The LHC takes a break before heading to new heights

CERN - European Organization for Nuclear Research logo.

30 July 2016

The Large Hadron Collider (LHC). Image Credit: CERN

The Large Hadron Collider (LHC) has been on Olympic form recently. In just two months, the accelerator delivered almost five times as much data as in the whole of 2015, smashing one record after another for luminosity, i.e. the number of collisions. The counter for integrated luminosity, which indicates the cumulative number of collisions delivered to the experiments, is approaching 20 inverse femtobarns (fb^-1), not far from the 25 fb^-1 target for 2016 as a whole!  This is great news for the experiments, which have been able to add data to their analyses ahead of presenting their latest results at the ICHEP 2016 (link is external) conference, which begins in a week’s time in Chicago in the United States.

The LHC operators have been clocking up long periods of operation, during which the beams have been circulating and colliding without a single hiccup along the way. You might think that the operators just sit there twiddling their thumbs while the beams circulate, but this couldn’t be further from the truth. The LHC is operating so well thanks to their constant checks and adjustments, which improve the operation of the accelerator and its thousands of components. And sometimes they stop the collisions altogether to carry out detailed studies of the accelerator, as is the case this week. Twenty days each year are devoted to these so-called machine development periods.

Image above: In the CERN Control Centre, Jan Uythoven and his colleagues perform studies to improve the operation of the LHC. (Image: Maximilien Brice/CERN).

“Studies like those we are carrying out this week have helped to pave the way for the excellent performance at the LHC in recent months,” says Jan Uythoven, who is in charge of the current machine development period. “The tests we’re doing are essential to maintain and even improve the performance of the LHC over the coming months and years.”

One of the main goals of the tests is to increase the luminosity even further. To do this, the operators can play with the size of the beam at the collision points in the centre of the experiments. The more the proton bunches that form the beam are compressed, the better the chances of collisions. “We are testing new settings for the quadrupole magnets that focus the beam,” explains Jan Uythoven. Another area being studied is beam instability, which is one of the operators’ pet hates. Each time that beam intensity is increased or the way in which the accelerator is filled is changed, the operators have to adjust all of the machine’s parameters to avoid the beams becoming unstable. When instabilities arise, the operators have to stop the beams and dump them. Another aspect of the current tests concerns the optimisation of the process for injecting proton bunches, in order to reduce the spreading of the beam.

After six days of studies, the LHC will resume its collision marathon next Monday.

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:

Large Hadron Collider (LHC): http://home.cern/topics/large-hadron-collider

ICHEP 2016: https://www.ichep2016.org/

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

Image (mentioned), Text, Credits: CERN/Corinne Pralavorio.

Five Years Post-Launch, Juno Is at a Turning Point

NASA - JUNO Mission logo.

July 29, 2016

Artist's view of Juno spacecraft over Jupiter. Image Credit: NASA

Five years after departing Earth, and a month after slipping into orbit around Jupiter, NASA's Juno spacecraft is nearing a turning point. On July 31 at 12:41 p.m. PDT (3:41 p.m. EDT), Juno will reach the farthest point in its orbit of Jupiter for the first time, known as “apojove,” 5 million miles (8.1 million kilometers) from the giant planet. After that point, Jupiter's gravitational grip on Juno will cause the spacecraft to begin falling back toward the planet for another pass, this time with its scientific eyes wide open.

The spacecraft is currently executing the first of two long orbits prior to beginning its science mission. Each capture orbit is nearly two months long -- quite the wait for the mission's eager team of scientists -- but it's nothing compared to the long wait the team endured on the trek to Jupiter.

Juno launched on Aug. 5, 2011. The spacecraft took a long, looping path around the inner solar system to set up an Earth flyby, in which our planet's gravity flung the spinning probe onward toward Jupiter.

"For five years we've been focused on getting to Jupiter. Now we're there, and we're concentrating on beginning dozens of flybys of Jupiter to get the science we're after," said Scott Bolton, Juno principal investigator at Southwest Research Institute in San Antonio.

Image above: This diagram shows the Juno spacecraft's orbits, including its two long, stretched-out capture orbits. The spacecraft's position on July 31 is indicated at left. Image Credits: NASA/JPL-Caltech.

Juno arrived at Jupiter on July 4, firing its main rocket engine as planned for 35 minutes. The flawless maneuver allowed Jupiter's gravity to capture the solar powered spacecraft into the first of two 53.4-day-long orbits, referred to as capture orbits. Following the capture orbits, Juno will fire its engine once more to shorten its orbital period to 14 days and begin its science mission.

But before that happens, on Aug. 27, Juno must finish its first lap around Jupiter, with a finish line that represents the mission's closest pass over the gas giant. During the encounter, Juno will skim past Jupiter at a mere 2,600 miles (4,200 kilometers) above the cloud tops.

Juno's science instruments were turned off during orbit insertion, to simplify spacecraft operations during that critical maneuver. In contrast, all the instruments will be collecting data during the Aug. 27 pass, which serves as a trial run before the mission gets to work collecting the precious data it came for.

"We're in an excellent state of health, with the spacecraft and all the instruments fully checked out and ready for our first up-close look at Jupiter," said Rick Nybakken, Juno project manager at NASA's Jet Propulsion Laboratory, Pasadena, California.

With its powerful suite of science instruments, Juno will probe Jupiter's deep structure, atmospheric circulation and the high-energy physics of its magnetic environment. What Juno finds there will reveal important clues to Jupiter's formation and evolution, along with insights about how our planetary system and others are built.

JPL manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. Juno is part of NASA's New Frontiers Program, which is managed at NASA's Marshall Space Flight Center in Huntsville, Alabama, for NASA's Science Mission Directorate. Caltech in Pasadena manages JPL for NASA.

More information on the Juno mission is available at: http://www.nasa.gov/juno

The public can follow the mission on Facebook and Twitter at:

http://www.facebook.com/NASAJuno

http://www.twitter.com/NASAJuno

Images (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Preston Dyches/DC Agle.

Greetings, Orbiter.ch

Hubble Gazes at Long-dead Star

NASA - Hubble Space Telescope patch.

July 29, 2016

This NASA/ESA Hubble Space Telescope image captures the remnants of a long-dead star. These rippling wisps of ionized gas, named DEM L316A, are located some 160,000 light-years away within one of the Milky Way’s closest galactic neighbors — the Large Magellanic Cloud (LMC).

The explosion that formed DEM L316A was an example of an especially energetic and bright variety of supernova, known as a Type Ia. Such supernova events are thought to occur when a white dwarf star steals more material than it can handle from a nearby companion, and becomes unbalanced. The result is a spectacular release of energy in the form of a bright, violent explosion, which ejects the star’s outer layers into the surrounding space at immense speeds. As this expelled gas travels through the interstellar material, it heats up and ionizes it, producing the faint glow that Hubble’s Wide Field Camera 3 has captured here.

The LMC orbits the Milky Way as a satellite galaxy and is the fourth largest in our group of galaxies, the Local Group. DEM L316A is not the only supernova remnant in the LMC; Hubble came across another one in 2010 with SNR 0509, and in 2013 it snapped SNR 0519.

For more information about the Hubble Space Telescope, visit:

http://hubblesite.org/
http://www.nasa.gov/hubble
https://www.spacetelescope.org/

Image credits: ESA (European Space Agency)/Hubble & NASA, Y. Chu/Text credits: ESA/NASA/Rob Garner.

Greetings, Orbiter.ch

Mars Gullies Likely Not Formed by Liquid Water

NASA - Mars Reconnaissance Orbiter (MRO) logo.

July 29, 2016

Animation above: Martian gullies as seen in the top image from HiRISE on NASA's Mars Reconnaissance Orbiter resemble gullies on Earth that are carved by liquid water. However, when they are observed with the addition of mineralogical information from CRISM, no evidence for alteration by water appears. Animation Credits: NASA/JPL-Caltech/UA/JHUAPL.

New findings using data from NASA's Mars Reconnaissance Orbiter show that gullies on modern Mars are likely not being formed by flowing liquid water. This new evidence will allow researchers to further narrow theories about how Martian gullies form, and reveal more details about Mars' recent geologic processes.

Scientists use the term "gully" for features on Mars that share three characteristics in their shape:  an alcove at the top, a channel, and an apron of deposited material at the bottom. Gullies are distinct from another type of feature on Martian slopes, streaks called "recurring slope lineae," or RSL, which are distinguished by seasonal darkening and fading, rather than characteristics of how the ground is shaped. Water in the form of hydrated salt has been identified at RSL sites. The new study focuses on gullies and their formation process by adding composition information to previously acquired imaging.

Researchers from the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, examined high-resolution compositional data from more than 100 gully sites throughout Mars. These data, collected by the orbiter's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), were then correlated with images from the same spacecraft's High Resolution Imaging Science Experiment (HiRISE) camera and Context Camera (CTX).

Images above: Martian gullies as seen in the top image from HiRISE on NASA's Mars Reconnaissance Orbiter resemble gullies on Earth that are carved by liquid water. However, when they are observed with the addition of mineralogical information from CRISM (bottom), no evidence for alteration by water appears. Images Credits: NASA/JPL-Caltech/UA/JHUAPL.

The findings showed no mineralogical evidence for abundant liquid water or its by-products, thus pointing to mechanisms other than the flow of water -- such as the freeze and thaw of carbon dioxide frost -- as being the major drivers of recent gully evolution.

The findings were published in Geophysical Research Letters: http://onlinelibrary.wiley.com/doi/10.1002/2016GL068956/full

Gullies are a widespread and common feature on the Martian surface, mostly occurring between 30 and 50 degrees latitude in both the northern and southern hemispheres, generally on slopes that face toward the poles. On Earth, similar gullies are formed by flowing liquid water; however, under current conditions, liquid water is transient on the surface of Mars, and may occur only as small amounts of brine even at RSL streaks. The lack of sufficient water to carve gullies has resulted in a variety of theories for the gullies' creation, including different mechanisms involving evaporation of water and carbon dioxide frost.

"The HiRISE team and others had shown there was seasonal activity in gullies -- primarily in the southern hemisphere -- over the past couple of years, and carbon dioxide frost is the main mechanism they suspected of causing it. However, other researchers favored liquid water as the main mechanism," said Jorge Núñez of APL, the lead author of the paper. "What HiRISE and other imagers were not able to determine on their own was the composition of the material in gullies, because they are optical cameras. To bring another important piece in to help solve the puzzle, we used CRISM, an imaging spectrometer, to look at what kinds of minerals were present in the gullies and see if they could shed light on the main mechanism responsible."

Núñez and his colleagues took advantage of a new CRISM data product called Map-projected Targeted Reduced Data Records. It allowed them to more easily perform their analyses and then correlate the findings with HiRISE imagery.

Artist's view of Mars Reconnaissance Orbiter (MRO). Image Credit: NASA

"On Earth and on Mars, we know that the presence of phyllosilicates -- clays -- or other hydrated minerals indicates formation in liquid water," Núñez said. "In our study, we found no evidence for clays or other hydrated minerals in most of the gullies we studied, and when we did see them, they were erosional debris from ancient rocks, exposed and transported downslope, rather than altered in more recent flowing water. These gullies are carving into the terrain and exposing clays that likely formed billions of years ago when liquid water was more stable on the Martian surface."

Other researchers have created computer models that show how sublimation of seasonal carbon dioxide frost can create gullies similar to those observed on Mars, and how their shape can mimic the types of gullies that liquid water would create. The new study adds support to those models.

APL built and operates CRISM, one of six instruments with which the Mars Reconnaissance Orbiter project has been examining Mars since 2006. NASA's Jet Propulsion Laboratory, a division of the Caltech in Pasadena, California manages the project for the NASA Science Mission Directorate in Washington. Lockheed Martin Space Systems of Denver built the orbiter and supports its operations.

Related links:

Map-projected Targeted Reduced Data Records: http://crism.jhuapl.edu/newscenter/articles/20160317.php

Mars Reconnaissance Orbiter project: http://www.nasa.gov/mro

Mars Reconnaissance Orbiter (MRO): http://www.nasa.gov/mission_pages/MRO/main/index.html

Images (mentioned), Animation (mentioned), Text, Credits; NASA/Tony Greicius/JPL/Guy Webster/Johns Hopkins University Applied Physics Laboratory/Geoff Brown.

Greetings, Orbiter.ch

New furnace a step towards future collider development

CERN - European Organization for Nuclear Research logo.

July 28, 2016

A new furnace arrived at CERN’s Large Magnet Facility last month and is currently being installed and tested.

The furnace completes the equipment required for the production of superconducting coils, which are needed for the High-Luminosity LHC (HL-LHC) upgrade and future circular colliders.

Superconducting accelerator magnets are key for reaching higher energies and luminosities in particle accelerators.

Image above: The new furnace is currently being installed and tested. (Image: Friedrich Lackner/CERN).

The HL-LHC upgrade aims for magnetic fields up to 11T for the dipole magnets while the Future Circular Collider study explores using magnets with a field of 16 Tesla, almost double the 8.3 Tesla of the superconducting magnets used in the LHC.

To reach these goals new superconducting materials are needed.

“Nb₃Sn has been chosen for the next generation of superconducting magnets. The field achieved with this material can reach up to 16T. The production of such coils is complex as we must first wind the coils and then perform the heat treatment that allows the tin and niobium to react and turn into the superconducting Nb3Sn compound.” explains Friedrich Lackner, a project engineer who supervises the coil production for HL-LHC.

Once the material has undergone this heat treatment it becomes very brittle, which is why this process is performed after the winding process — the opposite to magnets in the LHC.

The new 32-metre-long furnace, called GL010000, will allow the heat treatment of coils with a length up to 11m and can reach temperatures up to 900°C providing a sufficient margin for future challenges.

This treatment involves a two week long process during which the coils are raised to different temperature plateaus up to 665°C. A special feature of this oven is that it is able to raise the coils to such high temperatures completely uniformly throughout the entire oven, making sure one part doesn’t heat more or less than another.

The installation of the new furnace at CERN’s Large Magnet Facility (LMF) will help scientists researching and developing the new materials needed for future colliders to understand the superconductor development based on this  Nb₃Sn alloy, and will allow CERN to lead the production of superconducting coils and the development of high-field magnets.

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:

High-Luminosity LHC (HL-LHC): http://home.cern/topics/high-luminosity-lhc

Future Circular Collider study: http://home.cern/about/accelerators/future-circular-collider

Nb₃Sn: http://home.cern/cern-people/updates/2016/07/once-upon-time-there-was-superconducting-niobium-tin

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

Image (mentioned), Text, Credits: CERN/Harriet Jarlett, Panagiotis Charitos.

Best regards, Orbiter.ch

United Launch Alliance Successfully Launches NROL-61

ULA - NROL-61 Mission logo.

July 28, 2016

United Launch Alliance Successfully Launches NROL-61 Payload for the National Reconnaissance Office

Image above: A United Launch Alliance Atlas V rocket carrying the classifed NROL-61 satellite launches. Image Credit: ULA.

A United Launch Alliance (ULA) Atlas V rocket carrying a payload for the National Reconnaissance Office (NRO) lifted off from Space Launch Complex-41 July 28 at 8:37 a.m. EDT. Designated NROL-61, the mission is in support of national defense. This is ULA’s 6th launch in 2016 and the 109th successful launch since the company was formed in December 2006.

“Thank you to the entire mission team for years of hard work and collaboration on today’s successful launch of NROL-61. We are proud the U.S. Air Force and NRO Office of Space Launch have entrusted ULA with delivering this critical asset for our nation’s security,” said Laura Maginnis, ULA vice president of Custom Services.  “Our continued one launch at a time focus and exceptional teamwork make launches like today’s successful.”

Atlas V NROL-61 Launch Highlights 

This mission was launched aboard an Atlas V Evolved Expendable Launch Vehicle (EELV) 421 configuration vehicle, which includes a 4-meter-diameter Extra Extended Payload Fairing (XEPF). The Atlas booster for this mission was powered by the RD AMROSS RD-180 engine, and the Centaur upper stage was powered by the Aerojet Rocketdyne RL10C-1 engine.

ULA's next launch is the Delta IV AFSPC-6 satellite for the U.S. Air Force. The launch is scheduled for Aug. 19 from Space Launch Complex-37 at Cape Canaveral Air Force Station, Florida.

ULA - Atlas V / NROL-61 Mission poster

The EELV program was established by the U.S. Air Force to provide assured access to space for Department of Defense and other government payloads. The commercially developed EELV program supports the full range of government mission requirements, while delivering on schedule and providing significant cost savings over the heritage launch systems.

With more than a century of combined heritage, United Launch Alliance is the nation’s most experienced and reliable launch service provider. ULA has successfully delivered more than 100 satellites to orbit that provide critical capabilities for troops in the field, aid meteorologists in tracking severe weather, enable personal device-based GPS navigation and unlock the mysteries of our solar system.

For more information on ULA, visit the ULA website at http://www.ulalaunch.com. Join the conversation at http://www.facebook.com/ulalaunch, http://twitter.com/ulalaunch and http://instagram.com/ulalaunch.

Image, Poster, Video, Text, Credit: United Launch Alliance (ULA).

Greetings, Orbiter.ch

Researchers Measure, Monitor and Mitigate Potential Health Risks of Long Duration Spaceflight

ISS - International Space Station logo.

July 28, 2016

NASA closely monitors astronaut health during missions and throughout their lifetime. These medical monitoring programs, as well as prospective studies and medical research, help understand potential health risks related to long duration spaceflight, including the agency’s Journey to Mars.

Biomedical research that aims to prevent heart disease is an important part of the NASA Human Research Program. One example is the Cardio Ox study, which uses the unique microgravity environment of the International Space Station to understand changes to the cardiovascular system in astronauts living and working in low-Earth orbit.

Radiation is another top health concern for astronauts. Crew members who travel beyond low-Earth orbit will be exposed to more and different types of radiation because they will not be protected by Earth’s magnetosphere. The National Space Biomedical Research Institute, a non-governmental organization with funding from NASA’s Human Research Program, supported a recent study published in Scientific Reports that looked at the rate of cardiovascular disease among Apollo astronauts.

Image above: Koichi Wakata, Expedition 38 Flight Engineer (FE), performs ultrasound data collection for the Cardio Ox experiment, in the Columbus Module. Image Credit: NASA.

With the current limited astronaut data referenced in the study it is not possible to determine whether cosmic ray radiation affected the Apollo astronauts. The study group comprised seven of the 24 men who flew in the Apollo program; five women and 30 men who have flown in low-Earth orbit; and 33 astronauts—three women and 32 men—who have not flown on missions. In addition to the small study size, limitations of the research include lifestyle factors that cannot be quantified, such as family genetics and diet, which are known risk factors for cardiovascular disease.

The agency recognizes the importance of this research area and supports a comprehensive program to assess the potential health effects for crew members from space radiation exposure. NASA uses ground research facilities to study how radiation affects biological systems, and more importantly, how to protect them. Scientists also are developing unique ways to monitor and measure how radiation affects people while living in space, and to identify biological countermeasures. Finally, NASA is exploring methods to optimize radiation shielding for spacecraft and habitats.

NASA research on both acute and long-term health risks from space radiation include studies about possible increased incidence of cancer and acute radiation sickness, degenerative tissue damage, diseases such as heart disease and cataracts, and early and late central nervous system damage.

International Space Station (ISS). Image Credit: NASA

NASA's Human Research Program enables space exploration by reducing the risks to human health and performance through a focused program of basic, applied, and operational research. This leads to the development and delivery of: human health, performance, and habitability standards; countermeasures and risk mitigation solutions; and advanced habitability and medical support technologies.

For more information on NASA’s Human Research Program, visit: https://www.nasa.gov/hrp

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

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

Journey to Mars: https://www.nasa.gov/topics/journeytomars/index.html

Cardio Ox study: http://www.nasa.gov/mission_pages/station/research/news/heart_health_cardio_ox

Images (mentioned), Text, Credits: NASA/Sarah Loff.

Best regards, Orbiter.ch

Tile Bonding Begins for Orion’s First Mission Atop Space Launch System Rocket

NASA - Space Launch System (SLS) logo / NASA - Orion Exploration Crew Vehicle patch.

July 28, 2016

A crucial part of preparing NASA’s next Orion spacecraft for flight now is underway. Technicians recently began the process of bonding thermal protection system (TPS) tiles to panels that will be installed on Orion.

The tiles will protect the spacecraft from the searing heat of re-entry when it returns from deep space missions.

The first integrated mission of NASA’s Space Launch System (SLS) rocket with Orion, Exploration Mission 1, or EM-1, will lift off from Launch Complex 39B at NASA's Kennedy Space Center in Florida. On the mission, the spacecraft will venture 40,000 miles beyond the orbit of the moon, farther than any spacecraft built for humans has ever traveled, testing the systems needed for the agency’s journey to Mars. The mission will conclude with Orion re-entering through the Earth's atmosphere at 25,000 mph, generating heat at about 5,000 degrees Fahrenheit.

Image above: In the Neil Armstrong Operations and Checkout Building at NASA’s Kennedy Space Center, technicians have begun bonding thermal protection system tiles to the nine panels the will cover the Orion crew module for the agency’s first unpiloted flight test with the Space Launch System (SLS) on the agency’s Journey to Mars. Image Credits: NASA/Cory Huston.

According to Joy Huff, a thermal protection system engineer in the Materials Science Branch of Kennedy Engineering, Orion’s back shell panels and forward bay cover, which helps protect the spacecraft during re-entry, will be protected by silica tiles similar to those used for more than 30 years on the space shuttle.

 “The seven to eight technicians and two quality inspectors with Arctic Slope Research Corp. doing the work are veterans of bonding tiles to the shuttle orbiters." she said. "The tiles are manufactured here in Kennedy’s Thermal Protection System Facility.”

Denver-based Lockheed Martin Space Systems Co. is the prime contractor for the Orion spacecraft.

The company provides digital, computer-aided design information that defines the size and shape of each tile. At Kennedy’s TPSF, that information is used to manufacture the tiles. A 3-D camera then scans the as-built shape for comparison to the design information. This ensures that the manufactured tile meets the design requirements before it is placed on one of nine tile panels or the forward bay cover.

The bonding process began in July and will take several months. The work is taking place in the high bay of the Neil Armstrong Operations and Checkout Building where assembly of the Orion crew module’s pressure vessel, or underlying structure, has been taking place since it arrived at the Florida spaceport in February.

Image above: Technicians prepare to bond thermal protection system tiles on the Orion crew module for the agency’s Exploration Mission-1 with the Space Launch System (SLS) rocket. Orion requires about 1,300 tiles. Many of the Orion tiles are standard, except for those which fit around windows, thrusters or antennae. Along with the spacecraft’s heatshield, the tiles will protect Orion from the 5,000 degree Fahrenheit heat of re-entry. Image Credits: NASA/Cory Huston.

Orion will need about 1,300 tiles to protect it. On average, the tiles are 8-inches by 8-inches and many are standard in size allowing them to have the same dimensions with the same part number.

“Some tiles on Orion are a unique design to fit around windows, thrusters and antennas,” Huff said.

Huff noted that Orion tiles incorporate a stronger coating called “toughened uni-piece fibrous insulation,” or TUFI coating, which was used toward the end of the Space Shuttle Program.

“The ‘tougher’ tiles are important to Orion as they will help limit damage during ground processing and by debris in orbit,” Huff said.

Once the tile bonding is complete, the nine panels and forward bay cover will be installed on the crew module after it is mated to its service module.

“For EM-1, the back shell panels will have a different look than Orion’s first test flight,” said Huff.

Orion’s inaugural mission, known as Exploration Flight Test-1, or EFT-1, was flown on Dec. 5, 2014. On that flight, the tiles gave the crew module a black look.

Image above: During Exploration Mission-1, NASA’s Orion spacecraft will venture 40,000 miles beyond the orbit of the moon, farther than any spacecraft built for humans has ever traveled. Image Credit: NASA.

“For EM-1, we will place an aluminized coating over the tiles, giving it a shiny silver look,” she said.

Following deep-space missions, Orion will make a comet-like re-entry through Earth's atmosphere, protected by the tiles and the largest and most advanced heat shield ever constructed. The spacecraft then will splashdown in the ocean.

“The fact that Orion lands in the ocean, requires we replace the tiles after each mission,” Huff said. “The tiles are waterproofed to protect them from fresh water, such as rain. But during re-entry the waterproofing material burns out of the tiles so they do absorb salt water while in the ocean and that adds contaminants that would make their reuse impossible.”

Installing TPS tiles will be a part of preparation for each mission. The work taking place now will help perfect the process.

For EM-1, Orion will travel well beyond the moon for about three weeks, collecting data and allowing mission controllers to assess the performance of the spacecraft.

“We’re looking forward to EM-1,” Huff said. “SLS is the largest rocket ever built. It will help confirm we’re doing things the right way on Orion, and we’ll be another step closer to Mars.”

Related articles:

Engineers Prepare for Orion Water-Impact Testing with Precision to Protect Future Astronauts
http://orbiterchspacenews.blogspot.ch/2015/12/engineers-prepare-for-orion-water.html

NASA Completes Critical Design Review for Space Launch System
http://orbiterchspacenews.blogspot.ch/2015/10/nasa-completes-critical-design-review.html

LIFTOFF! Orion Begins New Era in Space Exploration!
http://orbiterchspacenews.blogspot.ch/2014/12/liftoff-orion-begins-new-era-in-space.html

Related links:

Journey to Mars: https://www.nasa.gov/topics/journeytomars/index.html

Orion Spacecraft: https://www.nasa.gov/exploration/systems/orion/index.html

Images (mentioned), Text, Credits: NASA's Kennedy Space Center, by Bob Granath.

Greetings, Orbiter.ch

Chorus of Black Holes Sings in X-Rays

NASA - Nuclear Spectroscopic Telescope Array (NuStar) patch.

July 28, 2016

Supermassive black holes in the universe are like a raucous choir singing in the language of X-rays. When black holes pull in surrounding matter, they let out powerful X-ray bursts. This song of X-rays, coming from a chorus of millions of black holes, fills the entire sky -- a phenomenon astronomers call the cosmic X-ray background.

NASA's Chandra mission has managed to pinpoint many of the so-called active black holes contributing to this X-ray background, but the ones that let out high-energy X-rays -- those with the highest-pitched "voices" -- have remained elusive.

Image above: The blue dots in this field of galaxies, known as the COSMOS field, show galaxies that contain supermassive black holes emitting high-energy X-rays. Image Credits: NASA/JPL-Caltech.

New data from NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, have, for the first time, begun to pinpoint large numbers of the black holes belting out the high-energy X-rays. Or, in astronomer-speak, NuSTAR has made significant progress in resolving the high-energy X-ray background.

"We've gone from resolving just two percent of the high-energy X-ray background to 35 percent," said Fiona Harrison, the principal investigator of NuSTAR at Caltech in Pasadena and lead author of a new study describing the findings in an upcoming issue of The Astrophysical Journal.  "We can see the most obscured black holes, hidden in thick gas and dust."

The results will ultimately help astronomers understand how the feeding patterns of supermassive black holes change over time. This is a key factor in the growth of not only black holes, but also the galaxies that host them. The supermassive black hole at the center of our Milky Way galaxy is dormant now, but at some point in the past, it too would have siphoned gas and bulked up in size.

As black holes grow, their intense gravity pulls matter toward them. The matter heats up to scorching temperatures, and particles get boosted to close to the speed of light. Together, these processes make the black hole surroundings glow with X-rays. A supermassive black hole with a copious supply of fuel, or gas, will give off more high-energy X-rays.

Nuclear Spectroscopic Telescope Array, or NuSTAR. Image Credits: NASA/JPL-Caltech

NuSTAR is the first telescope capable of focusing these high-energy X-rays into sharp pictures.

"Before NuSTAR, the X-ray background in high energies was just one blur with no resolved sources," said Harrison. "To untangle what's going on, you have to pinpoint and count up the individual sources of the X-rays."

"We knew this cosmic choir had a strong high-pitched component, but we still don't know if it comes from a lot of smaller, quiet singers, or a few with loud voices," said co-author Daniel Stern, the project scientist for NuSTAR at NASA's Jet Propulsion Laboratory in Pasadena, California. "Now, thanks to NuSTAR, we're gaining a better understanding of the black holes and starting to address these questions."

High-energy X-rays can reveal what lies around the most buried supermassive black holes, which are otherwise hard to see. In the same way that medical X-rays can travel through your skin to reveal pictures of bones, NuSTAR can see through the gas and dust around black holes, to get a deeper view of what's going on inside.

With NuSTAR's more complete picture of the supermassive black hole populations, astronomers can begin to puzzle together how they evolve and change over time. When did they start and stop feeding? What is the distribution of the gas and dust that both feed and hide the black holes?

The team expects to resolve more of the high-energy X-ray background over time with NuSTAR -- and better decipher the X-ray voices of our universe's rowdiest choir.

NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR's mission operations center is at UC Berkeley, and the official data archive is at NASA's High Energy Astrophysics Science Archive Research Center. ASI provides the mission's ground station and a mirror archive. JPL is managed by Caltech for NASA.

For more information, visit:

http://www.nasa.gov/nustar

http://www.nustar.caltech.edu/

Images (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Elizabeth Landau/Caltech, written by Whitney Clavin.

Best regards, Orbiter.ch

How comets are born

ESA - Rosetta Mission patch.

28 July 2016

Detailed analysis of data collected by Rosetta show that comets are the ancient leftovers of early Solar System formation, and not younger fragments resulting from subsequent collisions between other, larger bodies.

Understanding how and when objects like Comet 67P/Churyumov–Gerasimenko took shape is of utmost importance in determining how exactly they can be used to interpret the formation and early evolution of our Solar System.

Rosetta's comet

A new study addressing this question led by Björn Davidsson of the Jet Propulsion Laboratory, California Institute of Technology in Pasadena (USA), has been published in Astronomy & Astrophysics.

If comets are primordial, then they could help reveal the properties of the solar nebula from which the Sun, planets and small bodies condensed 4.6 billion years ago, and the processes that transformed our planetary system into the architecture we see today.

The alternative hypothesis is that they are younger fragments resulting from collisions between older ‘parent’ bodies such as icy trans-Neptunian objects (TNOs). They would then provide insight into the interior of such larger bodies, the collisions that disrupted them, and the process of building new bodies from the remains of older ones.

“Either way, comets have been witness to important Solar System evolution events, and this is why we have made these detailed measurements with Rosetta – along with observations of other comets – to find out which scenario is more likely,” says Matt Taylor, ESA’s Rosetta project scientist.

During its two-year sojourn at Comet 67P/Churyumov–Gerasimenko, Rosetta has revealed a picture of the comet as a low-density, high-porosity, double-lobed body with extensive layering, suggesting that the lobes accumulated material over time before they merged.

Profile of a primordial comet

The unusually high porosity of the interior of the nucleus provides the first indication that this growth cannot have been via violent collisions, as these would have compacted the fragile material. Structures and features on different size scales observed by Rosetta’s cameras provide further information on how this growth may have taken place.

Earlier work showed that the head and body were originally separate objects, but the collision that merged them must have been at low speed in order not to destroy both of them. The fact that both parts have similar layering also tells us that they must have undergone similar evolutionary histories and that survival rates against catastrophic collision must have been high for a significant period of time.

Merging events may also have happened on smaller scales. For example, three spherical ‘caps’ have been identified in the Bastet region on the small comet lobe, and suggestions are that they are remnants of smaller cometesimals that are still partially preserved today.

At even smaller scales of just a few metres across, there are the so-called ‘goosebumps’ and ‘clod’ features, rough textures observed in numerous pits and exposed cliff walls in various locations on the comet.

While it is possible that this morphology might arise from fracturing alone, it is actually thought to represent an intrinsic ‘lumpiness’ of the comet’s constituents. That is, these ‘goosebumps’ could be showing the typical size of the smallest cometesimals that accumulated and merged to build up the comet, made visible again today through erosion due to sunlight.

According to theory, the speeds at which cometesimals collide and merge change during the growth process, with a peak when the lumps have sizes of a few metres. For this reason, metre-sized structures are expected to be the most compact and resilient, and it is particularly interesting that the comet material appears lumpy on that particular size scale.

Further lines of evidence include spectral analysis of the comet’s composition showing that the surface has experienced little or no in situ alteration by liquid water, and analysis of the gases ejected from sublimating ices buried deeper within the surface, which finds the comet to be rich in supervolatiles such as carbon monoxide, oxygen, nitrogen and argon.

How are comets born?

These observations imply that comets formed in extremely cold conditions and did not experience significant thermal processing during most of their lifetimes. Instead, to explain the low temperatures, survival of certain ices and retention of supervolatiles, they must have accumulated slowly over a significant time period.

“While larger TNOs in the outer reaches of the Solar System appear to have been heated by short-lived radioactive substances, comets don’t seem to show similar signs of thermal processing. We had to resolve this paradox by taking a detailed look at the time line of our current Solar System models, and consider new ideas,” says Björn.

Björn and colleagues propose that the larger members of the TNO population formed rapidly within the first one million years of the solar nebula, aided by turbulent gas streams that rapidly accelerated their growth to sizes of up to 400 km.

Around three million years into the Solar System’s history, gas had disappeared from the solar nebula, only leaving solid material behind. Then, over a much longer period of around 400 million years, the already massive TNOs slowly accreted further material and underwent compaction into layers, their ices melting and refreezing, for example. Some TNOs even grew into Pluto or Triton-sized objects.

Comets took a different path. After the rapid initial growth phase of the TNOs, leftover grains and ‘pebbles’ of icy material in the cold, outer parts of the solar nebula started to come together at low velocity, yielding comets roughly 5 km in size by the time gas has disappeared from the solar nebula. The low speeds at which the material accumulated led to objects with fragile nuclei with high porosity and low density.

This slow growth also allowed comets to preserve some of the oldest, volatile-rich material from the solar nebula, since they were able to release the energy generated by radioactive decay inside them without heating up too much.

The larger TNOs played a further role in the evolution of comets. By ‘stirring’ the cometary orbits, additional material was accreted at somewhat higher speed over the next 25 million years, forming the outer layers of comets. The stirring also made it possible for the few kilometre-sized objects in size to bump gently into each other, leading to the bi-lobed nature of some observed comets.

“Comets do not appear to display the characteristics expected for collisional rubble piles, which result from the smash-up of large objects like TNOs. Rather, we think they grew gently in the shadow of the TNOs, surviving essentially undamaged for 4.6 billion years,” concludes Björn.

“Our new model explains what we see in Rosetta’s detailed observations of its comet, and what had been hinted at by previous comet flyby missions.”

“Comets really are the treasure-troves of the Solar System,” adds Matt.

“They give us unparalleled insight into the processes that were important in the planetary construction yard at these early times and how they relate to the Solar System architecture that we see today.”

Notes for Editors:

“The primordial nucleus of Comet 67P/Churyumov–Gerasimenko,” by B. Davidsson et al is published in Astronomy & Astrophysics: http://www.aanda.org/articles/aa/abs/2016/08/aa26968-15/aa26968-15.html

Related links:

Comet viewer tool: http://sci.esa.int/comet-viewer/

Where is Rosetta?: http://sci.esa.int/where_is_rosetta/

For more information about Rosetta mission, visit: http://www.esa.int/Our_Activities/Space_Science/Rosetta

Rosetta overview: http://www.esa.int/Our_Activities/Space_Science/Rosetta_overview

Rosetta in depth: http://sci.esa.int/rosetta

Text, Credits: ESA/Markus Bauer/Bjorn Davidsson/Matt Taylor/Images: Rosetta/NavCam – CC BY-SA IGO 3.0; Insets: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; Fornasier et al. (2015); ESA/Rosetta/MPS for COSIMA Team MPS/CSNSM/UNIBW/TUORLA/IWF/IAS/ESA/BUW/MPE/LPC2E/LCM/FMI/UTU/LISA/UOFC/vH&S; Langevin et al. (2016).

Best regards, Orbiter.ch

ExoMars - Engine burn gives Mars mission a kick

ESA - ExoMars Mission logo.

28 July 2016

Following a lengthy firing of its powerful engine this morning, ESA’s ExoMars Trace Gas Orbiter is on track to arrive at the Red Planet in October.

ExoMars made its first critical manoeuvre since its 14 March launch this morning, firing its engine for 52 minutes to help it intercept Mars on 19 October.

ExoMars, a joint mission with Russia’s Roscosmos, was launched on 14 March and has already travelled well over half way of its nearly 500 million km journey.

 ExoMars enroute to Mars

The ExoMars Trace Gas Orbiter, TGO, is carrying the Schiaparelli entry, descent and landing demonstrator. Upon arrival, Schiaparelli will test the technology needed for the 2020 rover to make a controlled landing, while its parent craft will brake into an elliptical orbit around Mars.

Over the following months, TGO will shave the outer reaches of the atmosphere to lower its orbit. Its final circular orbit at about 400 km altitude will allow it to begin its five-year scientific mission in December 2017.

TGO will analyse rare gases in the planet’s atmosphere, especially methane, which on Earth may indicate either active geological or biological processes.

Lining up to intercept Mars

Today’s deep-space firing began automatically at 09:30 GMT (11:30 CEST), after commands to orient itself and ignite the 424 N main engine were uploaded on Tuesday.

The manoeuvre was closely monitored by ESA’s mission control in Darmstadt, Germany, who followed the craft’s signals via the highly sensitive radio dish at New Norcia, Australia.

New Norcia station

“The engine provides about the same force as that needed to lift a 45 kg weight in a fitness studio, and it ran for about 52 minutes, so that’s quite a significant push,” says Silvia Sangiorgi, deputy spacecraft operations manager.

The firing was planned well in advance, and its duration was carefully calculated to minimise fuel consumption for the overall set of cruise and Mars capture manoeuvres. These include a second burn on 11 August and smaller ‘trim’ manoeuvres on 19 September and 14 October.

A brief burn was made on 18 July to test the engine for the first time. The performance that day was not as expected because of a misconfiguration, so a repeat test was done on 21 July, which ran perfectly.

“Today’s burn was the biggest of the four planned that will enable ExoMars to intercept Mars and precisely deliver the Schiaparelli lander on 19 October onto Meridiani Planum, a large, flat region near the equator,” says flight operations director Michel Denis.

Mission controllers

Calculating today’s burn was done with the assistance of an ultra-precise navigation technique that pinpoints the craft’s position to within 1000 m at a distance of 150 million km from Earth.

In addition to the firing slots available in September and October, which will provide final fine adjustments to the trajectory before the separation of Schiaparelli on 16 October, ExoMars must also raise its orbit on 17 October and manoeuvre into Mars orbit on 19 October.

Teams have been using the relatively quiet cruise phase to test spacecraft systems, including the Schiaparelli lander and the radio unit that will be used to relay data from rovers on Mars, and to check TGO’s four science instruments.

Related links:

New Norcia: http://www.esa.int/Our_Activities/Operations/Estrack/New_Norcia_-_DSA_1

TGO’s four science instruments: http://www.esa.int/Our_Activities/Space_Science/ExoMars/Trace_Gas_Orbiter_instruments

Robotic exploration of Mars: http://exploration.esa.int/

ExoMars frequently asked questions: http://www.esa.int/Our_Activities/Space_Science/ExoMars/ExoMars_frequently_asked_questions

ExoMars in depth: http://exploration.esa.int/mars/

Mission operations in depth: http://www.esa.int/Our_Activities/Operations/ExoMars_TGO_operations

ExoMars Factsheet: http://www.esa.int/Our_Activities/Space_Science/ExoMars/ExoMars_Factsheet

Images, Text, Credits: ESA/ATG medialab.

Best regards, Orbiter.ch

NASA’s Next Planet Hunter Will Look Closer to Home

TESS - Transiting Exoplanet Survey Satellite logo.

July 27, 2016

As the search for life on distant planets heats up, NASA’s Transiting Exoplanet Survey Satellite (TESS) is bringing this hunt closer to home. Launching in 2017-2018, TESS will identify planets orbiting the brightest stars just outside our solar system using what’s known as the transit method.

When a planet passes in front of, or transits, its parent star, it blocks some of the star's light. TESS searches for these telltale dips in brightness, which can reveal the planet's presence and provide additional information about it.

TESS will be able to learn the sizes of the planets it sees and how long it takes them to complete an orbit. These two pieces of information are critical to understanding whether a planet is capable of supporting life. Nearly all other planet classifications will come from follow up observations, by both TESS team ground telescopes as well as ground- and space-based observations, including NASA's James Webb Space Telescope launching in 2018.

Compared to the Kepler mission, which has searched for exoplanets thousands to tens of thousands of light-years away from Earth towards the constellation Cygnus, TESS will search for exoplanets hundreds of light-years or less in all directions surrounding our solar system.

TESS will survey most of the sky by segmenting it into 26 different segments known as tiles. The spacecraft's powerful cameras will look continuously at each tile for just over 27 days, measuring visible light from the brightest targets every two minutes. TESS will look at stars classified as twelfth apparent magnitude and brighter, some of which are visible to the naked eye. The higher the apparent magnitude, the fainter the star. For comparison, most people can see stars as faint as sixth magnitude in a clear dark sky and the faintest star in the Big Dipper ranks as third magnitude.

Image above: TESS will look at the nearest, brightest stars to find planetary candidates that scientists will observe for years to come. Image Credits: NASA's Goddard Space Flight Center.

Among the stars TESS will observe, small bright dwarf stars are ideal for planet identification, explained Joshua Pepper, co-chair of the TESS Target Selection Working Group. One of the TESS science goals is to find Earth- and super-Earth-sized planets. These are difficult to discover because of their small size compared to their host stars, but focusing TESS on smaller stars makes finding these small planets much easier. This is because the fraction of the host star's light that a planet blocks is proportional to the planet’s size.

Scientists expect TESS to observe at least 200,000 stars during the two years of its spaceflight mission, resulting in the discovery of thousands of new exoplanets.

While the search for transiting exoplanets is the primary goal of the mission, TESS will also make observations of other astrophysical objects through the Guest Investigator (GI) Program. Because TESS is conducting a near all-sky survey, it has the capability to perform interesting studies on many different types of astronomical target.

“The goal of the GI Program is to maximize the amount of science that comes out of TESS,” said Padi Boyd, director of the Guest Investigator Program Office at NASA’s Goddard Space Flight Center. "Although TESS was designed to be capable of detecting planets transiting in front of stars, its unique mission characteristics mean that the potential science TESS can do includes far more than just exoplanets.” According to Boyd, the broad range of objects TESS could detect as part of the GI Program include flaring young stars, binary pairs of stars, supernovae in nearby galaxies, and even supermassive black holes in distant active galaxies. “We hope the broader science community will come up with many unique science ideas for TESS, and we hope to encourage broad participation from the larger community,” she said.

With the potential to expand our knowledge of the universe for years to come, researchers are excited about the potential discoveries TESS could bring.

“The cool thing about TESS is that one of these days I’ll be able to go out in the country with my daughter and point to a star and say ‘there’s a planet around that one,’” said TESS Project Scientist Stephen Rinehart.

Related links:

James Webb Space Telescope (JWST): http://www.jwst.nasa.gov/

Kepler mission: http://www.nasa.gov/kepler

For more information about TESS, visit: http://tess.gsfc.nasa.gov/
 
TESS (Transiting Exoplanet Survey Satellite): https://www.nasa.gov/subject/5613/tess

Image (mentioned), Text, Credits: NASA's Goddard Space Flight Center, by Elaine Hunt/Ashley Morrow.

Greetings, Orbiter.ch

New Heart and DNA Research in Space Benefiting Health

ISS - Expedition 48 Mission patch.

July 27, 2016

New science unloaded from the latest SpaceX Dragon to visit the International Space Station is under way. The variety of new and ongoing space research is designed to benefit life on Earth and astronauts on long duration missions.

Astronaut Kate Rubins, a biological researcher on Earth, is lifting her science expertise to new heights today setting up a microscope in space for the first time. The new microscope will observe heart cells to help doctors understand how the human heart adapts in space and improve crew health.

Japanese astronaut Takuya Onishi checked the habitat for the Mouse Epigenetics experiment today. That study is researching how microgravity alters the gene expression in mice and DNA in their offspring.

Image above: Astronaut Kate Rubins works to set up a new microscope for the Heart Cells study. Image Credit: NASA TV.

Commander Jeff Williams joined cosmonaut Alexey Ovchinin for ultrasound scans today to investigate how fluids shift from the lower body to the upper body. The study is exploring how these fluid shifts affect fluid pressure in an astronaut’s head and eyes potentially affecting vision.

Cosmonauts Oleg Skripochka and Anatoly Ivanishin partnered together for a study of the upper body that observes changes in the cardiovascular and respiratory systems. The research explores breathing and blood pressure in microgravity to maintain the health of crews living in space.

Related article:

Dragon Spacecraft Arrives at the International Space Station
http://orbiterchspacenews.blogspot.ch/2016/07/dragon-spacecraft-arrives-at.html

Related links:

Mouse Epigenetics experiment: http://www.nasa.gov/mission_pages/station/research/experiments/1992.html

Cardiovascular and respiratory systems: http://www.energia.ru/en/iss/researches/human/19.html

Image (mentioned), Text, Credits: NASA/Mark Garcia.

Greetings, Orbiter.ch

Farewell, silent Philae

ESA - Rosetta Mission patch.

July 27, 2016

Today, 27 July 2016 at 09:00 UTC / 11:00 CEST, the Electrical Support System Processor Unit (ESS) on Rosetta will be switched off. The ESS is the interface used for communications between Rosetta and the lander, Philae, which has remained silent since 9 July 2015.

Switching off the ESS is part of the preparations for Rosetta's end of mission. By the end of July 2016, the spacecraft will be some 520 million km from the Sun, and will start facing a significant loss of power – about 4W per day. In order to continue scientific operations over the next two months and to maximise their return, it became necessary to start reducing the power consumed by the non-essential payload components on board.

Image above: This artist's concept of the Rosetta mission's Philae lander on the surface of comet 67P/Churyumov-Gerasimenko. Image Credit: ESA.

No signal has been received by Rosetta from Philae since last July and earlier this year the lander was considered to be in a state of eternal hibernation. In spite of this, the ESS was kept on until now in the unlikely chance that Philae would re-gain contact. Although Rosetta has reached altitudes well below 10 km over the surface of Comet 67P/Churyumov-Gerasimenko, however, no signal from the lander was received since July 2015.

The decision was taken by the mission manager and will be implemented by the Rosetta Mission Operations Centre, in coordination with the DLR Lander Control Center and the Rosetta Science Ground Segment.

Related links:

Comet viewer tool: http://sci.esa.int/comet-viewer/

Where is Rosetta?: http://sci.esa.int/where_is_rosetta/

For more information about Rosetta mission, visit: http://www.esa.int/Our_Activities/Space_Science/Rosetta

Rosetta overview: http://www.esa.int/Our_Activities/Space_Science/Rosetta_overview

Rosetta in depth: http://sci.esa.int/rosetta

Images (mentioned), Text, Credits: European Space Agency (ESA).

Best regards, Orbiter.ch

Astronomers Gain New Insight into Magnetic Field Of Sun and Its Kin

NASA - Chandra X-ray Observatory patch.

July 27, 2016

Astronomers have used data from NASA’s Chandra X-ray Observatory to make a discovery that may have profound implications for understanding how the magnetic field in the Sun and stars like it are generated.

Researchers have discovered that four old red dwarf stars with masses less than half that of the Sun are emitting X-rays at a much lower rate than expected.

Image above: An artist's illustration depicts the interior of a low-mass star, such as GJ 3253, a low-mass red dwarf star about 31 light years away from Earth, seen in an X-ray image from Chandra in the inset. Image Credits: X-ray: NASA/CXC/Keele Univ./N. Wright et al; Optical: DSS.

X-ray emission is an excellent indicator of a star’s magnetic field strength so this discovery suggests that these stars have much weaker magnetic fields than previously thought.

Since young stars of all masses have very high levels of X-ray emission and magnetic field strength, this suggests that the magnetic fields of these stars weakened over time. While this is a commonly observed property of stars like our Sun, it was not expected to occur for low-mass stars, as their internal structure is very different.

The Sun and other stars are giant spheres of superheated gas. The Sun's magnetic field is responsible for producing sunspots, its 11-year cycle, and powerful eruptions of particles from the solar surface. These solar storms can produce spectacular auroras on Earth, damage electrical power systems, knock out communications satellites, and affect astronauts in space.

“We have known for decades that the magnetic field on the Sun and other stars plays a huge role in how they behave, but many details remain mysterious,” said lead author Nicholas Wright of Keele University in the United Kingdom. “Our result is one step in the quest to fully understand the Sun and other stars.”

The rotation of a star and the flow of gas in its interior both play a role in producing its magnetic field. The rotation of the Sun and similar stars varies with latitude (the poles versus the equator) as well as in depth below the surface. Another factor in the generation of magnetic field is convection. Similar to the circulation of warm air inside an oven, the process of convection in a star distributes heat from the interior of the star to its surface in a circulating pattern of rising cells of hot gas and descending cooler gas.

Convection occurs in the outer third (by radius) of the Sun, while the hot gas closer to the core remains relatively still. There is a difference in the speed of rotation between these two regions. Many astronomers think this difference is responsible for generating most of the magnetic field in the Sun by causing magnetic fields along the border between the convection zone and the core to wind up and strengthen. Since stars rotate more slowly as they age, this also plays a role in how the magnetic field of such stars weakens with time

Chandra X-ray Observatory. Image Credit: NASA

“In some ways you can think of the inside of a star as an incredibly complicated dance with many, many dancers,” said co-author Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “Some dancers move with each other while others move independently. This motion generates magnetic field, but how it works in detail is extremely challenging to determine.”

For stars much less massive than the Sun, convection occurs all the way into the core of the star. This means the boundary between regions with and without convection, thought to be crucial for generating magnetic field in the Sun, does not exist. One school of thought has been that magnetic field is generated mostly by convection in such stars. Since convection does not change as a star ages, their magnetic fields would not weaken much over time.

By studying four of these low-mass red dwarf stars in X-rays, Wright and Drake were able to test this hypothesis. They used NASA’s Chandra X-ray Observatory to study two of the stars and data from the ROSAT satellite to look at two others.

“We found that these smaller stars have magnetic fields that decrease as they age, exactly as it does in stars like our Sun,” said Wright. “This really goes against what we would have expected.”

These results imply that the interaction along the convection zone-core boundary does not dominate the generation of magnetic field in stars like our Sun, since the low mass stars studied by Wright and Drake lack such a region and yet their magnetic properties are very similar.

A paper describing these results by Wright and Drake appears in the July 28th issue of the journal Nature. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Read More from NASA's Chandra X-ray Observatory: http://chandra.harvard.edu/photo/2016/gj3253/

For more Chandra images, multimedia and related materials, visit: http://www.nasa.gov/chandra

Images (mentioned), Text, Credits: NASA/Lee Mohon/Chandra X-ray Center/Megan Watzke/Marshall Space Flight Center/Molly Porter.

Greetings, Orbiter.ch