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Microlensing Study Suggests Most Common Outer Planets Likely Neptune-mass
A new statistical study of planets found by a technique called gravitational microlensing suggests that Neptune-mass worlds are likely the most common type of planet to form in the icy outer realms of planetary systems. The study provides the first indication of the types of planets waiting to be found far from a host star, where scientists suspect planets form most efficiently. 
"We've found the apparent sweet spot in the sizes of cold planets. Contrary to some theoretical predictions, we infer from current detections that the most numerous have masses similar to Neptune, and there doesn't seem to be the expected increase in number at lower masses," said lead scientist Daisuke Suzuki, a post-doctoral researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland Baltimore County. "We conclude that Neptune-mass planets in these outer orbits are about 10 times more common than Jupiter-mass planets in Jupiter-like orbits."
 Gravitational microlensing takes advantage of the light-bending effects of massive objects predicted by Einstein's general theory of relativity. It occurs when a foreground star, the lens, randomly aligns with a distant background star, the source, as seen from Earth. As the lensing star drifts along in its orbit around the galaxy, the alignment shifts over days to weeks, changing the apparent brightness of the source. The precise pattern of these changes provides astronomers with clues about the nature of the lensing star, including any planets it may host.
"We mainly determine the mass ratio of the planet to the host star and their separation," said team member David Bennett, an astrophysicist at Goddard. "For about 40 percent of microlensing planets, we can determine the mass of the host star and therefore the mass of the planet."
More than 50 exoplanets have been discovered using microlensing compared to thousands detected by other techniques, such as detecting the motion or dimming of a host star caused by the presence of planets. Because the necessary alignments between stars are rare and occur randomly, astronomers must monitor millions of stars for the tell-tale brightness changes that signal a microlensing event.
However, microlensing holds great potential. It can detect planets hundreds of times more distant than most other methods, allowing astronomers to investigate a broad swath of our Milky Way galaxy. The technique can locate exoplanets at smaller masses and greater distances from their host stars, and it's sensitive enough to find planets floating through the galaxy on their own, unbound to stars.
NASA's Kepler and K2 missions have been extraordinarily successful in finding planets that dim their host stars, with more than 2,500 confirmed discoveries to date. This technique is sensitive to close-in planets but not more distant ones. Microlensing surveys are complementary, best probing the outer parts of planetary systems with less sensitivity to planets closer to their stars.
"Combining microlensing with other techniques provides us with a clearer overall picture of the planetary content of our galaxy," said team member Takahiro Sumi at Osaka University in Japan.
From 2007 to 2012, the Microlensing Observations in Astrophysics (MOA) group, a collaboration between researchers in Japan and New Zealand, issued 3,300 alerts informing the astronomical community about ongoing microlensing events. Suzuki's team identified 1,474 well-observed microlensing events, with 22 displaying clear planetary signals. This includes four planets that were never previously reported.
To study these events in greater detail, the team included data from the other major microlensing project operating over the same period, the Optical Gravitational Lensing Experiment (OGLE), as well as additional observations from other projects designed to follow up on MOA and OGLE alerts.
From this information, the researchers determined the frequency of planets compared to the mass ratio of the planet and star as well as the distances between them. For a typical planet-hosting star with about 60 percent the sun's mass, the typical microlensing planet is a world between 10 and 40 times Earth's mass. For comparison, Neptune in our own solar system has the equivalent mass of 17 Earths.
The results imply that cold Neptune-mass worlds are likely to be the most common types of planets beyond the so-called snow line, the point where water remained frozen during planetary formation. In the solar system, the snow line is thought to have been located at about 2.7 times Earth's mean distance from the sun, placing it in the middle of the main asteroid belt today.
A paper detailing the findings was published in The Astrophysical Journal on Dec. 13.
"Beyond the snow line, materials that were gaseous closer to the star condense into solid bodies, increasing the amount of material available to start the planet-building process," said Suzuki. "This is where we think planetary formation was most efficient, and it's also the region where microlensing is most sensitive."
NASA's Wide Field Infrared Survey Telescope (WFIRST), slated to launch in the mid-2020s, will conduct an extensive microlensing survey. Astronomers expect it will deliver mass and distance determinations of thousands of planets, completing the work begun by Kepler and providing the first galactic census of planetary properties.
NASA's Ames Research Center manages the Kepler and K2 missions for NASA's Science Mission Directorate. The Jet Propulsion Laboratory (JPL) in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.
WFIRST is managed at Goddard, with participation by JPL, the Space Telescope Science Institute in Baltimore, the Infrared Processing and Analysis Center, also in Pasadena, and a science team comprising members from U.S. research institutions across the country.
 For more information on how NASA’s Kepler is working with ground-based efforts, including the MOA and OGLE groups, to search for planets using microlensing, please visit:  
By Francis Reddy
NASA's Goddard Space Flight Center in Greenbelt, Maryland
The Image: 
Neptune-mass exoplanets like the one shown in this artist's rendering may be the most common in the icy regions of planetary systems. Beyond a certain distance from a young star, water and other substances remain frozen, leading to an abundant population of icy objects that can collide and form the cores of new planets. In the foreground, an icy body left over from this period drifts past the planet.
Credits: NASA/Goddard/Francis Reddy
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Spitzer Hears Stellar 'Heartbeat' from Planetary Companion
A planet and a star are having a tumultuous romance that can be detected from 370 light-years away.
NASA's Spitzer Space Telescope has detected unusual pulsations in the outer shell of a star called HAT-P-2. Scientists' best guess is that a closely orbiting planet, called HAT-P-2b, causes these vibrations each time it gets close to the star in its orbit.
"Just in time for Valentine's Day, we have discovered the first example of a planet that seems to be causing a heartbeat-like behavior in its host star," said Julien de Wit, postdoctoral associate at the Massachusetts Institute of Technology, Cambridge. A study describing the findings was published today in Astrophysical Journal Letters.
 The star's pulsations are the most subtle variations of light from any source that Spitzer has ever measured. A similar effect had been observed in binary systems called "heartbeat stars" in the past, but never before between a star and a planet.
 Weighing in at about eight times the mass of Jupiter, HAT-P-2b is a relatively massive planet. It's a "hot Jupiter," meaning an exoplanet that is extremely warm and orbits its star tightly. But this hot Jupiter is tiny in relation to its host star, which is about 100 times more massive. That size difference makes the pulsation effect all the more unusual (For comparison, our sun is about 1,000 times more massive than Jupiter).
"It's remarkable that this relatively small planet seems to affect the whole star in a way that we can see from far away," said Heather Knutson, assistant professor of geological and planetary sciences at Caltech in Pasadena, California.
Known to the exoplanet community since 2007, HAT-P-2b was initially interesting to astronomers because of its "eccentric," or elliptical orbit. The planet spends most of its time relatively far from the star, but comes around for a close encounter every 5.6 days. Those are indeed hot dates for this planet, as it receives as much as 10 times the amount of light per unit area at closest approach than at its farthest point in the orbit.
 Each time the planet swings around for that close approach, it appears to gives its star a little "kiss" as the gravitational forces of these two bodies interact. The star, in turn, beats like a heart as the planet travels around in its orbit again. For a less lovey-dovey analogy: The planet's gravity hits the star like a bell on closest approach, making it ring throughout the planet's orbit.  
 "We had intended the observations to provide a detailed look at HAT-P-2b’s atmospheric circulation," said Nikole Lewis, co-author and astronomer at Space Telescope Science Institute, Baltimore. "The discovery of the oscillations was unexpected but adds another piece to the puzzle of how this system evolved."
 Spitzer watched the planet-star interactions from the vantage point of our own solar system, in the telescope's Earth-trailing orbit around the sun, for about 350 hours between July 2011 and November 2015. Because of the system's alignment with respect to Earth, Spitzer was able to observe the planet cross directly in front of the star (in a process called a "transit") as well as behind it (called a "secondary eclipse"). These eclipses of the planet allowed scientists to determine that the pulsations originate from the star, not the planet. The point of closest approach occurs between the transit and secondary eclipse. 
The planetary system still has scientists stumped. Calculations by co-author Jim Fuller, Caltech postdoctoral scholar, predicted that the pitter-patter of the star's vibrations should be quieter and at a lower frequency than what Spitzer found.
"Our observations suggest that our understanding of planet-star interactions is incomplete," said de Wit. "There's more to learn from studying stars in systems like this one and listening for the stories they tell through their 'heartbeats.'"
JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena, California. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. For more information about Spitzer, visit:  
Elizabeth Landau
>Jet Propulsion Laboratory, Pasadena, Calif.
The Image: 
This illustration shows how the planet HAT-P-2b, left, appears to cause heartbeat-like pulsations in its host star, HAT-P-2.
Credits: NASA/JPL-Caltech
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SpaceX Mission Poised for Notable Achievements
NASA's first cargo resupply mission of 2017 is poised to lift off from Kennedy Space Center in Florida loaded with almost 5,500 pounds of science experiments, research equipment and supplies bound for the International Space Station and its resident astronauts.
The gear is packed into a SpaceX Dragon capsule that will fly into orbit aboard the company's Falcon 9 rocket. It will take two days for the Dragon to catch up to the space station and move within reach of the station's 57-foot-long robotic arm.
Astronauts Shane Kimbrough of NASA and Thomas Pesquet of the European Space Agency will use the arm to capture Dragon and maneuver it to its berthing port on the station. The uncrewed Dragon is pressurized so astronauts aboard the orbiting laboratory can unpack the cargo and later fill it up with completed experiments and used equipment for return to Earth.
This cargo mission by SpaceX also will set a milestone as the first launch from Launch Complex 39A since the space shuttle fleet retired in 2011. It will mark a turning point for Kennedy's transition to a multi-user spaceport geared to support public and private missions, as well as those conducted in partnership with NASA.
Some of humanity's greatest adventures in orbit began at Launch Complex 39A. Astronauts lifted off from this pad six times between 1969 and 1972 to walk upon lunar soil. Flying inside Apollo spacecraft atop massive Saturn V rockets, the astronauts left Florida and the Earth behind for two weeks, while they ventured to the moon.
In 1981, it began hosting the world's first reusable spacecraft, NASA's space shuttles, on missions that would make working in space more accessible, while still achieving breathtaking science and accomplishing engineering feats that would have been out of reach before.
Some of the first pieces of the International Space Station began their operational lives with fiery liftoffs from the site including NASA's first station construction mission, STS-88 in 1998.
Although the majority of the supplies and experiments will be used inside the station, one of the major payloads of SpaceX’s CRS-10 mission will be attached to the outside of the station to survey aspects of Earth's atmosphere. The SAGE III project, short for Stratospheric Aerosol and Gas Experiment, is the latest version of an experiment that began in 1979 to carefully monitor and precisely measure ozone, aerosols, nitrogen dioxide and water vapor in the stratosphere and troposphere high above Earth. For details about the SAGE III mission, go to  
SpaceX's CRS-10 mission will also carry the Raven experiment, an advanced instrument designed to test sensors and avionics that are being developed so spacecraft can autonomously guide themselves through space to rendezvous and dock with other spacecraft. Raven's two-year mission on the station will see it compare trajectories and calculations with the actual flight paths of the many spacecraft that fly to the station.
The Dragon also carries an experiment coordinated by CASIS that will crystalize a human monoclonal antibody that has been developed by Merck Research Labs to treat immunological diseases. Crystalizing experiments on Earth have not produced high quality samples for study. It is hoped that larger crystals formed in the microgravity of space – where they won't collapse under their own weight as they grow – will show how to make the medicines usable in injected form instead of intravenously.
The SpaceX mission is expected to last about a month with the Dragon capsule being detached from the station by the robotic arm. The Dragon will fly the return flight path on its own as SpaceX and NASA mission controllers watch over its progress. Flying into the atmosphere protected by a heat shield, the Dragon will splashdown in the Pacific Ocean, where it will be recovered and its payloads dispatched to researchers.
By Steven Siceloff,
>NASA's Kennedy Space Center, Florida
The Image
A SpaceX Dragon cargo-carrying spacecraft like the one that will launch for the CRS-10 mission is seen connected to the International Space Station in August 2016.
Credits: NASA
Feb. 16, 2017
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Cygnus Packed with Experiments to Support Future Exploration
The International Space Station serves as the world’s leading orbital laboratory where crews conduct cutting-edge research and technology development. A crucial resupply line of spacecraft keeps work going that will enable human and robotic exploration of destinations beyond low-Earth orbit.
The next mission to the orbiting outpost will be Orbital ATK's seventh commercial resupply services (CRS-7) mission. Liftoff is scheduled for no earlier than March 27, 2017, from Space Launch Complex 41 at Cape Canaveral Air Force Staton. The recent date change allows the launch team additional time to troubleshoot a hydraulic issue discovered on required ground support equipment.
Cygnus consists of a pressurized cargo module for crew supplies, scientific experiments and equipment, together with an associated service module providing solar power and propulsion.
When members of the space station's Expedition 50 crew opens the hatch, they will be greeted with a sign noting the spacecraft was named in honor of John Glenn.
The spacecraft will launch on a United Launch Alliance Atlas V. The booster and Centaur upper stage for the mission arrived at Port Canaveral, Florida, Feb. 6. From the port, the launch vehicle was transported to the hangar at the Atlas Spaceflight Operations Center, located south of pad 41. After the Atlas V completed final testing in that facility, it was moved to the Vertical Integration Facility for stacking.
The Orbital ATK Cygnus pressurized cargo module arrived at the Space Station Processing Facility (SSPF) at NASA's Kennedy Space Center Jan. 9. The Cygnus service module arrived shortly thereafter.
In the SSPF, technicians and engineers loaded supplies, equipment and scientific research materials aboard a Cygnus PCM. Once mated to its service module, the spacecraft was transported to the Payload Hazardous Servicing Facility for propellant loading and final stowage of supplies.
After the Cygnus was encapsulated in its payload faring, it was transported to pad 41 to be mated atop the Atlas booster for final launch preparations.
When Orbital ATK CRS-7 arrives at the space station, Expedition 50 Commander Shane Kimbrough of NASA and Flight Engineer Thomas Pesquet of ESA (European Space Agency) will capture Cygnus with the station's robotic arm. After receiving ground commands, the arm will rotate and install Cygnus on the bottom of the station’s Unity module.
The space station crew will unpack the Cygnus and begin working with the experiments that include the following:
Genes in Space II
It is well known the rigors of spaceflight induce changes within the human body. The Genes in Space II experiment is designed to study one such change, a shift in the dynamics of telomeres, critical protective caps on the tips of chromosomes. A chromosome is a packaged and organized structure containing most of the DNA, or deoxyribonucleic acid, of a living organism -- the instructions each cell in an organism on Earth needs to live. The shortening of telomeres over time, as an individual ages, is natural, but stresses -- such as those experienced by astronauts -- can lead to deviations in regulation of telomere length, which has been implicated in a variety of diseases. This investigation seeks to determine whether telomeric DNA can be measured during spaceflight.
Biomolecule Sequencer
The Biomolecule Sequencer investigation is designed to determine if it is possible to establish the order of base pairs in a section of DNA while in Earth orbit. A space-based DNA sequencer could identify microbes, diagnose diseases and understand crew member health and potentially help detect DNA-based life elsewhere in the solar system.
As part of the Biomolecule Sequencer experiment in August 2016, DNA was successfully sequenced in microgravity for the first time by NASA astronaut Kate Rubins during Expedition 48. Sequencing DNA in space may allow astronauts to diagnose an illness, or identify microbes growing in the space station and determine whether or not they represent a health threat.
Saffire III
The Cygnus spacecraft will spend approximately four months attached to the space station. Cygnus will remain until June 21, 2017, when the spacecraft will depart. On June 28, it will return through a controlled destructive re-entry into Earth’s atmosphere over the Pacific Ocean.
But even the re-entry will offer an opportunity for further research. The third Spacecraft Fire Experiment, or Saffire III, will provide a unique environment for studying fires in microgravity. After Cygnus separates from the station a flame will be lit. The ignition is controlled from a ground station that will activate a hot wire, beginning an experiment that lasts about two-and-a-half hours. These experiments will advance capabilities for flammability tests and provide a testbed for the technology development for devices that detect gases and particulates from a fire, as well as scrub the atmosphere after a fire so it is safe for the crew.
Transformative capabilities and cutting-edge technologies such as those being launched aboard Orbital ATK CRS-7 are examples of expertise being developed, tested and flown today to support human exploration beyond the moon and ultimately, to Mars.
By Bob Granath
>NASA's Kennedy Space Center, Florida
March 21, 2017
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Auroras over Northern Canada
Explanation: Gusting solar winds and blasts of charged particles from the Sun resulted in several rewarding nights last December for those anticipating auroras. The above image captured dramatic auroras stretching across a sky near the town of Yellowknife in northern Canada. The auroras were so bright that they not only inspired awe, but were easily visible on an image exposure of only 1.3 seconds. A video taken concurrently shows the dancing sky lights evolving in real time as tourists, many there just to see auroras, respond with cheers. The conical dwellings on the image right are teepees, while far in the background, near the image center, is the constellation of Orion.
2014 July 14
Image Credit & Copyright: Kwon, O Chul (TWAN)
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Interstellar: Crossing the Cosmic Void
Humanity’s great leap into the space between the stars has, in a sense, already begun. NASA's Voyager 1 probe broke through the sun’s magnetic bubble to touch the interstellar wind. Voyager 2 isn’t far behind. New Horizons shot past Pluto on its way to encounters with more distant dwarf worlds, the rubble at the solar system’s edge.
Closer to home, we’re working on techniques to help us cross greater distances. Astronauts feast on romaine lettuce grown aboard the International Space Station, perhaps a preview of future banquets en route to Mars, or to deep space.
For the moment, sending humans to other stars remains firmly in the realm of science fiction—as in the new film, “Passengers,” when hibernating travelers awaken in midflight. But while NASA so far has proposed no new missions beyond our solar system, scientists and engineers are sketching out possible technologies that might one day help to get us there.
NASA’s Journey to Mars, a plan aimed at building on robotic missions to send humans to the red planet, could be helping lay the groundwork.
“Propulsion, power, life support, manufacturing, communication, navigation, robotics: the Journey to Mars is going to force us to make advances in every one of these areas,” said Jeffrey Sheehy, NASA’s Space Technology Missions Directorate chief engineer in Washington, D.C. “Those systems are not going to be advanced enough to do an interstellar mission. But Mars is stepping us that much farther into space. It’s a step along the way to the stars.”
Charting the unknown
Hurling ourselves, Passengers-style, just to the nearest star, Proxima Centauri, would require crossing almost inconceivably vast distances. We would need truly exotic technology, such as suspended animation or multi-generational life support. That places in-person visits well out of reach, at least for the near term.
 But the possibility of robotic interstellar probes is coming into much sharper focus. Space probe pioneers say the radiation, energy and particle-bathed space between the stars—the so-called interstellar medium—is itself a worthy science destination.
 “We need more explorers, more of these local probes into this region, so we can understand better these interface conditions between our sun and the interstellar medium," said Leon Alkalai, an engineering fellow at NASA’s Jet Propulsion Laboratory in Pasadena, California, and co-author of a 2015 report on exploring interstellar space. "Like the ancient mariners, we want to start creating a map.”
Alkalai’s report, “Science and Enabling Technologies for the Exploration of the Interstellar Medium,” maps out the knowns and unknowns of largely uncharted regions, from the dark, distant, dwarf worlds of the Kuiper Belt to the “bow shock”—the turbulent transition thought to separate the sun’s bubble of plasma from the interstellar wind. Drawing on the work of more than 30 specialists during two workshops at the Keck Institute for Space Studies, the report poses pressing questions about the structure, composition and energy flow in this cosmic vastness. And it paints one of the most detailed pictures yet of a possible interstellar probe using present-day technology.
Part of the report focuses on a “Design Reference Mission,” a conceptual starting point that allowed workshop scientists to begin teasing out some of the technical requirements of an interstellar probe. The resulting probe concept was meant to be “daring, challenging, inspirational to the public,” and “a rational first step towards attempting to reach another star,” the report said. It’s the latest in a long line of interstellar probe concepts by NASA scientists stretching back to the 1970s.
 In this conceptual scenario, the disk-shaped probe in a bullet-shaped housing is launched as a payload on the Space Launch System, NASA’s next big rocket, in the late 2020s. With gravitational boosts from Earth, Jupiter and the sun itself, it could reach interstellar space in just 10 years. By comparison, it took Voyager 1 36 years to reach the heliopause, or the boundary of interstellar space.
 The probe would rely on both rockets and electrical power from next-generation radioisotope thermoelectric generators, enhanced versions of the kind now onboard the Mars Curiosity Rover. Such a probe would carry a variety of sensors and a communications antenna. It could investigate the interstellar medium and its boundary with the solar system, and perhaps even conduct a flyby of a Kuiper Belt object, one of the many unknown space bodies that orbit the sun far beyond Pluto.
 Future studies could examine the possibility of electric propulsion for the probe, or solar or electric sails.
Solar gravity: a window on another world
One of the most extraordinary conceptual spacecraft detailed in the report also would exit the solar system, but only just. And its focus, literally, would be on alien worlds.
This conceptual spacecraft would be parked in near interstellar space to use our sun as a gigantic lens, allowing zoomed-in close-ups of planets orbiting other stars. A space telescope would be lofted to a position far beyond Pluto, some 550 times the distance from Earth to the sun, or farther. It would take advantage of an effect described by Einstein: the power of gravity to bend light rays.
The stream of light from a distant star and its planet would be bent around the edges of the sun, like water flowing around a rock, meeting on the other side at a focal point—where it would be greatly magnified. The telescope would be placed in just the right position to capture these images.
The images would be smeared into a ring around the sun, called an Einstein ring, and the technical challenges would be immense: the distortions would have to be corrected and the fragmentary images reassembled. But if successful, the lens could be powerful enough to reveal surface features of an exoplanet—a planet around another star.
“It would almost be like the Earthrise picture from the moon,” Alkalai said, recalling the iconic image sent back by the Apollo 8 astronauts in 1968. “You would see clouds and continents and oceans, that kind of scale of images. From Earth, every image of an exoplanet is a single pixel, so you’re looking with a straw at the exoplanet. If you want to image continents on an exoplanet, you need something like the solar gravitational lens.”
Once we are ready to take the giant stride to another star, the problem of propulsion takes center stage. Carrying bulky fuel tanks could increase the mass of an interstellar probe beyond the realm of feasibility.
But reaching even one-tenth the speed of light would allow a space probe to arrive at the nearest star in a 50-year time frame, Sheehy said.
“We would never be able to accelerate to that kind of velocity using a chemical reaction,” such as those in present-day rockets, he said.
One answer that might just possibly be within reach, he said, involves “beamed energy.” A powerful laser array, either on Earth’s surface or in orbit, could be used to accelerate space probes equipped with sails to some fraction of the speed of light. NASA’s Innovative Advanced Concepts Program (NIAC) recently chose one such project, led by Philip Lubin at the University of California, Santa Barbara, to receive a second grant for further development.
NIAC also recently provided funding for a conceptual project that might warm the hearts of “Passengers” fans. Called “Advanced Torpor Inducing Transfer Habitats for Human Stasis to Mars,” this research effort by John Bradford of Space Works Inc., in Atlanta, investigates how to place astronauts in a deep sleep state with reduced metabolic rates for trips between Earth and Mars. While it isn’t true suspended animation or intended for interstellar travel, such a project highlights the extreme technical difficulties involved in sending fragile human bodies across the reaches of interstellar space.
Printing a pizza
If our species ever attempts such trips, they could take many decades or even centuries, perhaps requiring some kind of suspension and revival or vessels that can sustain human life for several generations.
“Maybe the people we launch won’t be the people who actually reach Alpha Centauri,” Sheehy said. “It will be their kids. But you’ve got to eat for those 80 years.”
Learning to grow food in space could help, he said, though growing plants from seeds requires “real estate in space. A tomato plant is so big, a head of lettuce is a certain size.”
Another possibility is using 3-D printers that “build 3-D objects up layer by layer. Why couldn’t we build a cell that way? Why couldn’t we build food that way? Could you print a pizza?”
Alkalai also considers human interstellar travel an extremely distant prospect.
“The notion of sending humans to interstellar space is so far out in the sense that people need to have resources on the scale of a planet,” he said. “The only sci-fi story that I like, that might have some scientific basis, is not to build a Star Trek Enterprise but to really hijack an asteroid.
“Imagine a population that would be able to be on a binary asteroid. Then they could use one of them to swing the other one into interstellar space. Then you have resources on the asteroid, a source of iron, carbon, other materials. They could mine that as a source of resources for living, for energy. You would have to imagine something like this designed for many, many generations.”
But the daunting challenges even to sending robotic probes to the stars should be motivating, not discouraging, Sheehy said.
“Anywhere we’ve ever gone as humans, we always learn something, even if it’s just over the next mountain range,” he said. “A lot of times you discover something about yourself on a journey like that. We always find something that surprises us.”
The Image:
An annotated illustration of the interstellar medium. The solar gravity lens marks the point where a conceptual spacecraft in interstellar space could use our sun as a gigantic lens, allowing zoomed-in close-ups of planets orbiting other stars.
Credits: Charles Carter/Keck Institute for Space Studies
Last Updated: Dec. 21, 2016
Editor: Tony Greicius
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Fly Me to the Moon
Explanation: No, this is not a good way to get to the Moon. What is pictured is a chance superposition of an airplane and the Moon. The contrail would normally appear white, but the large volume of air toward the setting Sun preferentially knocks away blue light, giving the reflected trail a bright red hue. Far in the distance, to the right of the plane, is the young Moon. This vast world shows only a sliver of itself because the Sun is nearly lined up behind it. Captured two weeks ago, the featured image was framed by an eerie maroon sky, too far from day to be blue, too far from night to be black. Within minutes the impromptu sky show ended. The plane crossed the Moon. The contrail dispersed. The Sun set. The Moon set. The sky faded to black, only to reveal thousands of stars that had been too faint to see through the rustic red din.
Image Credit & Copyright: Tamas Ladanyi (TWAN)
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The Dramatic Center of the Orion Nebula (2017)
Star Is Missing Link to a System that Flew Apart Over 500 Years Ago
In the 1400s, two power struggles were taking place quadrillions of miles apart. In England, two rival branches of the royal House of Plantagenet were battling each other for control of the country's throne. And, in a nebula far, far away, a cluster of stars was waging a real-life star wars, with the stellar members battling each other for supremacy in the Orion Nebula. The gravitational tussle ended with the system breaking apart and at least three stars being ejected in different directions.
Astronomers spotted two of the speedy, wayward stars over the past few decades. They traced both stars back 540 years to the same location and suggested they were part of a now-defunct multiple-star system. But the duo's combined energy, which is propelling them outward, didn't add up. The researchers reasoned there must be at least one other culprit that robbed energy from the stellar toss-up. Now NASA's Hubble Space Telescope has helped astronomers find the final piece of the puzzle by nabbing a third runaway star, which was a member of the same system as the two previously known stars. The stars reside in a small region of young stars called the Kleinmann-Low Nebula, near the center of the vast Orion Nebula complex, located 1,300 light-years from Earth.
About this image
This dramatic view of the center of the Orion Nebula is the home of a grouping of hefty, young stars, called the Trapezium Cluster. Several hundred stars are sprinkled throughout the image. Many of them appear red because their light is being scattered by dust.
The Full Story
As British royal families fought the War of the Roses in the 1400s for control of England's throne, a grouping of stars was waging its own contentious skirmish — a star wars far away in the Orion Nebula.
The stars were battling each other in a gravitational tussle, which ended with the system breaking apart and at least three stars being ejected in different directions. The speedy, wayward stars went unnoticed for hundreds of years until, over the past few decades, two of them were spotted in infrared and radio observations, which could penetrate the thick dust in the Orion Nebula.
The observations showed that the two stars were traveling at high speeds in opposite directions from each other. The stars' origin, however, was a mystery. Astronomers traced both stars back 540 years to the same location and suggested they were part of a now-defunct multiple-star system. But the duo's combined energy, which is propelling them outward, didn't add up. The researchers reasoned there must be at least one other culprit that robbed energy from the stellar toss-up.
Now NASA's Hubble Space Telescope has helped astronomers find the final piece of the puzzle by nabbing a third runaway star. The astronomers followed the path of the newly found star back to the same location where the two previously known stars were located 540 years ago. The trio reside in a small region of young stars called the Kleinmann-Low Nebula, near the center of the vast Orion Nebula complex, located 1,300 light-years away.
"The new Hubble observations provide very strong evidence that the three stars were ejected from a multiple-star system," said lead researcher Kevin Luhman of Penn State University in University Park, Pennsylvania. "Astronomers had previously found a few other examples of fast-moving stars that trace back to multiple-star systems, and therefore were likely ejected. But these three stars are the youngest examples of such ejected stars. They're probably only a few hundred thousand years old. In fact, based on infrared images, the stars are still young enough to have disks of material leftover from their formation."
All three stars are moving extremely fast on their way out of the Kleinmann-Low Nebula, up to almost 30 times the speed of most of the nebula's stellar inhabitants. Based on computer simulations, astronomers predicted that these gravitational tugs-of-war should occur in young clusters, where newborn stars are crowded together. "But we haven't observed many examples, especially in very young clusters," Luhman said. "The Orion Nebula could be surrounded by additional fledging stars that were ejected from it in the past and are now streaming away into space."
The team's results will appear in the March 20, 2017 issue of The Astrophysical Journal Letters.
Luhman stumbled across the third speedy star, called "source x," while he was hunting for free-floating planets in the Orion Nebula as a member of an international team led by Massimo Robberto of the Space Telescope Science Institute in Baltimore, Maryland. The team used the near-infrared vision of Hubble's Wide Field Camera 3 to conduct the survey. During the analysis, Luhman was comparing the new infrared images taken in 2015 with infrared observations taken in 1998 by the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). He noticed that source x had changed its position considerably, relative to nearby stars over the 17 years between Hubble images, indicating the star was moving fast, about 130,000 miles per hour.
The astronomer then looked at the star's previous locations, projecting its path back in time. He realized that in the 1470s source x had been near the same initial location in the Kleinmann-Low Nebula as two other runaway stars, Becklin-Neugebauer (BN) and "source I."
BN was discovered in infrared images in 1967, but its rapid motion wasn't detected until 1995, when radio observations measured the star's speed at 60,000 miles per hour. Source I is traveling roughly 22,000 miles per hour. The star had only been detected in radio observations; because it is so heavily enshrouded in dust, its visible and infrared light is largely blocked.
The three stars were most likely kicked out of their home when they engaged in a game of gravitational billiards, Luhman said. What often happens when a multiple system falls apart is that two of the member stars move close enough to each other that they merge or form a very tight binary. In either case, the event releases enough gravitational energy to propel all of the stars in the system outward. The energetic episode also produces a massive outflow of material, which is seen in the NICMOS images as fingers of matter streaming away from the location of the embedded source I star.
Future telescopes, such as the James Webb Space Telescope, will be able to observe a large swath of the Orion Nebula. By comparing images of the nebula taken by the Webb telescope with those made by Hubble years earlier, astronomers hope to identify more runaway stars from other multiple-star systems that broke apart.
The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.
NASA, ESA, K. Luhman (Penn State University), and M. Robberto (STScI)
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Milky Way over Bosque Alegre Station in Argentina
Explanation: What are those streaks of light in the sky? First and foremost, the arching structure is the central band of our Milky Way galaxy. Visible in this galactic band are millions of distant stars mixed with numerous lanes of dark dust. Harder to discern is a nearly vertical beam of light rising from the horizon, just to the right of the image center. This beam is zodiacal light, sunlight scattered by dust in our Solar System that may be surprisingly prominent just after sunset or just before sunrise. In the foreground are several telescopes of the Bosque Alegre Astrophysical Station of the National University of Cordoba in Argentina. The station schedules weekend tours and conducts research into the nature of many astronomical objects including comets, active galaxies, and clusters of galaxies. The featured image was taken early this month.
Image Credit & Copyright: Sebastián D' Alessandro; Rollover Annotation: Judy Schmidt
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NGC 7793: Black Hole Blows Big Bubble
A microquasar has been discovered in the nearby galaxy NGC 7793.
In these systems, a stellar-mass black hole is being fed by a companion star.
The black hole in the microquasar is generating two powerful jets, which are blowing outward and creating huge bubbles of hot gas.
Microquasars are miniature versions of powerful quasars in distant galaxies and therefore useful to study.
This composite image shows a powerful microquasar containing a black hole in the outskirts of the nearby (12.7 million light years) galaxy NGC 7793. The large image contains data from the Chandra X-ray Observatory in red, green and blue, optical data from the Very Large Telescope in light blue, and optical emission by hydrogen ("H-alpha") from the CTIO 1.5-m telescope in gold.
The upper inset shows a close-up of the X-ray image of the microquasar, which is a system containing a stellar-mass black hole being fed by a companion star. Gas swirling toward the black hole forms a disk around the black hole. Twisted magnetic fields in the disk generate strong electromagnetic forces that propel some of the gas away from the disk at high speeds in two jets, creating a huge bubble of hot gas about 1,000 light years across. The faint green/blue source near the middle of the upper inset image corresponds to the position of the black hole, while the red/yellow (upper right) and yellow (lower left) sources correspond to spots where the jets are plowing into surrounding gas and heating it. The nebula produced by energy from the jets is clearly seen in the H-alpha image shown in the lower inset.
The jets in the NGC 7793 microquasar are the most powerful ever seen from a stellar-mass black hole and the data show that a surprising amount of energy from the black hole is being carried away by the jets, rather than by radiation from material being pulled inward. The power of the jets is estimated to be about ten times larger than that of the very powerful ones seen from the famous microquasar in our own galaxy, SS433. This system in NGC 7793 is a miniature version of the powerful quasars and radio galaxies, which contain black holes that range from millions to billions of times the mass of the Sun.
A paper describing this work is being published in the July 8th, 2010, issue of Nature. The authors are Manfred Pakull from the University of Strasbourg in France, Roberto Soria from University College London, and Christian Motch, also from the University of Strasbourg.
Credit X-ray (NASA/CXC/Univ of Strasbourg/M. Pakull et al); Optical (ESO/VLT/Univ of Strasbourg/M. Pakull et al); H-alpha (NOAO/AURA/NSF/CTIO 1.5m)
Release Date July 07, 2010
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