The Sun's Evil Twin | Nemesis | Dwarf Sun | Documentary

The Sun's Evil Twin

In 1983, a scientist named Richard Muller came up with an interesting theory to explain the almost regular interavals between mass extinctions on Earth.

Roughly every 26 million years, the Earth suffers a massive extinction event in which whole species and ecosystems disappear.  It's widely believed and accepted by the scientific community  that the extinction events are precipitated by the impacts of comets and asteroid impacts, but what Muller devised to explain the almost regular event was rather scandalous - what if the sun had an evil twin brother?

Muller theorized that, orbiting the sun at a great distance, is another star - possibly a red or brown dwarf which orbits the sun once every 26 million years at a distance of 1 to 3 light years (this is very distant when you consider that the closest known star, Proxima Centauri, is only 4.2 light years away!)  When the star, which Muller named Nemesis after the Greek goddess of divine retribution, gets close to the sun thanks to an irregular orbit, it disturbs the Oort Cloud, the grouping of icy comets and bodies at the edge of our solar system, and sends them on a collision course towards the inner planets.

But wait a minute, if Nemesis really is out there, why can't we see it?  According to scientist who support the theory, Nemesis is a brown dwarf star which is a fancy way of saying it's a failed star.  It would be too small to sustain nuclear fusion and would simply be nothing more than a big ball of gas making it dark and very hard to find.

However, Muller's theory does fall under some scrutiny.  No where in the known galaxy have astronomers found a star that orbits at the distance that he described.   For this and other reasons, support for the Nemesis theory has waned, but it hasn't died.

Who knows... future surveys may detect the star, but until then, whenever you look up at the night sky, think of the possible evil twin of our sun that may exist in a distant orbit, waiting to unleash yet another flurry of extinction upon our world.

Scientist x

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Nasa | Animation Asteroid Retrieval Initiative | Another Great Mission

NASA's FY2014 budget proposal includes a plan to robotically capture a small near-Earth asteroid and redirect it safely to a stable orbit in the Earth-moon system where astronauts can visit and explore it. 

Performing these elements for the proposed asteroid initiative integrates the best of NASA's science, technology andhuman exploration capabilities and draws on the innovation of America's brightest scientists and engineers. It uses current and developing capabilities to find both large asteroids that pose a hazard to Earth and small asteroids that could be candidates for the initiative, accelerates our technology development activities in high-powered solar electric propulsion and takes advantage of our hard work on the Space Launch System rocket and Orion spacecraft, helping to keep NASA on target to reach the President's goal of sending humans to Mars in the 2030s. 

When astronauts don their spacesuits and venture out for a spacewalk on the surface of an asteroid, how they move and take samples of it will be based on years of knowledge built by NASA scientists and engineers who have assembled and operated the International Space Station, evaluated exploration mission concepts, sent scientific spacecraft to characterize near-Earth objects and performed ground-based analog missions. 

As early as the 1970s, NASA examined potential ways to use existing hardware to visit an asteroid to understand better its characteristics. On the International Space Station, scientific investigations and technology demonstrations are improving knowledge of how humans can live and work in space. The agency also has examined many possible mission concepts to help define what capabilities are needed to push the boundaries of space exploration. 

The Long and Storied Path to Human Asteroid Exploration

During the early space shuttle flights and through assembly of the space station, NASA has relied on testing both in space and on Earth to try out ideas through a host of analog missions, or field tests, that simulate the complexity of endeavors in space. 

Through 16 missions in the National Oceanic and Atmospheric Administration's underwater Aquarius Reef Base off the coast of Key Largo, Fla., aquanauts have tested techniques for human space exploration. These underwater tests have been built upon the experience gained by training astronauts in the Neutral Buoyancy Laboratory at NASA’s Johnson Space Center in Houston to assemble and maintain the space station. The NASA Extreme Environment Mission Operations (NEEMO) 15 and 16 missions in 2011 and 2012, respectively, simulated several challenges explorers will face when visiting an asteroid, including how to anchor to and move around the surface of a near-Earth object and how to collect samples of it. 

NASA also has simulated an asteroid mission as part of its 2012 Research and Technology Studies ground test at Johnson. During the simulation, a team evaluated how astronauts might do a spacewalk on an asteroid and accomplish other goals. While performing a spacewalk on a captured asteroid will involve different techniques than the activities performed during recent analog exercises, decisions made about ways to best sample an asteroid will be informed by the agency’s on-going concept development and past work. 

Scientific missions also have investigated the nature of asteroids to provide a glimpse of the origins of the solar system. From the Pioneer 10 spacecraft, which in 1972 was the first to venture into the Main Asteroid Belt, to the Dawn mission, which recently concluded its investigations of asteroid Vesta and is on its way to the dwarf planet Ceres, NASA's forays help us understand the origins of the solar system and inform decisions about how to conduct missions to distant planetary bodies. Scientists both at NASA and across the world also continue to study asteroids to shed light on their unique characteristics.

As NASA ventures farther into the solar system, the agency continues to simulate and evaluate operations and technical concepts for visiting an asteroid. 

N.A.S.A

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Life on Mars | Scientist Explains | Disclosure is near 2013

Life on Mars | Scientist Explains | Disclosure is near 2013

For centuries people have speculated about the possibility of life on Mars owing to the planet's proximity and similarity to Earth. Serious searches for evidence of life began in the 19th century, and continue via telescopic investigations and landed missions. While early work focused on phenomenology and bordered on fantasy, modern scientific inquiry has emphasized the search for water, chemical biosignatures of life in the soil and rocks at the planet's surface, and the search for biomarker gases in the atmosphere.

Mars is of particular interest for the study of the origins of life, because of its similarity to the early Earth. This is especially so as Mars has a cold climate and lacks plate tectonics or continental drift, and has remained pretty much unchanged since the end of the Hesperian period. At least two thirds of Mars' surface is more than 3.5 billion years old, and Mars may thus hold the best record of the prebiotic conditions leading to abiogenesis, even if life does not or has never existed there.

Fictional Martians have been a recurring feature of popular entertainment of the 20th and 21st centuries, and it remains an open question whether life currently exists on Mars, or has existed there in the past.

Historical map of Mars from Giovanni Schiaparelli.		Mars canals illustrated by astronomerPercival Lowell, 1898.

Mars' polar ice caps were observed as early as the mid-17th century, and they were first proven to grow and shrink alternately, in the summer and winter of each hemisphere, by William Herschel in the latter part of the 18th century. By the mid-19th century, astronomers knew that Mars had certain other similarities to Earth, for example that the length of a day on Mars was almost the same as a day on Earth. They also knew that its axial tilt was similar to Earth's, which meant it experienced seasons just as Earth does — but of nearly double the length owing to its much longer year. These observations led to the increase in speculation that the darker albedo features were water, and brighter ones were land. It was therefore natural to suppose that Mars may be inhabited by some form of life.

In 1854, William Whewell, a fellow of Trinity College, Cambridge, who popularized the word scientist, theorized that Mars had seas, land and possibly life forms. Speculation about life on Mars exploded in the late 19th century, following telescopic observation by some observers of apparent Martian canals — which were later found to be optical illusions. Despite this, in 1895, American astronomer Percival Lowell published his book Mars, followed by Mars and its Canals in 1906, proposing that the canals were the work of a long-gone civilization. This idea led British writer H. G. Wells to write The War of the Worlds in 1897, telling of an invasion by aliens from Mars who were fleeing the planet’s desiccation.

Spectroscopic analysis of Mars' atmosphere began in earnest in 1894, when U.S. astronomer William Wallace Campbell showed that neither water nor oxygen were present in the Martian atmosphere. By 1909 better telescopes and the best perihelic opposition of Mars since 1877 conclusively put an end to the canal theory.

Missions

Mariner 4 probe performed the first successful flyby of the planet Mars, returning the first pictures of the Martian surface in 1965. The photographs showed an arid Mars without rivers, oceans, or any signs of life. Further, it revealed that the surface (at least the parts that it photographed) was covered in craters, indicating a lack of plate tectonics and weathering of any kind for the last 4 billion years. The probe also found that Mars has no global magnetic field that would protect the planet from potentially life-threatening cosmic rays. The probe was able to calculate the atmospheric pressure on the planet to be about 0.6 kPa (compared to Earth's 101.3 kPa), meaning that liquid water could not exist on the planet's surface. After Mariner 4, the search for life on Mars changed to a search for bacteria-like living organisms rather than for multicellular organisms, as the environment was clearly too harsh for these.

Mariner Crater, as seen by Mariner 4 in 1965. Pictures like this suggested that Mars is too dry for any kind of life.		Streamlined Islands seen by Viking orbiter showed that large floods occurred on Mars. Image is located inLunae Palus quadrangle.

Viking orbiters

Liquid water is necessary for known life and metabolism, so if water was present on Mars, the chances of it having supported life may have been determinant. The Viking orbiters found evidence of possible river valleys in many areas, erosion and, in the southern hemisphere, branched streams.

Viking experiments

The primary mission of the Viking probes of the mid-1970s was to carry out experiments designed to detect microorganisms in Martian soil because the favorable conditions for the evolution of multicellular organisms ceased some four billion years ago on Mars. The tests were formulated to look for microbial life similar to that found on Earth. Of the four experiments, only the Labeled Release (LR) experiment returned a positive result, showing increased ¹⁴CO₂ production on first exposure of soil to water and nutrients. All scientists agree on two points from the Viking missions: that radiolabeled ¹⁴CO₂ was evolved in the Labeled Release experiment, and that the GC-MS detected no organic molecules. However, there are vastly different interpretations of what those results imply.

One of the designers of the Labeled Release experiment, Gilbert Levin, believes his results are a definitive diagnostic for life on Mars. However, this result is disputed by many scientists, who argue that superoxidant chemicals in the soil could have produced this effect without life being present. An almost general consensus discarded the Labeled Release data as evidence of life, because the gas chromatograph & mass spectrometer, designed to identify natural organic matter, did not detect organic molecules. The results of the Viking mission concerning life are considered by the general expert community, at best, as inconclusive.

In 2007, during a Seminar of the Geophysical Laboratory of the Carnegie Institution (Washington, D.C., USA), Gilbert Levin's investigation was assessed once more. Levin still maintains that his original data were correct, as the positive and negative control experiments were in order. Moreover, Levin's team, on 12 April 2012, reported a statistical speculation, based on old data —reinterpreted mathematically through complexity analysis— of the Labeled Release experiments, that may suggest evidence of "extant microbial life on Mars." Critics counter that the method has not yet been proven effective for differentiating between biological and non-biological processes on Earth so it is premature to draw any conclusions.

Ronald Paepe, an edaphologist (soil scientist), communicated to the European Geosciences Union Congress that the discovery of the recent detection of silicate minerals on Mars may indicate pedogenesis, or soil development processes, extended over the entire surface of Mars. Paepe's interpretation views most of Mars surface as active soil, colored red by eons of widespread wearing by water, vegetation and microbial activity.

A research team from the National Autonomous University of Mexico headed by Rafael Navarro-González, concluded that the equipment (TV-GC-MS) used by the Viking program to search for organic molecules, may not be sensitive enough to detect low levels of organics. Because of the simplicity of sample handling, TV–GC–MS is still considered the standard method for organic detection on future Mars missions, so Navarro-González suggests that the design of future organic instruments for Mars should include other methods of detection.

Carl Sagan poses next to a replica of the Viking landers.

Phoenix lander, 2008

The Phoenix mission landed a robotic spacecraft in the polar region of Mars on May 25, 2008 and it operated until November 10, 2008. One of the mission's two primary objectives was to search for a "habitable zone" in the Martian regolith where microbial life could exist, the other main goal being to study the geological history of water on Mars. The lander has a 2.5 meter robotic arm that was capable of digging shallow trenches in the regolith. There was an electrochemistry experiment which analysed the ions in the regolith and the amount and type of antioxidants on Mars. The Viking program data indicate that oxidants on Mars may vary with latitude, noting that Viking 2 saw fewer oxidants than Viking 1 in its more northerly position. Phoenix landed further north still. Phoenix's preliminary data revealed that Mars soil contains perchlorate, and thus may not be as life-friendly as thought earlier. The pH and salinity level were viewed as benign from the standpoint of biology. The analysers also indicated the presence of bound water and CO₂.

An artist's concept of the Phoenix spacecraft

Reported by: SCIENTIST X

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Aliens Exist | 100% Disclosure On TV | No One Can Hide It

“Do Aliens Exist?“

“This is a very tough question to answer definitively, and for many people has both frightening and amazing implications if the answer turns out to be yes.“

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Most of us with half a brain have asked ourselves this strange question once or twice, and even people who laugh at the subject socially probably wonder about it in their private thoughts.

“Do you believe they exist?“ It is a question which will lead your mind down some very interesting, and sometimes frightening paths.

You can use the buttons on the right and the tabs above to investigate the Mystery for yourself, but be warned - it is easier to start looking into than it is to stop . . .

Click Play Below - Out Of The Blue UFO Documentary

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I first became intrigued by this subject years ago when myself and two friends were walking home one cold clear winter night.

As a local hill came into view one of us said something like “Check how bright the moon is tonight“ as there was a glowing light shinning up from behind the hill, illuminating the underside of some low clouds.

One of my friends said “thats not the moon, the moons over there . . . “ no one spoke for about 5 seconds as we were all thinking “what is it then ! ?“

And we became even more glued to the spot when the pointed corner of a bright triangular object began to emerge slowly from behind the hill, revealing itself as the source of the eerie glow our eyes were fixed on.

Once about half of the object had emerged it produced a bright white flash that cannot of lasted longer than one fifth of a second, I’ve never been able to work out if it flashed and disappeared or the flash was it accelerating away at high speed.

But of course the three of us were high as kites talking non stop about it for the next hour or so, none of us wanting to walk home because we would have to separate in the dark!

Our sighting wasn’t such a big deal by today’s standards of giant swirling vortexes in the sky above Sydney being posted on YouTube or daylight camera footage of large UFOs wobbling over mexico city, but to our 14 year old brains back in 1996 it was amazing and had a major enough impact to kick-start a life long interest in the subject.

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So what does mainstream science have to say about the do aliens exist question? oddly enough The Drake Equation is widely accepted in the scientific community while the idea that extra-terrestrials have already visited earth gets laughed out of court.

For those of you who don’t know The Drake Equation was invented in 1961 by Doctor Frank Drake as a way to logically and mathematically work out the number of planets which could harbor intelligent life.

The mere fact that We exist raises the probability of intelligent life developing elsewhere above zero, when you add the fact that there are more stars in the sky than we can possibly count (think about that) and that many of these stars are much like our own sun, with their own planets and moons orbiting at various distances, the possibility of life and intelligent life becomes certain.

Even our own Milky Way Galaxy has no fewer than 100 billion suns! Can you imagine 100 billion suns? it’s difficult to do, imagine all the orbiting planets, moons and possibilities . . . feel small? me to.

Warning! If Head Hurts Stop Imagining Actual Size!

So Doctor Frank Drake was working at the National Radio Astronomy observatory in West Virginia and he and his colleagues became absorbed with the question do intelligent aliens exist?

They proceeded to aim a radio telescope at 2 nearby stars to see if they could pick up any intelligent transmissions, they did pick up some noise which was latter ruled out as being military radar (but was it?).

A year later Doctor Drake was asked by the U.S. National Academy Of Sciences to host a meeting of scientists to explore the possibility of intelligent civilizations beyond our small Earth.

While preparing for this meeting of minds he wrote down all the questions they would need to answer in order to predict the number of civilizations in the Galaxy, he then realized that if all these questions were multiplied together you would have the estimate for the number of civilizations, and this was the birth of The Drake Equation.

Doctor Frank Drake’s present day solution to The Drake Equation lists 10 thousand possible intelligent civilizations in our Milky Way Galaxy alone, so why does mainstream science have such mocking viewpoint on the idea that some UFOs are under Intelligent alien control?

One of they’re favourite arguments states that these intelligent beings could not travel the great distances to reach us . . why not? because we can’t yet?, besides, what if they have always been here?

Thankfully though the whole subject of ufo discloser and alien races interacting with people both past and present is fast becoming much less of a joke subject for most of us.

This is largely due to highly credible ex-government workers coming forward to testify about their amazing experiences, and also to the hard work of excellent investigators like Jim Marrs, Jenny Randles, David Icke, Stanton Friedman, Art Bell and Dr Stephen Greer to name but a few.

So if you are new to the subject and even a little skeptical I wish you all the best on your journey of discovery, and I’m envious of the interesting information you are about to uncover for the first time, as you attempt to answer the questions “Do Aliens Exist?” and“are aliens real?“.

Reported by: SCIENTIST X

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J-2X NASA Test | New Toy for NASA

Overview: J-2X Engine

J-2X is a highly efficient and versatile advanced rocket engine with the ideal thrust and performance characteristics to power the upper stage of NASA's Space Launch System, a new heavy-lift launch vehicle capable of missions beyond low-Earth orbit. Fueled by liquid oxygen and liquid hydrogen, the J-2X builds on heritage designs but relies on nearly a half-century of NASA spaceflight experience and technological and manufacturing advances to deliver up to 294,000 pounds of thrust, powering exploration to new destinations in our solar system. 

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Orion Exploration HD Animation | Nasa and Scientist X

Orion Exploration

Orion Exploration, L.L.C. is a privately held exploration and production company based in Tulsa,
OK, which was
founded to pursue horizontal coal bed methane (CBM) prospects in the Arkoma Basin. In 2004,
Orion shifted focus
 to horizontally drilling Paleozoic-aged carbonate rocks in north-central Oklahoma. Currently,
Orion is focused
on the early-stage acquisition and drilling of large-scale internally generated prospects in the
 Mid-Continent.
We use technology to reduce exploration risk in exploring rich, fertile basins where
hydrocarbons are known to
exist.

Orion’s staff has over 100 years of experience, including geologists, landmen, engineers and
other technical front
office personnel devoted to internal prospect generation and identification of potential drilling
locations.

Orion’s current horizontal drilling exploration activity is focused on developing oil reserves from
Mississippian
reservoirs in several core areas, in both Oklahoma and Kansas, as well as utilizing dewatering
 techniques in
hydrocarbon extraction from the Hunton reservoir in a core area located in Central Oklahoma. 

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Neil Tyson Talks About Apophis | End of World 2029

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Space Shuttle Columbia Destroyed

IN MEMORY
The crew of STS-107. L to R: Brown,Husband, Clark, Chawla, Anderson, McCool,Ramon

The Space Shuttle Columbia disaster occurred on February 1, 2003, when shortly before it was scheduled to conclude its 28th mission, STS-107, the Space Shuttle Columbia disintegrated over Texas and Louisiana during re-entry into the Earth's atmosphere, resulting in the death of all seven crew members. Debris from Columbia fell to Earth in Texas. A debris field has been mapped along a path stretching from south of Fort Worth to Hempill, Texas, as well as into parts of Louisiana.

The loss of Columbia was a result of damage sustained during launch when a piece of foam insulation the size of a small briefcase broke off from theSpace Shuttle external tank (the 'ET' main propellant tank) under the aerodynamic forces of launch. The debris struck the leading edge of the left wing, damaging the Shuttle's thermal protection system (TPS), which shields the vehicle from the intense heat generated from atmospheric compression during re-entry. While Columbia was still in orbit, some engineers suspected damage, but NASA managers limited the investigation, under the rationale that the Columbia crew could not have fixed the problem. The Columbia Accident Investigation Board (CAIB) later concluded that a rescue mission using Atlantis may have been possible.

NASA's original shuttle design specifications stated that the external tank was not to shed foam or other debris; therefore, strikes upon the vehicle were safety issues that needed to be resolved before a launch was cleared. Launches were often given the go-ahead as engineers came to see the foam shedding and debris strikes as inevitable and unresolvable, with the rationale that they were either not a threat to safety, or an acceptable risk. The majority of shuttle launches recorded such foam strikes and thermal tile scarring. On STS-112, two launches before, a chunk of foam broke away from the ET bipod ramp and hit the SRB-ET Attach Ring near the bottom of the left solid rocket booster (SRB) causing a dent four inches wide and three inches deep in it. After that mission, the situation was analyzed and NASA decided to press ahead under the justification that "The ET is safe to fly with no new concerns (and no added risk)" of further foam strikes, justification that was revisited while Columbia was still in orbit and Chair of the Mission Management Team (MMT) Linda Ham re-assessed, stating that the “Rationale was lousy then and still is”. Ham as well as Shuttle Program Manager Ron Dittemore had both been present at the October 31, 2002, meeting where this decision to continue with launches was made.

During re-entry of STS-107, the damaged area allowed hot gases to penetrate and destroy the internal wing structure, rapidly causing the in-flight breakup of the vehicle. An extensive ground search in parts of Texas, Louisiana, and Arkansas recovered crew remains and many vehicle fragments.

Mission STS-107 was the 113th Space Shuttle launch. The mission was delayed 18 times over the two years from the planned launch date of January 11, 2001, to the actual launch date of January 16, 2003. (It was preceded by STS-113.) A launch delay due to cracks in the shuttle's propellant distribution system occurred one month before a July 19, 2002, launch date. The Columbia Accident Investigation Board determined that this delay had nothing to do with the catastrophic failure six months later.

The Columbia Accident Investigation Board's recommendations addressed both technical and organizational issues. Space Shuttle flight operations were delayed for over two years, similar to the delay following the Challenger accident. Construction of the International Space Station was put on hold, and for 29 months the station relied entirely on the Russian Federal Space Agency for resupply until Shuttle flights resumed with STS-114 and 41 months for crew rotation until STS-121. Major changes to shuttle operations, after missions resumed, included a thorough on-orbit inspection to determine how well the shuttle's thermal protection system had endured the ascent, and keeping a designated rescue mission at the ready in case irreparable damage was found. Also it had been decided that all missions would be flown only to the ISS so that the crew could use that spacecraft as a "safe haven" if need be. Later NASA decided it would be an acceptable risk to make one exception to that policy for one final mission to repair the Hubble Space Telescope in its high-altitude low-inclination orbit.

Space Shuttle Columbia disaster

STS-107 flight insignia
Date	1 February 2003
Time	08:59 EST (13:59 UTC)
Location	Over Texas and Louisiana
Outcome	Grounding of the Space Shuttle fleet for over two years during which various safety measures, improvement in crew restraint, effective ways to deal with catastrophic cabin depressurization and an automated parachute system were initiated.
Casualties
Rick D. Husband William C. McCool Michael P. Anderson Kalpana Chawla David M. Brown Laurel Clark Ilan Ramon
Inquiries	Columbia Accident Investigation Board

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Another Planet Like Earth was Discovered!

A new Earth

Is there anybody out there? Astronomers and dreamers have been asking this question since the dawn of humanity — and yet, the mystery remains. Are we the only life forms in the universe, or are neighbors like us lurking just beyond the reaches of our solar system? NASA has made it a mission to discover the truth. In March 2009, the space agency launched the Kepler Mission, a NASA Discovery program designed to look for possible life-supporting planets. In just the first 16 months of operation, Kepler has discovered 2,326 potential planets. Once confirmed by follow-up studies, these potential discoveries could significantly raise the tally of exoplanets (planets outside our solar system) well over its current count of 702. Here are 10 images from NASA depicting these wild worlds.

 

Pictured here is an artist’s depiction of Kepler-22, which was the first exoplanet discovered by Kepler to orbit in a star’s habitable zone. This means that Kepler-22 may have liquid water on it like Earth, making it our closest possible sister planet. As NASA writes, “the planet is 2.4 times the size of Earth, making it the smallest yet found to orbit in the middle of the habitable zone of a star like our sun.” 

REPORTED BY : (Text: Katherine Butler)

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New Planet With LIFE 100% SURE | GLIESE 581g

Gliese 581 g

Gliese 581 g

Extrasolar planet		List of extrasolar planets
Parent star
Star		Gliese 581
Constellation		Libra
Right ascension	(α)	15h 19m 26s
Declination	(δ)	−07° 43′ 20″
Apparent magnitude	(mV)	10.55
Distance		20.3 ± 0.3 ly (6.2 ± 0.1 pc)
Spectral type		M3V
Mass	(m)	0.31 M☉
Radius	(r)	0.29 R☉
Temperature	(T)	3480 ± 48 K
Metallicity	[Fe/H]	−0.33 ± 0.12
Age		7 – 11 Gyr
Orbital elements Epoch JD 2451409.762
Semimajor axis	(a)	0.14601 ± 0.00014 AU
Eccentricity	(e)	0
Orbital period	(P)	36.562 ± 0.052 d (0.100 y)
		(877 h)
Mean anomaly	(M)	271 ± 48°
Semi-amplitude	(K)	1.29 ± 0.19 m/s
Physical characteristics
Minimum mass	(m sini)	3.1 ± 0.4 M⊕
Discovery information
Discovery date		September 29, 2010
Discoverer(s)		Steven S. Vogt et al.
Detection method		Radial Velocity
Discovery site		Keck Observatory,Hawaii
Discovery status		Unconfirmed
Database references
Extrasolar Planets Encyclopaedia		data
SIMBAD		data

The W. M. Keck Observator at twilight, where Gliese 581 g was discovered

Gliese 581 g , also Gl 581 g or GJ 581 g, is an unconfirmed extrasolar planet claimed to orbit the red dwarf star Gliese 581, 22 light-years from Earth in the constellation of Libra. It is the sixth planet purportedly discovered orbiting the star. The discovery was announced by the Lick-Carnegie Exoplanet Survey in late September 2010, after a decade of observation. However, the ESO/HARPS survey team was not able to confirm that the planet exists.

Gliese 581 g has attracted attention because it is near the middle of the habitable zone of its parent star. That means it could sustain liquid water on its surface and could potentially host life similar to that on Earth. (The planet is expected to have temperatures around −37 to −12 °C, however). If it is a rocky planet, favorable atmospheric conditions could permit the presence of liquid water, a necessity for all known life, on its surface. With a mass 3.1 to 4.3 times Earth's, Gliese 581 g is considered a super-Earth and is the planet closest in size to Earth known in a habitable zone. This makes it the most Earth-like Goldilocks planet found outside the Solar System and the exoplanet with the greatest recognized potential for harboring life.

The supposed detection of Gliese 581 g after such a short period of searching and at such close proximity has led some astronomers to hypothesize that the proportion of stars with habitable planets may be greater than ten percent.

SCIENTIST X

Discovery

The six-planet model of the Gliese 581planetary system with circular orbits.

The planet was claimed to be detected by astronomers in the Lick-Carnegie Exoplanet Survey, led by principal investigator Steven S. Vogt, professor of astronomy and astrophysics at the University of California, Santa Cruz and co-investigator R. Paul Butler of the Carnegie Institution of Washington. The discovery was made using radial velocity measurements, combining 122 observations obtained over 11 years from the High Resolution Echelle Spectrometer (HIRES) instrument of the Keck 1 telescope with 119 measurements obtained over 4.3 years from the High Accuracy Radial Velocity Planet Searcher (HARPS) instrument of the European Southern Observatory's 3.6 m telescope at La Silla Observatory.

After subtracting the signals of the previously known Gliese 581 planets, b, c, d and e, the signals of two additional planets were apparent: a 445-day signal from a newly recognized outermost planet designated f, and the 37-day signal from Gliese 581 g. The probability that the detection of the latter was spurious was estimated at only 2.7 in a million. The authors stated that while the 37-day signal is "clearly visible in the HIRES data set alone", "the HARPS data set alone is not able to reliably sense this planet" and concluded, "It is really necessary to combine both data sets to sense all these planets reliably." The Lick–Carnegie team explained the results of their research in a paper published in the Astrophysical Journal. Although not sanctioned by the IAU's naming conventions, Vogt's team informally refers to the planet as "Zarmina's World" after his wife, and some cases simply as Zarmina.

Nondetection in new HARPS data analysis

Two weeks after the announcement of the discovery of Gliese 581 g, astronomer Francesco Pepe of theGeneva Observatory reported that in a new analysis of 179 measurements taken by the HARPS spectrograph over 6.5 years, neither planet g nor planet f was detectable. Vogt responded to the latest concerns by saying, "I am not overly surprised by this as these are very weak signals, and adding 60 points onto 119 does not necessarily translate to big gains in sensitivity." He cautioned that not finding the planet in this study does not make a strong case for it not existing, because both data sets may be needed to detect it. More recently, Vogt added, "I feel confident that we have accurately and honestly reported our uncertainties and done a thorough and responsible job extracting what information this data set has to offer. I feel confident that anyone independently analyzing this data set will come to the same conclusions."

Differences in the two groups' results may involve the planetary orbital characteristics assumed in calculations. According to MIT astronomer Sara Seager, Vogt postulated the planets around Gliese 581 had perfectly circular orbits whereas the Swiss group thought the orbits were moreeccentric. This difference in approach may be the reason for the disagreement, according to Alan Boss. Butler remarked that with additional observations, "I would expect that on the time scale of a year or two this should be settled." Other astronomers also supported a deliberate evaluation: Seager stated, "We will have consensus at some point; I don't think we need to vote right now." and Ray Jayawardhana noted, "Given the extremely interesting implications of such a discovery, it's important to have independent confirmation." Gliese 581 g is listed as "unconfirmed" in the Extrasolar Planets Encyclopaedia.

In December 2010, a claimed methodological error was reported in the data analysis that led to the discovery of Gliese 581 f and g. The team around Steven Vogt inferred the number of exoplanets by using a reduced chi-square, although the orbital models are nonlinear in the model parameters. Therefore, reduced chi-square is not a trustworthy diagnostic. In fact, an investigation of the fit residuals showed that the data used by Vogt's team actually prefers a model with four planets, not six, in agreement with the results of Francesco Pepe's team.

Further analyses of HIRES/HARPS data

Another re-analysis found no clear evidence for a fifth planetary signal in the combined HIRES/HARPS data set. The claim was made that the HARPS data provided only some evidence for 5 planet signals, while incorporation of both data sets actually degraded the evidence for more than four planets (i.e., none for 581 f or 581 g). Mikko Tuomi of the University of Hertfordshire performed a Bayesian re-analysis of the HARPS and HIRES data with the result that they "do not imply the conclusion that there are two additional companions orbiting GJ 581".

"I have studied [the paper] in detail and do not agree with his conclusions," Steven Vogt said in reply, concerned that Gregory has considered the HIRES data as more uncertain. The question of Gliese 581g's existence won't be settled definitively until researchers gather more high-precision radial velocity data, Vogt said. However Vogt expects further analysis to strengthen the case for the planet.

By performing a number of statistical tests, Guillen Anglada-Escude of the Carnegie Institute of Washington concluded that the existence of Gl 581 g was well supported by the available data, despite the presence of a statistical degeneracy that derives from an alias of the first eccentric harmonic of another planet in the system In a forthcoming paper, Anglada-Escude and Rebekah Dawson claim “With the data we have, the most likely explanation is that this planet is still there.”

Physical characteristics

Gliese 581 g has an orbital period of 37 days, orbiting at a distance of 0.146 AU from its parent star. It is believed to have a mass of 3.1 to 4.3 times Earth's and a radius of 1.3 to 2.0 times Earth's (1.3 to 1.5 times larger if predominantly rocky, 1.7 to 2.0 times larger if predominantly water ice). Its mass indicates it is probably a rocky planet with a solid surface. The planet's surface gravity is expected to be in the range of 1.1 to 1.7 times Earth's, enough to hold on to an atmosphere likely to be denser than Earth's.

Main article: Habitability of red dwarf systems

Planetary orbits in the Gliese 581 system compared to those of our own Solar System ("g" designates Gliese 581g)

Because of Gliese 581 g's proximity to its parent star, it is predicted to be tidally locked to Gliese 581. Just as Earth's Moon always presents the same face to the Earth, the length of Gliese 581 g's sidereal day would then precisely match the length of its year, meaning it would be permanently light on one half and permanently dark on the other half of its surface. Tidal locking also means the planet would have no axial tilt and therefore no seasonality in a conventional sense.

With one side of the planet always facing the star, temperatures could range from blazing hot in the bright side to freezing cold in the dark side if atmospheric heat transport is limited. The atmosphere's inventory of volatile compounds such as water and carbon dioxide could then permanently freeze on the dark side. However, an atmosphere of the expected density would be likely to moderate these extremes.

Atmospheric effects

Whether or not a tide-locked planet with the orbital characteristics of Gliese 581g is actually habitable depends on the composition of the atmosphere and the nature of the planetary surface. A comprehensive modeling study  including atmospheric dynamics, realistic radiative transfer and the physics of formation of sea ice (if the planet has an ocean) indicates that the planet can become as hot as Venus if it is dry and allows carbon dioxide to accumulate in its atmosphere. The same study identified two habitable states for a water-rich planet. If the planet has a very thin atmosphere, a thick ice crust forms over most of the surface, but the substellar point remains hot enough to yield a region of thin ice or even episodically open water. If the planet has an atmosphere with Earthlike pressures, containing approximately 20% (molar) carbon dioxide, then the greenhouse effect is sufficiently strong to maintain a pool of open water under the substellar point with temperatures comparable to the Earth's tropics. This state has been dubbed "Eyeball Earth" by the author.An atmosphere that is dense will circulate heat, potentially allowing a wide area on the surface to be habitable. For example, Venus has a solar rotation rate approximately 117 times slower than Earth's, producing prolonged days and nights. Despite the uneven distribution of sunlight over 
time intervals shorter than several months, unilluminated areas of Venus are kept almost as hot as the day side by globally circulating winds. Simulations have shown that an atmosphere containing appropriate levels of greenhouse CO₂ and H₂O need only be a tenth the pressure of Earth's atmosphere (100 mbar) to effectively distribute heat to the night side. Current technology cannot determine the atmospheric or surface composition of the planet due to the overpowering light of its parent star.

Modeling of the effect of tidal locking on Gliese 581 g's possible atmosphere, using a general circulation model employing an atmosphere with Earthlike surface pressure but a highly idealized representation of radiative processes, indicates that for a solid-surface planet the locations of maximum warmth would be distributed in a sideways chevron-shaped pattern centered near the substellar point.

Temperatures

It is estimated that the average global equilibrium temperature (the temperature in the absence of atmospheric effects) of Gliese 581 g ranges from 209 to 228 K (−64 to −45 °C, or −84 to −49 °F) for Bond albedos (reflectivities) from 0.5 to 0.3 (with the latter being more characteristic of the inner Solar System). Adding an Earth-like greenhouse effect yields an average surface temperature in the range of 236 to 261 K (−37 to −12 °C, or −35 to 10 °F). Gliese 581g is in an orbit where a silicate weathering thermostat can operate, and this can lead to accumulation of sufficient carbon dioxide in the atmosphere to permit liquid water to exist at the surface, provided the planet's composition and tectonic behavior can support sustained outgassing.

Temperature comparisons	Venus	Earth	Gliese 581 g	Mars
Global equilibrium temperature	307 K 34 °C 93 °F	255 K −18 °C −0.4 °F	209 K to 228 K −64 °C to −45 °C −83 °F to −49 °F	206 K −67 °C −88.6 °F
+ Venus' GHG effect	737 K 464 °C 867 °F
+ Earth's GHG effect		288 K 15 °C 59 °F	236 K to 261 K −37 °C to −12 °C −35 °F to 10 °F
+ Mars' GHG effect				210 K −63 °C −81 °F
Tidally locked	Almost	No	yes	No
Global Bond Albedo	0.9	0.29	0.5 to 0.3	0.25
Refs.

By comparison, Earth's present global equilibrium temperature is 255 K (−18 °C), which is raised to 288 K (15 °C) by greenhouse effects. However, when life evolved early in Earth's history, the Sun's energy output is thought to have been only about 75% of its current value, which would have correspondingly lowered Earth's equilibrium temperature under the same albedo conditions. Yet Earth maintained equable temperatures in that era, perhaps with a more intense greenhouse effect, or a lower albedo, than at present.

Current Martian surface temperatures vary from lows of about −87 °C (−125 °F) during polar winter to highs of up to −5 °C (23 °F) in summer. The wide range is due to the rarefied atmosphere, which cannot store much solar heat, and the low thermal inertia of the soil. Early in its history, a denser atmosphere may have permitted the formation of an ocean on Mars.

Two previously discovered planets in the same system, Gliese 581 c and d (inward and outward from planet g, respectively), were also regarded as potentially habitable following their discovery. Both were later evaluated as being outside the conservatively defined habitable zone, leading Vogt et al. to remark that "The GJ 581 system has a somewhat checkered history of habitable planet claims". However, a subsequent downward revision of the period of planet d from 83 to 67 days has bolstered its habitability prospects, although a large greenhouse effect would be needed.

Potential for life

Further information: Planetary habitability

In an interview with Lisa-Joy Zgorski of the National Science Foundation, Steven Vogt was asked what he thought about the chances of life existing on Gliese 581 g. Vogt was optimistic: "I'm not a biologist, nor do I want to play one on TV. Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say that, my own personal feeling is that the chances of life on this planet are 100%. I have almost no doubt about it." In the same article Dr. Seager is quoted as saying "Everyone is so primed to say here's the next place we're going to find life, but this isn't a good planet for follow-up." According to Vogt, the long lifetime of red dwarfs improves the chances of life being present. "It's pretty hard to stop life once you give it the right conditions", he said. "Life on other planets doesn't mean E.T. Even a simple single-cell bacteria or the equivalent of shower mold would shake perceptions about the uniqueness of life on Earth."

Implications

Scientists have monitored only a relatively small number of stars in the search for exoplanets. The discovery of a potentially habitable planet like Gliese 581 g so early in the search might mean that habitable planets are more widely distributed than had been previously believed. According to Vogt, the discovery "implies an interesting lower limit on the fraction of stars that have at least one potentially habitable planet as there are only 116 known solar-type or later stars out to the 6.3 parsec distance of Gliese 581". This finding foreshadows what Vogt calls a new, second Age of Discovery in exoplanetology:

Confirmation by other teams through additional high-precision RVs would be most welcome. But if GJ 581g is confirmed by further RV scrutiny, the mere fact that a habitable planet has been detected this soon, around such a nearby star, suggests that η_⊕ could well be on the order of a few tens of percent, and thus that either we have just been incredibly lucky in this early detection, or we are truly on the threshold of a second Age of Discovery.

If the fraction of stars with potentially habitable planets is on the order of a few tens of percent as Vogt proposes, and the Sun's stellar neighborhood is a typical sample of the galaxy, then the discovery of Gliese 581 g in the habitable zone of its star points to the potential of billions of Earth-like planets in our Milky Way galaxy alone.

Reported By : SCIENTIST X 

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