Measuring the Mass of a Mars-size Exoplanet

NASA - Kepler Mission patch.

June 17, 2015

Determining the size of an Earth-size exoplanet by the amount of starlight it blocks hundreds of light-years away once was the realm of science fiction. Measuring the mass of such a small planet based on its gravity was another level entirely, but astronomers have done just that for an exoplanet fifty percent the size of Earth.

Researchers using NASA's Kepler mission data have measured the mass of a Mars-size exoplanet that is about one tenth the mass of Earth. Called Kepler-138b, it is the first exoplanet smaller than Earth to have both its mass and size measured. This significantly extends the range of planets with measured densities.

Image above: The artistic concept shows the planetary system harboring Kepler-138b, the first exoplanet smaller than Earth with both a mass and size measurement. The sizes of the planets relative to the star have been exaggerated. Image Credits: SETI Institute/Danielle Futselaar.

To determine a planet's mass, astronomers typically measure the miniscule movement of the star caused by the gravitational tug of an orbiting planet. For planets the mass of Earth detecting such a tiny tug is extraordinarily challenging with current technology. Fortunately, when a star hosts multiple planets that orbit closely together, scientists have developed another way to get at the planets’ masses.

Daniel Jontof-Hutter, a research associate at the Pennsylvania State University’s Center for Exoplanets and Habitable Worlds, led a team of astronomers in a study to measure the mass of all three planets by precisely observing the times each planet passed in front of, or transited, the star Kepler-138.

"Each planet periodically slows down and accelerates ever so slightly from the gravity of its neighboring planets. The slight change in time between transits allows us to measure the masses of the planets," said Jontof-Hutter.

Each time a planet transits a star it blocks a small fraction of the star's light, allowing astronomers to measure the size of the planet. This is how the Kepler spacecraft has detected thousands of planets around other stars.

By measuring both the mass and size of an exoplanet, scientists can calculate the density and infer the bulk composition to determine if a planet is predominantly made of rock, water or gas. Tiny Kepler-138b's density is consistent with a rocky composition like Earth or Mars, but further observations are needed before astronomers can definitively say that it is a rocky world.

Kepler-138b is the innermost of three planets that orbit Kepler-138, a star less than half the size of our sun and roughly 30 percent cooler. The Kepler-138 system is located about 200 light-years from Earth in the direction of the constellation Lyra.

The outer two planets, Kepler-138c and Kepler-138d, are approximately the size of Earth. Kepler-138c is likely to be rocky, whereas Kepler-138d is less dense and cannot be made of the same mix of material as Earth. All three planets orbit too close to their star for liquid water to exist on the surface and support life, as we know it.

Image above: This plot shows the masses and sizes of the smallest exoplanets for which both quantities have been measured. The solar system planets (shown in red) are for comparison.The three Kepler-138 planets (shown in orange) are among the four smallest exoplanets with both size and mass measurements. Kepler-138b is the first exoplanet smaller than Earth to have both its mass and size measured. This significantly extends the range of planets with measured densities. Image Credits: NASA Ames/W Stenzel.

"The substantial difference between the densities of the two larger planets tells us that not all planets similar to Earth in size are rocky," said Jack Lissauer, co-author and planetary scientist at NASA's Ames Research Center in Moffett Field, Calif. "Further study of small planets will help provide more understanding of the diversity that exists in nature, and will help determine if rocky planets like Earth are common or rare."

Much like astronomers in the early 20^th century studied a wide variety of stars to characterize and classify different types, astronomers in the 21^st century are doing the same to understand the diversity and demographics of planet populations in our Milky Way galaxy.

Mass measurement of a Mars-size exoplanet

Video above: A team of astronomers have measured the mass and size of the smallest exoplanet yet, a Mars-sized planet named Kepler-138b orbiting a red dwarf star about 200 light years from the Solar System. The animation shows the mass-radius diagram based on measurements of 127 exoplanets. The video begins by showing planets with masses similar to Jupiter and slowly zooms towards small masses and radii planets to display a comparison of the physical properties of the Kepler-138 planets relative to Earth, Venus, Mars and Mercury. The planet Kepler-138b is the first exoplanet smaller than the Earth to have both its mass and its size measured, and is one of three planets that orbit the star Kepler-138, and pass in front of it, or transit, every orbit. Each time a planet transits the star, it blocks a small fraction of the star's light, allowing astronomers to measure the size of the planet. All three planets were identified by NASA's Kepler mission that has discovered over a thousand planets around other stars. Video Credits: Jason Rowe, NASA Ames/SETI Institute.

Scientists are working to use these new measurements of small planets from Kepler and NASA's upcoming Transiting Exoplanet Survey Satellite to identify patterns in the relationship between mass and size. These insights will provide context for understanding the history of Earth and other planets in our own solar system, and inform the next generation planet hunters as they search for life beyond the solar system.

A previous study had measured the masses of the two outer planets. This new study performed a more detailed analysis of the Kepler-138 system using additional Kepler data. This enabled the measurement of the mass of the Mars-size inner planet and improved the accuracy of the size and mass measurements for the outer planets. The results will appear in this Thursday's issue of the journal Nature.

Ames Research Center in Moffett Field, California, manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corp. operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

For more information on the Kepler mission, visit: http://www.nasa.gov/kepler.

Images (mentioned), Video (mentioned), Text, Credits: NASA/Ames Research Center/Michele Johnson.

Best regards, Orbiter.ch

Best Observational Evidence of First Generation Stars in the Universe

ESO - European Southern Observatory logo.

17 June 2015

VLT discovers CR7, the brightest distant galaxy, and signs of Population III stars

Artist’s impression of CR7: the brightest galaxy in the early Universe

Astronomers using ESO’s Very Large Telescope have discovered by far the brightest galaxy yet found in the early Universe and found strong evidence that examples of the first generation of stars lurk within it. These massive, brilliant, and previously purely theoretical objects were the creators of the first heavy elements in history — the elements necessary to forge the stars around us today, the planets that orbit them, and life as we know it. The newly found galaxy, labelled CR7, is three times brighter than the brightest distant galaxy known up to now.

Astronomers have long theorised the existence of a first generation of stars — known as Population III stars — that were born out of the primordial material from the Big Bang [1]. All the heavier chemical elements — such as oxygen, nitrogen, carbon and iron, which are essential to life — were forged in the bellies of stars. This means that the first stars must have formed out of the only elements to exist prior to stars: hydrogen, helium and trace amounts of lithium.

These Population III stars would have been enormous — several hundred or even a thousand times more massive than the Sun — blazing hot, and transient — exploding as supernovae after only about two million years. But until now the search for physical proof of their existence had been inconclusive [2].

A team led by David Sobral, from the Institute of Astrophysics and Space Sciences, the Faculty of Sciences of the University of Lisbon in Portugal, and Leiden Observatory in the Netherlands, has now used ESO’s Very Large Telescope (VLT) to peer back into the ancient Universe, to a period known as reionisation, approximately 800 million years after the Big Bang. Instead of conducting a narrow and deep study of a small area of the sky, they broadened their scope to produce the widest survey of very distant galaxies ever attempted.

Their expansive study was made using the VLT with help from the W. M. Keck Observatory and the Subaru Telescope as well as the NASA/ESA Hubble Space Telescope. The team discovered — and confirmed — a number of surprisingly bright very young galaxies. One of these, labelled CR7 [3], was an exceptionally rare object, by far the brightest galaxy ever observed at this stage in the Universe [4]. With the discovery of CR7 and other bright galaxies, the study was already a success, but further inspection provided additional exciting news.

The X-shooter and SINFONI instruments on the VLT found strong ionised helium emission in CR7 but — crucially and surprisingly — no sign of any heavier elements in a bright pocket in the galaxy. This meant the team had discovered the first good evidence for clusters of Population III stars that had ionised gas within a galaxy in the early Universe [5].

“The discovery challenged our expectations from the start,” said David Sobral, “as we didn’t expect to find such a bright galaxy. Then, by unveiling the nature of CR7 piece by piece, we understood that not only had we found by far the most luminous distant galaxy, but also started to realise that it had every single characteristic expected of Population III stars. Those stars were the ones that formed the first heavy atoms that ultimately allowed us to be here. It doesn’t really get any more exciting than this.”

 Artist’s impression of CR7: the brightest galaxy in the early Universe

Within CR7, bluer and somewhat redder clusters of stars were found, indicating that the formation of Population III stars had occurred in waves — as had been predicted. What the team directly observed was the last wave of Population III stars, suggesting that such stars should be easier to find than previously thought: they reside amongst regular stars, in brighter galaxies, not just in the earliest, smallest, and dimmest galaxies, which are so faint as to be extremely difficult to study.

Jorryt Matthee, second author of the paper, concluded: “I have always wondered where we come from. Even as a child I wanted to know where the elements come from: the calcium in my bones, the carbon in my muscles, the iron in my blood. I found out that these were first formed at the very beginning of the Universe, by the first generation of stars. With this discovery, remarkably, we are starting to actually see such objects for the first time.”

Further observations with the VLT, ALMA, and the NASA/ESA Hubble Space Telescope are planned to confirm beyond doubt that what has been observed are Population III stars, and to search for and identify further examples.

Notes:

[1] The name Population III arose because astronomers had already classed the stars of the Milky Way as Population I (stars like the Sun, rich in heavier elements and forming the disc) and Population II (older stars, with a low heavy-element content, and found in the Milky Way bulge and halo, and globular star clusters).

[2] Finding these stars is very difficult: they would have been extremely short-lived, and would have shone at a time when the Universe was largely opaque to their light. Previous findings include: Nagao, et al., 2008, where no ionised helium was detected; De Breuck et al., 2000, where ionised helium was detected, but alongside carbon and oxygen, as well as clear signatures of an active galactic nucleus; and Cassata et al., 2013, where ionised helium was detected, but of a very low equivalent width, or weak intensity, and alongside carbon and oxygen.

[3] CR7’s nickname is an abbreviation of COSMOS Redshift 7, a measure of its place in terms of cosmic time. The higher the redshift, the more distant the galaxy and the further back in the history of the Universe it is seen. A1689-zD1, one of the oldest galaxies ever observed, for example, has a redshift of 7.5.

CR7 is located in the COSMOS field, an intensely studied patch of sky in the constellation of Sextans (The Sextant).

The nickname was inspired by the great Portuguese footballer, Cristiano Ronaldo, who is known as CR7.

[4] CR7 is three times brighter in terms of ultraviolet light emission than the previous titleholder, Himiko, which was thought to be one of a kind at this very early time. Dusty galaxies, at later stages in the history of the Universe, may radiate far more total energy than CR7 in the form of infrared radiation from warm dust. The energy coming from CR7 is mostly ultraviolet/visible light.

[5] The team considered two alternate theories: that the source of the light was either from an AGN or Wolf–Rayet stars. The lack of heavy elements, and other evidence strongly refutes both these theories. The team also considered that the source may be a direct-collapse black hole, which are themselves exceptional exotic and purely theoretical objects. The lack of a broad emission line and the fact that the hydrogen and helium luminosities were much greater than what has been predicted for such a black hole indicate that this, too, is unlikely. A lack of X-ray emissions would further refute this possibility, but additional observations are needed.

More information:

This research was presented in a paper entitled “Evidence for PopIII-like stellar populations in the most luminous Lyman-α emitters at the epoch of re-ionisation: spectroscopic confirmation”, by D. Sobral, et al., is accepted for publication in The Astrophysical Journal.

The team is composed of David Sobral (Instituto de Astrofísica e Ciências do Espaço, Universidade de Lisboa, Lisbon, Portugal; Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal; Leiden Observatory, Leiden University, Leiden, The Netherlands), Jorryt Matthee (Leiden Observatory), Behnam Darvish (Department of Physics and Astronomy, University of California, Riverside, California, USA), Daniel Schaerer (Observatoire de Genève, Département d’Astronomie, Université de Genève, Versoix, Switzerland; Centre National de la Recherche Scientifique, IRAP, Toulouse, France), Bahram Mobasher (Department of Physics and Astronomy, University of California, Riverside, California, USA), Huub J. A. Röttgering (Leiden Observatory), Sérgio Santos (Instituto de Astrofísica e Ciências do Espaço, Universidade de Lisboa; Departamento de Física, Universidade de Lisboa, Portugal) and Shoubaneh Hemmati (Department of Physics and Astronomy, University of California, Riverside, California, USA).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links:

Research paper: http://www.eso.org/public/archives/releases/sciencepapers/eso1524/eso1524a.pdf

Photos of the VLT: http://www.eso.org/public/images/archive/category/paranal/

Image, Video, Text, Credits: ESO/M. Kornmesser.

Greetings, Orbiter.ch

Dissolving Titan

ESA - Cassini Mission to Saturn logo.

17 June 2015

Saturn’s moon Titan is home to seas and lakes filled with liquid hydrocarbons, but what makes the depressions they lie in? A new study suggests that the moon’s surface dissolves in a similar process that creates sinkholes on Earth.

Apart from Earth, Titan is the only body in the Solar System known to possess surface lakes and seas, as seen by the international Cassini mission. But at roughly –180°C, the surface of Titan is very cold and liquid methane and ethane, rather than water, dominate the ‘hydrological’ cycle.

Lakes and seas on Titan

Indeed, methane and ethane-filled topographic depressions are distinctive features near the moon’s poles. Two forms have been identified by Cassini. There are vast seas several hundred kilometres across and up to several hundred metres deep, fed by river-like dendritic channels. Then there are numerous smaller, shallower lakes, with rounded edges and steep walls, and generally found in flat areas. Many empty depressions are also observed.

The lakes are generally not associated with rivers, and are thought fill up by rainfall and liquids flooding up from underneath. Some of the lakes fill and dry out again during the 30-year seasonal cycle on Saturn and Titan.

But quite how the depressions hosting the lakes came about in the first place is poorly understood.

A team of scientists have turned to home for the answer and discovered that Titan’s lakes are reminiscent of ‘karstic’ landforms seen on Earth. These are terrestrial landscapes that result from erosion of soluble rocks such as limestone and gypsum in groundwater and rainfall percolating through rocks. Over time, this leads to features including sinkholes and caves under humid climates, and salt-pans under more arid climates.

The rate of erosion depends on factors such as the chemistry of the rocks, the rainfall rate and the surface temperature. While all of these aspects clearly differ between Titan and Earth, the underlying process may be surprisingly similar.

Titan’s lakes close up

A team lead by ESA’s Thomas Cornet calculated how long it would take for patches of Titan’s surface to dissolve to create these features. They assumed that the surface is covered in solid organic material, and that the main dissolving agent is liquid hydrocarbons, and took into account present-day models of Titan’s climate.

The scientists found that it would take around 50 million years to create a 100 m-deep depression at Titan’s relatively rainy high polar latitudes, consistent with the youthful age of the moon’s surface.

“We compared the erosion rates of organics in liquid hydrocarbons on Titan with those of carbonate and evaporite minerals in liquid water on Earth,” describes Thomas.

“We found that the dissolution process occurs on Titan some 30 times slower than on Earth due to the longer length of Titan’s year and the fact it only rains during Titan summer.

“Nevertheless, we believe that dissolution is a major cause of landscape evolution on Titan, and could be the origin of its lakes.”

Ligeia Mare

In addition, the scientists calculated how long it would take to form lake depressions at lower latitudes, where the rainfall is reduced. The much longer timescale of 375 million years is consistent with the relative absence of depressions in these geographical locations.

“Of course, there are a few uncertainties: the composition of Titan’s surface is not that well constrained, and neither are the long-term precipitation patterns, but our calculations are still consistent with the features we see today on Titan’s relatively youthful billion-year-old surface,” says Thomas.

Cassini Titan flyby

“By comparing Titan’s surface features with examples on Earth and applying a few simple calculations, we have found similar land-shaping processes that could be operating under very different climate and chemical regimes,” says Nicolas Altobelli, ESA’s Cassini–Huygens project scientist.

“This is a great comparative study between our home planet and a dynamic world more than a billion kilometres away in the outer Solar System.”

More information:

“Dissolution on Titan and on Earth: Towards the age of Titan’s karstic landscapes,” by T. Cornet et al. is accepted for publication in the Journal of Geophysical Research – Planets, doi: 10.1002/2014JE004738

Cassini–Huygens is a cooperative project of NASA, ESA and ASI, the Italian space agency.

Related links:

At Saturn and Titan: http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Cassini-Huygens in depth: http://sci.esa.int/huygens

NASA JPL Cassini site: http://saturn.jpl.nasa.gov/

Italian Space Agency: http://www.asi.it/en

Images, Text, Credits: ESA/NASA/JPL-Caltech/ASI/USGS/Acknowledgement: T. Cornet.

Greetings, Orbiter.ch

Crew Trains for Seventh Dragon Mission

ISS - Expedition 44 Mission patch.

June 17, 2015

Image above: Astronaut Samantha Cristoforetti captured this image while on the International Space Station. It shows cloud cover over England, Baltic Sea and the Persian Gulf.

SpaceX engineers are in the final weeks of processing of the Falcon 9 rocket that will launch their Dragon commercial cargo craft to the International Space Station late next week. On orbit, a pair of Expedition 43 crew members reviewed the procedures they will use when the Dragon supply ship arrives a few days later.

During ongoing orbital station maintenance today, advanced microgravity science took place as the orbiting trio continues to explore phenomena that can only be observed in space. The crew researched acoustic methods to locate micrometeoroid impacts on the station for the Proboy study. They also explored the effects of weightlessness in the carotid artery and the redistribution of blood in the upper half of a crew member’s body.

SpaceX will launch the Falcon 9 rocket carrying the SpaceX Dragon cargo craft to the station June 26. It will arrive June 29 to be captured by the Canadarm2 with One-Year crew member Scott Kelly at the controls. Kelly will capture Dragon with the assistance of station commander Gennady Padalka who will monitor Dragon systems before it is berthed to the Harmony Node.

Orbital Trio Presses on With Year-Long Science and Dragon Preps

Image above: NASA Astronaut Scott Kelly works aboard the International Space Station on May 30, 2015 on a number of science experiments and maintenance of the stations equipment.

The three residents aboard the International Space Station conducted advanced microgravity science and trained for the arrival of the seventh SpaceX Dragon mission scheduled for the end of the month.

One-Year crew members Scott Kelly and Mikhail Kornienko partnered up for the Fine Motor Skills study, part of a suite of yearlong studies planned for the pair. That experiment explores how astronauts operate and repair interactive, touch-based and sensitive technologies in space. Kornienko later studied the possibility of using 3-D manuals, or virtual manuals, to improve training techniques on science hardware.

Kelly joined Commander Gennady Padalka in the afternoon for rendezvous training as they prepare for the next SpaceX Dragon launch scheduled for June 26. The duo will be in the cupola monitoring Dragon and waiting to capture it with the Canadarm2 when it arrives June 29.

Related links:

Fine Motor Skills study: http://www.nasa.gov/mission_pages/station/research/experiments/1767.html

3-D manuals: http://www.energia.ru/en/iss/researches/develop/05.html

Expedition 44: https://blogs.nasa.gov/spacestation/category/expedition-44/

One-Year Crew: https://blogs.nasa.gov/spacestation/category/one-year-crew-2/

Dragon: https://blogs.nasa.gov/spacestation/tag/dragon/

International Space Station (ISS): http://www.nasa.gov/mission_pages/station/main/index.html

Images, Text, Credits: NASA/NASA TV.

Best regards, Orbiter.ch

Moon Engulfed in Permanent, Lopsided, Dust Cloud

NASA - LADEE Mission patch.

June 16, 2015

New science results from NASA’s Lunar Atmosphere and Dust Environment Explorer, or LADEE, mission indicate that the moon is engulfed in a permanent, but lopsided, dust cloud that increases in density when annual events like the Geminids meteor shower spew shooting stars, according to a new study led by University of Colorado Boulder.

LADEE discovered dust clouds around the Moon

"Knowledge about the dusty environments in space has practical applications," said CU-Boulder physics Professor Mihaly Horanyi. "Knowing where the dust is and where it is headed in the solar system could help mitigate hazards for future human exploration, including dust particles damaging spacecraft or harming astronauts."

The cloud was discovered using data from a detector on board LADEE called the Lunar Dust Experiment (LDEX) designed and built by CU-Boulder. LDEX charted more than 140,000 impacts during the six-month long mission, which launched in September 2013 and orbited the moon for about six months. NASA’s Ames Research Center in Moffett Field, California, was responsible for spacecraft design, development, testing and mission operations, in addition to managing the overall mission.

“It's been over a year since LADEE completed its fully successful mission by impacting the lunar surface as planned on April 18, 2014,” said LADEE project scientist at Ames, Rick Elphic. “The LADEE science team has been busy analyzing the returned data, figuring out how the exosphere breathes and changes, and how the moon's tenuous dust shroud varies in time and space.”

According to Horanyi, the cloud is primarily made up of tiny dust grains kicked up from the moon’s surface by the impact of high-speed, interplanetary dust particles. A single dust particle from a comet striking the moon’s surface lofts thousands of smaller dust specks into the airless environment, and the lunar cloud is maintained by regular impacts from such particles.

“Identifying this permanent dust cloud engulfing the moon was a nice gift from this mission,” said Horanyi, the principal investigator on LDEX and the lead author of the study. “We can carry these findings over to studies of other airless planetary objects like the moons of other planets and asteroids.”

A paper on the subject appears in the June 17 issue of Nature. Co-authors on the study include Jamey Szalay, Sascha Kempf, Eberhard Grun and Zoltan Sternovsky from CU-Boulder, Juergen Schmidt from the University Oulu in Finland, and Ralf Srama from the University of Stuttgart in Germany.

Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft orbiting the Moon

The first hints of a cloud of dust around the moon came in the late 1960s when NASA cameras aboard unmanned moon landers captured a bright glow during lunar sunsets. Several years later, Apollo astronauts orbiting the moon reported a significant glow above the lunar surface when approaching sunrise, a phenomenon brighter than the sun alone should have been able to create at that location.

Since the new findings don’t square with the Apollo reports of a thicker, higher dust cloud, conditions back then may have been somewhat different. The dust on the moon -- which is dark and sticky and regularly dirtied the suits of moonwalking astronauts -- was created over several billion years as interplanetary dust particles incessantly pounded the rocky lunar surface.

Many of the cometary dust particles impacting lunar surface are traveling at thousands of miles per hour in a retrograde, or counterclockwise orbit around the sun, the opposite orbital direction of the solar system’s planets. This causes high-speed, near head-on collisions with the dust particles and the moon’s leading surface as the Earth-moon system travel together around the sun.

For more information about Lunar Atmosphere and Dust Environment Explorer (LADEE) mission, visit: http://www.nasa.gov/mission_pages/ladee/main/index.html

Images, Text, Credits: NASA.

Greetings, Orbiter.ch

OPERA detects its fifth tau neutrino

CERN - European Organization for Nuclear Research logo.

June 16, 2015

The OPERA (Oscillation Project with Emulsion-tRacking Apparatus (link is external)) experiment at the Italian National Institute for Nuclear Physics (link is external) (INFN) at Gran Sasso in Italy has detected the fifth occurrence of a tau neutrino in the muon-neutrino beam from CERN. A particle that left CERN as a muon neutrino underwent "oscillation" during its 730-kilometre journey to Gran Sasso, arriving as a tau neutrino.

Researchers at Gran Sasso announced the result yesterday, naming it "5 sigma" on the scale that particle physicists use to describe the certainty of results. One sigma could be a random statistical fluctuation in the data, 3 sigma counts as evidence, but only a result of 5-sigma or more is ranked as a clear observation. By definition, the probability that a 5-sigma result is wrong is less than one in a million.

Image above: Super Proton Synchrotron (SPS) is the second-largest machine in CERN’s accelerator complex. Measuring nearly 7 kilometers in circumference, it takes particles from the Proton Synchrotron and accelerates them to provide beams for the OPERA experiment. Image Credit: CERN.

“The detection of a fifth tau neutrino is extremely important: We…can definitely report the discovery of the appearance of tau neutrinos in a muon neutrino beam,” said spokesperson Giovanni De Lellis of INFN in Naples, Italy, on behalf of the international research team.

Three types or "flavours" of neutrino exist in nature: the electron neutrino, the muon neutrino and the tau neutrino. But it seems that neutrinos are the chameleons of the particle world: they can change from one flavour into another. This phenomenon, called “oscillation”, occurs as neutrinos travel long distances through matter. The process is directly related to the neutrinos' tiny mass.

OPERA was designed to search for tau neutrinos in the muon-neutrino beam from CERN, which ran during 2006-2012; detecting tau neutrinos in this beam is proof that oscillation occurred during their particles' 730 km long flight.

Image above: The Oscillation Project with Emulsion-tRacking Apparatus (OPERA) experiment is designed to test the phenomenon of neutrino oscillations. Image Credit: Worldpress.

CERN produced the neutrino beams for Gran Sasso by firing pulses of protons from the Super Proton Synchrotron (SPS) at a graphite target. The collisions created particles called pions and kaons, which were fed into a system of two magnetic lenses to focus the particles into a parallel beam in the direction of Gran Sasso. The pions and kaons then decayed into muons and muon neutrinos in a 1-kilometre long pipe underground. At the end of the pipe, a block of graphite and metal 18 metres thick absorbed protons as well as pions and kaons that did not decay. Muons were stopped by the rock beyond, but the muon neutrinos remained to streak through the rock on their journey to Italy. As they hardly interact at all with matter, the neutrinos could travel the 730 kilometres from CERN to Gran Sasso directly through the rocks of the Earth's crust. When they arrived at Gran Sasso, a small fraction of the incoming neutrinos interacted with the OPERA detector, which can determine which type of neutrino passed through.

After detecting the first few muon neutrinos produced at CERN in 2006, the experiment collected data from 2008 to the end of 2012. The first tau neutrino was observed in 2010. The second and third events were reported in 2012 and 2013 respectively, while the fourth one was published in 2014.

Image above: The OPERA detector is housed in a tunnel in the Gran Sasso laboratory. OPERA's core. Image Credit: INFN.

“The achievement reported yesterday was made possible thanks to the continuous effort of all the researchers involved in the project, to the excellent performance of the CERN neutrino beam and to the support of all the funding agencies”, said De Lellis.

Scientists will continue to analyse the data collected, searching for other tau neutrinos produced from the oscillation of muon neutrinos. Technologies developed for the OPERA experiment will be used in forthcoming experiments in neutrino physics and other fields.

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.

Related links:

Oscillation Project with Emulsion-tRacking Apparatus (OPERA) experiment: http://operaweb.lngs.infn.it/

Italian National Institute for Nuclear Physics (INFN): http://www.infn.it/?lang=en

Super Proton Synchrotron (SPS): http://home.web.cern.ch/about/accelerators/super-proton-synchrotron

For more information about the European Organization for Nuclear Research (CERN), visit: http://home.web.cern.ch/

Images (mentioned), Text, Credits: CERN/Cian O'Luanaigh.

Greetings, Orbiter.ch

Tethys ‘Eyes’ Saturn

NASA - Cassini Mission to Saturn patch.

June 15, 2015

The two large craters on Tethys, near the line where day fades to night, almost resemble two giant eyes observing Saturn.

The location of these craters on Tethys’ terminator throws their topography into sharp relief. Both are large craters, but the larger and southernmost of the two shows a more complex structure. The angle of the lighting highlights a central peak in this crater. Central peaks are the result of the surface reacting to the violent post-impact excavation of the crater. The northern crater does not show a similar feature. Possibly the impact was too small to form a central peak, or the composition of the material in the immediate vicinity couldn’t support the formation of a central peak.

In this image Tethys is significantly closer to the camera, while the planet is in the background. Yet the moon is still utterly dwarfed by the giant Saturn.

This view looks toward the anti-Saturn side of Tethys. North on Tethys is up and rotated 42 degrees to the right. The image was taken in visible light with the Cassini spacecraft wide-angle camera on April 11, 2015.

The view was obtained at a distance of approximately 75,000 miles (120,000 kilometers) from Tethys. Image scale at Tethys is 4 miles (7 kilometers) per pixel.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov or http://www.nasa.gov/cassini. The Cassini imaging team homepage is at http://ciclops.org and http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Image, Text, Credits: NASA/JPL-Caltech/Space Science Institute/Tony Greicius.

Greetings, Orbiter.ch