PASADENA, Calif. -- NASA's Kepler mission confirmed the discovery of its first rocky planet, named Kepler-10b. Measuring 1.4 times the size of Earth, it is the smallest planet ever discovered outside our solar system.
The discovery of this planet, called an exoplanet, is based on more than eight months of data collected by the spacecraft from May 2009 to early January 2010.
"All of Kepler's best capabilities have converged to yield the first solid evidence of a rocky planet orbiting a star other than our sun," said Natalie Batalha, Kepler's deputy science team lead at NASA's Ames Research Center in Moffett Field, Calif., and primary author of a paper on the discovery accepted by the Astrophysical Journal. "The Kepler team made a commitment in 2010 about finding the telltale signatures of small planets in the data, and it's beginning to pay off."
Kepler's ultra-precise photometer measures the tiny decrease in a star's brightness that occurs when a planet crosses in front of it. The size of the planet can be derived from these periodic dips in brightness. The distance between the planet and the star is calculated by measuring the time between successive dips as the planet orbits the star.
Kepler is the first NASA mission capable of finding Earth-size planets in or near the habitable zone, the region in a planetary system where liquid water can exist on the planet's surface. However, since it orbits once every 0.84 days, Kepler-10b is more than 20 times closer to its star than Mercury is to our sun and not in the habitable zone.
Kepler-10 was the first star identified that could potentially harbor a small transiting planet, placing it at the top of the list for ground-based observations with the W.M. Keck Observatory 10-meter telescope in Hawaii. Scientists waiting for a signal to confirm Kepler-10b as a planet were not disappointed. Keck was able to measure tiny changes in the star's spectrum, called Doppler shifts, caused by the telltale tug exerted by the orbiting planet on the star.
"The discovery of Kepler 10-b is a significant milestone in the search for planets similar to our own," said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington. "Although this planet is not in the habitable zone, the exciting find showcases the kinds of discoveries made possible by the mission and the promise of many more to come."
Knowledge of the planet is only as good as the knowledge of the star it orbits. Because Kepler-10 is one of the brighter stars being targeted by Kepler, scientists were able to detect high-frequency variations in the star's brightness generated by stellar oscillations, or starquakes. This analysis allowed scientists to pin down Kepler-10b's properties.
There is a clear signal in the data arising from light waves that travel within the interior of the star. Kepler Asteroseismic Science Consortium scientists use the information to better understand the star, just as earthquakes are used to learn about Earth's interior structure. As a result of this analysis, Kepler-10 is one of the most well-characterized planet-hosting stars in the universe.
That's good news for the team studying Kepler-10b. Accurate stellar properties yield accurate planet properties. In the case of Kepler-10b, the picture that emerges is of a rocky planet with a mass 4.6 times that of Earth and with an average density of 8.8 grams per cubic centimeter -- similar to that of an iron dumbbell
Thursday, 10 March 2011
Image Documenting California Earthquake
This UAVSAR image, covering the time period from October 21, 2009 to April 13, 2010, shows ground deformation that is largely a result of the April 4, 2010 earthquake in Baja California. Black lines indicate interpreted faults, and red lines show where surface rupture was confirmed by geologists in the field. Image credit: NASA JPL/USGS/California Geological Survey/Google
Hot Plasma Explosions Inflate Saturn's Magnetic Field
A new analysis based on data from NASA's Cassini spacecraft finds a causal link between mysterious, periodic signals from Saturn's magnetic field and explosions of hot ionized gas, known as plasma, around the planet.
Scientists have found that enormous clouds of plasma periodically bloom around Saturn and move around the planet like an unbalanced load of laundry on spin cycle. The movement of this hot plasma produces a repeating signature "thump" in measurements of Saturn's rotating magnetic environment and helps to illustrate why scientists have had such a difficult time measuring the length of a day on Saturn.
"This is a breakthrough that may point us to the origin of the mysteriously changing periodicities that cloud the true rotation period of Saturn," said Pontus Brandt, the lead author on the paper and a Cassini team scientist based at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "The big question now is why these explosions occur periodically."
The data show how plasma injections, electrical currents and Saturn's magnetic field -- phenomena that are invisible to the human eye -- are partners in an intricate choreography. Periodic plasma explosions form islands of pressure that rotate around Saturn. The islands of pressure "inflate" the magnetic field.
A new animation showing the linked behavior is available at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .
The visualization shows how invisible hot plasma in Saturn's magnetosphere – the magnetic bubble around the planet -- explodes and distorts magnetic field lines in response to the pressure. Saturn's magnetosphere is not a perfect bubble because it is blown back by the force of the solar wind, which contains charged particles streaming off the sun.
The force of the solar wind stretches the magnetic field of the side of Saturn facing away from the sun into a so-called magnetotail. The collapse of the magnetotail appears to kick off a process that causes the hot plasma bursts, which in turn inflate the magnetic field in the inner magnetosphere.
Scientists are still investigating what causes Saturn's magnetotail to collapse, but there are strong indications that cold, dense plasma originally from Saturn's moon Enceladus rotates with Saturn. Centrifugal forces stretch the magnetic field until part of the tail snaps back.
The snapping back heats plasma around Saturn and the heated plasma becomes trapped in the magnetic field. It rotates around the planet in islands at the speed of about 100 kilometers per second (200,000 mph). In the same way that high and low pressure systems on Earth cause winds, the high pressures of space cause electrical currents. Currents cause magnetic field distortions.
A radio signal known as Saturn Kilometric Radiation, which scientists have used to estimate the length of a day on Saturn, is intimately linked to the behavior of Saturn's magnetic field. Because Saturn has no surface or fixed point to clock its rotation rate, scientists inferred the rotation rate from timing the peaks in this type of radio emission, which is assumed to surge with each rotation of a planet. This method has worked for Jupiter, but the Saturn signals have varied. Measurements from the early 1980s taken by NASA's Voyager spacecraft, data obtained in 2000 by the ESA/NASA Ulysses mission, and Cassini data from about 2003 to the present differ by a small, but significant degree. As a result, scientists are not sure how long a Saturn day is.
"What's important about this new work is that scientists are beginning to describe the global, causal relationships between some of the complex, invisible forces that shape the Saturn environment," said Marcia Burton, the Cassini fields and particles investigation scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The new results still don't give us the length of a Saturn day, but they do give us important clues to begin figuring it out. The Saturn day length, or Saturn's rotation rate, is important for determining fundamental properties of Saturn, like the structure of its interior and the speed of its winds."
Plasma is invisible to the human eye. But the ion and neutral camera on Cassini's magnetospheric imaging instrument provides a three-dimensional view by detecting energetic neutral atoms emitted from the plasma clouds around Saturn. Energetic neutral atoms form when cold, neutral gas collides with electrically-charged particles in a cloud of plasma. The resulting particles are neutrally charged, so they are able to escape magnetic fields and zoom off into space. The emission of these particles often occurs in the magnetic fields surrounding planets.
By stringing together images obtained every half hour, scientists produced movies of plasma as it drifted around the planet. Scientists used these images to reconstruct the 3-D pressure produced by the plasma clouds, and supplemented those results with plasma pressures derived from the Cassini plasma spectrometer. Once scientists understood the pressure and its evolution, they could calculate the associated magnetic field perturbations along the Cassini flight path. The calculated field perturbation matched the observed magnetic field "thumps" perfectly, confirming the source of the field oscillations.
"We all know that changing rotation periods have been observed at pulsars, millions of light years from our solar system, and now we find that a similar phenomenon is observed right here at Saturn," said Tom Krimigis, principal investigator of the magnetospheric imaging instrument, also based at the Applied Physics Laboratory and the Academy of Athens, Greece. "With instruments right at the spot where it's happening, we can tell that plasma flows and complex current systems can mask the real rotation period of the central body. That's how observations in our solar system help us understand what is seen in distant astrophysical objects."
Scientists have found that enormous clouds of plasma periodically bloom around Saturn and move around the planet like an unbalanced load of laundry on spin cycle. The movement of this hot plasma produces a repeating signature "thump" in measurements of Saturn's rotating magnetic environment and helps to illustrate why scientists have had such a difficult time measuring the length of a day on Saturn.
"This is a breakthrough that may point us to the origin of the mysteriously changing periodicities that cloud the true rotation period of Saturn," said Pontus Brandt, the lead author on the paper and a Cassini team scientist based at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "The big question now is why these explosions occur periodically."
The data show how plasma injections, electrical currents and Saturn's magnetic field -- phenomena that are invisible to the human eye -- are partners in an intricate choreography. Periodic plasma explosions form islands of pressure that rotate around Saturn. The islands of pressure "inflate" the magnetic field.
A new animation showing the linked behavior is available at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .
The visualization shows how invisible hot plasma in Saturn's magnetosphere – the magnetic bubble around the planet -- explodes and distorts magnetic field lines in response to the pressure. Saturn's magnetosphere is not a perfect bubble because it is blown back by the force of the solar wind, which contains charged particles streaming off the sun.
The force of the solar wind stretches the magnetic field of the side of Saturn facing away from the sun into a so-called magnetotail. The collapse of the magnetotail appears to kick off a process that causes the hot plasma bursts, which in turn inflate the magnetic field in the inner magnetosphere.
Scientists are still investigating what causes Saturn's magnetotail to collapse, but there are strong indications that cold, dense plasma originally from Saturn's moon Enceladus rotates with Saturn. Centrifugal forces stretch the magnetic field until part of the tail snaps back.
The snapping back heats plasma around Saturn and the heated plasma becomes trapped in the magnetic field. It rotates around the planet in islands at the speed of about 100 kilometers per second (200,000 mph). In the same way that high and low pressure systems on Earth cause winds, the high pressures of space cause electrical currents. Currents cause magnetic field distortions.
A radio signal known as Saturn Kilometric Radiation, which scientists have used to estimate the length of a day on Saturn, is intimately linked to the behavior of Saturn's magnetic field. Because Saturn has no surface or fixed point to clock its rotation rate, scientists inferred the rotation rate from timing the peaks in this type of radio emission, which is assumed to surge with each rotation of a planet. This method has worked for Jupiter, but the Saturn signals have varied. Measurements from the early 1980s taken by NASA's Voyager spacecraft, data obtained in 2000 by the ESA/NASA Ulysses mission, and Cassini data from about 2003 to the present differ by a small, but significant degree. As a result, scientists are not sure how long a Saturn day is.
"What's important about this new work is that scientists are beginning to describe the global, causal relationships between some of the complex, invisible forces that shape the Saturn environment," said Marcia Burton, the Cassini fields and particles investigation scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The new results still don't give us the length of a Saturn day, but they do give us important clues to begin figuring it out. The Saturn day length, or Saturn's rotation rate, is important for determining fundamental properties of Saturn, like the structure of its interior and the speed of its winds."
Plasma is invisible to the human eye. But the ion and neutral camera on Cassini's magnetospheric imaging instrument provides a three-dimensional view by detecting energetic neutral atoms emitted from the plasma clouds around Saturn. Energetic neutral atoms form when cold, neutral gas collides with electrically-charged particles in a cloud of plasma. The resulting particles are neutrally charged, so they are able to escape magnetic fields and zoom off into space. The emission of these particles often occurs in the magnetic fields surrounding planets.
By stringing together images obtained every half hour, scientists produced movies of plasma as it drifted around the planet. Scientists used these images to reconstruct the 3-D pressure produced by the plasma clouds, and supplemented those results with plasma pressures derived from the Cassini plasma spectrometer. Once scientists understood the pressure and its evolution, they could calculate the associated magnetic field perturbations along the Cassini flight path. The calculated field perturbation matched the observed magnetic field "thumps" perfectly, confirming the source of the field oscillations.
"We all know that changing rotation periods have been observed at pulsars, millions of light years from our solar system, and now we find that a similar phenomenon is observed right here at Saturn," said Tom Krimigis, principal investigator of the magnetospheric imaging instrument, also based at the Applied Physics Laboratory and the Academy of Athens, Greece. "With instruments right at the spot where it's happening, we can tell that plasma flows and complex current systems can mask the real rotation period of the central body. That's how observations in our solar system help us understand what is seen in distant astrophysical objects."
NASA Aids in Characterizing Super-Earth Atmosphere
PASADENA, Calif. -- A team of astronomers, including two NASA Sagan Fellows, has made the first characterizations of a super-Earth's atmosphere, by using a ground-based telescope. A super-Earth is a planet up to three times the size of Earth and weighing up to 10 times as much. The findings, reported in the Dec. 2 issue of the journal Nature, are a significant milestone toward eventually being able to probe the atmospheres of Earth-like planets for signs of life.
The team determined the planet, GJ 1214b, is either blanketed with a thin layer of water steam or surrounded by a thick layer of high clouds. If the former, the planet itself would have an icy composition. If the latter, the planet would be rocky or similar to the composition of Neptune, though much smaller.
"This is the first super-Earth known to have an atmosphere," said Jacob Bean, a NASA Sagan Fellow and astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "But even with these new measurements, we can't say yet what that atmosphere is made of. This world is being very shy and veiling its true nature from us."
GJ 1214b, first discovered in December 2009, is 2.7 times the size of Earth and 6.5 times as massive. Previous observations of the planet's size and mass demonstrated it has a low density for its size, leading astronomers to conclude the planet is some kind of solid body with an atmosphere.
The planet orbits close to its dim star, at a distance of 0.014 astronomical units. An astronomical unit is the distance between Earth and the sun, approximately 93 million miles. GJ 1214b circles too close to its star to be habitable by any life forms.
Bean and his team observed infrared light as the planet crossed in front of its star. During such transits, the star's light filters through the atmosphere. Gases absorb the starlight at particular wavelengths, leaving behind chemical fingerprints detectable from Earth. This same type of technique has been used to study the atmospheres of distant "hot Jupiters," or Jupiter-like planets orbiting close to their stars, and found gases like hydrogen, methane and sodium vapor.
In the case of the super-Earth, no chemical fingerprints were detected; however, this doesn't mean there are no chemicals present. Instead, this information ruled out some possibilities for GJ 1214b's atmosphere, and narrowed the scope to either an atmosphere of water steam or high clouds. Astronomers believe it's more likely the atmosphere is too thin around the planet to let enough light filter through and reveal chemical fingerprints.
"A steamy atmosphere would have to be very dense - about one-fifth water vapor by volume -- compared to our Earth, with an atmosphere that's four-fifths nitrogen and one-fifth oxygen with only a touch of water vapor," Bean said. "During the next year, we should have some solid answers about what this planet is truly like."
The team, which included Bean's co-authors -- Eliza Miller-Ricci Kempton, a NASA Sagan Fellow at the University of California in Santa Cruz, and Derek Homeier of the Institute for Astrophysics in Gottingen, Germany -- examined GJ 1214b using the ground-based Very Large Telescope at Paranal Observatory in Chile.
"This is an important step forward, narrowing our understanding of the atmosphere of this planet," said NASA Exoplanet Exploration Program Scientist Douglas Hudgins at NASA Headquarters in Washington. "Bizarre worlds like this make exoplanet science one of the most compelling areas in astrophysics today."
The team determined the planet, GJ 1214b, is either blanketed with a thin layer of water steam or surrounded by a thick layer of high clouds. If the former, the planet itself would have an icy composition. If the latter, the planet would be rocky or similar to the composition of Neptune, though much smaller.
"This is the first super-Earth known to have an atmosphere," said Jacob Bean, a NASA Sagan Fellow and astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "But even with these new measurements, we can't say yet what that atmosphere is made of. This world is being very shy and veiling its true nature from us."
GJ 1214b, first discovered in December 2009, is 2.7 times the size of Earth and 6.5 times as massive. Previous observations of the planet's size and mass demonstrated it has a low density for its size, leading astronomers to conclude the planet is some kind of solid body with an atmosphere.
The planet orbits close to its dim star, at a distance of 0.014 astronomical units. An astronomical unit is the distance between Earth and the sun, approximately 93 million miles. GJ 1214b circles too close to its star to be habitable by any life forms.
Bean and his team observed infrared light as the planet crossed in front of its star. During such transits, the star's light filters through the atmosphere. Gases absorb the starlight at particular wavelengths, leaving behind chemical fingerprints detectable from Earth. This same type of technique has been used to study the atmospheres of distant "hot Jupiters," or Jupiter-like planets orbiting close to their stars, and found gases like hydrogen, methane and sodium vapor.
In the case of the super-Earth, no chemical fingerprints were detected; however, this doesn't mean there are no chemicals present. Instead, this information ruled out some possibilities for GJ 1214b's atmosphere, and narrowed the scope to either an atmosphere of water steam or high clouds. Astronomers believe it's more likely the atmosphere is too thin around the planet to let enough light filter through and reveal chemical fingerprints.
"A steamy atmosphere would have to be very dense - about one-fifth water vapor by volume -- compared to our Earth, with an atmosphere that's four-fifths nitrogen and one-fifth oxygen with only a touch of water vapor," Bean said. "During the next year, we should have some solid answers about what this planet is truly like."
The team, which included Bean's co-authors -- Eliza Miller-Ricci Kempton, a NASA Sagan Fellow at the University of California in Santa Cruz, and Derek Homeier of the Institute for Astrophysics in Gottingen, Germany -- examined GJ 1214b using the ground-based Very Large Telescope at Paranal Observatory in Chile.
"This is an important step forward, narrowing our understanding of the atmosphere of this planet," said NASA Exoplanet Exploration Program Scientist Douglas Hudgins at NASA Headquarters in Washington. "Bizarre worlds like this make exoplanet science one of the most compelling areas in astrophysics today."
Cassini Finds Warm Cracks on Enceladus
PASADENA, Calif. – New images and data from NASA's Cassini spacecraft give scientists a unique Saturn-lit view of active fissures through the south polar region of Saturn's moon Enceladus. They reveal a more complicated web of warm fractures than previously thought.
The new images are available at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.
Scientists working jointly with Cassini's composite infrared spectrometer and its high-resolution imaging camera have constructed the highest-resolution heat intensity maps yet of the hottest part of a region of long fissures spraying water vapor and icy particles from Enceladus. These fissures have been nicknamed "tiger stripes." Additional high-resolution spectrometer maps of one end of the tiger stripes Alexandria Sulcus and Cairo Sulcus reveal never-before-seen warm fractures that branch off like split ends from the main tiger stripe trenches. They also show an intriguing warm spot isolated from other active surface fissures.
"The ends of the tiger stripes may be the places where the activity is just getting started, or is winding down, so the complex patterns of heat we see there may give us clues to the life cycle of tiger stripes," said John Spencer, a Cassini team scientist based at Southwest Research Institute in Boulder, Colo.
The images and maps come from the Aug. 13, 2010, Enceladus flyby, Cassini's last remote sensing flyby of the moon until 2015. The geometry of the many flybys between now and 2015 will not allow Cassini to do thermal scans like these, because the spacecraft will be too close to scan the surface and will not view the south pole. This Enceladus flyby, the 11th of Cassini's tour, also gave Cassini its last look at any part of the active south polar region in sunlight.
The highest-resolution spectrometer scan examined the hottest part of the entire tiger stripe system, part of the fracture called Damascus Sulcus. Scientists used the scan to measure fracture temperatures up to190 Kelvin (minus 120 degrees Fahrenheit). This temperature appears slightly higher than previously measured temperatures at Damascus, which were around 170 Kelvin (minus 150 degrees Fahrenheit).
Spencer said he isn't sure if this tiger stripe is just more active than it was the last time Cassini's spectrometer scanned it, in 2008, or if the hottest part of the tiger stripe is so narrow that previous scans averaged its temperature out over a larger area. In any case, the new scan had such good resolution, showing details as small as 800 meters (2,600 feet), that scientists could see for the first time warm material flanking the central trench of Damascus, cooling off quickly away from the trench. The Damascus thermal scan also shows large variations in heat output within a few kilometers along the length of the fracture. This unprecedented resolution will help scientists understand how the tiger stripes deliver heat to the surface of Enceladus.
Cassini acquired the thermal map of Damascus simultaneously with a visible-light image where the tiger stripe is lit by sunlight reflecting off Saturn. The visible-light and thermal data were merged to help scientists understand the relationships between physical heat processes and surface geology.
"Our high-resolution images show that this section of Damascus Sulcus is among the most structurally complex and tectonically dynamic of the tiger stripes," said imaging science team associate Paul Helfenstein of Cornell University, Ithaca, N.Y. Some details in the appearance of the landforms, such as a peculiar pattern of curving striations along the flanks of Damascus, had not previously been noticed in ordinary sunlit images.
The day after the Enceladus flyby, Cassini swooped by the icy moon Tethys, collecting images that helped fill in gaps in the Tethys global map. Cassini's new views of the heavily cratered moon will help scientists understand how tectonic forces, impact cratering, and perhaps even ancient resurfacing events have shaped the moon's appearance.
Dawn of the Universe Recreated
Just weeks after the world's largest particle accelerator began smashing together heavy lead ions to create little Big Bangs, the experiment has produced a primordial state of matter akin to what existed at the dawn of the universe.
The Large Hadron Collider (LHC), a 17-mile-long (27 kilometer) underground ring run by the European Organization for Nuclear Research (CERN) near Geneva, began colliding lead ions together Nov. 8. These atomic nuclei contain 82 protons, and are much heavier than the lone protons the accelerator was previously colliding.
Now two experiments at the LHC – called ATLAS and CMS, respectively – have reported a phenomenon called "jet quenching" that scientists say could reveal secrets about the nature of matter and the evolution of the universe.
After two ions crash into each other, detectors measure jets of particles that emerge from the high-energy collision. Jets are formed as the basic constituents of nuclear matter, called quarks and gluons, fly away from the collision point.
In proton collisions, jets usually appear in pairs, emerging back to back. However, in the tumultuous conditions created by heavy ion collisions such as those made by lead nuclei, the jets interact with a hot dense medium created when temperatures are so high that the basic constituents of matter break apart.
This leads to a characteristic signal, known as jet quenching, in which the energy of the jets can be severely degraded, signaling interactions with the medium more intense than ever seen before.
"ATLAS is the first experiment to report direct observation of jet quenching," said ATLAS spokesperson Fabiola Gianotti in a statement. "The excellent capabilities of ATLAS to determine jet energies enabled us to observe a striking imbalance in energies of pairs of jets, where one jet is almost completely absorbed by the medium."
Jet quenching is a powerful tool for studying nature, especially the behavior of the medium of broken-down particles, called quark-gluon plasma. This plasma is created when super-high temperatures break apart protons into their constituent quarks and gluons. The quarks and gluons then float around in a kind of primordial soup that resembles the universe shortly after the Big Bang.
"It is truly amazing to be looking, albeit on a microscopic scale, at the conditions and state of matter that existed at the dawn of time," said CMS spokesperson Guido Tonelli. "Since the very first days of lead-ion collisions, the quenching of jets appeared in our data while other striking features, like the observation of Z particles, never seen before in heavy-ion collisions, are under investigation. The challenge is now to put together all possible studies that could lead us to a much better understanding of the properties of this new, extraordinary state of matter." (A Z particle is nearly identical to a massless photon yet is very massive.)
The quark-gluon plasma was created for the first time ever at a smaller particle accelerator called the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory on Long Island. That finding was announced in February 2010.
The ATLAS and CMS measurements offer a new possibility to use jets, which interact with the primordial soup, to probe this unique state of matter, scientists said. Future jet quenching and other measurements from the LHC experiments will provide powerful insight into the properties of the primordial plasma and the interactions among its quarks and gluons, they said.
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