. The first step was better model what happens as the dying star collapses. The data suggests that the black hole creates a strong magnetic field that initially overwhelms jets of matter and energy formed because of the explosion. Then, the magnetic field breaks down, the study authors said.

In the next phase, the magnetic field diminishes, allowing matter to dominate the jets. Before, scientists thought that jets could be dominated only by the magnetic field or matter — not both.

Another insight concerns what kind of radiation is responsible for the bright phase at the beginning of the burst, which astronomers call the “prompt” phase. Before, several types of radiation were considered, including so-called blackbody radiation (heat emission from an object) and inverse Compton radiation (which happens when accelerated particles transfer energy to photons), according to the statement. 

It turns out that a phenomenon called synchrotron radiation is behind the prompt phase. This kind of radiation happens when electrons accelerate in a curved or spiral pathway, propelled along by an organized magnetic field.

“Synchrotron radiation is the only emission mechanism that can create the same degree of polarization and the same spectrum we observed early in the burst,” Troja said. 

The fading afterglow of GRB 160625B, a gamma-ray burst recorded in June 2016. Here, data from Arizona State University’s Reionization And Transients Infrared (RATIR) camera, on a telescope at Mexico’s National Astronomical Observatory in Baja California, shows the burst from June 26 to Aug. 20, 2016.

“Our study provides convincing evidence that the prompt gamma-ray burst emission is driven by synchrotron radiation,” she added. “This is an important achievement because, despite decades of investigation, the physical mechanism that drives gamma-ray bursts had not yet been unambiguously identified.”

Gathering information about GRB 160625B required many telescopes to work together quickly. NASA’s Fermi Gamma-ray Space Telescope first saw the explosion, and the ground-based Russia’s MASTER-IAC telescope, which is located at the Teide Observatory in Spain’s Canary Islands, quickly joined with observations in optical light.

MASTER-IAC’s observations were key to understanding the evolution of GRB 160625B’s magnetic field, the research team said. The magnetic field can influence polarized light (light waves that vibrate in a single plane) emanating from the burst. In a rare achievement, the telescope measured the proportion of polarized light to total light through almost the entire explosion.

“There is very little data on polarized emission from gamma-ray bursts. This burst was unique because we caught the polarization state at an early stage,” said study co-author Alexander Kutyrev, an associate astronomy research scientist at the University of Maryland and an associate scientist at NASA’s Goddard Space Flight Center.

“This is hard to do because it requires a very fast reaction time, and there are relatively few telescopes with this capability,” Kutyrev added. “This paper shows how much can be done, but to get results like this consistently, we will need new rapid-response facilities for observing gamma-ray bursts.”

Other participating telescopes included NASA’s Swift Gamma-ray Burst Mission (X-ray and ultraviolet), the multi-institution Reionization and Transient Infrared/Optical Project camera (at Mexico’s National Astronomical Observatory in Baja California), the National Radio Astronomy Observatory’s Very Large Array in New Mexico, and the Commonwealth Scientific Industrial Research Organisation’s Australia Telescope Compact Array.

The new research was detailed today (July 26) in the journal Nature.

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Is Titan A Better Location Than Mars For Colonization

July 26, 2017 by  
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NASA and Elon Musk’s SpaceX are focused on getting astronauts to Mars and even one day establishing a colony on the Red Planet — but what if their attention is better directed elsewhere? A new paper in the Journal of Astrobiology & Outreach suggests that humans should instead establish a colony on Titan, a soupy orange moon of Saturn that has been likened to an early Earth, and which may harbor signs of “life not as we know it.”

“In many respects, Saturn’s largest moon, Titan, is one of the most Earth-like worlds we have found to date,” NASA says on its website. “With its thick atmosphere and organic-rich chemistry, Titan resembles a frozen version of Earth, several billion years ago, before life began pumping oxygen into our atmosphere.”

To be clear, Titan could have microbes — or, at the least, chemistry that resembles prebiotic life — but it is no Earth. The moon is perpetually covered in an orange cloud, and its atmosphere is not human-friendly. But Titan’s gravity is walkable (14 percent that of Earth), radiation on the surface is less than on Mars due to its thick clouds, and it offers various sources from which visitors might generate energy.

Hosted by Hanneke Weitering On July 20, 1969, human beings walked on the moon for the very first time! Apollo 11 astronauts Neil Armstrong and Buzz Aldrin exited their lunar lander and planted their moon boots on the lunar surface at about 11 p.m. Eastern Time. Armstrong led the way down the ladder. When he took his first step, he famously said, “That’s one small step for a man…one giant leap for mankind.” Once they found their footing, they got straight to work. They inspected the spacecraft to look for any damage from the landing, set up cameras, collected moon rocks and planted the American flag into the soil. They also strolled around the moon to assess the mobility of their spacesuits.

As the paper’s author, Amanda Hendrix, pointed out in a previous book that she co-authored, Beyond Earth: Our Path to a New Home in the Planets, Titan has massive deposits of hydrocarbons — compounds generally associated with petroleum and gas. Data from NASA’s Cassini probe has shown that Titan has hundreds of times more liquid hydrocarbons than all of the known oil and natural gas reserves on Earth.

Beyond Earth points out that people on Titan could get energy from these compounds if they use a separate combustion source that helps circumvent that fact that there’s no oxygen in the moon’s atmosphere. But Hendrix’s new research also discusses other ways of generating chemical energy, such as treating acetylene (an abundant compound) with hydrogen.

“In this paper, I wanted to dig into the chemical energy options a bit deeper and also look into alternative energy possibilities,” said Hendrix, a staff scientist at the non-profit Planetary Science Institute. “My co-author, Yuk Yung, and I looked at chemical, nuclear, geothermal, solar, hydropower, and wind power options at Titan. The paper is designed to be a high-level first look at some of these topics.”

While Hendrix said it’s possible to generate such energy using technology that we have available today, she noted that there are ways that we could get even more out of Titan’s environment with the proper study. For example, more solar power would be generated if we learned about the capabilities of different photovoltaic cell materials — and most importantly, how they would behave on Titan.

Hydro power would require better mapping of Titan’s abundant lake regions, including their topography and their flow rate. Even wind power would require some research into airborne wind turbines — but Hendrix said all of these options are promising.

“I imagine that, as here on Earth, a combination of energy sources will be useful on Titan,” she said. “In particular, solar energy (using large arrays) and wind power (using airborne wind turbines) may be particularly effective.”

Delivered properly, the energy needs would be more than enough for a small outpost. Instead of just sending humans on a one-shot mission to look for life on the surface, for example, Hendrix envisions a future that could generate power for years. One scenario — solar arrays over 10 percent of Titan’s surface area — would generate power needs of a population of roughly 300 million, equivalent to that of the United States.

“This is just an initial estimate, of course, but what we’re talking about is something much larger than a short-term human science mission to Titan,” Hendrix said.

With NASA’s stated goal of sending humans to Mars by the 2030s, however, space agencies remain focused on Mars exploration. While the Cassini robotic mission at Saturn and its moons wraps up observations this September, NASA and the European Space Agency are planning even more missions to Mars in the coming years. Saturn doesn’t really figure into the plans, although NASA is thinking about eventual missions to Uranus, Neptune, and Jupiter’s moon Europa.

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Does An Asteroid Start Off As A Giant Mud Rock

July 21, 2017 by  
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The most common asteroids in the solar system may have started out as giant balls of mud, rather than as rocks, as scientists previously thought, a new study finds.

Such mud balls could still exist today in the heart of the largest asteroids, according to the study.

More than 75 percent of known asteroids are carbonaceous in composition; these grayish asteroids probably consist of clay and stony rocks, and inhabit the main belt’s outer regions

One key reason scientists investigate carbonaceous asteroids is that they were probably the building blocks of the rocky planets of the solar system, said study lead author Philip Bland, a planetary scientist at the Curtin University of Technology in Australia. Analyzing these giant rocks could shed light on the origins of Earth, Mars and the other terrestrial planets.

However, the way carbonaceous asteroids formed in the early days of the solar system is still mysterious. “There have probably been about a dozen different models to explain the origins of these primitive objects over the years, and they’ve all been limited in one way or another,” Bland told Space.com.

Researchers have observed carbonaceous asteroids and analyzed meteorites thought to come from them to glean details about their composition. However, scientists had trouble devising a model that could explain all of these features of the asteroids, Bland said.

“For instance, one model might find there is a lot of water getting circulated around inside the asteroids, so they could lose heat — which would explain why meteorites from these asteroids appear to have experienced alterations at relatively low temperatures,” Bland said. “However, if you have a lot of water circulating inside asteroids, it would strip elements from the rock, and you would get a very different chemical composition than what we see in the meteorites.”

“If there wasn’t water inside the asteroids, you wouldn’t mess up the chemistry we see, but the asteroids would not lose heat as easily,” Bland added. “One way around that is to have the asteroids be smaller so they would cool down more easily, but we don’t see that today.”

All of these previous models assumed the asteroids had lithified — that is, had become rock. “Most people look at meteorites, and they’re rocks. So the natural thing to assume would be that the asteroids they came from were rocks, too,” Bland said. “We were interested in seeing what happened if we deleted that assumption.”

Prior work suggested that carbonaceous asteroids formed from round, porous mineral pellets known as chondrules, as well as fine-grained dust, and ice. When pockets of these materials got pulled together by their own gravity, they would not have become rock, the researchers suggested. Instead, when radioactive materials inside the dust and chondrules melted the ice, the result would have been a sludgy mud, they said.

“When you stop to think about it, there’s no reason that asteroids would be rocks right at the beginning,” Bland said.

The scientists devised computer models that simulated how pockets of dust, chondrules and ice might act with different concentrations of these various ingredients and the density at which these materials were packed together. They found that not only could asteroids emerge from these building blocks without lithification, but the way in which mud churned in these mud balls could help explain the chemical and thermal details seen from carbonaceous asteroids.

“I feel like this helps plug a gap in knowledge when it comes to the question of what happened inside what are amongst the most important objects in the history of our solar system,” Bland said.

After the mud balls formed, they could have lithified in various ways. For instance, if these mud balls hit each other, the force of the impacts would have generated heat that could have welded the components of these mud balls together into rock, Bland said.

As for whether the mud balls might still exist in the solar system, when the researchers modeled Ceres, the largest asteroid, they “found there was a reasonable chance of temperatures above freezing in its interior, so there could still be quite a bit of a mud ball inside Ceres,” Bland said.

Future research could explore how the other kinds of asteroids in the solar system were born, and how asteroids in other star systems might arise and, in turn, influence the formation of alien planets, Bland said.

Bland and his colleague Bryan Travis at the Planetary Science Institute in Tucson, Arizona, detailed their findings online July 14 in the journal Science Advances.

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Did Astronomers Find More Evidence That Planet 9 Exist

July 19, 2017 by  
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A new salvo has been fired in the back-and-forth debate about the existence of Planet Nine.

In 2014, astronomers Scott Sheppard and Chadwick Trujillo suggested that a giant unseen “perturber” may lurk in the far outer solar system. The duo based this hypothesis on peculiarities in the orbits of the dwarf planet Sedna, the newfound object 2012 VP113 and several other bodies beyond the orbit of Neptune (trans-Neptunian objects, or TNOs).

The case grew in January 2016, when astronomers Konstantin Batygin and Mike Brown found evidence that the orbits of additional TNOs had been sculpted. Batygin and Brown dubbed the hypothetical perturber “Planet Nine” and calculated that, if the world exists, it’s likely about 10 times more massive than Earth and lies perhaps 600 astronomical units (AU) from the sun. (One AU is the average Earth-sun distance — about 93 million miles, or 150 million kilometers.

Then, last summer, Sheppard and Trujillo found two new TNOs that Planet Nine may have tugged on, increasing the number of possibly affected bodies yet again.

But a team of researchers with the Outer Solar System Origins Survey (OSSOS) project recently cast doubt on the strength of all this evidence. The apparent “clustering” seen in the TNO orbits could simply result from observational biases, the OSSOS team reported in a paper that has been accepted for publication in The Astronomical Journal.

And that’s where the most recent salvo comes in. (But keep in mind that the above paragraphs provide an incomplete recounting; there have been many Planet Nine studies published over the past 18 months.) Two astronomers from the Complutense University of Madrid in Spain studied 22 “extreme” TNOs (ETNOs), which orbit the sun at an average distance of at least 150 AU and never get closer than Neptune. (Neptune lies about 30 AU from the sun and orbits on a roughly circular path.)

Specifically, the duo analyzed the ETNOs’ “nodes,” the two points at which the objects cross the plane of the solar system. (Distant bodies such as ETNOs tend not to lie in the same plane as the sun and the solar system’s eight officially recognized planets.)

The researchers found that the objects’ nodes generally aggregate at certain distances from the sun (as do those of 24 “extreme Centaurs,” very distant objects with some characteristics of asteroids and others of comets). In addition, they discovered a correlation between the nodes’ positions and an orbital parameter known as inclination.

“Assuming that the ETNOs are dynamically similar to the comets that interact with Jupiter, we interpret these results as signs of the presence of a planet that is actively interacting with them in a range of distances from 300 to 400 AU,” he told Spain’s Information and Scientific News Service, which is known by its Spanish acronym, SINC. “We believe that what we are seeing here cannot be attributed to the presence of observational bias.”

A number of research teams are scouring the outer solar system, looking for the putative Planet Nine and/or more objects that have fallen under its gravitational sway. So the new study, which was published late last month in the journal Monthly Notices of the Royal Astronomical Society: Letters, is far from the last word. Stay tuned.

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Astronomers Shed Light On Star Explosions

July 18, 2017 by  
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New looks at the heart of a supernova remnant are revealing clues about the deaths of massive stars and how these dramatic events affect their host galaxies, two recent studies report.

Observations made by the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile allowed one research team to construct a detailed 3D map of SN 1987A — the remains of a huge star that exploded three decades ago — and another group to spot several molecules previously undetected in the supernova remnant.

“When this supernova exploded, now more than 30 years ago, astronomers knew much less about the way these events reshape interstellar space and how the hot, glowing debris from an exploded star eventually cools and produces new molecules,” Rémy Indebetouw, an astronomer at the University of Virginia and the National Radio Astronomy Observatory in Charlottesville, said in a statement.

“Thanks to ALMA, we can finally see cold ‘star dust’ as it forms, revealing important insights into the original star itself and the way supernovas create the basic building blocks of planets,” added Indebetouw, who is a co-author on both recent studies.

SN 1987A formed in the aftermath of a Type II supernova, which results when a star at least 10 times more massive than the sun runs out of fuel and ceases pushing outward against the inward pull of its own gravity. The big star’s outer parts then come crashing back on the core, sparking a mammoth explosion that can be seen from great distances.

Indeed, SN 1987A lies 163,000 light-years away, in the Large Magellanic Cloud galaxy, and has been studied intensively by a variety of instruments since its light first reached Earth in February 1987. (The explosion actually occurred about 163,000 years ago, of course, but astronomers such as Indebetouw often refer to it happening in 1987 for simplicity’s sake.)

The supernova sent huge amounts of dust streaming into space, creating a veil that many telescopes have had trouble penetrating. And that’s where the newly reported ALMA observations come in: The radio dishes in the array can peer through the dust, revealing the structure deep within the remnant.

In one of the recent studies, scientists mapped out in 3D the abundances of many molecules that formed in the aftermath of the massive explosion (after SN 1987A had cooled sufficiently to allow this to happen). For example, the ALMA data revealed large amounts of silicon monoxide (SiO) and carbon monoxide (CO) clumping in the remnant’s heart, researchers said.

The other study team performed a molecular inventory of SN 1987A. They found a number of species, including the new detections formyl cation (HCO+) and sulfur monoxide (SO).

“These molecules had never been detected in a young supernova remnant before,” Indebetouw said. “HCO+ is especially interesting, because its formation requires particularly vigorous mixing during the explosion.”

Overall, the combined results reveal new insights about SN 1987A’s composition and how conditions within the supernova remnant have changed over time, researchers said. This information, in turn, could help astronomers better understand galactic evolution.

“The reason some galaxies have the appearance that they do today is in large part because of the supernovas that have occurred in them,” Indebetouw said. “Though less than 10 percent of stars become supernovas, they nonetheless are key to the evolution of galaxies.”

The 3D-mapping study was published last month in The Astrophysical Journal Letters, and the molecular-inventory paper was published in April in the Monthly Notices of the Royal Astronomical Society.

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Did Kepler Help Prove Rocky Planets Are Prevalent

July 11, 2017 by  
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Rocky planets are probably a whole lot more common in our galaxy than astronomers previously believed — according to the latest release of Kepler Space Telescope data last week — a scenario that enhances the prospects for extraterrestrial life in nearby solar systems. 

Kepler’s final tally of exoplanets in the Cygnus constellation — the most comprehensive and detailed catalogue of exoplanets to date — indicates 4,034 possible planets, of which 50 are Earth-sized and reside in the habitable zone of their stars. The set includes KOI 7711 (short for Kepler ‘object of interest’), which is just 30 percent larger than Earth and roughly the same distance from its star as the Earth is to the sun, meaning it receives a similar amount of energy. 

“Kepler has really and truly opened our eyes to these small terrestrial-sized worlds,” said Susan Thompson, Kepler research scientist at the SETI Institute, at the announcement of the new catalogue of planet candidates at NASA Ames Research Center in Mountain View, California. [7 Ways to Discover Alien Planets]

Scientists gathered at NASA Ames June 19-23 for the Kepler Science Conference to present their findings from the original mission as well as update their progress on K2, an extended, “second life” mission that will continue until the spacecraft runs out of fuel or something else goes wrong. 

Prior to Kepler’s launch in 2009, astronomers mainly knew about Jupiter and Neptune-sized planets orbiting at various periods around their stars. It took the continuous gaze of Kepler’s image sensor array at a patch of sky loaded with 200,000 stars to discover this sizable population of rocky-sized worlds, most of them three times the size of Earth or smaller. Many hover close to their stars, but some appear with long orbital periods putting their distance outside a habitable zone. About a half-dozen confirmed exoplanets, though, are circling within the habitable zone of G-dwarf stars — the same type of star as the sun.

“Are we alone?” said Mario Perez, Kepler program scientist in the Astrophysics Division of NASA’s Science Mission Directorate. “Kepler says we are probably not alone.”

Yet, the prospects for life on any single one of these planets remains vastly uncertain. We know virtually nothing about the size and composition of their atmospheres, or whether water is present. For example, at 1,700 light years away, KOI 7711, dubbed ‘Earth’s Twin,’ seems one of the most promising exoplanets for life that we know of to date, given its similar orbital period (it circles its star in 303 days) and size. But Thompson urged caution in drawing hasty conclusions. “There’s a lot we don’t know,” she said. ” I like to remind people that it looks like there are three planets in our habitable zone — Venus, Earth and Mars — and I only want to live on one of them.” 

The recently discovered TRAPPIST-1 star system, a mere 40 light years away from us, has a record-breaking seven rocky planets, raising all kinds of excitement at the possibility of panspermia, the seeding of life from one planet to a neighboring one. But given that they huddle close to their ultra-cool dwarf star, these planets are likely to be tidally locked, like Mercury. One side would be scorching and the other side frigid. Stellar flares could blast away the atmospheres of these planets or subject them to surges of UV radiation, a known detriment to earthly existence. 

But Courtney Dressing, a CalTech astronomer, offered some signs of hope, even for planets that look doomed. She pointed out that new research using sophisticated 3-D models is showing that if tidally-locked planets manage to hang onto their atmospheres, strong air currents could be evening out temperatures. “There’s a chance you could have a bunch of civilizations where maybe all the astronomers live on one side of the planet and everyone else enjoys the sunny, beach-y side close to the star,” she said. 

And UV radiation, which may have sparked life the formation of RNA on early Earth, may not be the end-all even in the form of sudden surges. For example, one study found that haloarchaea, an extremophile microorganism found in highly saline water, could withstand heavy blasts of UV radiation. “Even if the surface is a dangerous place, life could be thriving underground or underwater,” Dressing said. 

Stellar flaring and its impact on life is an area of active research in astrobiology, given that M dwarf stars, many of which are prone to flaring, are numerous in our galaxy and host rocky planets that are astronomers’ most accessible prospects for near-term bio-signature research.
“Regardless of whether any of these newly detected planet candidates are inhabited, the fact that Kepler has discovered 50 potentially habitable planets and planet candidates implies that such worlds are frequent,” wrote Dressing in an email.

Future instruments are what’s needed to move the science forward. Late next year, NASA (alongside the European Space Agency and Canadian Space Agency) is scheduled to launch the James Webb Space Telescope, a next generation space observatory that will be the best observation tool we have to measure the atmospheres of exoplanets close to us — a key to understanding other aspects of habitability. And also in development is the Wide Field Infrared Survey Telescope (WFIRST), which will expand the range of exoplanet exploration and build on Kepler’s foundation. 

“It feels a bit like the end of an era,” said Thompson, “but actually it feels like a new beginning.”

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Did Comets Bring The Building Blocks Of Life To Earth

June 20, 2017 by  
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Life on Earth may not have been possible without comet strikes.

A new study suggests that about 20 percent of the noble gas xenon in Earth’s atmosphere was delivered by comets long ago. And these icy wanderers likely brought lots of other stuff to our planet as well, researchers said. 

The “cometary contribution could have been significant for organic matter, especially prebiotic material, and could have contributed to shape the cradle of life on Earth,” said study lead author Bernard Marty, a geochemist at the University of Lorraine and the Centre de Recherches Pétrographiques et Géochimiques in France.  

Marty and his colleagues studied measurements made by the European Space Agency’s (ESA) Rosetta spacecraft, which orbited the 2.5-mile-wide (4 kilometers) Comet 67P/Churyumov-Gerasimenko from August 2014 through September of last year.

Specifically, they analyzed xenon-isotope data that Rosetta gathered during a series of low-altitude orbits of Comet 67P between May 14 and May 31, 2016. (Isotopes are versions of an element that contain different numbers of neutrons in their nuclei. “Heavy” isotopes have more neutrons compared to “lighter” ones.)

Rosetta’s observations revealed that 67P is deficient in heavy xenon. Furthermore, the team determined that the comet’s xenon isotope composition matches a signature of Earth xenon whose origin had been a mystery.

Scientists think asteroids delivered the vast majority of the water in Earth’s oceans, and these space rocks have been regarded as the chief suppliers of the planet’s other “volatiles” — substances with low boiling points, such as nitrogen, carbon dioxide and noble gases — as well. (Models suggest that Earth was extremely hot shortly after its formation about 4.5 billion years ago, so it probably lost its primordial volatiles early on.) 

This inference is drawn partly from the isotopic similarity of hydrogen, nitrogen and other materials on Earth to that of certain asteroids known as carbonaceous chondrites, as measured in meteorite samples, Marty said.

“There was also a dynamical argument: Jupiter and the other giant planets formed early, and the outer solar system (from which comets originate) was isolated early from the inner solar system by the giant planets’ gravitational fields,” he said. “Now our finding calls for a revision of such models.”

Comets are especially enriched in noble gases, explaining how their contribution of xenon (and perhaps other materials) to the early Earth can be outsized compared to the proportion of water these icy wanderers delivered, Marty added.

The newly analyzed Rosetta data also indicate that 67P’s xenon predates the solar system — that is, the comet contains samples of interstellar matter. That’s an exciting result that argues for further, more detailed study of pristine cometary material, Marty said. 

“Returning a cometary sample on Earth should be the highest priority, because it will permit analyses with unprecedented precision of such exotic material and could respond to questions such as: How long interstellar material can survive, which stars contributed to shape the cradle of the solar system, what is the origin(s) of the large isotopic variations of some of the elements (e.g., N, H, O), what was the role of irradiation of early solar system material, etc.,” he said. (N, H and O are nitrogen, hydrogen and oxygen, respectively.)

Rosetta launched in March 2004. A decade later, it became the first mission ever to orbit a comet and the first to touch down softly on one of these bodies. (The Rosetta orbiter dropped a lander called Philae onto 67P in November 2014.)

The mission ended when Rosetta intentionally crash-landed on 67P’s surface on Sept. 30, 2016.

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Amateur Astronomers Discover Prehistoric Supernova

June 7, 2017 by  
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More than 700 volunteer citizen scientists have helped identify more than 30,000 celestial objects, including a star explosion that occurred 970 million years ago, hundreds of millions of years before dinosaurs emerged on Earth. 

When a massive star reaches the end of its life, it creates a bright stellar explosion, also known as a supernova. The Australian National University (ANU) has invitied citizen scientists to join the hunt for supernovas. 

Using images taken by the SkyMapper telescope at the ANU Siding Spring Observatory, volunteer supernova hunters helped discover a star’s dying burst located roughly 970 million light-years from Earth, according to a statement from ANU. That means the star exploded millions of years before dinosaurs roamed the planet.  

“This is the exact type of supernova we’re looking for — Type Ia supernova — to measure properties of and distances across the universe,” Brad Tucker, co-lead researcher from the ANU Research School of Astronomy and Astrophysics, said in the statement. 

The exploding star, called SN2017dxh, is one of seven potential new supernovas reported to the Transient Name Server; the team is tracking another 18 potential supernovas as well, according to the statement.

Supernovas, “which are explosions as bright as 100 million billion billion billion lightning bolts,” researchers said in the statement, can be used to track how the universe is growing and to better understand mysterious dark energy. Based on the brightness and fading of light emitted by a supernova, astronomers can measure how far away a supernova is from Earth, the researchers said. 

The ANU project was set up on the Zooniverse platform and allows volunteers to look through images taken by the SkyMapper telescope for differences that may hint at the presence of a supernova. The volunteers note the differences they observe so that the researchers can follow up on them and determine what they mean. 

“In the first 24 hours, we had over 30,000 classifications” of new celestial objects, Anais Möller, another co-lead researcher from ANU, said in the statement. “We’ve almost reached 40,000 classifications, with more than 1,300 images classified, since the launch of our project.”

When the discovery is reported to the International Astronomical Union, the first three people to find a previously unknown supernova will be mentioned. You can participate in the ANU citizen science project online.

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