vendredi 1 mai 2020

Searching for matter–antimatter asymmetry in the Higgs boson–top quark interaction

CERN - European Organization for Nuclear Research logo.

May 1, 2020

The ATLAS and CMS collaborations used the full LHC Run 2 dataset to obtain new insights into the interaction

Image above: ATLAS and CMS's event displays where the Higgs boson is produced in association with top quarks (Image: CERN).

Recent years have seen the study of the Higgs boson progress from the discovery age to the measurement age. Among the latest studies of the properties of this unique particle by the ATLAS and CMS collaborations are measurements that shed further light on its interaction with top quarks – which, as the heaviest elementary particle, have the strongest interactions with the Higgs boson. In addition to allowing a determination of the strength of the top-Higgs interaction, the analyses open a new window on charge-parity (CP) violation.

Discovered unexpectedly more than 50 years ago, CP violation reveals a fundamental asymmetry in nature that causes rare differences in the rates of processes involving matter particles and their antimatter counterparts, and is therefore thought to be an essential ingredient to explaining the observed abundance of matter over antimatter in the universe. While the Standard Model of particle physics can explain CP violation, the amount of CP violation observed so far in experiments – recently in the behaviour of charm quarks by the LHCb collaboration – is too small to account for the cosmological matter–antimatter imbalance. Searching for new sources of CP violation is thus of great interest to physicists.

In their recent studies, the CMS and ATLAS teams independently performed a direct test of the properties of the top–Higgs interaction. The studies are based on the full dataset of Run 2 of the LHC, which allowed for more precise measurements and analyses of the collision events where the Higgs boson is produced in association with one or two top quarks before decaying into two photons. The detection of this extremely rare association, which was first observed by the two collaborations in 2018, required the full capacities of the detectors and analysis techniques.

Large Hadron Collider (LHC). Animation Credit: CERN

As predicted by the Standard Model, no signs of CP violation were found in the top–Higgs interaction by either experiment. The top–Higgs production rate, a measure of the strength of the interaction between the particles, was also found by both experiments to be in line with previous results and consistent with the Standard Model predictions.

Following these first investigations of CP violation in the top–Higgs interaction, ATLAS and CMS physicists plan to study other Higgs-boson decay channels as part of the decades-long search for the origin of the universe’s missing antimatter.


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 23 Member States.

Related articles:

ATLAS searches for rare Higgs boson decays into a photon and a Z boson

LHCb finds new hints of possible Standard Model deviations

Long live the doubly charmed particle

LHCb announces a charming new particle

Related links:


Compact Muon Solenoid (CMS):

Large Hadron Collider (LHC):

For more information about European Organization for Nuclear Research (CERN), Visit:

Image (mentioned), Animation (mentioned), Text, Credits: CERN/Thomas Hortala.

Best regards,

Space Station Science Highlights: Week of April 27, 2020

ISS - Expedition 63 Mission patch.

May 1, 2020

Aboard the International Space Station the week of April 27, crew members conducted scientific investigations that included research on a fiber optic cable blend, flames and free-flying robot assistants. NASA astronaut Chris Cassidy reviewed procedures and set up hardware for deploying small experimental satellites from the Cygnus space freighter once it departs the space station. Cygnus is scheduled for release by the Canadarm2 robotic arm for departure on May 11 after an 83-day stay in space.

Image above: The cities of San Diego, National City and Chula Vista around San Diego Bay, California, a few miles north of the U.S.-Mexican border appear in this image taken while the International Space Station was just off the coast above the Pacific Ocean. Image Credit: NASA.

Now in its 20th year of continuous human presence, the space station provides a platform for long-duration research in microgravity and for learning to live and work in space. Experience gained on the orbiting lab supports Artemis, NASA’s program to go forward to the Moon and on to Mars.

Here are details on some of the microgravity investigations currently taking place:

Making better optic fiber

The crew performed hardware collection and setup in the Microgravity Science Glovebox for the Manufacturing Fiber Optic Cable in Microgravity (Space Fibers) reflight mission. Space Fibers evaluates a method for producing fiber optic cable from a blend of zirconium, barium, lanthanum, sodium and aluminum, called ZBLAN, in space. ZBLAN produces glass one hundred times more transparent than silica-based glass, exceptional for fiber optics. Microgravity suppresses two mechanisms that commonly degrade fiber, and previous studies showed improved properties in fiber drawn in microgravity compared to that fabricated on the ground.

Testing robotic assistants

Astrobee consists of three self-contained free-flying robots designed to help scientists and engineers develop and test technologies for use in microgravity. Onboard the space station, they can assist astronauts with routine chores, give ground controllers additional eyes and ears and perform crew monitoring, sampling and logistics management. This support frees up astronauts to dedicate their time and effort to other science and engineering duties. Each robot accommodates up to three payloads with mechanical attachment, power and data connectivity. During the week, crew members worked on moving and positioning the robots.

Predicting flame structure

Image above: NASA astronaut Chris Cassidy works on the Combustion Integrated Rack, a device that enables safe fuel, flame and soot studies in microgravity. Image Credit: NASA.

During the week, the crew prepared for continuation of runs for Structure and Response of Spherical Diffusion Flames (s-Flame). This investigation advances prediction of the structure and dynamics of soot-free and sooty flames, which could contribute to development of engines with improved efficiency and reduced emissions on Earth. S-Flame is part of the Advanced Combustion via Microgravity Experiments (ACME) project, a series of independent studies of gaseous flames performed in the station’s Combustion Integrated Rack (CIR). The project’s primary goals are to improve fuel efficiency and reduce pollutant production in routine fuel combustion activities on Earth. A secondary goal is improving spacecraft fire prevention through innovative research focused on materials flammability.

Other investigations on which the crew performed work:

- Veggie PONDS uses the newly developed Passive Orbital Nutrient Delivery System to cultivate lettuce and mizuna greens in the Veggie plant growth facility aboard the space station.

- ISS Ham gives students an opportunity to talk directly with crew members via ham radio when the space station passes over their school. This interaction engages and educates students, teachers, parents and other members of the community in science, technology, engineering and math.

- Acoustic Diagnostics, an investigation sponsored by ESA (European Space Agency), tests the hearing of crew members before, during and after flight to assess possible adverse effects of noise and the microgravity environment of the space station.

Image above: This image shows the Japan Aerospace Exploration Agency (JAXA) Small Satellite Orbital Deployer (J-SSOD) shown releasing micro-satellites from the exterior of the space station for the J-SSOD-11 mission in June 2019. Image Credit: NASA.

- The Japan Aerospace Exploration Agency (JAXA) Small Satellite Orbital Deployer (J-SSOD) platform provides the capability for launching small satellites from the space station, with the Japanese Experiment Module Remote Manipulator System (JEMRMS) providing positioning and deployment for individual satellites.

Space to Ground: Remote Science: 05/01/2020

Related links:

Expedition 63:


Microgravity Science Glovebox:

Space Fibers:





ISS National Lab:

Spot the Station:

Space Station Research and Technology:

International Space Station (ISS):

Images (mentioned), Video (NASA), Text, Credits: NASA/Michael Johnson/John Love, Lead Increment Scientist Expedition 63.

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Newly Reprocessed Images of Europa Show 'Chaos Terrain' in Crisp Detail

NASA - Galileo Mission patch /  NASA - Europa Clipper Mission patch.

May 1, 2020

Image above: In this gallery of three newly reprocessed Europa images, details are visible in the variety of features on the moon's icy surface. This image of an area called Chaos Transition shows blocks that have moved and ridges possibly related to how the crust fractures from the force of Jupiter's gravity. Image Credits: NASA/JPL-Caltech/SETI Institute.

The surface of Jupiter's moon Europa features a widely varied landscape, including ridges, bands, small rounded domes and disrupted spaces that geologists call "chaos terrain." Three newly reprocessed images, taken by NASA's Galileo spacecraft in the late 1990s, reveal details in diverse surface features on Europa.

Europa Clipper. Image Credit: NASA

Although the data captured by Galileo is more than two decades old, scientists are using modern image processing techniques to create new views of the moon's surface in preparation for the arrival of the Europa Clipper spacecraft. The orbiter of Jupiter will conduct dozens of flybys of Europa to learn more about the ocean beneath the moon's thick icy crust and how it interacts with the surface. The mission, set to launch in the next several years, will be the first return to Europa since Galileo.

"We've only seen a very small part of Europa's surface at this resolution. Europa Clipper will increase that immensely," said planetary geologist Cynthia Phillips of NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena. As a Europa project staff scientist, she oversees a long-term research project to reanalyze images of the moon.

Image above: The above map shows locations where each image, showcasing a variety of features, was captured by Galileo during its eighth targeted flyby of Jupiter's moon Europa. Image Credits: NASA/JPL-Caltech.

All three images were captured along the same longitude of Europa as Galileo flew by on Sept. 26, 1998, in the eighth of the spacecraft’s 11 targeted flybys of Europa. High-resolution images revealing features as small as 500 yards (460 meters) across were taken through a clear filter in grayscale (black and white). Using lower-resolution color images of the same region from a different flyby, technicians mapped color onto the higher-resolution images — a painstaking process.

 Galileo spacecraft. Animation Credit: NASA

Enhanced-color images like these allow scientists to highlight geologic features with different colors. Such images don't show Europa as it would appear to the human eye, but instead exaggerate color variations to highlight different chemical compositions of the surface. Areas that appear light blue or white are made of relatively pure water ice, and reddish areas have more non-ice materials, such as salts.

Planetary scientists study high-resolution images of Europa for clues about how the surface formed. At an average of 40 million to 90 million years old, the surface we see today is much younger than Europa itself, which formed along with the solar system 4.6 billion years ago. In fact, Europa has among the youngest surfaces in the solar system, one of its many intriguing oddities.

Image above: This image of an area called Crisscrossing Bands shows ridges, which may form when a crack in the surface opens and closes repeatedly. In contrast, the smooth bands shown here form where a crack continues pulling apart horizontally, producing large, wide, relatively flat features. Image Credits: NASA/JPL-Caltech/SETI Institute.

The long, linear ridges and bands that crisscross Europa's surface are thought to be related to the response of Europa's icy surface crust as it is stretched and pulled by Jupiter's strong gravity. Ridges may form when a crack in the surface opens and closes repeatedly, building up a feature that's typically a few hundred yards tall, a few miles wide and can span horizontally for thousands of miles.

In contrast, bands are locations where cracks appear to have continued pulling apart horizontally, producing wide, relatively flat features.

Areas of so-called chaos terrain contain blocks that have moved sideways, rotated or tilted before being refrozen into their new locations. To understand how they might have formed, scientists study these blocks as if they are jumbled puzzle pieces.

Image above: This image shows chaos terrain where blocks of material have shifted, rotated, tilted and refrozen. Scientists use this as a puzzle for clues about how the surface has changed. The area is called Chaos Near Agenor Linea for its proximity to the wide band of that name at the bottom of the image. Image Credits: NASA/JPL-Caltech/SETI Institute.

The Galileo mission was managed by JPL for NASA's Science Mission Directorate in Washington. Additional information about Galileo and its discoveries is available on the Galileo mission home page at:

More information about Europa and Europa Clipper is available at:

Images (mentioned), Animation (mentioned), Text, Credits: NASA/Tony Greicius/Grey Hautaluoma/Alana Johnson/JPL/Gretchen McCartney.


jeudi 30 avril 2020

Expedition 63 Explores Free-Flying Robots and Heart Research

ISS - Expedition 63 Mission patch.

April 30, 2020

Free-flying robots and heart research filled the science schedule aboard the International Space Station today. The Expedition 63 crew also managed cargo activities in a pair of resupply ships and cleaned biology research gear.

Astrobee is a robotics investigation that explores the ability of a trio of cube-shaped, free-flying robots to assist crews aboard the station. Commander Chris Cassidy set up one of the autonomous robotic assistants in the afternoon for a test of its mobility and vision system. Astrobee could perform routine lab chores giving astronauts more time to conduct critical space research.

Image above: Expedition 63 Commander Chris Cassidy works on the Fluids Integrated Rack (FIR) replacing components in the research device that studies the behavior of fluids in microgravity. Image Credit: NASA.

Cassidy also finalized the cleaning of a mouse habitat that housed rodents monitored for changes to their genetic expression due to microgravity. The mice have since returned to Earth aboard the last SpaceX Dragon cargo mission on April 7.

Living and working in space impacts the human body and scientists are exploring measures to ensure astronauts adapt successfully to weightlessness. How heart performance changes in space is fundamental to keeping crews healthy during long-term missions.

Image above: Flying over South Atlantic Ocean, seen by EarthCam on ISS, speed: 27'556 Km/h, altitude: 428,81 Km, image captured by Roland Berga (on Earth in Switzerland) from International Space Station (ISS) using ISS-HD Now Live application with EarthCam's from ISS on April 28, 2020 at 17:27 UTC. Image Credits: ISS Live Now/ Aerospace/Roland Berga.

Cosmonauts Anatoly Ivanishin and Ivan Vagner continued a long-running Russian heart study today that utilizes the Lower Body Negative Pressure Suit. The investigation examines how the heart behaves as the specialized spacesuit prevents blood from pooling in a crewmember’s head reducing head and eye pressure.

The Russian duo then spent the afternoon transferring cargo to and from the Progress 74 and 75 space freighters. Ivanishin packed trash and old gear in the 74P which is due to complete its mission in July. Vagner unloaded new gear and supplies from the 75P which just arrived on April 25.

Related links:

Expedition 63:


Mouse habitat:

Genetic expression:

Heart study:

Lower Body Negative Pressure Suit:

Space Station Research and Technology:

International Space Station (ISS):

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

Best regards,

NASA Space Laser Missions Map 16 Years of Ice Sheet Loss

NASA - ICESat-2 Mission patch.

April 30, 2020

Using the most advanced Earth-observing laser instrument NASA has ever flown in space, scientists have made precise, detailed measurements of how the elevation of the Greenland and Antarctic ice sheets have changed over 16 years.

The results provide insights into how the polar ice sheets are changing, demonstrating definitively that small gains of ice in East Antarctica are dwarfed by massive losses in West Antarctica. The scientists found the net loss of ice from Antarctica, along with Greenland’s shrinking ice sheet, has been responsible for 0.55 inches (14 millimeters) of sea level rise between 2003 and 2019 – slightly less than a third of the total amount of sea level rise observed in the world’s oceans.

NASA Mission Maps 16 Years of Ice Loss

Video above: Using the most advanced Earth-observing laser instrument NASA has ever flown in space, scientists have made precise, detailed measurements of how the elevation of the Greenland and Antarctic ice sheets have changed over 16 years. Video Credits: NASA's Goddard Space Flight Center.

The findings come from NASA’s Ice, Cloud and land Elevation Satellite 2 (ICESat-2), which launched in 2018 to make detailed global elevation measurements, including over Earth’s frozen regions. By comparing the recent data with measurements taken by the original ICESat from 2003 to 2009, researchers have generated a comprehensive portrait of the complexities of ice sheet change and insights about the future of Greenland and Antarctica.

The study found that Greenland’s ice sheet lost an average of 200 gigatons of ice per year, and Antarctica’s ice sheet lost an average of 118 gigatons of ice per year.

One gigaton of ice is enough to fill 400,000 Olympic-sized swimming pools or cover New York’s Central Park in ice more than 1,000 feet (300 meters) thick, reaching higher than the Chrysler Building.

“If you watch a glacier or ice sheet for a month, or a year, you’re not going to learn much about what the climate is doing to it,” said Ben Smith, a glaciologist at the University of Washington and lead author of the new paper, published online in Science April 30. “We now have a 16-year span between ICESat and ICESat-2 and can be much more confident that the changes we’re seeing in the ice have to do with the long-term changes in the climate.”

ICESat-2’s instrument is a laser altimeter, which sends 10,000 pulses of light a second down to Earth’s surface, and times how long it takes to return to the satellite – to within a billionth of a second. The instrument’s pulse rate allows for a dense map of measurement over the ice sheet; its high precision allows scientists to determine how much an ice sheet changes over a year to within an inch.

The researchers took tracks of earlier ICESat measurements and overlaid the tracks of ICESat-2 measurements from 2019, and took data from the tens of millions of sites where the two data sets intersected. That gave them the elevation change, but to get to how much ice has been lost, the researchers developed a new model to convert volume change to mass change. The model calculated densities across the ice sheets to allow the total mass loss to be calculated.

“These first results looking at land ice confirm the consensus from other research groups, but they also let us look at the details of change in individual glaciers and ice shelves at the same time,” said Tom Neumann, ICESat-2 project scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Image above: Using data from the ICESat and ICESat-2 laser altimeters, scientists precisely measured how much ice has been lost from ice sheets in Antarctica and Greenland between 2003 and 2019. The Antarctic Peninsula, seen here, was one of the fastest changing regions of the continent. Image Credits: NASA/K. Ramsayer.

In Antarctica, for example, the detailed measurements showed that the ice sheet is getting thicker in parts of the continent’s interior as a result of increased snowfall, according to the study. But the loss of ice from the continent’s margins, especially in West Antarctica and the Antarctic Peninsula, far outweighs any gains in the interior. In those places, the loss is due to warming from the ocean.

In Greenland, there was a significant amount of thinning of coastal glaciers, Smith said. The Kangerlussuaq and Jakobshavn glaciers, for example, have lost 14 to 20 ft (4 to 6 m) of elevation per year; the glacial basins have lost 16 gigatons per year and 22 gigatons per year, respectively. Warmer summer temperatures have melted ice from the surface of the glaciers and ice sheets, and in some basins the warmer ocean water erodes away the ice at their fronts.

“The new analysis reveals the ice sheets’ response to changes in climate with unprecedented detail, revealing clues as to why and how the ice sheets are reacting the way they are,” said Alex Gardner, a glaciologist at NASA’s Jet Propulsion Laboratory in Southern California, and co-author on the Science paper.

The study also examined ice shelves – the floating masses of ice at the downstream end of glaciers. These ice shelves, which rise and fall with the tides, can be difficult to measure, said Helen Amanda Fricker, a glaciologist at Scripps Institution of Oceanography at the University of California San Diego, and co-author on the Science paper. Some of them have rough surfaces, with crevasses and ridges, but the precision and high resolution of ICESat-2 allows researchers to measure overall changes.

ICESat-2 satellite. Image Credit: NASA

This is one of the first times that researchers have used laser altimetry to measure loss of the floating ice shelves around Antarctica simultaneously with loss of the continent’s ice sheet.

The researchers found ice shelves are losing mass in West Antarctica, where many of the continent’s fastest-moving glaciers are located as well. Patterns of thinning over the ice shelves in West Antarctica show that Thwaites and Crosson ice shelves have thinned the most, an average of about 16 ft (5 m) and 10 ft (3 m) of ice per year, respectively.

Ice that melts from ice shelves doesn’t raise sea levels, since it’s already floating – just like an ice cube already in a full cup of water doesn’t overflow the glass when it melts. But the ice shelves do provide stability for the glaciers and ice sheets behind them.

“It’s like an architectural buttress that holds up a cathedral,” Fricker said. “The ice shelves hold the ice sheet up. If you take away the ice shelves, or even if you thin them, you’re reducing that buttressing force, so the grounded ice can flow faster.”

For more information on ICESat-2, visit or

Images (mentioned), Video (mentioned), Text, Credits: NASA/GSFC/Kate Ramsayer.


Shining a Light on Dark Matter

NASA - Hubble Space Telescope patch.

April 30, 2020

Dark matter, although invisible, makes up most of the universe’s mass and creates its underlying structure. Dark matter’s gravity drives normal matter (gas and dust) to collect and build up into stars and galaxies. Although astronomers cannot see dark matter, they can detect its influence by observing how the gravity of massive galaxy clusters, which contain dark matter, bends and distorts the light of more-distant galaxies located behind the cluster.

As seen in this image, large galaxy clusters contain both dark and normal matter. The immense gravity of all this material warps the space around the cluster, causing the light from objects located behind the cluster to be distorted and magnified. This phenomenon is called gravitational lensing. This sketch shows paths of light from a distant galaxy that is being gravitationally lensed by a foreground cluster.

In 1609, visionary scientist Galileo Galilei turned the newly invented optical device of his day — the telescope — to view the heavens. Almost four centuries later, the launch of NASA’s Hubble Space Telescope aboard the space shuttle Discovery in 1990 started another revolution in astronomy. Developed as a partnership between the United States space program and the European Space Agency, Hubble orbits 340 miles above Earth’s surface.

Hubble Space Telescope (HST)

Along with pictures of the telescope and the astronauts who launched and serviced it during six space shuttle missions, certain memorable science images have become cultural icons. They appear regularly on book covers, music albums, clothing, TV shows, movies and even ecclesiastical stained-glass windows.

Explore thirteen representative topics with eye-catching images and thought-provoking discoveries:

Additional images and information can be found at

Hubble Space Telescope (HST):

Dark Energy and Dark Matter:

Image, Animation, Text, Credits: NASA/Yvette Smith/ESA.

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NASA Names Companies to Develop Human Landers for Artemis Moon Missions

NASA - Artemis Program logo.

April 30, 2020

NASA has selected three U.S. companies to design and develop human landing systems (HLS) for the agency’s Artemis program, one of which will land the first woman and next man on the surface of the Moon by 2024. NASA is on track for sustainable human exploration of the Moon for the first time in history.

Image above: Illustration of Artemis astronauts on the Moon. Image Credit: NASA.

The human landing system awards under the Next Space Technologies for Exploration Partnerships (NextSTEP-2) Appendix H Broad Agency Announcement (BAA) are firm-fixed price, milestone-based contracts. The total combined value for all awarded contracts is $967 million for the 10-month base period.

The following companies were selected to design and build human landing systems:

- Blue Origin of Kent, Washington, is developing the Integrated Lander Vehicle (ILV) – a three-stage lander to be launched on its own New Glenn Rocket System and ULA Vulcan launch system.

- Dynetics (a Leidos company) of Huntsville, Alabama, is developing the Dynetics Human Landing System (DHLS) – a single structure providing the ascent and descent capabilities that will launch on the ULA Vulcan launch system.

- SpaceX of Hawthorne, California, is developing the Starship – a fully integrated lander that will use the SpaceX Super Heavy rocket.

“With these contract awards, America is moving forward with the final step needed to land astronauts on the Moon by 2024, including the incredible moment when we will see the first woman set foot on the lunar surface,” said NASA Administrator Jim Bridenstine. “This is the first time since the Apollo era that NASA has direct funding for a human landing system, and now we have companies on contract to do the work for the Artemis program.”

Artemis Announcement: NASA Selects Human Landing Systems

Video above: NASA has selected three American companies – Blue Origin, Dynetics and SpaceX – to design and develop human landing systems for the Artemis program. With these awards, NASA is on track to land the next astronauts on the lunar surface by 2024, and establish sustainable human exploration of the Moon by the end of the decade. Video Credit: NASA.

Fifty years ago, NASA’s Apollo Program proved it is possible to land humans on the Moon and return them safely to Earth. When NASA returns to the Moon in four years with the Artemis program, it will go in a way that reflects the world today – with government, industry, and international partners in a global effort to build and test the systems needed for challenging missions to Mars and beyond.

“We are on our way.” said Douglas Loverro, NASA’s associate administrator for Human Explorations and Operations Mission Directorate in Washington. “With these awards we begin an exciting partnership with the best of industry to accomplish the nation’s goals. We have much work ahead, especially over these next critical 10 months. I have high confidence that working with these teammates, we will succeed.” 

NASA’s commercial partners will refine their lander concepts through the contract base period ending in February 2021. During that time, the agency will evaluate which of the contractors will perform initial demonstration missions. NASA will later select firms for development and maturation of sustainable lander systems followed by sustainable demonstration missions. NASA intends to procure transportation to the lunar surface as commercial space transportation services after these demonstrations are complete. During each phase of development, NASA and its partners will use critical lessons from earlier phases to hone the final concepts that will be used for future lunar commercial services.

Blue Origin - Integrated Lander Vehicle (ILV). Image Credit: Blue Origin

"I am confident in NASA’s partnership with these companies to help achieve the Artemis mission and develop the human landing system returning us to the Moon" said Lisa Watson-Morgan, HLS program manager at NASA’s Marshall Space Flight Center in Huntsville, Alabama. "We have a history of proven lunar technical expertise and capabilities at Marshall and across NASA that will pave the way for our efforts to quickly and safely land humans on the Moon in 2024.”

NASA experts will work closely with the commercial partners building the next human landing systems, leveraging decades of human spaceflight experience and the speed of the commercial sector to achieve a Moon landing in 2024.  

The HLS program manager will assign NASA personnel to support the work of each contractor, providing direct, in-line expertise to the companies as requested in their proposals (e.g., design support, analysis, testing). The HLS program will also perform advanced development and risk reduction activities, working in parallel to better inform the approach for the 2024 mission and the necessary maturation of systems for the future sustaining architecture.

Charged with returning to the Moon in the next four years, NASA’s Artemis program will reveal new knowledge about the Moon, Earth, and our origins in the solar system. The human landing system is a vital part of NASA’s deep space exploration plans, along with the Space Launch System (SLS) rocket, Orion spacecraft, and Gateway.

NASA is returning to the Moon for scientific discovery, economic benefits, and inspiration for a new generation. Working with its partners throughout the Artemis program, the agency will fine-tune precision landing technologies and develop new mobility capabilities that allow robots and crew to travel greater distances and explore new regions of the Moon. On the surface, the agency has proposed building a new habitat and rovers, testing new power systems and much more to get ready for human exploration of Mars.

Learn more about each HLS concept:​

Learn more about America’s Moon to Mars exploration approach at:


Space Launch System (SLS):

Commercial Space:

Next Space Technologies for Exploration Partnerships (NextSTEP-2):

Images (mentioned), Video (mentioned), Text, Credits: NASA/Sean Potter/Gina Anderson/Matthew Rydin/Marshall Space Flight Center/Jena Rowe.


Hubble's impactful life alongside space debris

ESA - Hubble Space Telescope patch.

April 30, 2020

During its 30 years in orbit around Earth, the NASA/ESA Hubble Space Telescope has witnessed the changing nature of spaceflight as the skies have filled with greater numbers of satellites, the International Space Station was born and in-space crashes and explosions have created clouds of fast-moving space debris.

Hubble itself has felt the impact of this debris, accumulating tiny impact craters across its solar panels that evidence a long and eventful life in space. So what can we learn from these impacts, and what does the future hold for Hubble?

Astronaut Kathy Thornton throws damaged array into space

In 1993, the first Shuttle mission to ‘spruce up’ Hubble was conducted. By providing the space observatory with corrective optics, it was suddenly able to take the incredibly sharp images of the Universe loved by the world over.

While the astronauts were there, they replaced the observatory’s solar arrays which had been ‘jittering’ due to temperature fluctuations. One of the panels was disposed of in orbit, later burning up in Earth’s atmosphere, but the other was brought back down to Earth.

Part of ESA’s contribution to Hubble was to design, manufacture and provide its solar arrays in exchange for observation time, meaning the returned array was available for the Agency to inspect.

This was one of the earliest opportunities in the history of space exploration to see the impact of more than two years in space on an orbiting satellite. The team discovered hundreds of impact craters pocketing the surface of just a small section of the solar array, ranging from microns to millimetres in diameter.

ESA built-solar cells retrieved from the Hubble Space Telescope in 2002

Nine years later, the solar panels were again replaced and returned to Earth this time having accumulated almost a decade of impact craters.

This array is now on display at ESA’s Technology Centre (ESTEC) in The Netherlands, but a tiny piece came to the ESOC mission control in Germany, home to the Space Debris Office.

Array of evidence of Hubble’s early bombardment

Although we don't know exactly when each impact crater was formed, they must have occurred during the solar array’s period in orbit. As such, imprinted on them, is unique evidence of spaceflight activity during their time in space.

The impact craters were studied to determine their size and depth, but also to seek out potential new residues. Given that the chemical composition of the solar cell was known, ‘alien’ materials or elements could have been brought into the crater by the impactor.

Hubble solar cell impact damage

Metals like iron and nickel would suggest an impact from a natural source – fragments of asteroids and comets known as micrometeoroids. The craters found in Hubble’s solar arrays however contained small amounts of aluminium and oxygen, a strong indication of human activity in the form of ‘solid rocket motor’ firing residues.

The space debris team, as part of a larger effort with partners in industry and academia, were able to match the shape and size of these craters to models of rocket firings that were known to have happened at the time, finding a match between craters observed and craters expected.

Was Hubble hurt?

These tiny particles, ranging from micrometres up to a millimetre in size, would have struck Hubble at huge relative speeds of 10 km/s, however they didn't have a major impact on the craft which continues to take incredible images of our Universe.

Tapestry of blazing starbirth

Such impacts occur quite frequently for all satellites, the main effect being a continuous but gradual degradation in the amount of power the solar arrays can produce.

New missions make use of a model created by the space debris team, based on early Hubble impact data, to predict how many impacts can be expected for each mission and what effect this will have on solar power.

Hubble still lives with the threat of collision

Imagine the Hubble spacecraft in orbit, residing inside a 1 km x 1 km x 1km cube. On average, at any moment, a single piece of micron-sized debris shares that cube with Hubble, because for every cubic kilometre of space around Earth, there is about one tiny debris object.

This doesn't sound like a lot, but Hubble itself is travelling at 7.6 km/s relative to Earth and so are these tiny fragments of debris. A large fraction of collisions between the two don't happen head on, but at an angle, leading to relative impact speeds of about 10 km/s.

Hubble in free orbit

For simplicity, imagine these particles are travelling at 10 km/s relative to a still Hubble. This is the same as ten of these fast-moving objects crossing in and out of Hubble’s cubic space every second. Because Hubble’s solar panels take up a large surface area, measuring approximately 7x2 m, they are more likely to come face-to-face with large numbers of these projectiles.

Distribution of space debris in orbit around Earth

Hubble today faces a similar threat from small debris fragments as it did soon after it was launched. While micron-sized particles are still being created today, the atmosphere at this low altitude, 547 km above Earth’s surface, also sweeps a number of them away.

However, the risk from larger objects is unfortunately also increasing. Debris fragments ranging from about 1-10 cm in size are too small to be catalogued and tracked from ground, but have enough energy to destroy an entire satellite. At Hubble's altitude, the probability of a collision with one of these objects has doubled since the early 2000s, from a 0.15% chance per year to a 0.3% today.

Hubble lives where mega-constellations plan to reside

Some satellites are launched today without the capability to change their orbit. Instead of manoeuvring at the end of their life, they can be inserted into relatively low altitudes so that over time Earth’s atmosphere pulls them down to burn up, including the region that Hubble calls home.

Mega-constellation coverage

In addition, the total number of operational satellites being put into this region looks set to soon rapidly increase. Some broadband internet constellations, the largest of which are planned to contain thousands of satellites, have their sights set on these heights.

Space Safety at ESA

To help prevent the build-up of new debris through collisions, ESA's Space Safety programme is developing ‘automated collision avoidance’ technologies that will make the process of avoiding collisions more efficient, by automating the decision processes on the ground.

High-velocity impact sample

But what about the debris that’s already out there? In a world first, ESA has commissioned an active debris removal mission that will safely dispose of an item of debris currently in orbit. The ClearSpace-1 mission will target a 100 kg Vespa rocket part, left in orbit after the second flight of ESA’s Vega launcher back in 2013.

With a mass of 100 kg, the Vespa is close in size to a small satellite. Its relatively simple shape and sturdy construction make it a suitable first goal, before progressing to larger, more challenging captures by follow-up missions – eventually including multi-object capture.

Related links:

NASA/ESA Hubble Space Telescope:

Space debris:

ESA’s Technology Centre (ESTEC):

ESA's Space Safety programme:

ClearSpace-1 mission:

Images, Video, Text, Credits: NASA, ESA, and STScI; CC BY 4.0/Science Office.


mercredi 29 avril 2020

NASA Probes Environment, COVID-19 Impacts, Possible Links

NASA Goddard Space Flight Center logo.

April 29, 2020

Scientists are using information from NASA’s Earth-observing satellites, on-the-ground sensors and computer-based datasets to study the environmental, economic and societal impacts of the COVID-19 pandemic. In addition, the agency’s Earth Science Division recently sponsored new projects to examine how the shutdowns in response to the pandemic are changing the environment, especially the atmosphere, and determine what, if any, natural environmental phenomena might impact the spread of the pandemic.

“NASA has a unique role to play in response to this crisis,” said John Haynes, NASA’s program manager for Health and Air Quality Applications. “As we continue to collect Earth-observing satellite data on a global scale, we can aid in the understanding of global changes resulting from the pandemic, as well as investigate potential environmental signals that may influence the spread of COVID-19.”

Image above: In this night image from Jan. 29, 2012, human presence is clearly visible as the space station passed over the Gulf of Mexico looking north to the southeastern United States. The brightly lit metropolitan areas of Atlanta, Georgia, center, and Jacksonville, Florida, lower right, appear largest in the image with numerous other urban areas forming an interconnected network of light across the region. Image Credit: NASA.

NASA recently funded two new rapid-turnaround projects focused on COVID-19. Jennifer Kaiser at Georgia Institute of Technology in Atlanta and Elena Lind at Virginia Polytechnic Institute in Blacksburg, are examining the pandemic’s impact on air quality related to reduced airport traffic. Joanna Joiner and Bryan Duncan at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, are creating maps and images that show how COVID-19 has reduced air pollution across the world.

Air traffic in the time of COVID-19

“The world’s response to the pandemic is an unintended experiment that is giving us a chance to test our understanding of various air pollution emission sources,” said Barry Lefer, NASA’s program scientist for tropospheric composition.

Kaiser’s research is looking at how COVID-19 travel bans and lockdown orders are impacting air quality around airports. Current conditions create a unique opportunity to study airport-related pollutants, especially nitrogen dioxide and formaldehyde. It’s a footprint that will likely gradually return to its former shape as travel policies are relaxed.

“People are looking at COVID-19 impacts and seeing better air quality with less traffic,” Kaiser said. They might wonder if this is what the future could look like if we relied more heavily on electric vehicles than we do now. Yet, airplanes are not going to be electric anytime soon, Kaiser said.

“Airports are usually some of the hottest spots for nitrogen dioxide,” Kaiser said. Nitrogen dioxide is released when we burn fuel, either in airplanes or cars. When first released into the lower atmosphere, or the part of the atmosphere that we breathe, nitrogen dioxide reacts with other nearby chemicals and forms ozone. Airplane exhaust also forms formaldehyde, which is an indicator of ozone formation and another air toxin. Breathing in ozone can cause chest pain, coughing and throat irritation.

Kaiser and her team installed two sensors at both Baltimore-Washington International Airport (BWI) and Hartsfield-Jackson Atlanta International Airport. BWI’s overall traffic is down by around 60 percent and Atlanta’s is down by 70 percent.

The sensors, which are part of NASA’s Pandora Project, each use a spectrometer to identify chemicals in the air. Two instruments, each propped up with a tripod, sit at both airports. Their spectrometers use ultraviolet and visible wavelengths of light to detect ozone, nitrogen dioxide and formaldehyde at different altitudes of the atmosphere.

Kaiser is comparing the on-the-ground sensor information with satellite information from the European Space Agency (ESA)’s TROPOspheric Monitoring Instrument (TROPOMI), aboard the Copernicus Sentinel-5 Precursor satellite, launched in 2017 and managed by the European Commission in partnership with ESA, the EU Member States and EU agencies. She wants to know if we’re understanding the satellite data accurately for these locations by ground truthing them with the newly-installed Pandora sensors.

“We want to help our stakeholders, like policymakers, improve their understanding of the air we breathe,” Kaiser said, and how that air can be affected by pollution from airports.

Revealing lower fossil fuel emissions from space

Joiner and Duncan at NASA Goddard are also revealing lower nitrogen dioxide levels in the air, but on a global scale. Both work with data from the Dutch-Finnish Ozone Monitoring Instrument (OMI) aboard NASA’s Aura satellite (launched in 2004) to help reveal how COVID-19 policies are impacting air quality. OMI is a precursor to TROPOMI. Although TROPOMI provides higher resolution information, OMI has a longer record.

“We’re looking at changes in nitrogen dioxide to understand how economies are changing,” Duncan said. “If the amount of pollution emitted continues to grow over time, your economy is likely booming,” he said, but noted that pollution can decrease even as coal use remains the same because of improvements in efficiency and the implementation of emission control devices.

Image above: Tropospheric nitrogen dioxide column, March 15-April 15 2015-2019 Average, Southeast USA. Image Credits: NASA's Scientific Visualization Studio.

“When we started to hear about China shutting down, we started looking for changes in the nitrogen dioxide signal,” Duncan said. NASA’s Earth Observatory published an image from the TROPOMI instrument in early March 2020, showing a dramatic decrease.

The OMI team decided to make more data like this accessible to scientists, economists and health professionals to help them understand how atmospheric chemistry is changing, how economies are shrinking and whether lockdowns are effective for specific areas, Duncan said.

“We already had tools in place to do this kind of monitoring because we also monitor gases, like sulfur dioxide, related to volcanic eruptions,” Joiner said. However, while volcanoes have very obvious signals that are easy to see in the satellite data, COVID-related impacts are harder to see.

“The nitrogen dioxide isn’t very high to begin with, so changes are subtle,” Joiner said. “We need to determine if a change is due to weather, like wind, or if a change is due to decreases in transportation.”

With additional NASA funding, Joiner and Duncan are developing different ways to present new information. They put together a comparison of data from this year to an average of data from the five previous years. Their team wants to know when changes in nitrogen dioxide begin relative to different government actions. OMI’s record of data goes back to 2005.

“We have a good, long record to compare our current year to,” Joiner said.

Image above: Tropospheric nitrogen dioxide column, March 15-April 15 2020 Average, Southeast USA. Image Credits: NASA's Scientific Visualization Studio.

Changing seasons during COVID-19

Ben Zaitchik at Johns Hopkins University in Baltimore is investigating a question on many peoples’ minds: Will COVID-19 cases decrease in the summer because of the weather?

“Although cases will likely decrease as we move into summer, we want to know how much of that change is due to social-distancing policies and lockdown orders versus higher temperatures and humidity,” Kaitchik said.

Zaitchik’s COVID-19 focused research builds on his prior NASA-funded work studying how enteric infectious diseases spread. Enteric diseases, like cholera, are intestinal.

COVID-19, however, is an infectious respiratory disease. Although the diseases infect humans differently, they both may be affected by the weather. By applying Earth satellite data to public health data related to COVID-19, Zaitchik will be able to note if there are any significant links. For example, do cases decrease as temperature or humidity rise?

Zaitchik’s team is using data on temperature, precipitation, and other weather and climate information from a NASA data set called MERRA-2, short for Modern-Era Retrospective analysis for Research and Applications, Version 2. Once they find any potential links between weather and COVID-19 cases, they’ll verify them with higher resolution satellite data.

The team will pull in information about precipitation from the Global Precipitation Measurement mission (jointly run by the Japan Aerospace Exploration Agency and NASA), temperature from the MODerate Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA’s Earth Observing System Terra and Aqua satellites, and soil moisture and the water cycle from NASA’s Soil Moisture Active Passive mission (SMAP).

“We have the full arsenal of Earth observations at our disposal,” Zaitchik said. Furthermore, Zaitchik is working with the team behind the Johns Hopkins COVID-19 Dashboard. The dashboard displays information about the number of people infected, deceased and recovered due to the virus. “We have this big database that is collected by people around the world,” Zaitchik said.

“Right now, policymakers are observing trends while implementing policies,” Zaitchik said. “But there are so many unknowns right now.” The time between research and public discussion has been incredibly shortened, he noted. “People come out with a study and immediately it’s on the front page,” Zaitchik said.

If the team finds a link between weather and cases of COVID-19, it will influence how we think about this in terms of a potential second wave of cases during the fall, Zaitchik said. “And if there isn’t a link, we still need to know,” Zaitchik said.

For more information on NASA’s Earth Science and other efforts related to COVID-19, visit:

Related links:

NASA’s Pandora Project:

ESA’s TROPOspheric Monitoring Instrument (TROPOMI):

Ozone Monitoring Instrument (OMI):


Global Precipitation Measurement mission (GPM):

MODerate Resolution Imaging Spectroradiometer (MODIS):

NASA’s Soil Moisture Active Passive mission (SMAP):

Johns Hopkins COVID-19 Dashboard:

NASA’s Earth Science:

Earth Research Findings:

Images (mentioned), Text, Credits: NASA/Earth Science Division/Elizabeth Goldbaum.


Spacesuit Work and Heart Research Fill Crew Day

ISS - Expedition 63 Mission patch.

April 29, 2020

The three-member Expedition 63 crew aboard the International Space Station focused its attention on spacesuits and cardiac research today. The orbital residents also serviced science hardware and life support gear.

Commander Chris Cassidy worked on a pair of U.S. spacesuits in the Quest airlock today cleaning cooling loops, replacing components and checking for leaks. NASA is planning a series of spacewalks later this year to upgrade power and science systems on the orbiting lab.

Image above: Expedition 63 Commander Chris Cassidy works in the Combustion Integrated Rack, a research device that enables safe fuel, flame and soot studies in microgravity. Image Credit: NASA.

Cassidy, who last served in 2013 as an Expedition 36 flight engineer, also cleaned the Veggie PONDS botany research hardware after growing lettuce and mizuna greens in the Columbus lab module. Next, he swapped batteries in the Astrobee robotic assistant then set up audio software for a hearing assessment.

International Space Station (ISS). Animation Credit: NASA

Roscosmos Flight Engineers Anatoly Ivanishin and Ivan Vagner worked in the morning on a long-running study to understand how the human heart adapts to microgravity. The duo then split up for Earth observation studies and life support maintenance.

Related links:

Expedition 63:

Quest airlock:

Expedition 36:

Veggie PONDS:


Human heart:

Space Station Research and Technology:

International Space Station (ISS):

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

Best regards,

The asteroid 1998 OR2 safely passed Earth

Asteroid Watch logo.

April 29, 2020

Artist's concept of a near-Earth object. Image Credits: NASA/JPL-Caltech

A large asteroid close to Earth safely passed by our planet this Wednesday morning, offering astronomers an exceptional opportunity to study in detail the object 1.5 miles wide (2 kilometers wide).

The asteroid, called 1998 OR2, made its closest approach at 5:55 a.m. EDT (2:55 a.m. PDT). Although this is known as a "close approach" by astronomers, it is still a long way off: the asteroid will not approach approximately 3.9 million miles (6.3 million km), passing more than 16 times further than the Moon.

Animation above: This GIF, composed of observations by the Virtual Telescope Project, shows asteroid 1998 OR2 (the central dot) as it traversed the constellation Hydra five days before its closest approach to Earth. It was about 4.4 million miles (7.08 million kilometers) away from Earth at the time. Animation Credits: Dr. Gianluca Masi (Virtual Telescope Project).

Asteroid 1998 OR2 was discovered by the Near-Earth Asteroid Tracking program at NASA's Jet Propulsion Laboratory in July 1998, and for the past two decades astronomers have tracked it. As a result, we understand its orbital trajectory very precisely, and we can say with confidence that this asteroid poses no possibility of impact for at least the next 200 years. Its next close approach to Earth will occur in 2079, when it will pass by closer — only about four times the lunar distance.

Despite this, 1998 OR2 is still categorized as a large "potentially hazardous asteroid" because, over the course of millennia, very slight changes in the asteroid's orbit may cause it to present more of a hazard to Earth than it does now. This is one of the reasons why tracking this asteroid during its close approach — using telescopes and especially ground-based radar — is important, as observations such as these will enable an even better long-term assessment of the hazard presented by this asteroid.

Close approaches by large asteroids like 1998 OR2 are quite rare. The previous close approach by a large asteroid was made by asteroid Florence in September 2017. That 3-mile-wide (5-kilometer-wide) object zoomed past Earth at 18 lunar distances. On average, we expect asteroids of this size to fly by our planet this close roughly once every five years.

Since they are bigger, asteroids of this size reflect much more light than smaller asteroids and are therefore easier to detect with telescopes. Almost all near-Earth asteroids (about 98%) of the size of 1998 OR2 or larger have already been discovered, tracked and cataloged. It is extremely unlikely there could be an impact over the next century by one of these large asteroids, but efforts to discover all asteroids that could pose an impact hazard to Earth continue.

JPL hosts the Center for Near-Earth Object Studies (CNEOS) for NASA's Near-Earth Object Observations Program in NASA's Planetary Defense Coordination Office.

Related article & links:

Small Asteroid to Safely Fly by Earth

Virtual Telescope Project:

More information about CNEOS, asteroids and near-Earth objects can be found at:

For more information about NASA's Planetary Defense Coordination Office, visit:

For asteroid and comet news and updates, follow @AsteroidWatch on Twitter:


Image (mentioned), Animation (mentioned), Text, Credits: NASA/Tony Greicius/Josh Handal/JPL/Ian J. O'Neill/ Aerospace/Roland Berga.

Best regards,

Spitzer Telescope Reveals the Precise Timing of a Black Hole Dance

NASA - Spitzer Space Telescope patch.

April 29, 2020

The recently retired infrared observatory was the only telescope to spot a far-off flash of light that holds clues about the physical characteristics of these cosmic mysteries.

Image above: This image shows two massive black holes in the OJ 287 galaxy. The smaller black hole orbits the larger one, which is also surrounded by a disk of gas. When the smaller black hole crashes through the disk, it produces a flare brighter than 1 trillion stars. Image Credits: NASA/JPL-Caltech.

Black holes aren't stationary in space; in fact, they can be quite active in their movements. But because they are completely dark and can't be observed directly, they're not easy to study. Scientists have finally figured out the precise timing of a complicated dance between two enormous black holes, revealing hidden details about the physical characteristics of these mysterious cosmic objects.

The OJ 287 galaxy hosts one of the largest black holes ever found, with over 18 billion times the mass of our Sun. Orbiting this behemoth is another black hole with about 150 million times the Sun's mass. Twice every 12 years, the smaller black hole crashes through the enormous disk of gas surrounding its larger companion, creating a flash of light brighter than a trillion stars - brighter, even, than the entire Milky Way galaxy. The light takes 3.5 billion years to reach Earth.

Timing of Black Hole Dance Revealed by NASA Spitzer Space Telescope

Video above: The OJ 287 galaxy hosts one of the largest black holes ever found, with over 18 billion times the mass of our Sun. Orbiting this behemoth is another massive black hole. Twice every 12 years, the smaller black hole crashes through the enormous disk of gas surrounding its larger companion, creating a flash of light brighter than a trillion stars. Video Credits: NASA/JPL.

But the smaller black hole's orbit is oblong, not circular, and it's irregular: It shifts position with each loop around the bigger black hole and is tilted relative to the disk of gas. When the smaller black hole crashes through the disk, it creates two expanding bubbles of hot gas that move away from the disk in opposite directions, and in less than 48 hours the system appears to quadruple in brightness.

Because of the irregular orbit, the black hole collides with the disk at different times during each 12-year orbit. Sometimes the flares appear as little as one year apart; other times, as much as 10 years apart. Attempts to model the orbit and predict when the flares would occur took decades, but in 2010, scientists created a model that could predict their occurrence to within about one to three weeks. They demonstrated that their model was correct by predicting the appearance of a flare in December 2015 to within three weeks.

Then, in 2018, a group of scientists led by Lankeswar Dey, a graduate student at the Tata Institute of Fundamental Research in Mumbai, India, published a paper with an even more detailed model they claimed would be able to predict the timing of future flares to within four hours. In a new study published in the Astrophysical Journal Letters, those scientists report that their accurate prediction of a flare that occurred on July 31, 2019, confirms the model is correct.

Spitzer Space Telescope. Animation Credit: NASA

The observation of that flare almost didn't happen. Because OJ 287 was on the opposite side of the Sun from Earth, out of view of all telescopes on the ground and in Earth orbit, the black hole wouldn't come back into view of those telescopes until early September, long after the flare had faded. But the system was within view of NASA's Spitzer Space Telescope, which the agency retired in January 2020.

After 16 years of operations, the spacecraft's orbit had placed it 158 million miles (254 million kilometers) from Earth, or more than 600 times the distance between Earth and the Moon. From this vantage point, Spitzer could observe the system from July 31 (the same day the flare was expected to appear) to early September, when OJ 287 would become observable to telescopes on Earth.

"When I first checked the visibility of OJ 287, I was shocked to find that it became visible to Spitzer right on the day when the next flare was predicted to occur," said Seppo Laine, an associate staff scientist at Caltech/IPAC in Pasadena, California, who oversaw Spitzer's observations of the system. "It was extremely fortunate that we would be able to capture the peak of this flare with Spitzer, because no other human-made instruments were capable of achieving this feat at that specific point in time."

Ripples in Space

Scientists regularly model the orbits of small objects in our solar system, like a comet looping around the Sun, taking into account the factors that will most significantly influence their motion. For that comet, the Sun's gravity is usually the dominant force, but the gravitational pull of nearby planets can change its path, too.

Determining the motion of two enormous black holes is much more complex. Scientists must account for factors that might not noticeably impact smaller objects; chief among them are something called gravitational waves. Einstein's theory of general relativity describes gravity as the warping of space by an object's mass. When an object moves through space, the distortions turn into waves. Einstein predicted the existence of gravitational waves in 1916, but they weren't observed directly until 2015 by the Laser Interferometer Gravitational Wave Observatory (LIGO).

The larger an object's mass, the larger and more energetic the gravitational waves it creates. In the OJ 287 system, scientists expect the gravitational waves to be so large that they can carry enough energy away from the system to measurably alter the smaller black hole's orbit - and therefore timing of the flares.

While previous studies of OJ 287 have accounted for gravitational waves, the 2018 model is the most detailed yet. By incorporating information gathered from LIGO's detections of gravitational waves, it refines the window in which a flare is expected to occur to just 1 1/2 days.

To further refine the prediction of the flares to just four hours, the scientists folded in details about the larger black hole's physical characteristics. Specifically, the new model incorporates something called the "no-hair" theorem of black holes.

Published in the 1960s by a group of physicists that included Stephen Hawking, the theorem makes a prediction about the nature of black hole "surfaces." While black holes don't have true surfaces, scientists know there is a boundary around them beyond which nothing - not even light - can escape. Some ideas posit that the outer edge, called the event horizon, could be bumpy or irregular, but the no-hair theorem posits that the "surface" has no such features, not even hair (the theorem's name was a joke).

In other words, if one were to cut the black hole down the middle along its rotational axis, the surface would be symmetric. (The Earth's rotational axis is almost perfectly aligned with its North and South Poles. If you cut the planet in half along that axis and compared the two halves, you would find that our planet is mostly symmetric, though features like oceans and mountains create some small variations between the halves.)

Finding Symmetry

In the 1970s, Caltech professor emeritus Kip Thorne described how this scenario - a satellite orbiting a massive black hole - could potentially reveal whether the black hole's surface was smooth or bumpy. By correctly anticipating the smaller black hole's orbit with such precision, the new model supports the no-hair theorem, meaning our basic understanding of these incredibly strange cosmic objects is correct. The OJ 287 system, in other words, supports the idea that black hole surfaces are symmetric along their rotational axes.

So how does the smoothness of the massive black hole's surface impact the timing of the smaller black hole's orbit? That orbit is determined mostly by the mass of the larger black hole. If it grew more massive or shed some of its heft, that would change the size of smaller black hole's orbit. But the distribution of mass matters as well. A massive bulge on one side of the larger black hole would distort the space around it differently than if the black hole were symmetric. That would then alter the smaller black hole's path as it orbits its companion and measurably change the timing of the black hole's collision with the disk on that particular orbit.

"It is important to black hole scientists that we prove or disprove the no-hair theorem. Without it, we cannot trust that black holes as envisaged by Hawking and others exist at all," said Mauri Valtonen, an astrophysicist at University of Turku in Finland and a coauthor on the paper.

Spitzer science data continues to be analyzed by the science community via the Spitzer data archive located at the Infrared Science Archive housed at IPAC at Caltech in Pasadena. JPL managed Spitzer mission operations for NASA's Science Mission Directorate in Washington. Science operations were conducted at the Spitzer Science Center at IPAC at Caltech. Spacecraft operations were based at Lockheed Martin Space in Littleton, Colorado. Caltech manages JPL for NASA.

For more information about Spitzer, visit:

Image (mentioned), Video (mentioned), Animation (mentioned), Text, Credits: NASA/JPL/Calla Cofield.