'Zombie' Planet's Rogue Orbit Around Star Shocks Scientists

The unbalanced orbit of a so-called "zombie planet" in a dusty star system has astronomers struggling to explain the exoplanet's behavior.

New observations of the planet Fomalhaut b by the Hubble Space Telescope revealed the oddball orbit, which has wild extremes between its closest and farthest points from the parent star and appears to cross through a vast minefield of dusty debris. 

"We are shocked. This is not what we expected," said study leader Paul Kalas, an astronomer with the University of California at Berkeley and the SETI Institute in Mountain View, Calif., in a statement Tuesday (Jan. 8).

'Zombie planet' gets weirder

Fomalhaut b is a giant alien planet that is nearly three times the mass of Jupiter. It was the first alien planet ever directly imaged in visible light. The planet orbits the dust-shrouded star Fomalhaut and is located about 25 light-years away in the constellation Piscis Austrinus. 

In October, scientists dubbed the world a "zombie planet" because it appeared to rise from the academic grave. After first being discovered in 2008, subsequent studies suggested the planet was nothing more than a huge dust cloud. In 2012, astronomers resurrected Fomalhaut b's planet status when new observations proved there was a planetary object embedded in a free-floating dust cloud. [Gallery: The Strangest Alien Planets]

The latest observations of the odd planetary system revealed that the dusty debris disk surrounding the star Fomalhaut is much wider than previously thought. The debris belt spans a vast region of space between 14 billion and 20 billion miles (22.5 billion to 32.1 billion kilometers) around the star.

Stranger still: The planet Fomalhaut b appears to approach with 4.6 billion miles (7.4 billion km) of its star at the closest point in its orbit, then swing way out to a point about 27 billion miles (43.4 billion km) away at the farthest point. Scientists call the extremes of such a planet’s path a highly eccentric orbit.

Fomalhaut b's path, scientists say, sends the planet crashing through the surrounding debris disk during its 2,000-year orbit around its parent star. The research was unveiled Tuesday at the 221st meeting of the American Astronomical Society in Long Beach, Calif.

A hidden planet around Fomalhaut?

Among the several theories to explain Fomalhaut b's extreme orbit is the possibility that the exoplanet had an encounter with another planet, a yet-to-be discovered neighbor. The cosmic close encounter could have gravitationally ejected Fomalhaut b into its current orbit, scientists said.

"Hot Jupiters get tossed through scattering events, where one planet goes in and one gets thrown out," study co-investigator Mark Clampin, of NASA's Goddard Space Flight Center in Greenbelt, Md., said in a statement.  "This could be the planet that gets thrown out."

Hubble telescope images revealed an apparent gap in the dust and ice debris around Fomalhaut, a region that could have been swept clean by the presence of the undetected planet, researchers said.

Another theory suggests that Fomalhaut b could have once had a small dwarf planet as a neighbor, but that the giant planet obliterated the smaller world in a catastrophic collision. Such a crash could explain why the star Fomalhaut has a narrow outer debris disk that is less than 10,000 years old, scientists said.

Does Fomalhaut b have rings?

Another tantalizing theory suggests Fomalhaut b may have Saturn-like rings and be destined for a spectacular crash through the debris disk around the star Fomalhaut in the year 2032. [Photos of Saturn’s Glorious Rings]

A set of rings or a nearby shroud of dust and ice could explain why Fomalhaut b appears so bright in visible light images, but is relatively dim in infrared light, according to Kalas. The rings or dust around the planet would reflect starlight, making the planet bright. A dust cloud could be created impacts on moons around Fomalhaut b, if they exist, researchers said.

In 2032, astronomers expect to solve one riddle that has perplexed scientists since Fomalhaut b's discovery: Is the exoplanet in the plane of the debris disk around its star, or not?

If the planet is on the same plane as the debris disk, than it will be bombarded by dust and ice in 2032 when it crosses through the disk during the outbound leg of its orbit, researchers said. That would make the planet increase its brightness in infrared light, they added. Impacts from the debris could create a celestial light show on the planet similar to that seen on Jupiter when the comet Shoemaker-Levy 9 battered the gas giant in 1994.

If Fomalhaut b is not in the same plane as the debris disk, then it should gradually get dimmer as it gets farther and farther from its parent star, researchers said. One way or another, the clues should come out starting in 2032, scientists said.

Hubble telescope officials said astronomers plan to continue to monitor the Fomalhaut star system over the next few years and decades to see how the star system changes over time.

You can follow SPACE.com Managing Editor Tariq Malik on Twitter @tariqjmalik. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

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Could Natural Nuclear Reactors Have Boosted Life on This and Other Planets? (SPACE.com)

Clara Moskowitz, Astrobiology Magazine
Space.com Clara Moskowitz, Astrobiology Magazine
space.com – Fri Dec 2, 10:15 am ET

While modern-day humans use the most advanced engineering to build nuclear reactors, Nature sometimes makes them by accident.

Evidence for a cluster of natural nuclear reactors has been found on Earth, and some scientists say our planet may have had many more in its ancient past. There's also reason to think other planets might have had their own naturally occurring nuclear reactors, though evidence to confirm this is hazy. If they did exist, the large amounts of radiation and energy released by such reactors would have had complicated effects on any life developing on this or other worlds, experts say.

Natural nuclear reactors occur when deposits of the radioactive element uranium build up in one spot, and eventually ignite a self-sustaining nuclear chain reaction where uranium divides, in a process called fission, producing other elements. The reaction releases a powerful punch of energy.

This energy could prove beneficial and highly detrimental to developing life, depending on the circumstances. [7 Theories on the Origin of Life]

Only example

The only known examples of natural nuclear reactors on Earth were discovered in the Oklo region of Gabon, Africa, in 1972. French miners discovered that the uranium samples they extracted were depleted in the rare isotope uranium 235, the only naturally occurring material on Earth capable of sustaining fission reactions. It was as if the material had already gone through a nuclear reaction and been used up.

In fact, that's the scenario most supported by studies. Scientists think a concentration of uranium 235 there went critical around 2 billion years ago and underwent fission, just as it does inside man-made nuclear reactors.

"As far as we know, we only have evidence of natural reactors forming and operating at the one site in Gabon, but that demonstrates that it's possible, and our calculations suggest it was much more probable earlier in Earth's history," said Jay Cullen of the University of Victoria in Canada.

Cullen and Laurence A. Coogan, a colleague at the University of Victoria, researched how likely these reactions were when Earth was much younger, based on how much uranium in a given area is necessary for the material to go critical and start a self-sustaining fission reaction. They found that during the Archean epoch, between around 2.5 billion and 4 billion years ago, natural nuclear reactors could have been relatively frequent.

"It certainly seems more than likely that these sorts of reactors would have been much more common in the Earth's early history because the amount [of uranium] you need is actually quite small," Cullen told Astrobiology Magazine.

However, because there is such a poor geologic record left from so long ago, scientists have very little way of confirming this idea.

The spark of life

If natural nuclear reactors were present on early Earth, they could have had interesting effects on any nascent life.

The ionizing radiation released by a nuclear reaction can damage DNA, the precious instruction code built into every cell of life. If organisms were living too close to the site of a reactor, they could have been wiped out completely. However, life hanging out on the outskirts of a nuclear reactor might have received a smaller dose of radiation — not enough to kill it, but enough to introduce mutations in its genetic code that could have boosted the diversity in the local population.

"The ionizing radiation would actually provide some genetic variation," Cullen said. “That’s the quantity that natural selection is going to act upon, and it might help to promote change in organisms with time. I think that most people view ionizing radiation as a bad thing, but that’s not always necessarily so."

Furthermore, the nuclear reactors themselves could have provided an even greater boon to life by giving it the spark it needed to originate in the first place, some scientists think. Zachary Adam, now a graduate student at Montana State University in Bozeman, suggested the possibility in a 2007 paper in the journal Astrobiology, which he wrote  as a graduate student at the University of Washington.

Scientists don't know for sure how life got started on Earth, but they think it required some kind of burst of energy to start it off. This energy would have been required to break the bonds of simple elements such as carbon, nitrogen, hydrogen and oxygen, so that they could recombine to form the first complex organic molecules.

Other researchers have suggested that a strike of lightning might have provided the requisite energy, but Adam thinks that the energy released by a natural nuclear reactor might have provided the catalyst.

"I think it is at least as possible as other ideas, if not more plausible, but I realize everyone is partial to their own ideas," Adam said.

Life elsewhere?

If natural nuclear reactors might have helped life arise on this planet, it's also possible they've played a role in seeding life elsewhere.

So far, scientists' limited knowledge of the geology of extrasolar planets means they can't say how common natural nuclear reactors might be on other worlds. Adam said that some elements on early Earth that might have helped these reactors form don't seem to be as abundant on the surfaces of other planets.

For example, the moon's tidal forces on Earth, which used to be stronger than they are today due to the moon's closer proximity long ago, played a vital role in causing heavy minerals like uranium 235 to collect in dense patches on beaches, Adam said. The Earth had also differentiated into separate layers, including a crust and a mantle, which helped to separate out and concentrate the heavy radioactive elements.

These characteristics, especially crustal differentiation like that on Earth, don't seem to be as common among the other planets of the solar system, Adam said.

But not all experts are pessimistic about natural nuclear reactors on other worlds.

Plasma physicist John Brandenburg of Orbital Technologies Corp. analyzed results from NASA's Mars Odyssey Orbiter, which surveyed the surface of the Red Planet with various instruments, including a gamma-ray spectrometer. Brandenburg says the gamma-ray results show evidence of an abundance of radioactive uranium, thorium and potassium, especially in one particular spot on Mars, which he attributes to a major nuclear reaction taking place there around half a billion years ago.

"Basically it looked as though Mars was covered with a thick layer of radioactive substances, and also the atmosphere was full of radiogenic products," Brandenburg said. "It's kind of a no-brainer at that point. There appears to have been a large radiological event on Mars and it appears to have been violent."

If such a huge nuclear event did occur, it would have been disastrous for any budding Martian life.

"It would have been a terrible catastrophe," Brandenburg said. "Whatever biosphere was on Mars at the time probably suffered a massive extinction event, and it really set back life on Mars."

However, many Mars geologists have greeted Brandenburg's proposal with skepticism.

"This hypothesis is not likely to be true," the University of Arizona's William Boynton, principal investigator for Mars Odyssey's gamma-ray spectrometer, wrote in an email. "Yes, we did find both thorium and uranium, and they are natural elements found everywhere. The amount varies, but the explanations are very mundane."

Boynton said he doubts that natural nuclear reactors like the ones in Gabon are common elsewhere.

"The natural reactor in Africa is real, but the reason it was of so much interest is that it is so rare," Boynton said. "I would say it is all but impossible that any natural reactor has happened anywhere else in the solar system. It may be it has only happened once on Earth!"

This story was provided by Astrobiology Magazine, a web-based publication sponsored by the NASA astrobiology program.

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Astronomers Discover 18 Huge New Alien Planets (SPACE.com)

Astronomers have found 18 new alien planets, all of them Jupiter-size gas giants that circle stars bigger than our sun, a new study reports.

The discoveries increase the number of known planets orbiting massive stars by 50 percent. The exoplanet bounty should also help astronomers better understand how giant planets form and grow in nascent alien solar systems, researchers said.

The haul comes just a few months after a different team of researchers announced the discovery of 50 newfound alien worlds, including one rocky planet that could be a good candidate for life. The list of known alien planets is now well over 700 and climbing fast.

Staring at 'retired' stars

The researchers surveyed about 300 stars using the Keck Observatory in Hawaii and instruments in Texas and Arizona. They focused on so-called "retired" type A stars that are at least 1.5 times more massive than our own sun.

These stars are just beyond the main stage of life — hence the name "retired" — and are now ballooning out to become what's known as subgiant stars.

The team scrutinized these stars, looking for slight wobbles caused by the gravitational tug of orbiting planets. This process revealed 18 new alien worlds, all of them with masses similar to Jupiter's. All 18 planets also orbit relatively far from their stars, at a distance of at least 0.7 times the span from Earth to the sun (about 93 million miles, or 150 million kilometers). [Gallery: The Strangest Alien Planets]

Planet-formation theories

In addition to boosting the ever-growing alien planet tally, the new finds lend support to one of two theories that attempt to explain the formation and evolution of planets, researchers said.

This theory, called core accretion, posits that planets grow as gas and dust glom onto seed particles in a protoplanetary disk. Core accretion predicts that the characteristics of a planetary system — the number and size of planets, for example — depend strongly on the mass of the star.

The main competing theory, called gravitational collapse, holds that planets form when big clouds of gas and dust in the disk spontaneously collapse into clumps that become planets. According to this idea, stellar mass should have little impact on planet size, number and other characteristics.

As the exoplanet finds pile up, it seems that stellar mass does in fact play an important role. The 18 huge newfound alien worlds, which all orbit massive stars, add more evidence in support of core accretion, researchers said.

"It's nice to see all these converging lines of evidence pointing toward one class of formation mechanisms," study lead author John Johnson, of Caltech in Pasadena, said in a statement.

Johnson and his colleagues reported their results in the December issue of the Astrophysical Journal Supplement Series.

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In Hunt for Alien Planets, Frustration Lingers Over Canceled Missions (SPACE.com)

Geoff Marcy is mad.

Not mad as in 'crazy,' although many scientists thought he was nuts when he first started hunting for planets orbiting far-distant stars over 20 years ago. 

Now that over 500 exoplanets have been detected and the Kepler space telescope has over 1,200 candidate planets waiting to be confirmed, Marcy's dedication and hard work (and his sanity) have been vindicated.

But Marcy is still mad at NASA for canceling exoplanet missions like the Terrestrial Planet Finder (TPF) and the Space Interferometry Mission (SIM). He's also angered by what he sees as a lack of leadership and cooperation for exoplanet missions within NASA and the larger astrophysics community. [Gallery: The Strangest Alien Planets]

Marcy expressed his ire at a recent exoplanet symposium hosted by MIT planetary scientist Sara Seager."I'm unhappy about the last 10 years, and the next 10 years," he said.

Mission meltdowns

While the Kepler mission has been a huge success, and potentially will allow astronomers to discover a truly Earth-like planet, Marcy mourns the loss of other missions that would've helped characterize exoplanets, as well as find planets that Kepler could never detect.

"I think the case for TPF is more compelling thanks to Kepler," Marcy said.

The goal of TPF had been to study all aspects of exoplanets — according to a NASA web site, "from their formation and development in disks of dust and gas around nearly-forming stars, to their suitability as abodes of life."

Marcy criticized the 2010 astronomy and astrophysics Decadal Survey, an influential review complied by the National Research Council that recommends missions for space science over the next ten years.

"TPF was not even mentioned in the Decadal Survey," he said. "How is this possible?"

The previous Decadal Survey, released in 2001, had recommended that NASA proceed with TPF, with the caveat that astronomers first had to determine that terrestrial planets are common around sun-like stars. Data from Kepler and other exoplanet studiesindicate that this may in fact be the case. [Infographic: Stacking Up Alien Solar Systems]

Marcy said that part of the blame for the current lack of large exoplanet missions should be placed on the scientific community, which did not advocate more strongly for TPF. Not too long ago, TPF was considered the most important and exciting mission for exoplanet science.

"I think TPF is our human genome project,” said Marcy. Without such a mission to help identify exoplanet characteristics, planet hunters become census-takers, just as astronomers 100 years ago counted the stars and put them into star category plots. "Now we count planets and put them into a period/radius diagram," he said.

Marcy said the astronomy community lost 10 years due to internal squabbling over which missions should receive funding. TPF scientists battled SIM scientists for supremacy, and then in 2004, when NASA decided to split TPF into two different missions — one with a coronagraph (TPF-C) and one with an interferometer  (TPF-I) -- the problem only grew worse.

The coronagraph and interferometer each would block light from a star in order to detect any planets orbiting them.

The TPF-Interferometer would've had several small telescopes, either on a fixed structure or on separated spacecraft floating in formation, that looked for the infrared emission, or heat, from exoplanets. The TPF-Coronagraph would’ve used a single large mirror to collect the very dim reflected visible light from exoplanets.

In 2007, NASA deferred both TPF missions "indefinitely" due to budget constraints. 

"Free-flying interferometers in space are the only plausible future for astrophysics," Macy declared. He felt coronagraphs were not the best option, but noted that NASA saw it differently and supported TPF-C at the expense of other exoplanet missions. "Lots of interferometers and radial velocity missions got junked."

He said that some in the community, notably Roger Angel of the University of Arizona, had advocated for a cheaper, scaled-down version called TPF-Lite, but this was rejected because many feared it would eliminate motivation for a bigger TPF mission. 

"So now, we have nothing," said Marcy.

For awhile it looked like SIM was the last mission standing when it came to large-scale exoplanet missions after the cancelation of TPF. SIM would have surveyed the closest 100 stars, looking for planets of a few Earth-masses, using astrometry: the precise measurement of star movement caused by planetary orbits.

A scaled-down version, called SIM-Lite, wasnot recommended by the 2010 Decadal Survey for development.  Because of this, and despite the years of study and the $600 million NASA already had invested in the mission, SIM was canceled.

Marcy said there hasn't been any meaningful discussion about lessons learned after the downfall of TPF and SIM. 

"Where’s the insight?" he asked. "What's the culture that allows mistakes like this to happen?"

A house divided

Wesley Traub of the Jet Propulsion Laboratory seemed eager to address these criticisms. He jumped to his feet after Marcy spoke, and only reluctantly agreed to wait for the scheduled question-and-answer period.

Traub defended TPF-C, saying it had the advantage of being a single telescope that didn’t need to be cooled. However, he felt the switch in focus for TPF from interferometry to a coronograph was mainly due to perception than science. [Video: Kepler Reveals Lots of Planets: Some Habitable?]

Calling the history of exoplanet mission development a "sociology experiment," Traub said that interferometers were simply not popular -- they didn’t employ enough people, and students wanted to collect data, not dedicate their time to building a new instrument. 

But Traub, who worked on both SIM and TPF and is currently Chief Scientist for NASA's Exoplanet Exploration Program, also shared many of Marcy’s concerns about the state of exoplanet missions. Speaking about the cancellation of SIM, Traub said, "That was the most embarrassing thing I've seen in my life."

David Charbonneau, of the Harvard-Smithsonian Center for Astrophysics and a Kepler team member, spoke in support of the Decadal Survey. "If you're frustrated, read all the white papers."

Charbonneau said they reveal the caustic in-fighting that was taking place within the community which resulted in missions like SIM-lite not being recommended. Another problem, he said, was the lack of external cost evaluations, which could’ve helped in judging which missions were fiscally possible.

It was left to the symposium moderator, Sara Seager, to put in a good word for NASA, and she pointed out that the space agency had supported everyone gathered there that day. She also said that the current situation called to mind Abraham Lincoln’s phrase, "A house divided against itself shall not stand." 

Summing up the history of mission development, Seager said, "In exoplanets, we divided and got conquered."

The symposium, "The Next 40 Years of Exoplanets," took place May 27 at the Massachusetts Institute of Technology in Cambridge, Mass. This full day of talks also included discussions about astrobiology, Sara Seager's ExoPlanetSat, Geoff Marcy's call to send a mission to Alpha Centauri, and many other topics of relevance to exoplanets.

This story was provided to SPACE.com by Astrobiology Magazine. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

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