Higgs Boson's like Boson Found at CERN : A Ground Breaking Discovery in Particle Physics

Fig : A proton-proton collision event in the CMS experiment producing two high-energy photons (red towers). This is what we would expect to see from the decay of a Higgs boson but it is also consistent with background Standard Model physics processes. © CERN 2012

By CERN, Geneva

Published on 4 July 2012. 

At a seminar held at CERN today as a curtain raiser to the year’s major particle physics conference, ICHEP2012 in Melbourne, the ATLAS and CMS experiments presented their latest preliminary results in the search for the long sought Higgs particle. Both experiments observe a new particle in the mass region around 125-126 GeV.

“We observe in our data clear signs of a new particle, at the level of 5 sigma, in the mass region around 126 GeV. The outstanding performance of the LHC and ATLAS and the huge efforts of many people have brought us to this exciting stage,” said ATLAS experiment spokesperson Fabiola Gianotti, “but a little more time is needed to prepare these results for publication.”

"The results are preliminary but the 5 sigma signal at around 125 GeV we’re seeing is dramatic. This is indeed a new particle. We know it must be a boson and it’s the heaviest boson ever found,” said CMS experiment spokesperson Joe Incandela. “The implications are very significant and it is precisely for this reason that we must be extremely diligent in all of our studies and cross-checks."

“It’s hard not to get excited by these results,” said CERN Research Director Sergio Bertolucci. “ We stated last year that in 2012 we would either find a new Higgs-like particle or exclude the existence of the Standard Model Higgs. With all the necessary caution, it looks to me that we are at a branching point: the observation of this new particle indicates the path for the future towards a more detailed understanding of what we’re seeing in the data.”

The results presented today are labelled preliminary. They are based on data collected in 2011 and 2012, with the 2012 data still under analysis.  Publication of the analyses shown today is expected around the end of July. A more complete picture of today’s observations will emerge later this year after the LHC provides the experiments with more data.

The next step will be to determine the precise nature of the particle and its significance for our understanding of the universe. Are its properties as expected for the long-sought Higgs boson, the final missing ingredient in the Standard Model of particle physics? Or is it something more exotic? The Standard Model describes the fundamental particles from which we, and every visible thing in the universe, are made, and the forces acting between them. All the matter that we can see, however, appears to be no more than about 4% of the total. A more exotic version of the Higgs particle could be a bridge to understanding the 96% of the universe that remains obscure.

“We have reached a milestone in our understanding of nature,” said CERN Director General Rolf Heuer. “The discovery of a particle consistent with the Higgs boson opens the way to more detailed studies, requiring larger statistics, which will pin down the new particle’s properties, and is likely to shed light on other mysteries of our universe.”

Positive identification of the new particle’s characteristics will take considerable time and data. But whatever form the Higgs particle takes, our knowledge of the fundamental structure of matter is about to take a major step forward.

Cracks in the standard model

The latest results from the BaBar experiment may suggest a surplus over standard model predictions of a type of particle decay called “B to D-star-tau-nu.” In this conceptual art, an electron and positron collide, resulting in a B meson (not shown) and an antimatter B-bar meson, which then decays into a D meson and a tau lepton as well as a smaller antineutrino. Credit: Greg Stewart, SLAC National Accelerator Laboratory

Published by Science and Technology Facilities Council, United Kingdom
Published: June 19, 2012

Recently analyzed data from BaBar, a high-energy physics experiment in the U.S., may suggest possible flaws in the standard model of particle physics — the reigning description of how the universe works on subatomic scales. The data from BaBar, a particle accelerator at the U.S. Department of Energy’s (DOE) SLAC National Accelerator Laboratory, which was built by 10 countries including the United Kingdom, show that a particular type of particle decay happens more often than the standard model says it should.

The data refers to a particle called the B-bar meson that decays into a D meson, an antineutrino, and a tau lepton. This particular decay of a B meson should, theoretically, only happen in one in every 100 cases, but the new results from BaBar show it is happening too often. While the level of certainty of the difference, or excess, is not enough to claim a break from the standard model, the results are a potential sign of something amiss and are likely to impact existing theories.

“The excess over the standard model prediction is exciting,” said Michael Roney from the University of Victoria in Canada. “The results are significantly more sensitive than previously published studies of these decays. But before we can claim an actual discovery, other experiments have to replicate it and rule out the possibility this isn’t just an unlikely statistical fluctuation.”

“This result is very interesting, and, if confirmed, could be a sign of physics beyond the standard model,” said Adrian Bevan from Queen Mary, University of London.

“Our current theory about the fundamental forces of the universe, which has been around for nearly 40 years, is beginning to show signs of failure,” said Fergus Wilson from STFC’s Rutherford Appleton Laboratory. “Just as exciting, our new measurement indicates that any replacement theory will need to be more exotic and complex than we could have hoped or imagined. Although we must not jump to conclusions based on just one measurement, this new result is one of the most compelling yet. It follows on from previous indications recently reported by us, all of which point in the same direction.”

The BaBar experiment, which collected data from 1999 to 2008, was designed to explore various mysteries of particle physics, including why the universe contains matter but no antimatter. Data from the collaboration, which includes 75 institutions from Canada, France, Germany, Italy, Norway, Russia, Spain, the United Kingdom, and the U.S., helped confirm a matter-antimatter theory for which two researchers won the 2008 Nobel Prize in physics. At its peak, some 90 British particle physicists and engineers from 11 institutions took part in the experiment.

Researchers continue to apply BaBar data to a variety of questions in particle physics. “This result will help guide teams of researchers looking for potentially related new physics effects at the Large Hadron Collider and at other particle physics labs around the world,” said Bevan.

“If the excess decays shown are confirmed, it will be exciting to figure out what is causing it," said Abner Soffer from Tel Aviv University in Israel. “Other theories involving new physics are waiting in the wings, but the BaBar results already rule out one important model called the Two Higgs Doublet Model. We hope our results will stimulate theoretical discussion about just what the data are telling us about new physics.”

The researchers also hope their colleagues in the Belle collaboration, which studies the same types of particle collisions, see something similar. "If they do, the combined significance could be compelling enough to suggest how we can finally move beyond the standard model,” said Roney.

NASA Mars rover team aims for landing closer to prime science site

This image shows changes in the target landing area for Curiosity, the rover of NASA's Mars Science Laboratory project. The larger ellipse was the target area prior to early June 2012, when the project revised it to the smaller ellipse centered nearer to the foot of Mount Sharp, inside Gale Crater. Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS

By NASA Headquarters, Washington, D.C.

Published: June 18, 2012
 
NASA has narrowed the target for its most advanced Mars rover, Curiosity, which will land on the Red Planet in August. The car-sized rover will arrive closer to its ultimate destination for science operations, but also closer to the foot of a mountain slope that poses a landing hazard.

"We're trimming the distance we'll have to drive after landing by almost half," said Pete Theisinger from NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. "That could get us to the mountain months earlier."

It was possible to adjust landing plans because of increased confidence in precision landing technology aboard the Mars Science Laboratory (MSL) spacecraft, which is carrying the Curiosity rover. That spacecraft can aim closer without hitting Mount Sharp at the center of Gale Crater. Rock layers located in the mountain are the prime location for research with the rover.

Curiosity is scheduled to land at approximately 1:31 a.m. EDT August 6. Following checkout operations, Curiosity will begin a two-year study of whether the landing vicinity ever offered an environment favorable for microbial life.

The landing target ellipse had been approximately 12 miles (20 kilometers) wide and 16 miles (25km) long. Continuing analysis of the new landing system's capabilities has allowed mission planners to shrink the area to approximately 4 miles (7km) wide and 12 miles (20km) long, assuming winds and other atmospheric conditions are as predicted.

Even with the smaller ellipse, Curiosity will be able to touch down at a safe distance from steep slopes at the edge of Mount Sharp.

"We have been preparing for years for a successful landing by Curiosity, and all signs are good," said Dave Lavery from NASA. "However, landing on Mars always carries risks, so success is not guaranteed. Once on the ground, we'll proceed carefully. We have plenty of time since Curiosity is not as life-limited as the approximate 90-day missions like NASA’s Mars Exploration Rovers and the Phoenix lander.”

Since the spacecraft was launched in November 2011, engineers have continued testing and improving its landing software. MSL will use an upgraded version of flight software installed on its computers during the past two weeks. Additional upgrades for Mars surface operations will be sent to the rover about a week after landing.

Other preparations include upgrades to the rover's software and understanding effects of debris coming from the drill the rover will use to collect samples from rocks on Mars. Experiments at JPL indicate that Teflon from the drill could mix with the powdered samples. Testing will continue past landing with copies of the drill. The rover will deliver the samples to onboard instruments that can identify mineral and chemical ingredients.

"The material from the drill could complicate but will not prevent analysis of carbon content in rocks by one of the rover's 10 instruments. There are workarounds,” said John Grotzinger from the California Institute of Technology in Pasadena. "Organic carbon compounds in an environment are one prerequisite for life. We know meteorites deliver non-biological organic carbon to Mars, but not whether it persists near the surface. We will be checking for that and for other chemical and mineral clues about habitability."

Curiosity will be in good company as it nears landing. Two NASA Mars orbiters, along with a European Space Agency (ESA) orbiter, will be in position to listen to radio transmissions as MSL descends through Mars' atmosphere.

Soil Moisture Climate Data Record observed from Space

                     Fig : Dry areas and moist areas - a map created from satellite data

Published by Vienna University of Technology and Free University of Amsterdam

Date : 19th June, 2012

The future of the world’s climate is determined by various parameters, such as the density of clouds or the mass of the Antarctic ice sheet. One of these crucial climate parameters is soil moisture, which is hard to measure on a global scale. Now, the European Space Agency (ESA), in cooperation with the Vienna University of Technology (Institute of Photogrammetry and Remote Sensing) and the Free University of Amsterdam, is presenting a data set, containing global soil moisture data from 1978 to 2010. This was possible by extensive mathematical analysis of satellite data

Warmer Climate Changes Soil MoistureEven though soil moisture makes up only about 0.001 % of the total water found on earth, it plays a crucial rule in the climate system. “The link between climate and soil moisture is still not well understood, because so far reliable long-term data has not been available”, says professor Wolfgang Wagner (Vienna University of Technology). One of the predicted consequences of global warming is that warming will lead to higher evaporation rates and hence soil drying in some regions. But drier soils themselves will heat up the air near the land surface. This positive feedback mechanism may thus act to increase the number of extreme heat waves similar to those experienced in Western Europe in 2003 and Russia in 2010. On the other hand, hot air can hold more water and lead to increased precipitation in some regions. “The effects of climate change vary from region to region”, says Wolfgang Werner, “this makes it all the more important to have reliable long-term data for the whole globe.”

Microwaves from SpaceSoil moisture can be measured with satellites using microwave radiation. Unlike visible light, microwaves can penetrate clouds. Satellites can either measure the earths natural microwave radiation to calculate the local soil moisture (passive measurement) or the satellite sends out microwave pulses and measures how strongly the pulse is reflected by the surface (active measurement). Over the years, various satellites with different measurement methods have been used. “It is a great challenge to extract reliable soil moisture data from these very different datasets, spanning several decades”, says Wolfgang Wagner.

To address the current lack of long-term soil moisture data the European Space Agency (ESA) has been supporting the development of a global soil moisture data record derived by merging measurements acquired by a series of European and American satellites. ESA is now happy to announce that the release of the first soil moisture data record spanning the period 1978 to 2010. The soil moisture data record was generated by merging two soil moisture data sets, one derived from active microwave observations and the other from passive microwave observations. The active data set was generated by the Vienna University of Vienna (TU Wien) based on observations from the C-band scatterometers on board of ERS-1, ERS-2 and METOP-A; the passive data set was generated by the VU University Amsterdam in collaboration with NASA based on passive microwave observations.

Technological ChallengesThe harmonization of these datasets aimed to take advantage of both microwave techniques, but still the challenges were significant. Amongst other issues, the potential influences of mission specifications, sensor degradation, drifts in calibration, and algorithmic changes had to be accounted for as accurately as possible. Also, it had to be guaranteed that the soil moisture data retrieved from the different active and passive microwave instruments are physically consistent. As this is the first release of such a product, not all caveats and limitations of the data are yet fully understood. It will therefore require the active cooperation of the remote sensing and climate modeling communities to jointly validate the satellite and model data, and advance the science in both fields along the way.

Black Holes as Particle Detectors

Fig : Artist's impression of a black hole, surrounded by axions.

Published by Vienna University of Technology
Date : 18th June, 2012 



Finding new particles usually requires high energies – that is why huge accelerators have been built, which can accelerate particles to almost the speed of light. But there are other creative ways of finding new particles: At the Vienna University of Technology, scientists presented a method to prove the existence of hypothetical “axions”. These axions could accumulate around a black hole and extract energy from it. This process could emit gravity waves, which could then be measured.

Axions  are hypothetical particles with a very low mass. According to Einstein, mass is directly related to energy, and therefore very little energy is required to produce axions. “The existence of axions is not proven, but it is considered to be quite likely”, says Daniel Grumiller. Together with Gabriela Mocanu he calculated at the Vienna University of Technology (Institute for Theoretical Physics), how axions could be detected.

Astronomically Large ParticlesIn quantum physics, every particle is described as a wave. The wavelength corresponds to the particle’s energy. Heavy particles have small wavelengths, but the low-energy axions can have wavelengths of many kilometers. The results of Grumiller and Mocanu, based on works by Asmina Arvanitaki and Sergei Dubovsky (USA/Russia), show that axions can circle a black hole, similar to electrons circling the nucleus of an atom. Instead of the electromagnetic force, which ties the electrons and the nucleus together, it is the gravitational force which acts between the axions and the black hole.

The Boson-CloudHowever, there is a very important difference between electrons in an atom and axions around a black hole: Electrons are fermions – which means that two of them can never be in the same state. Axions on the other hand are bosons, many of them can occupy the same quantum state at the same time. They can create a “boson-cloud” surrounding the black hole. This cloud continuously sucks energy from the black hole and the number of axions in the cloud increases.

Sudden CollapseSuch a cloud is not necessarily stable. “Just like a loose pile of sand, which can suddenly slide, triggered by one single additional grain of sand, this boson cloud can suddenly collapse”, says Daniel Grumiller. The exciting thing about such a collapse is that this “bose-nova” could be measured. This event would make space and time vibrate and emit gravity waves. Detectors for gravity waves have already been developed, in 2016 they are expected to reach an accuracy at which gravity waves should be unambiguously detected. The new calculations in Vienna show that these gravity waves can not only provide us with new insights about astronomy, they can also tell us more about new kinds of particles.

Jupiter’s Trojans on an Atomic Scale

 Fig : The Bohr model assumes that the electron moves around the nucleus, much like a planet around its star.

By Vienna University of Technology

Published on 24th January, 2012

Planets can orbit a star for billions of years. Electrons circling the atomic nucleus are often visualized as tiny planets. But due to quantum effects, the behavior of atoms usually differs significantly from planetary systems. Austrian and US-American scientists have now succeeded in keeping electrons on planet-like orbits for a long time. This was done using an idea from astronomy: Jupiter stabilizes the orbits of asteroids (the so called “Trojans”), and in a very similar way, the orbits of electrons around the nucleus can be stabilized using an electromagnetic field. The results of this experiment have now been published in the journal “Physical Review Letters”.

Giant AtomsThey are probably the largest atoms on earth: “The diameter of the electronic orbits is several hundredths of a millimeter – an enormous distance on an atomic scale”, says Shuhei Yoshida (Vienna UT). The atoms are even larger than erythrocytes. Yoshida made the calculations at Vienna University of Technology, the experiment was carried out at Rice University in Houston (Texas).

The Electron is not a PlanetThe idea that atoms are similar to planetary systems dates back to Niels Bohr: he came up with the first atomic model, in which electrons circle the nucleus in well-defined orbits. This view, however, is now seen to be outdated. In quantum physics, the electron is described as a quantum wave, or a “probability cloud”, that surrounds the atomic nucleus. The location of an electron in the ground state (the lowest possible energy level) is not well defined. Relative to the nucleus, it is situated in all possible directions at the same time. Asking about its “real position” or its orbit just does not make sense. Only if the electron is transferred into a state of higher energy, it can be manipulated in such a way that it moves along orbit-like paths.

Jupiter’s trick – Used for the AtomUnlike planets, electrons will not keep moving in such an orbit for ever. “Without additional stabilization, the electron-wave would become delocalized after a few cycles”, says Professor Joachim Burgdörfer, head of the Institute for Theoretical Physics at Vienna UT. A simple idea on how to stabilize orbits has been known in astronomy for a long time: the gravity of Jupiter, the heaviest planet in our solar system, stabilizes the orbits of the “Trojans” – thousands of small asteroids. They aggregate around so-called “Lagrange points” on Jupiter’s orbital path. Staying close to these Lagrange points, the asteroids circle the sun together with the planet – with exactly the same orbital velocity, so that the asteroids never collide with Jupiter.

In the experiment, the stabilizing influence of Jupiter’s gravity is substituted by a cleverly designed electromagnetic field. The field oscillates precisely with the frequency corresponding to the orbital period of the electron around the nucleus. It sets the pace for the electron, and that way the electron-wave is kept at a specific point for a long time – much like a large number of asteroids, staying close to Jupiter’s Lagrange points on their orbit around the sun. Quantum physics even allows manipulations which are impossible in a planetary system: using the electromagnetic field, the electron can by shifted into a different orbit – as if the orbit of Jupiter and its asteroids was suddenly shifted to the orbit of Saturn.

Big and SmallThe physicists succeeded in creating an atomic miniature version of a solar system and preparing atoms which are remarkably close to the historic Bohr model. In future, the researchers want to prepare atoms in which several electrons move on planetary orbits at the same time. Using such atoms, it should be possible to investigate in greater detail how the quantum-world of tiny objects corresponds to the classical world as we perceive it.

Overfed Black Holes Shut Down Galactic Star-Making

PASADENA, Calif. -- The Herschel Space Observatory has shown galaxies with the most powerful, active black holes at their cores produce fewer stars than galaxies with less active black holes. The results are the first to demonstrate black holes suppressed galactic star formation when the universe was less than half its current age. Credit: Illustration: NASA/ESA/JPL-Caltech/STScI/R. Hurt (SSC)

Published : May 9, 2012
By JPL

"We want to know how star formation and black hole activity are linked," said Mathew Page of University College London's Mullard Space Science Laboratory in the United Kingdom and lead author of a paper describing these findings in this week's journal Nature. "The two processes increase together up to a point, but the most energetic black holes appear to turn off star formation."

Supermassive black holes, weighing as much as millions of suns, are believed to reside in the hearts of all large galaxies. When gas falls upon these monsters, the material is accelerated and heated around the black hole, releasing great torrents of energy. Earlier in the history of the universe, these giant, luminous black holes, called active galactic nuclei, were often much brighter and more energetic. Star formation was also livelier back then.

Studies of nearby galaxies suggest active black holes can squash star formation. The revved-up, central black holes likely heat up and disperse the galactic reservoirs of cold gas needed to create new stars. These studies have only provided "snapshots" in time, however, leaving the overall relationship of active galactic nuclei and star formation unclear, especially over the cosmic history of galaxy formation.

"To understand how active galactic nuclei affect star formation over the history of the universe, we investigated a time when star formation was most vigorous, between eight and 12 billion years ago," said co-author James Bock, a senior research scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and co-coordinator of the Herschel Multi-tiered Extragalactic Survey. "At that epoch, galaxies were forming stars 10 times more rapidly than they are today on average. Many of these galaxies are incredibly luminous, more than 1,000 times brighter than our Milky Way."

For the new study, Page and colleagues used Herschel data that probed 65 galaxies at wavelengths equivalent to the thickness of several sheets of office paper, a region of the light spectrum known as far-infrared. These wavelengths reveal the rate of star formation, because most of the energy released by developing stars heats surrounding dust, which then re-radiates starlight out in far-infrared wavelengths.

The researchers compared their infrared readings with X-rays streaming from the active central black holes in the survey's galaxies, measured by NASA's Chandra X-ray Observatory. At lower intensities, the black holes' brightness and star formation increased in sync. However, star formation dropped off in galaxies with the most energetic central black holes. Astronomers think inflows of gas fuel new stars and supermassive black holes. Feed a black hole too much, however, and it starts spewing radiation into the galaxy that prevents raw material from coalescing into new stars.

"Now that we see the relationship between active supermassive black holes and star formation, we want to know more about how this process works," said Bill Danchi, Herschel program scientist at NASA Headquarters in Washington. "Does star formation get disrupted from the beginning with the formation of the brightest galaxies of this type, or do all active black holes eventually shut off star formation, and energetic ones do this more quickly than less active ones?"

Herschel is a European Space Agency cornerstone mission, with science instruments provided by consortia of European institutes and important participation by NASA. NASA's Herschel Project Office is based at JPL.

NASA's WISE mission sees skies ablaze with blazars

Fig : This image taken by NASA's Wide-field Infrared Survey Explorer (WISE) shows a blazar — a voracious supermassive black hole inside a galaxy with a jet that happens to be pointed right toward Earth. These objects are rare and hard to find, but astronomers have discovered that they can use the WISE all-sky infrared images to uncover new ones. So far, researchers have found more than 200 new blazars, and they say WISE has the potential to find many more. Active black holes are often found at the hearts of elliptical galaxies. Not all black holes have jets, but when they do, the jets can be pointed in any direction. If a jet happens to shine at Earth, the object is called a blazar. 

Published By NASA/JPL
Published on : April 16, 2012

Astronomers are actively hunting a class of supermassive black holes throughout the universe called blazars thanks to data collected by NASA’s Wide-field Infrared Survey Explorer (WISE). The mission has revealed more than 200 blazars and has the potential to find thousands more. Blazars are among the most energetic objects in the universe. They consist of supermassive black holes actively “feeding,” or pulling matter onto them, at the cores of giant galaxies. As the matter is dragged toward the supermassive hole, some of the energy is released in the form of jets traveling at nearly the speed of light. Blazars are unique because their jets are pointed directly at us.

“Blazars are extremely rare because it’s not too often that a supermassive black hole’s jet happens to point towards Earth,” said Francesco Massaro of the Kavli Institute for Particle Astrophysics and Cosmology near Palo Alto, California, and principal investigator of the research. “We came up with a crazy idea to use WISE’s infrared observations, which are typically associated with lower-energy phenomena, to spot high-energy blazars, and it worked better than we hoped.”

The findings ultimately will help researchers understand the extreme physics behind super-fast jets and the evolution of supermassive black holes in the early universe. WISE surveyed the entire celestial sky in infrared light in 2010, creating a catalog of hundreds of millions of objects of all types. Its first batch of data was released to the larger astronomy community in April 2011, and the full-sky data were released last month.

Massaro and his team used the first batch of data, covering more than half of the sky, to test their idea that WISE could identify blazars. Astronomers often use infrared data to look for the weak heat signatures of cooler objects. Blazars are not cool; they are scorching hot and glow with the highest-energy type of light, called gamma rays. However, they also give off a specific infrared signature when particles in their jets are accelerated to almost the speed of light. One of the reasons the team wants to find new blazars is to help identify mysterious spots in the sky sizzling with high-energy gamma rays, many of which are suspected to be blazars. NASA’s Fermi mission has identified hundreds of these spots, but other telescopes are needed to narrow in on the source of the gamma rays. Sifting through the early WISE catalog, the astronomers looked for the infrared signatures of blazars at the locations of more than 300 gamma-ray sources that remain mysterious. The researchers were able to show that a little more than half of the sources are most likely blazars. “This is a significant step toward unveiling the mystery of the many bright gamma-ray sources that are still of unknown origin,” said Raffaele D’Abrusco, a co-author of the papers from the Harvard Smithsonian Center for Astrophysics in Cambridge, Massachusetts. “WISE’s infrared vision is actually helping us understand what’s happening in the gamma-ray sky.”

The team also used WISE images to identify more than 50 additional blazar candidates and observed more than 1,000 previously discovered blazars. According to Massaro, the new technique, when applied directly to WISE’s full-sky catalog, has the potential to uncover thousands more. “We had no idea when we were building WISE that it would turn out to yield a blazar gold mine,” said Peter Eisenhardt, WISE project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, who is not associated with the new studies. “That’s the beauty of an all-sky survey. You can explore the nature of just about any phenomenon in the universe.”

Milky way may swarm with nomad planets

Figure : This image is an artistic rendition of a nomad object wandering the interstellar medium. The object is intentionally blurry to represent uncertainty about whether it has an atmosphere. A nomadic object may be an icy body akin to an object found in the outer solar system, a more rocky material akin to asteroids, or even a gas giant similar in composition to the most massive solar system planets and exoplanets.

By Stanford University
Published: February 24, 2012

Our galaxy may be awash in homeless planets, wandering through space instead of orbiting a star. In fact, there may be 100,000 times more nomad planets in the Milky Way than stars, according to a new study by researchers at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) in Stanford, California.

If observations confirm the estimate, this new class of celestial objects will affect current theories of planet formation and could change our understanding of the origin and abundance of life.

“If any of these nomad planets are big enough to have a thick atmosphere, they could have trapped enough heat for bacterial life to exist,” said Louis Strigari from KIPAC. Although nomad planets don’t bask in the warmth of a star, they may generate heat through internal radioactive decay and tectonic activity.

Searches over the past two decades have identified more than 500 planets outside our solar system, almost all of which orbit stars. Last year, researchers detected about a dozen nomad planets, using a technique called gravitational microlensing, which looks for stars whose light is momentarily refocused by the gravity of passing planets.

The research produced evidence that roughly two nomads exist for every typical, main sequence star in our galaxy. The new study estimates that nomads may be up to 50,000 times more common than that.

To arrive at what Strigari called “an astronomical number,” the KIPAC team took into account the known gravitational pull of the Milky Way Galaxy, the amount of matter available to make such objects, and how that matter might divvy itself up into objects ranging from the size of Pluto to larger than Jupiter. Not an easy task, considering no one is quite sure how these bodies form. According to Strigari, some were probably ejected from solar systems, but research indicates that not all of them could have formed in that fashion.

“To paraphrase Dorothy from The Wizard of Oz, if correct, this extrapolation implies that we are not in Kansas anymore, and in fact we never were in Kansas,” said Alan Boss from the Carnegie Institution for Science in Washington, D.C. “The universe is riddled with unseen planetary-mass objects that we are just now able to detect.”

A good count, especially of the smaller objects, will have to wait for the next generation of big survey telescopes, especially the space-based Wide-Field Infrared Survey Telescope and the ground-based Large Synoptic Survey Telescope, both set to begin operation in the early 2020s.

A confirmation of the estimate could lend credence to another possibility mentioned in the paper — that as nomad planets roam their starry pastures, collisions could scatter their microbial flocks to seed life elsewhere.

“Few areas of science have excited as much popular and professional interest in recent times as the prevalence of life in the universe,” said Roger Blandford from KIPAC. “What is wonderful is that we can now start to address this question quantitatively by seeking more of these erstwhile planets and asteroids wandering through interstellar space, and then speculate about hitchhiking bugs.”

Latest Findings on Moon’s Impact History

Figure: Post-lunar cataclysm diagram of our solar system.
Credit: LPI/Marchi/Bottke/Kring/Morbidelli

Published : February 28, 2012
By : NASA's Ames Research Center in Moffett Field, California

During Earth’s earliest days, our planet and other bodies in the inner solar system, including the Moon, experienced repeated impacts from debris that formed the building blocks of the planets. Over time, as material was swept up and incorporated into the inner planets, the rate of impacts decreased. Then, roughly 4 billion years ago, a second wave of impacts appears to have taken place, with lunar projectiles hitting at much higher speeds. This increase could reflect the origin of the debris where main belt asteroids were dislodged and sent into the inner solar system by shifts in the orbits of the giant planets.

A team of researchers from the NASA Lunar Science Institute (NLSI) at NASA’s Ames Research Center in Moffett Field, California, has discovered that debris that caused a “lunar cataclysm” on the Moon 4 billion years ago struck it at much higher speeds than those that made the most ancient craters. The scientists found evidence supporting this scenario by examining the history of crater formation on the Moon.

Scientists analyzed digital maps of the lunar surface to learn about its history. Their analysis shows that craters formed near the 533-mile-diameter (860 kilometers) Nectaris impact basin were created by projectiles hitting twice as fast as those found on more ancient terrains. This was represented by a subtle shift in crater sizes, with the craters themselves 30 to 40 percent larger on average than those found in comparable populations with older craters. The scientists believe this can be best explained by an increase in the velocities of the projectiles that produced the younger craters.

The increase in velocities may indicate a change in the solar system when the craters were created. The analysis supports the lunar cataclysm hypothesis that the brief pulse of impacting objects 4 billion years ago was due to gravitational disturbances caused by the reorganization of the giant planets as their orbits changed. Nectaris, a crater close to the Apollo 16 landing site, appears to have recorded the spike in asteroid impacts during the lunar cataclysm.

Determining the magnitude and duration of any impact cataclysm and testing that hypothesis is a top science priority for future exploration of the Moon, according to a previously published report by the National Research Council.

When Apollo astronauts gathered rock samples from the Moon, many samples had ages dating back 3.9 to 4 billion years ago, suggesting an enhanced pulse of bombardment. If a bombardment of asteroids hit the Moon as theorized, there could be indicators left on the lunar surface that would help validate the theory. Detailed mapping by the United States Geological Survey has previously identified small regions of the lunar surface that might contain clues about the bombardment. The team re-studied those ancient surfaces and measured the sizes of the impact craters using new data obtained from the Lunar Orbiter Laser Altimeter, an instrument on NASA’s Lunar Reconnaissance Orbiter (LRO) currently orbiting around the Moon.

“This is an exciting time for lunar research with LRO and other spacecraft providing so much new data,” said Simone Marchi from NLSI. “Collaborating with scientists of different disciplines allowed us to link these observational data to dynamical models to put new constraints on solar system history.”

The inferred increase in velocity seems to have occurred after the Moon’s 1,550-mile-diameter (2,500km) South Pole-Aitken Basin was produced, but before the formation of the largest lava-filled impact basins on the lunar nearside, visible from backyards around the world.

“It is fascinating that the surface of our own Moon records evidence of orbital changes in Jupiter and Saturn that took place so long ago,” said Yvonne Pendleton from NLSI.