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Planet Nine Could Be Our Solar System's Missing 'Super Earth'

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A possible “Planet Nine” in Earth’s solar system would orbit far beyond Neptune’s orbit (visible as a bright ring around the sun in this artist’s illustration).

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.” [The Evidence for ‘Planet Nine’ in Our Solar System (Gallery)]

Credit: by Karl Tate, Infographics artist

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 and Google+. Original article on Space.com.

Space.com is the premier source of space exploration, innovation and astronomy news, chronicling (and celebrating) humanity's ongoing expansion across the final frontier. We transport our visitors across the solar system and beyond through accessible, comprehensive coverage of the latest news and discoveries. For us, exploring space is as much about the journey as it is the destination. So from skywatching guides and stunning photos of the night sky to rocket launches and breaking news of robotic probes visiting other planets, at Space.com you’ll find something amazing every day.

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In Pictures: Sierra Nevada's Dream Chaser Aces Glide Test Flight

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Free-Flying

Credit: NASA

The glide test success indicates the program is one step closer to orbital exercises.

Ready for Testing

Ready for Testing

Credit: Ken Ulbrich/NASA

The spacecraft was moved from inside the facility by a transport to prepare for the test.

Gear in Place

Gear in Place

Credit: Ken Ulbrich/NASA

Apparatus attached atop the Dream Chaser enabled a helicopter to raise the craft for the release and flight.

Up and Away

Up and Away

Credit: Ken Ulbrich/NASA

The full scale Dream Chaser craft, shown here lifted by a Columbia Helicopters Model 234-UT Chinook helicopter, flew a pre-planned flight path after its release.

Safe and Secure

Safe and Secure

Credit: Ken Ulbrich/NASA

The successful test flight ended at Edwards Air Force Base on Runway 22L.

Big Plans

Big Plans

Credit: Ken Ulbrich/NASA

The first trip to the International Space Station for the Dream Chaser is planned for 2020.

Practicing for the Big Journey

Practicing for the Big Journey

Credit: Ken Ulbrich/NASA

The Dream Chaser is scheduled for at least six missions under NASA’s Commercial Resupply Services 2 contract, beginning as early as 2020.

Proof

Proof

Credit: NASA

This atmosphere Free-Flight test verified the craft has the design and capabilities to return and land safely.

Free-Flight

Free-Flight

Credit: NASA

Sierra Nevada Corporation’s Dream Chaser has displayed the ability to provide safe and reliable orbital flight, according to corporate vice president, Mark Sirangelo.

Approaching the Runway

Approaching the Runway

Credit: NASA

With NASA on board, Sierra Nevada Corporation will analyze the test data.

Wheels Down

Wheels Down

Credit: Ken Ulbrich/NASA

Using results from this Free-Flight test, engineers can perfect the aerodynamics of the Dream Chaser, making it even safer for future flights.

Catching Some Air

Catching Some Air

Credit: Ken Ulbrich/NASA

As the full-scale test vehicle is raised by the Chinook helicopter on Nov. 13, 2017, Sierra Nevada Corporation looks to the future of this spacecraft.

Rollout

Rollout

Credit: Ken Ulbrich/NASA

The Dream Chaser spacecraft is readied for the atmospheric Free-Flight test.

Suspended Suspense

Suspended Suspense

Credit: Ken Ulbrich/NASA

Rising high into the atmosphere, the Dream Chaser begins the atmospheric Free-Flight test.

Teamwork

Teamwork

Credit: Ken Ulbrich/NASA

The Flight Crew prepares Sierra Nevada Corporation’s full-scale Dream Chaser test vehicle for the upcoming Free-Flight test.

Last Minute Checks

Last Minute Checks

Credit: Ken Ulbrich/NASA

The Flight Crew for the Dream Chaser spacecraft completes preflight checks before the craft participates in the monumental test.

Future at Hand

Future at Hand

Credit: Ken Ulbrich/NASA

Sierra Nevada Corporation’s Dream Chaser spacecraft looks to be the next phase in NASA’s journey into space.

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Apollo 17 Astronaut Begins Releasing Diary 45 Years After Moon Mission

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Apollo 17 astronaut Harrison Schmitt, seen here during the first of his three moonwalks in December 1972, has begun to release his diary of the last lunar landing mission 45 years later.

Harrison Schmitt went for a walk on Dec. 11, 1972. Forty-five years later, he is almost ready to share his diary of that day.

The last of the twelve NASA astronauts to step foot onto the surface of the moon — and the only geologist to do so — Schmitt was the lunar module pilot on NASA’s Apollo 17 mission, the sixth, last, and as Schmitt puts it, “most recent human visit to the moon.” Now, on the 45th anniversary of his lunar journey, Schmitt is beginning to take the public on a stroll through history, his memories and the findings that came from exploring Taurus Littrow Valley on the moon.

“This project began 45 years ago,” explains Schmitt. “I am gradually getting to the point where the drafting, I think, is good enough that I can let other people share in what my impressions were during the mission, as well as what the whole operation was about.” [The Apollo Moon Landings: How They Worked (Infographic)]

Apollo 17: Diary of the Twelfth Man” quietly debuted as a new section of Schmitt’s website in early November when he uploaded the fourth chapter, “30 Days and Counting.” Although the first through third chapters still remain to be published, Schmitt chose the fourth to begin “because the interval between its online publication date and the launch date coincides with the chapter title,” he wrote in a note to accompanying the post.

On Friday (Dec. 7), 45 years to the day after he lifted off with Apollo 17 commander Eugene Cernan and command module pilot Ronald Evans, Schmitt posted the diary’s fifth chapter, “30 Seconds and Counting!” — an almost 49,000 word account of the Saturn V launch that follows Schmitt and his crewmates from the ground to leaving Earth orbit for the moon.

“[Seven and a half] 7.5 million pounds of thrust would lift us slowly at first and then faster and faster toward orbit on a trail of brilliant flame, not visible to us but splitting open the night for everyone below,” recounts Schmitt. “Pulsing waves of sound and searing streams of light buffeted the bodies and minds of onlookers, bringing spontaneous and unexpected hugs, cries and tears.”

The Apollo 17 launch marked the first time NASA had sent astronauts into space at night.

“Once again, a life-tipped pillar of fire, the Saturn rocket, a massive tribute to boldness and imagination, became a blazing symbol of human potential for greatness. Except for reflected light coming through the small window in front of Gene and another in the boost protective cover over the [crew] hatch, I had only a vague sense of the brilliant flame beneath us,” writes Schmitt.

Schmitt pulls from a wide variety of sources for the content of the diary. Amid his own observations, Schmitt cites from NASA air to ground radio transcripts, public affairs reports and the recollections of others. He has also formatted the journal to help readers keep track of the topics at hand.

“A complication to reading diaries is their instantaneous jump from subject to subject. In addition to the liberal use of endnotes, distinguishing between subjects and sources is aided by the consistent use of different font styles and colors in the text,” Schmitt explains in his preface.

Harrison Schmitt is releasing “Apollo 17: Diary of the Twelfth Man” in chapters on his website.

Credit: NASA

For example, Schmitt turns the text red when discussing anomalies, or problems, during the mission. He uses blue when writing of Earth observations and he uses purple for views about the moon. He reserves turquoise for “probable dialog” between he and his two crewmates, as he can best derive from his memory.

“On the horizon, bands of orange and blue lay below the black of space,” Schmitt writes, describing — in blue text — and captioning a photograph of his first view of Earth from space. “Outside, darkness finally had been broken by a spectacular sunrise that had provided what I described a few minutes later as ‘the biggest rainbow I’d ever seen,’ extending along the entire pre-sunrise horizon.”

“Like childhood’s home, we really see the Earth only as we prepare to leave,” waxes Schmitt.

“It [the diary] is both technical and philosophical, in some aspects,” Schmitt told collectSPACE.

Schmitt, who is now 82, logged a total of 75 hours on the lunar surface, including 22 hours out on three moonwalks. With Cernan’s death in January, Schmitt became the final living member of the Apollo 17 crew (Evans died in 1990).

Although 45 years have already passed for Schmitt to feel ready to prepare and share the diary, he still sees it as a “long-running project” that will not be completed within just the 12-day span of the mission.

“The 45th anniversary seemed like a good time to begin,” he said. “It is going to take a long time still. There is a lot to be said.”

To read “Apollo 17: Diary of the Twelfth Man,” see Harrison Schmitt’s website, americasuncommonsense.com.

Follow collectSPACE.com on Facebook and on Twitter at @collectSPACE. Copyright 2017 collectSPACE.com. All rights reserved.

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How Was Mars Made? | Formation of Mars

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The planet Mars was formed, along with the rest of the solar system, about 4.6 billion years ago. But exactly how the planets formed remains a subject of debate. Currently, two theories are duking it out for the role of champion.

The first and most widely accepted theory, core accretion, works well with the formation of the terrestrial planets like Mars but has problems with giant planets. The second, the disk instability method, may account for the creation of these giant planets. 

Artist’s conception of our solar system’s solar nebula, the cloud of gas and dust from which the planets formed.

Credit: Painting copyright William K. Hartmann, Planetary Science Institute, Tucson

Scientists are continuing to study planets in and out of the solar system in an effort to better understand which of these methods is most accurate. 

The leading theory, known as core accretion, is that the solar system began as a large, lumpy cloud of cold gas and dust, called the solar nebula. The nebula collapsed because of its own gravity and flattened into a spinning disk. Matter was drawn to the center of the disk, forming the sun.  

Other particles of matter stuck together to form clumps called planetesimals. Some of these combined to form asteroids, comets, moons and planets. The solar wind — charged particles streaming out from the sun — swept away the lighter elements, such as hydrogen and helium, leaving behind mostly small, rocky worlds. In the outer regions, however, gas giants made up of mostly hydrogen and helium formed because the solar wind was weaker.

Exoplanet observations seem to confirm core accretion as the dominant formation process. Stars with more “metals” — a term astronomers use for elements other than hydrogen and helium — in their cores have more giant planets than their metal-poor cousins. According to NASA, core accretion suggests that small, rocky worlds should be more common than the more massive gas giants.

The 2005 discovery of a giant planet with a massive core orbiting the sun-like star HD 149026 is an example of an exoplanet that helped strengthen the case for core accretion.

“This is a confirmation of the core accretion theory for planet formation and evidence that planets of this kind should exist in abundance,” said Greg Henry in a press release. Henry, an astronomer at Tennessee State University, Nashville, detected the dimming of the star.

In 2018, the European Space Agency plans to launch the CHaracterising ExOPlanet Satellite (CHEOPS), which will study exoplanets ranging in sizes from super-Earths to Neptune. Studying these distant worlds may help determine how planets in the solar system formed.

“In the core accretion scenario, the core of a planet must reach a critical mass before it is able to accrete gas in a runaway fashion,” said the CHEOPS team

“This critical mass depends upon many physical variables, among the most important of which is the rate of planetesimals accretion.”

By studying how growing planets accrete material, CHEOPS will provide insight into how worlds grow.

Core accretion was first postulated in the late 18th century by Immanuel Kant and Pierre Laplace. Nebula theory helps explain how the planets in our solar system were formed. But with the discovery of “Super-Earth” planets orbiting other stars, a new theory, known as disk instability was proposed. 

Although the core accretion model works fine for terrestrial planets, gas giants would have needed to evolve rapidly to grab hold of the significant mass of lighter gases they contain. But simulations have not been able to account for this rapid formation. According to models, the process takes several million years, longer than the light gases were available in the early solar system. At the same time, the core accretion model faces a migration issue, as the baby planets are likely to spiral into the sun in a short amount of time.

According to a relatively new theory, disk instability, clumps of dust and gas are bound together early in the life of the solar system. Over time, these clumps slowly compact into a giant planet. These planets can form faster than their core accretion rivals, sometimes in as little as a thousand years, allowing them to trap the rapidly-vanishing lighter gases. They also quickly reach an orbit-stabilizing mass that keeps them from death-marching into the sun.

According to exoplanetary astronomer Paul Wilson, if disk instability dominates the formation of planets, it should produce a wide number of worlds at large orders. The four giant planets orbiting at significant distances around the star HD 9799 provides observational evidence for disk instability. Fomalhaut b, an exoplanet with a 2,000-year orbit around its star, could also be an example of a world formed through disk instability, though the planet could also have been ejected due to interactions with its neighbors.

The biggest challenge to core accretion is time — building massive gas giants fast enough to grab the lighter components of their atmosphere. Recent research on how smaller, pebble-sized objects fused together to build giant planets up to 1000 times faster than earlier studies.

“This is the first model that we know about that you start out with a pretty simple structure for the solar nebula from which planets form, and end up with the giant-planet system that we see,” study lead author Harold Levison, an astronomer at the Southwest Research Institute (SwRI) in Colorado, told Space.com in 2015.

In 2012, researchers Michiel Lambrechts and Anders Johansen from Lund University in Sweden proposed that tiny pebbles, once written off, held the key to rapidly building giant planets.

“They showed that the leftover pebbles from this formation process, which previously were thought to be unimportant, could actually be a huge solution to the planet-forming problem,” Levison said.

Levison and his team built on that research to model more precisely how the tiny pebbles could form planets seen in the galaxy today. While previous simulations, both large and medium-sized objects consumed their pebble-sized cousins at a relatively constant rate, Levison’s simulations suggest that the larger objects acted more like bullies, snatching away pebbles from the mid-sized masses to grow at a far faster rate.

“The larger objects now tend to scatter the smaller ones more than the smaller ones scatter them back, so the smaller ones end up getting scattered out of the pebble disk,” study co-author Katherine Kretke, also from SwRI, told Space.com. “The bigger guy basically bullies the smaller one so they can eat all the pebbles themselves, and they can continue to grow up to form the cores of the giant planets.”

In 2018, NASA will launch the InSight mission to Mars that will study the planet’s interior.

“But InSight is more than a Mars mission — it is a terrestrial planet explorer that will address one of the most fundamental issues of planetary and solar system science — understanding the processes that shaped the rocky planets of the inner solar system (including Earth) more than four billion years ago,” according to NASA.

“InSight seeks to answer one of science’s most fundamental questions: How did the terrestrial planets form?”

Whether Mars got its start through disk instability or core or pebble accretion, it continued to pack on the weight as it grew. Models suggest that the Red Planet should be about as large as Venus and Earth if gas and dust were smoothly spread through the solar system. Instead, Mars is only 10 percent as massive, suggesting that it formed in a region low on planetary building blocks.

Enter the Grand Tack model, the leading theory to explain the so-called “small Mars problem.” According to the model, Jupiter and Saturn migrated toward the sun shortly after their birth before tacking like a sailboat and returning to the outer solar system. Along the way, they would have swept up much of the debris that should have fed Mars’ formation.

The western scarp of Olympus Mons has both steep and gentle slopes with clear channels, some likely created by flowing liquid, perhaps water, and some apparently carved by glaciers.

The western scarp of Olympus Mons has both steep and gentle slopes with clear channels, some likely created by flowing liquid, perhaps water, and some apparently carved by glaciers.

Credit: Nature/ESA/G. Neukum

“Provided that Jupiter changed direction close to 1.5 AU, the growth of Mars would be successfully stunted while leaving enough material closer to the sun to form Earth and Venus,” John Chambers of the Carnegie Institution for Science wrote in a 2014 “Perspectives” piece published in the journal Nature.

Another possibility is that regions of low density formed naturally in the protoplanetary disk. 

“If this partial gap survived long enough, it could have been preserved in the distribution of planetesimals and planetary embryos that formed subsequently,” Chambers writes. “The simulations performed by Izidoro show that reducing the number of planetary building blocks near Mars’ current orbit by 50 to 75 percent favors the formation of a puny Red Planet.”

Another option is that Mars actually got its start in the asteroid belt, then migrated toward the sun because of its interaction with planetesimals.

“Since Mars is more massive than the planetesimals, it tends to lose energy when it scatters these planetesimals because it passes them to Jupiter, which then ejects them from the solar system,” Ramon Brasser, lead author and associate professor at the Tokyo Institute of Technology’s Earth-Life Science Institute, told Space.com.

Like all planets, Mars became hot as it formed because of the energy from these collisions. The planet’s interior melted and denser elements such as iron sank to the center, forming the core. Lighter silicates formed the mantle, and the least-dense silicates formed the crust. Mars probably had a magnetic field for a few hundred million years, but as the planet cooled, the field died. 

The young Mars had active volcanoes, which spewed lava across its surface, and water and carbon dioxide into the atmosphere. But there is no tectonic activity on Mars, so the volcanoes remained stationary and grew with each new eruption.

The volcanic activity also probably gave Mars a thicker atmosphere. Mars’ magnetic field protected the planet from radiation and solar wind. With a higher atmospheric pressure, water probably flowed on Mars’ surface, studies indicate. But about 3.5 billion years ago, Mars began to cool. Volcanoes erupted less and less and the magnetic field disappeared. The unprotected atmosphere was blown away by solar wind and the surface was bombarded by radiation.

Under these conditions, liquid water cannot exist on the surface. Studies suggest water is be trapped underground in both liquid and frozen forms and in the ice sheets of the polar ice caps.

All life as we know it requires liquid water, so there is much interest in finding evidence of it on Mars.

— Additional reporting by Nola Taylor Redd, Space.com Contributor

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