Magnetic oceans and electric Earth

ESA - SWARM Mission logo.


3 October 2016

Oceans might not be thought of as magnetic, but they make a tiny contribution to our planet’s protective magnetic shield. Remarkably, ESA’s Swarm satellites have not only measured this extremely faint field, but have also led to new discoveries about the electrical nature of inner Earth.

The magnetic field shields us from cosmic radiation and charged particles that bombard Earth from the Sun. Without it, the atmosphere as we know it would not exist, rendering life virtually impossible.

Ocean-Monitoring Satellites Could Help Study Earth's Interior Composition

Scientists need to learn more about our protective field to understand many natural processes, from those occurring deep inside the planet, to weather in space caused by solar activity. This information will then yield a better understanding of why Earth’s magnetic field is weakening.

Although we know that the magnetic field originates in different parts of Earth and that each source generates magnetism of different strengths, exactly how it is generated and why it changes is not fully understood.

This is why, in 2013, ESA launched its trio of Swarm satellites.

While the mission is already shedding new light on how the field is changing, this latest result focuses on the most elusive source of magnetism: ocean tides.

When salty ocean water flows through the magnetic field, an electric current is generated and this, in turn, induces a magnetic response in the deep region below Earth’s crust – the mantle.  Because this response is such a small portion of the overall field, it was always going to be a challenge to measure it from space.

Earth's protective shield

Last year, scientists from the Swiss Federal Institute of Technology, ETH Zurich, showed that if it could be measured from space – never done before – it should also tell us something about Earth’s interior. However, this all remained a theory – until now.

Thanks to Swarm’s precise measurements along with those from Champ – a mission that ended in 2010 after measuring Earth’s gravity and magnetic fields for more than 10 years – scientists have not only been able to find the magnetic field generated by ocean tides but, remarkably, they have used this new information to image the electrical nature of Earth’s upper mantle 250 km below the ocean floor.

Alexander Grayver, from ETH Zurich, said, “The Swarm and Champ satellites have allowed us to distinguish between the rigid ocean ‘lithosphere’ and the more pliable ‘asthenosphere’ underneath.”

The lithosphere is the rigid outer part of the earth, consisting of the crust and upper mantle, while the asthenosphere lies just below the lithosphere and is hotter and more fluid than the lithosphere.

“Effectively, ‘geo-electric sounding from space’, this result is a first for space exploration,” he continues.

Magnetic field sources

“These new results are important for understanding plate tectonics, the theory of which argues that Earth’s lithosphere consists of rigid plates that glide on the hotter and less rigid asthenosphere that serves as a lubricant, enabling plate motion.”

Roger Haagmans, ESA’s Swarm mission scientist, explained, “It’s astonishing that the team has been able to use just two years’ worth of measurements from Swarm to determine the magnetic tidal effect from the ocean and to see how conductivity changes in the lithosphere and upper mantle.

“Their work shows that down to about 350 km below the surface, the degree to which material conducts electric currents is related to composition.

Swarm constellation over Earth

“In addition, their analysis shows a clear dependence on the tectonic setting of the ocean plate. These new results also indicate that, in the future, we could get a full 3D view of conductivity below the ocean.”

Rune Floberghagen, ESA’s Swarm mission manager, added, “We have very few ways of probing deep into the structure of our planet, but Swarm is making a valuable contribution to understanding Earth’s interior, which then adds to our knowledge of how Earth works as a whole system.”

The research paper was published in Science Advances on 30 September: http://advances.sciencemag.org/content/2/9/e1600798

Related links:

Geophysical Research Letters:
Can we probe the conductivity of the lithosphere and upper mantle using satellite tidal magnetic signals?: https://www.ethz.ch/content/dam/ethz/special-interest/erdw/geophysics/epm-dam/images/Tides/Schnepf_Kuvshinov_Sabaka_2015_GRL.pdf

ETH Zurich Earth and Planetary Magnetism Group: http://www.epm.ethz.ch/

CIRES: http://cires.colorado.edu/

DTU Space: http://www.space.dtu.dk/english

NASA Goddard Space Flight Centre: https://www.nasa.gov/goddard

Access Swarm data: https://earth.esa.int/web/guest/missions/esa-operational-eo-missions/swarm

For more information about SWARM, visit: http://www.esa.int/Our_Activities/Observing_the_Earth/Swarm

Images, Video, Text, Credits: ESA/ATG medialab/DTU Space/AOES Medialab.

Best regards, Orbiter.ch

GPM Analyzes Matthew as it Strengthens Toward a Category 5

NASA & JAXA - Global Precipitation Measurement (GPM) logo.

Oct. 2, 2016

Matthew (Atlantic Ocean)

Matthew rapidly intensified Thursday evening, Sept. 29 and by Friday Sept. 30 at 11 p.m. EDT it became a Category 5 Hurricane on the Saffir-Simpson Hurricane Wind Scale. The Global Precipitation Measurement mission or GPM core satellite analyzed the major hurricane's rainfall.

Image above: On Sept. 30 at 5:46 a.m. EDT GPM’s radar saw a very intense feeder band of thunderstorms southeast Matthew's center where rainfall rates were greater than 229 (9 inches) per hour and storm top heights in the feeder band were reaching heights above 16 km (9.9 miles). Image Credits: NASA/JAXA, Hal Pierce.

The GPM core observatory satellite flew over Hurricane Matthew on Sept. 30, 2016 at 0946Z (5:46 a.m. EDT). A rainfall analysis from GPM's Microwave Imager (GMI) and Dual-Frequency Precipitation Radar (DPR) showed that the Matthew had heavy rainfall in the northern side of the newly formed eye wall. G

GPM’s radar area of coverage included a very intense feeder band on the southeastern side of the hurricane. DPR measured rain falling at a rate of greater than 229 (9 inches) per hour in that area. A 3-D radar analysis using data from GPM's DPR Ku Band showed that storm top heights in the feeder band were reaching heights above 16 km (9.9 miles).

Images of the storm in 3-D were created at NASA's Goddard Space Flight Center in Greenbelt, Maryland. GPM is a joint mission between NASA and the Japanese space agency JAXA.

Matthew reached Category 5 hurricane status at 11 p.m. EDT on Sept. 30, and by Oct. 1 at 5 a.m. EDT, dropped to a Category 4 hurricane on the Saffir-Simpson Wind Scale. Major hurricanes are Category 3, 4, and 5.

At 11 a.m. EDT on Saturday, Oct. 1, Matthew remained a Category 4, major hurricane as it moved through the Caribbean Sea. A Hurricane Watch is in effect for Jamaica, Haiti from the southern border with the Dominican Republic to Le Mole St. Nicholas.

At 11 a.m. EDT (1500 UTC) on Oct. 1, NOAA's National Hurricane Center (NHC) said the eye of Hurricane Matthew was located near latitude 13.4 North, longitude 73.4 West.  Matthew was moving toward the west near 6 mph (9 kph).  A turn toward the west-northwest is forecast later today, followed by a turn toward the north-northwest on Sunday and toward the north on Monday, Oct.3.

On the forecast track, the center of Matthew will move across the central Caribbean Sea today and Sunday, and approach Jamaica and southwestern Haiti Sunday night and Monday.

Image above: Visualization of the GPM Core Observatory and Partner Satellites. Image Credits: NASA/JAXA.

Data from an Air Force Reserve Hurricane Hunter aircraft indicate that maximum sustained winds are near 145 mph (230 kph) with higher gusts.  Matthew is a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale.  Some fluctuations in intensity are possible this weekend, but Matthew is expected to remain a powerful hurricane through Monday. The latest minimum central pressure measured by the aircraft was 947 millibars.

The National Hurricane Center noted the effects expected by Matthew:

Rainfall totals of 2 to 4 inches with isolated higher amounts are expected over Aruba, Bonaire and Curacao through Saturday.  Rainfall totals of 2 to 4 inches with isolated higher amounts are expected along the coast of Colombia from the Venezuelan border to Barranquilla.  Rainfall totals of 1 to 3 inches with isolated higher amounts are expected along the coast of Venezuela from Coro to the Colombian border.

Rainfall totals of 10 to 15 inches with isolated maximum amounts of 25 inches are expected across Jamaica and southern and southwestern Haiti.  This rainfall could produce life-threatening flash floods and mud slides.

SURF:  Swells generated by Matthew are expected to affect portions of the coasts of Puerto Rico, Hispaniola, Jamaica, Aruba, Bonaire, Curacao, Venezuela, Colombia, eastern Cuba, and the Caribbean coastline of Central America during the next few days.  These swells are likely to cause life-threatening surf and rip current conditions.

Related article:

Matthew Becomes Major Hurricane in Caribbean
http://orbiterchspacenews.blogspot.ch/2016/09/matthew-becomes-major-hurricane-in.html

For updated forecasts, please visit: http://www.nhc.noaa.gov

For more information about GPM (Global Precipitation Measurement): http://www.nasa.gov/mission_pages/GPM/main/index.html and http://global.jaxa.jp/projects/sat/gpm/

Images (mentioned), Text, Credits: NASA's Goddard Space Flight Center/Rob Gutro/Hal Pierce.

Greetings, Orbiter.ch

ISS - BEAM Open for Tests & Expedition 49 Trio Wrapping Up Busy September

ISS - Expedition 49 Mission patch.

October 1, 2016

BEAM, the new expandable module attached to the International Space Station, was opened up today for tests and equipment checks. The Expedition 49 crew also explored eating right in space, adapting to new technology and studied a variety of other life science and physics research.

Flight Engineer Kate Rubins opened up and entered the Bigelow Expandable Activity Module on September 29, 2016. She temporarily installed gear inside BEAM for a test to measure the loads and vibrations the module experiences. Rubins started her day with a performance test on a mobile tablet device then videotaped her observations of the living conditions aboard the space station.

Image above: BEAM, the Bigelow Expandable Activity Module, is pictured installed on the Tranquility module and expanded to its full-size volume. Image Credit: NASA.

Japanese astronaut Takuya Onishi started an 11-day run today to document his meals while wearing a monitor that will take water samples and measure his breathing. The ENERGY experiment will help doctor’s understand metabolism in space and ensure astronauts are properly nourished to maintain the energy required for a long-term mission. Onishi is also continuing to set up the Group Combustion fuel burning study and checked for pressure leaks in the experiment gear.

In the Russian side of the orbital laboratory, Commander Anatoly Ivanishin resumed studying charged particle systems trapped in a magnetic field. He also participated in a pair of Earth photography experiments observing how natural and man-made disasters including industrial activities affect the land and sea.

Expedition 49 Trio Wrapping Up Busy September

September was a busy month on the International Space Station filled with a wide variety of space research, a spacewalk, a crew departure and a test of the new BEAM module. One science highlight this month includes a new experiment that may improve how medicine works.

This week, astronaut Kate Rubins tested the endurance of the new Bigelow Expandable Aerospace Module in the vacuum of space. She also explored how solids dissolve in liquids to help the medicine industry design better performing drugs for humans on Earth and astronauts in space.

Image above: Astronaut Kate Rubins works on an experiment inside the Microgravity Science Glovebox. Image Credit: NASA.

A new fuel burning study is about to start soon after Japanese astronaut Takuya Onishi completes the installation of the Group Combustion experiment. Results from the fire research could help engineers design advanced rocket engines and industrial furnaces. Onishi is also documenting his meals over the next few days for the ENERGY study. Onishi’s meal data in conjunction with his water and breath samples will help scientists understand the nutritional requirements necessary for long-term space missions.

Cosmonaut Anatoly Ivanishin, who took command of Expedition 49 on Sept. 6, has been working on the continuous upkeep of the Russian segment of the space station. The veteran cosmonaut has been preparing a Progress resupply ship for its Oct. 14 undocking. Some of the numerous Russian science experiments Ivanishin has been conducting have been observing the condition of the Earth and exploring human research.

Related links:

Bigelow Expandable Activity Module: http://www.nasa.gov/mission_pages/station/research/experiments/1804.html

ENERGY experiment: http://www.nasa.gov/mission_pages/station/research/experiments/397.html

Group Combustion fuel burning study: http://www.nasa.gov/mission_pages/station/research/experiments/1077.html

Charged particle systems study: http://www.energia.ru/en/iss/researches/popular/02.html

Natural and man-made disasters: http://www.energia.ru/en/iss/researches/study/09.html

Industrial activities: http://www.energia.ru/en/iss/researches/study/10.html

Solids dissolve in liquids: http://www.nasa.gov/mission_pages/station/research/experiments/2275.html

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

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

Best regards, Orbiter.ch

Matthew Becomes Major Hurricane in Caribbean

NOAA / NASA - GOES Satellite Mission logo / NASA - Suomi NPP Satellite logo.

Sept. 30, 2016

Matthew (Atlantic Ocean)

Image above: NOAA's GOES-East satellite captured a visible-light image of Hurricane Matthew on Sept. 30, 2016, at 1:45 p.m. EDT as it was strengthening into a major hurricane. Image Credits: NASA/NOAA GOES Project.

NOAA's GOES-East satellite captured a visible-light image of Hurricane Matthew on Sept. 30 at 1:45 p.m. EDT as it was strengthening into a major hurricane.

At NASA's Goddard Space Flight Center in Greenbelt, Maryland, the NASA/NOAA GOES Project used data from NOAA's GOES-East satellite to create an image of the Caribbean Sea's major hurricane. The eye was visible in satellite imagery.

At 2 p.m. EDT a tropical storm warning is in effect for the Colombia-Venezuela border to Riohacha.

Data from a NOAA Hurricane Hunter aircraft indicate that maximum sustained winds have increased to near 120 mph (195 kph) with higher gusts. Matthew is a category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Little change in strength is forecast during the next 48 hours.

The eye of Hurricane Matthew was located near 13.6 degrees north latitude and 71.3 degrees west longitude. Matthew is moving toward the west-southwest near 12 mph (19 kph). A westward motion at a slower forward speed is expected later today and tonight. A turn toward the west-northwest is forecast by Saturday night, followed by a turn toward the northwest by early Sunday. On the forecast track, the center of Matthew will pass north of the Guajira Peninsula this afternoon and tonight and remain over the central Caribbean Sea through early Sunday.

Image above: On Sept. 29, 2016, at 1 p.m. EDT (17:00 UTC) NASA-NOAA's Suomi NPP satellite captured this visible image of then-Tropical Storm Matthew in the Caribbean Sea. Image Credits: NOAA/NASA Goddard MODIS Rapid Response Team.

On Sept. 29 at 1 p.m. EDT (17:00 UTC) the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard the NASA-NOAA Suomi NPP satellite captured a visible image of Tropical Storm Matthew south of Puerto Rico, and moving west in the Caribbean Sea.

On Sept. 30 at 8 a.m. EDT, NOAA's National Hurricane Center (NHC) noted that a tropical storm watch was in effect for Aruba and the Colombia/Venezuela border to Riohacha. A tropical storm watch means that tropical storm conditions are possible within the watch area, in this case within the next 24 to 36 hours.

At NASA's Goddard Space Flight Center in Greenbelt, Maryland, the NASA/NOAA GOES Project combined infrared and visible imagery from NOAA's GOES-East satellite into an animation of Matthew. The animation of imagery from Sept. 27 to Sept. 30 shows Tropical Storm Matthew move into the Caribbean Sea, where it became a hurricane.

Matthew Becomes a Hurricane in Caribbean

Video above: This animation of NOAA's GOES-East satellite imagery from Sept. 27 to Sept. 30, 2016, shows Tropical Storm Matthew move into the Caribbean Sea where it became a hurricane. Image Credits: NASA/NOAA GOES Project.

At 8 a.m. EDT (1200 UTC) on Sept. 30 the center of Hurricane Matthew was located by an Air Force Reserve Hurricane Hunter aircraft near 13.8 degrees north latitude and 70.3 degrees west longitude. That's about 130 miles (210 km) northeast of Punta Gallinas, Colombia, and about 520 miles (840 km) east-southeast of Kingston, Jamaica.

Matthew was moving toward the west-southwest near 14 mph (22 kph). NHC said a turn toward the west is expected later today, and this westward motion with a decrease in forward speed are forecast through Saturday.  A turn toward the northwest is expected Saturday night or Sunday, Oct. 2. The latest minimum central pressure reported by the aircraft was 971 millibars.

NHC noted that data from the aircraft indicate that maximum sustained winds have increased to near 105 mph (165 km/h) with higher gusts. Additional strengthening is forecast during the next 48 hours, and Matthew could become a major hurricane later today or tonight, Sept. 30.

NHC said interests elsewhere along the coasts of Venezuela and Colombia should monitor the progress of Matthew. Interests in Jamaica, Hispaniola, and eastern Cuba should also monitor the progress of Matthew. A hurricane watch may be required for Jamaica later today.

Related links:

NASA-NOAA Suomi NPP satellite: http://www.nasa.gov/mission_pages/NPP/main/index.html

GOES (Geostationary Environmental Operational Satellites): http://www.nasa.gov/goes/

For hurricane effects, visit the NHC website: http://www.nhc.noaa.gov.

Images (mentioned), Video (mentioned), Text, Credits: NASA's Goddard Space Flight Center, by Rob Gutro.

Greetings, Orbiter.ch

Hubble Explores the Hidden Dark Side of NGC 24

NASA - Hubble Space Telescope patch.

Sept. 30, 2016

This shining disk of a spiral galaxy sits approximately 25 million light-years away from Earth in the constellation of Sculptor. Named NGC 24, the galaxy was discovered by British astronomer William Herschel in 1785, and measures some 40,000 light-years across.

This picture was taken using the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys, known as ACS for short. It shows NGC 24 in detail, highlighting the blue bursts (young stars), dark lanes (cosmic dust), and red bubbles (hydrogen gas) of material peppered throughout the galaxy’s spiral arms. Numerous distant galaxies can also been seen hovering around NGC 24’s perimeter.

However, there may be more to this picture than first meets the eye. Astronomers suspect that spiral galaxies like NGC 24 and the Milky Way are surrounded by, and contained within, extended haloes of dark matter. Dark matter is a mysterious substance that cannot be seen; instead, it reveals itself via its gravitational interactions with surrounding material. Its existence was originally proposed to explain why the outer parts of galaxies, including our own, rotate unexpectedly fast, but it is thought to also play an essential role in a galaxy’s formation and evolution. Most of NGC 24’s mass — a whopping 80 percent — is thought to be held within such a dark halo.

Hubble and the sunrise over Earth

For more information about the Hubble Space Telescope, visit:

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

Image, Video, Credits: NASA/ESA/Text, Credits: European Space Agency/NASA/Karl Hille.

Greetings, Orbiter.ch

Mission complete: Rosetta’s journey ends in daring descent to comet

ESA - Rosetta Mission patch.

30 September 2016

ESA’s historic Rosetta mission has concluded as planned, with the controlled impact onto the comet it had been investigating for more than two years.

Confirmation of the end of the mission arrived at ESA’s control centre in Darmstadt, Germany at 11:19 GMT (13:19 CEST) with the loss of Rosetta’s signal upon impact.

Rosetta carried out its final manoeuvre last night at 20:50 GMT (22:50 CEST), setting it on a collision course with the comet from an altitude of about 19 km. Rosetta had targeted a region on the small lobe of Comet 67P/Churyumov–Gerasimenko, close to a region of active pits in the Ma’at region.

Comet landing site

The descent gave Rosetta the opportunity to study the comet’s gas, dust and plasma environment very close to its surface, as well as take very high-resolution images.

Pits are of particular interest because they play an important role in the comet’s activity. They also provide a unique window into its internal building blocks.

The information collected on the descent to this fascinating region was returned to Earth before the impact. It is now no longer possible to communicate with the spacecraft.

“Rosetta has entered the history books once again,” says Johann-Dietrich Wörner, ESA’s Director General. “Today we celebrate the success of a game-changing mission, one that has surpassed all our dreams and expectations, and one that continues ESA’s legacy of ‘firsts’ at comets.”

Comet from 51 m – wide-angle camera

“Thanks to a huge international, decades-long endeavour, we have achieved our mission to take a world-class science laboratory to a comet to study its evolution over time, something that no other comet-chasing mission has attempted,” notes Alvaro Giménez, ESA’s Director of Science.

“Rosetta was on the drawing board even before ESA’s first deep-space mission, Giotto, had taken the first image of a comet nucleus as it flew past Halley in 1986.

“The mission has spanned entire careers, and the data returned will keep generations of scientist busy for decades to come.”

“As well as being a scientific and technical triumph, the amazing journey of Rosetta and its lander Philae also captured the world’s imagination, engaging new audiences far beyond the science community. It has been exciting to have everyone along for the ride,” adds Mark McCaughrean, ESA’s senior science advisor.

Since launch in 2004, Rosetta is now in its sixth orbit around the Sun. Its nearly 8 billion-kilometre journey included three Earth flybys and one at Mars, and two asteroid encounters.

The craft endured 31 months in deep-space hibernation on the most distant leg of its journey, before waking up in January 2014 and finally arriving at the comet in August 2014.

Comet landing sites in context

After becoming the first spacecraft to orbit a comet, and the first to deploy a lander, Philae, in November 2014, Rosetta continued to monitor the comet’s evolution during their closest approach to the Sun and beyond.

“We’ve operated in the harsh environment of the comet for 786 days, made a number of dramatic flybys close to its surface, survived several unexpected outbursts from the comet, and recovered from two spacecraft ‘safe modes’,” says operations manager Sylvain Lodiot.

“The operations in this final phase have challenged us more than ever before, but it’s a fitting end to Rosetta’s incredible adventure to follow its lander down to the comet.”

The decision to end the mission on the surface is a result of Rosetta and the comet heading out beyond the orbit of Jupiter again. Further from the Sun than Rosetta has ever journeyed before, there would be little power to operate the craft.

Mission operators were also faced with an imminent month-long period when the Sun is close to the line-of-sight between Earth and Rosetta, meaning communications with the craft would have become increasingly more difficult.

“With the decision to take Rosetta down to the comet’s surface, we boosted the scientific return of the mission through this last, once-in-a-lifetime operation,” says mission manager Patrick Martin.

Rosetta’s final path

Many surprising discoveries have already been made during the mission, not least the curious shape of the comet that became apparent during Rosetta’s approach in July and August 2014. Scientists now believe that the comet’s two lobes formed independently, joining in a low-speed collision in the early days of the Solar System.

Long-term monitoring has also shown just how important the comet’s shape is in influencing its seasons, in moving dust across its surface, and in explaining the variations measured in the density and composition of the coma, the comet’s ‘atmosphere’.

Visualising Rosetta's descent

Some of the most unexpected and important results are linked to the gases streaming from the comet’s nucleus, including the discovery of molecular oxygen and nitrogen, and water with a different ‘flavour’ to that in Earth’s oceans.

Together, these results point to the comet being born in a very cold region of the protoplanetary nebula when the Solar System was still forming more than 4.5 billion years ago.

While it seems that the impact of comets like Rosetta’s may not have delivered as much of Earth’s water as previously thought, another much anticipated question was whether they could have brought ingredients regarded as crucial for the origin of life.

Rosetta impact

Rosetta did not disappoint, detecting the amino acid glycine, which is commonly found in proteins, and phosphorus, a key component of DNA and cell membranes. Numerous organic compounds were also detected ¬by Rosetta from orbit, and also by Philae in situ on the surface.

“It’s a bittersweet ending, but in the end the mechanics of the Solar System were simply against us: Rosetta’s destiny was set a long time ago. But its superb achievements will now remain for posterity and be used by the next generation of young scientists and engineers around the world.”

While the operational side of the mission has finished today, the science analysis will continue for many years to come.

Overall, the results delivered by Rosetta so far paint comets as ancient leftovers of early Solar System formation, rather than fragments of collisions between larger bodies later on, giving an unparalleled insight into what the building blocks of the planets may have looked like 4.6 billion years ago.

Comet outbursts

“Just as the Rosetta Stone after which this mission was named was pivotal in understanding ancient language and history, the vast treasure trove of Rosetta spacecraft data is changing our view on how comets and the Solar System formed,” says project scientist Matt Taylor.

“Inevitably, we now have new mysteries to solve. The comet hasn’t given up all of its secrets yet, and there are sure to be many surprises hidden in this incredible archive. So don’t go anywhere yet – we’re only just beginning.”

Notes for Editors:

Rosetta was an ESA mission with contributions from its Member States and NASA. Rosetta’s Philae lander was provided by a consortium led by DLR, MPS, CNES and ASI. Rosetta was the first mission in history to rendezvous with a comet and escort it as they orbited the Sun together. It was also the first to deploy a lander to a comet’s surface, and later end its mission in a controlled impact on the comet.

Comets are time capsules containing primitive material left over from the epoch when the Sun and its planets formed. By studying the gas, dust and structure of the nucleus and organic materials associated with the comet, via both remote and in situ observations, the Rosetta mission is a key to unlocking the history and evolution of our Solar System.

Related links:

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

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, Videos, Text, Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/CIVA: ESA/Rosetta/Philae/CIVA; NAVCAM: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0; OSIRIS: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; ROLIS: ESA/Rosetta/Philae/ROLIS/DLR/ATG medialab.

Best regards, Orbiter.ch

NASA's Fermi Finds Record-breaking Binary in Galaxy Next Door

NASA - Fermi Gamma-ray Space Telescope logo.

Sept. 29, 2016

Using data from NASA's Fermi Gamma-ray Space Telescope and other facilities, an international team of scientists has found the first gamma-ray binary in another galaxy and the most luminous one ever seen. The dual-star system, dubbed LMC P3, contains a massive star and a crushed stellar core that interact to produce a cyclic flood of gamma rays, the highest-energy form of light.

"Fermi has detected only five of these systems in our own galaxy, so finding one so luminous and distant is quite exciting," said lead researcher Robin Corbet at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Gamma-ray binaries are prized because the gamma-ray output changes significantly during each orbit and sometimes over longer time scales. This variation lets us study many of the emission processes common to other gamma-ray sources in unique detail."

These rare systems contain either a neutron star or a black hole and radiate most of their energy in the form of gamma rays. Remarkably, LMC P3 is the most luminous such system known in gamma rays, X-rays, radio waves and visible light, and it's only the second one discovered with Fermi.

NASA's Fermi Finds Record-breaking Binary Star

Video above: Dive into the Large Magellanic Cloud and see a visualization of LMC P3, an extraordinary gamma-ray binary system discovered by NASA's Fermi Gamma-ray Space Telescope. Video Credits: NASA's Goddard Space Flight Center/Scott Wiessinger, producer.

A paper describing the discovery will appear in the Oct. 1 issue of The Astrophysical Journal and is now available online: http://iopscience.iop.org/article/10.3847/0004-637X/829/2/105

LMC P3 lies within the expanding debris of a supernova explosion located in the Large Magellanic Cloud (LMC), a small nearby galaxy about 163,000 light-years away. In 2012, scientists using NASA's Chandra X-ray Observatory found a strong X-ray source within the supernova remnant and showed that it was orbiting a hot, young star many times the sun's mass. The researchers concluded the compact object was either a neutron star or a black hole and classified the system as a high-mass X-ray binary (HMXB).

In 2015, Corbet's team began looking for new gamma-ray binaries in Fermi data by searching for the periodic changes characteristic of these systems. The scientists discovered a 10.3-day cyclic change centered near one of several gamma-ray point sources recently identified in the LMC. One of them, called P3, was not linked to objects seen at any other wavelengths but was located near the HMXB. Were they the same object?

Image above: Observations from Fermi's Large Area Telescope (magenta line) show that gamma rays from LMC P3 rise and fall over the course of 10.3 days. The companion is thought to be a neutron star. Illustrations across the top show how the changing position of the neutron star relates to the gamma-ray cycle. Image Credits: NASA's Goddard Space Flight Center.

To find out, Corbet's team observed the binary in X-rays using NASA's Swift satellite, at radio wavelengths with the Australia Telescope Compact Array near Narrabri and in visible light using the 4.1-meter Southern Astrophysical Research Telescope on Cerro Pachón in Chile and the 1.9-meter telescope at the South African Astronomical Observatory near Cape Town.

The Swift observations clearly reveal the same 10.3-day emission cycle seen in gamma rays by Fermi. They also indicate that the brightest X-ray emission occurs opposite the gamma-ray peak, so when one reaches maximum the other is at minimum. Radio data exhibit the same period and out-of-phase relationship with the gamma-ray peak, confirming that LMC P3 is indeed the same system investigated by Chandra.

"The optical observations show changes due to binary orbital motion, but because we don't know how the orbit is tilted into our line of sight, we can only estimate the individual masses," said team member Jay Strader, an astrophysicist at Michigan State University in East Lansing. "The star is between 25 and 40 times the sun's mass, and if we're viewing the system at an angle midway between face-on and edge-on, which seems most likely, its companion is a neutron star about twice the sun's mass." If, however, we view the binary nearly face-on, then the companion must be significantly more massive and a black hole.

Image above: LMC P3 (circled) is located in a supernova remnant called DEM L241 in the Large Magellanic Cloud, a small galaxy about 163,000 light-years away. The system is the first gamma-ray binary discovered in another galaxy and is the most luminous known in gamma rays, X-rays, radio waves and visible light. Image Credit: NASA.

Both objects form when a massive star runs out of fuel, collapses under its own weight and explodes as a supernova. The star's crushed core may become a neutron star, with the mass of half a million Earths squeezed into a ball no larger than Washington, D.C. Or it may be further compacted into a black hole, with a gravitational field so strong not even light can escape it.

The surface of the star at the heart of LMC P3 has a temperature exceeding 60,000 degrees Fahrenheit (33,000 degrees Celsius), or more than six times hotter than the sun's. The star is so luminous that pressure from the light it emits actually drives material from the surface, creating particle outflows with speeds of several million miles an hour.

In gamma-ray binaries, the compact companion is thought to produce a "wind" of its own, one consisting of electrons accelerated to near the speed of light. The interacting outflows produce X-rays and radio waves throughout the orbit, but these emissions are detected most strongly when the compact companion travels along the part of its orbit closest to Earth. 

Through a different mechanism, the electron wind also emits gamma rays. When light from the star collides with high-energy electrons, it receives a boost to gamma-ray levels. Called inverse Compton scattering, this process produces more gamma rays when the compact companion passes near the star on the far side of its orbit as seen from our perspective.

Prior to Fermi's launch, gamma-ray binaries were expected to be more numerous than they've turned out to be. Hundreds of HMXBs are cataloged, and these systems are thought to have originated as gamma-ray binaries following the supernova that formed the compact object.

"It is certainly a surprise to detect a gamma-ray binary in another galaxy before we find more of them in our own," said Guillaume Dubus, a team member at the Institute of Planetology and Astrophysics of Grenoble in France. "One possibility is that the gamma-ray binaries Fermi has found are rare cases where a supernova formed a neutron star with exceptionally rapid spin, which would enhance how it produces accelerated particles and gamma rays."

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

Related links:

Fermi Gamma-Ray Space Telescope: http://www.nasa.gov/mission_pages/GLAST/main/index.html

NASA's Chandra X-ray Observatory: https://www.nasa.gov/mission_pages/chandra/main/index.html

NASA's Swift satellite: https://www.nasa.gov/mission_pages/swift/main

Southern Astrophysical Research Telescope: http://www.ctio.noao.edu/soar/

South African Astronomical Observatory: http://www.saao.ac.za/

Images (mentioned), Video (mentioned), Text, Credits: NASA's Goddard Space Flight Center, by Francis Reddy/Rob Garner.

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