A new era of precision for antimatter research

CERN – European Organization for Nuclear Research logo.

April 7, 2018

The ALPHA collaboration has reported the most precise direct measurement of antimatter ever made, revealing the spectral structure of the antihydrogen atom in unprecedented colour. The result, published today in Nature, is the culmination of three decades of research and development at CERN, and opens a completely new era of high-precision tests between matter and antimatter.

The humble hydrogen atom, comprising a single electron orbiting a single proton, is a giant in fundamental physics, underpinning the modern atomic picture. Its spectrum is characterised by well-known spectral lines at certain wavelengths, corresponding to the emission of photons of a certain frequency or colour when electrons jump between different orbits. Measurements of the hydrogen spectrum agree with theoretical predictions at the level of a few parts in a quadrillion (1015) — a stunning achievement that antimatter researchers have long sought to match for antihydrogen.

ALPHA experiment (Image: Maximilien Brice/CERN)

Comparing such measurements with those of antihydrogen atoms, which comprise an antiproton orbited by a positron, tests a fundamental symmetry called charge-parity-time (CPT) invariance. Finding any slight difference between the two would rock the foundations of the Standard Model of particle physics and perhaps shed light on why the universe is made up almost entirely of matter, even though equal amounts of antimatter should have been created in the Big Bang. Until now, however, it has been all but impossible to produce and trap sufficient numbers of delicate antihydrogen atoms, and to acquire the necessary optical interrogation technology, to make serious antihydrogen spectroscopy possible.

The ALPHA team makes antihydrogen atoms by taking antiprotons from CERN’s Antiproton Decelerator (AD) and binding them with positrons from a sodium-22 source. Next it confines the resulting antihydrogen atoms in a magnetic trap, which prevents them from coming into contact with matter and annihilating. Laser light is then shone onto the trapped antihydrogen atoms, their response measured and finally compared with that of hydrogen.

In 2016, the ALPHA team used this approach to measure the frequency of the electronic transition between the lowest-energy state and the first excited state (the so-called 1S to 2S transition) of antihydrogen with a precision of a couple of parts in ten billion, finding good agreement with the equivalent transition in hydrogen. The measurement involved using two laser frequencies — one matching the frequency of the 1S–2S transition in hydrogen and another “detuned” from it — and counting the number of atoms that dropped out of the trap as a result of interactions between the laser and the trapped atoms.

The latest result from ALPHA takes antihydrogen spectroscopy to the next level, using not just one but several detuned laser frequencies, with slightly lower and higher frequencies than the 1S–2S transition frequency in hydrogen. This allowed the team to measure the spectral shape, or spread in colours, of the 1S–2S antihydrogen transition and get a more precise measurement of its frequency. The shape matches that expected for hydrogen extremely well, and ALPHA was able to determine the 1S–2S antihydrogen transition frequency to a precision of a couple of parts in a trillion—a factor of 100 better than the 2016 measurement.

ALPHA: A new era of precision for antimatter research

Video above: ALPHA spokesperson Jeffrey Hangst explains the new results. (Video: Jacques Fichet/CERN).

“The precision achieved in the latest study is the ultimate accomplishment for us,” explains Jeffrey Hangst, spokesperson for the ALPHA experiment. “We have been trying to achieve this precision for 30 years and have finally done it.”

Although the precision still falls short of that for ordinary hydrogen, the rapid progress made by ALPHA suggests hydrogen-like precision in antihydrogen — and thus unprecedented tests of CPT symmetry — are now within reach. “This is real laser spectroscopy with antimatter, and the matter community will take notice,” adds Hangst. “We are realising the whole promise of CERN’s AD facility; it’s a paradigm change.”


CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.

Related links:

Nature: http://dx.doi.org/10.1038/s41586-018-0017-2

Standard Model of particle physics: https://home.cern/about/physics/standard-model

Antiproton Decelerator (AD): https://home.cern/about/accelerators/antiproton-decelerator

For more information about European Organization for Nuclear Research (CERN), Visit: https://home.cern/

Image (mentioned), Video (mentioned), Text, Credits: CERN/Ana Lopes.

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What’s Happening in Orion’s Horsehead Nebula?

The Horsehead Nebula is shown in red and green against the surrounding cold molecular cloud (blue). The red areas are carbon monoxide molecules sheltered in the dense nebula and the green areas are carbon atoms and ions that have been affected by the radiation from nearby stars. Credits: NASA/SOFIA/J. Bally et. al

Two research teams used a map from NASA’s Stratospheric Observatory for Infrared Astronomy, SOFIA, to uncover new findings about stars forming in Orion’s iconic Horsehead Nebula. The map reveals vital details for getting a complete understanding of the dust and gas involved in star formation.

The Horsehead Nebula is embedded in the much larger Orion B giant molecular cloud and is extremely dense, with enough mass to make about 30 Sun-like stars. It marks the boundary between the surrounding cold molecular cloud — filled with the raw materials needed to make stars and planetary systems — and the area to the west where massive stars have already formed. But the radiation from the stars erodes those raw materials. While the cold molecules, like carbon monoxide, deep within the dense nebula are sheltered from this radiation, molecules on the surface are exposed to it. This triggers reactions that can affect star formation, including the transformation of carbon monoxide molecules into carbon atoms and ions, called ionization.

A team, led by John Bally at the Center for Astrophysics and Space Astronomy, at the University of Colorado in Boulder, wanted to learn if the intense radiation from nearby stars is strong enough to compress the gas within the nebula and trigger new star formation. They combined data from SOFIA and two other observatories to get a multifaceted view of the structure and motion of the molecules there.

Bally’s team found that the radiation from the nearby stars creates hot plasma that compresses the cold gas inside the Horsehead, but the compression is insufficient to trigger the birth of additional stars. Nevertheless, they learned key details about the nebula’s structure. 
The radiation caused a destructive ionization wave to crash over the cloud. That wave was stopped by the dense Horsehead portion of the cloud, causing the wave to wrap around it. The Horsehead developed its iconic shape because it was dense enough to block the destructive forces of the ionization wave.

“The shape of the iconic Horsehead Nebula speaks to the movement and velocity of this process,” said Bally. “It really illustrates what happens when a molecular cloud is destroyed by ionized radiation.”
Researchers are trying to understand how stars formed in the Horsehead Nebula —  and why additional stars did not — because its proximity to Earth allows astronomers to study it in great detail. This provides clues to how stars may form in distant galaxies that are too far away for fine details to be observed clearly by even the most powerful telescopes. 
“In studies such as this, we are learning that star formation is a self-limiting process,” said Bally.  “The first stars to form in a cloud can prevent the birth of additional stars nearby by destroying adjacent parts of the cloud.” 
In another study based on SOFIA’s map, a team of researchers lead by Cornelia Pabst, of Leiden University, Netherlands, analyzed the structure and brightness of the gas within cold dark regions in and around the Horsehead Nebula. This region has very little star formation compared to the Orion B Cloud or the Great Nebula in Orion, southwest of the Horsehead Nebula. Pabst and her team wanted to understand the physical conditions in the dark region that may be affecting the star formation rate.
They found that the shape, structure and brightness of the gas in the nebula do not fit existing models. 
Further observations are necessary to explore why the models do not match with what was observed.
“We’re just beginning to understand that, even though we only looked at a very small portion of this molecular cloud, everything is more complicated than what the models initially indicated,” said Pabst. “This map is beautiful, valuable data that we can combine with future observations to help us understand how stars form locally, in our galaxy, so we can then relate that to extragalactic research.”

The studies were published in The Astronomical Journal and Astronomy and Astrophysics

The Horsehead Nebula map used by both teams was created using SOFIA’s upgraded GREAT instrument. It was upgraded to use 14 detectors simultaneously, so the map was created significantly faster than it could have been on previous observatories, which used only a single detector.

“We could not have done this research without SOFIA and its upgraded instrument, upGREAT.” said Bally. “Because it lands after each flight, its instruments can be adjusted, upgraded and improved in ways not possible on space-based observatories. SOFIA is fundamental to developing ever more powerful and reliable instruments for future use in space.”
SOFIA is a Boeing 747SP jetliner modified to carry a 100-inch diameter telescope. It is a joint project of NASA and the German Aerospace Center, DLR. NASA’s Ames Research Center in California’s Silicon Valley manages the SOFIA program, science and mission operations in cooperation with the Universities Space Research Association headquartered in Columbia, Maryland, and the German SOFIA Institute (DSI) at the University of Stuttgart. The aircraft is based at NASA’s Armstrong Flight Research Center’s Hangar 703, in Palmdale, California.

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Space Station Science Highlights: Week of April 2, 2018

ISS – Expedition 55 Mission patch.

April 6, 2018

It has been another exciting week of science aboard the International Space Station. Two days after its Monday launch from Cape Canaveral Air Force Station in Florida, the SpaceX-14 Dragon arrived to the orbiting laboratory with 5,800 pounds of fresh science, hardware and supplies.

This week, Expedition 55 crew members were busy conducting research in the fields of biotechnology, physical science, technology development, education and more.

Animation above: Polar as it is unpacked from the Dragon capsule. Polar is a Cold Stowage managed facility that provides transport and storage of science samples at cryogenic temperatures (-80ºC) to and from the Space Station. Image Credit: NASA.

Following the arrival of SpaceX-14, crew members and ground controls began early activations and transfers of Invitrobone, Multi-use Variable-g Platform (MVP), Fruit Fly Lab-3, Mouse Stress Defense, NanoRacks-NDC-CCSJ-Beta-Amyloid Peptide and Tangolab Payload Card-6, which houses a few different investigations.

Take a look at some of the science that happened this week aboard your orbiting laboratory:

Crew members collect body samples to create baseline standard for station

The Microbial Observatory of Pathogenic Viruses, Bacteria, and Fungi Project (Microbial Tracking-2) investigation seeks to catalog and characterize potential disease-causing microorganisms aboard the space station. The development of an all-encompassing, integrated, comprehensive microbial database enables various strategies of screening for, and identifying, specific subsets of microorganisms. This dataset creates a capability to compare fluctuating viral and microbial communities to “baseline” standards, enables more accurate assessments of crew health associated with a given mission and future mission planning.

Image above: The SpaceX Dragon carried more than 5,800 pounds of science, hardware and supplies to the space station. Image Credit: NASA.

This week, a crew member collected saliva and body samples and inserted them into the Minus Eighty Degree Celsius Laboratory Freezer for ISS (MELFI) for storage before completing a body sample questionnaire.

ACME chamber prepared for initiation of experiment

The Advanced Combustion Microgravity Experiment (ACME) investigation is a set of five independent studies of gaseous flames to be conducted in the Combustion Integration Rack (CIR), one of which being E-Fields Flame. ACME’s goals are to improve fuel efficiency and reduce pollutant production in practical combustion on Earth and to improve spacecraft fire prevention through innovative research focused on materials flammability.

This week, crew members removed the ACME Mesh negative Power Supply and installed the ACME Mesh Positive Power Supply, replaced an ignitor tip and replaced other hardware within the chamber, all in preparation for the next series of data collection with a positive field.

Crew conducts successful trial runs for SmoothNav investigation

Many future space exploration and space-based business enterprise models, such as on-orbit satellite servicing, on-orbit assembly, and orbital debris removal, necessitate the use of fully autonomous multi-satellite systems. Smoothing-Based Relative Navigation (SmoothNav) develops an estimation algorithm aggregating relative state measurements between multiple, small, and potentially differently-instrumented spacecraft.

Image above: NASA astronaut Drew Feustel conducts a test run as a part of the SmoothNav investigation. Image Credit: NASA.

The algorithm obtains the most probable estimate of the relative positions and velocities between all spacecraft using all available sensor information, including past measurements. The algorithm remains portable between different satellite platforms with different onboard sensors, adaptable in the case that one or more satellites become inoperable, and tolerant to delayed measurements or measurements received at different frequencies.

This week, the crew completed 15 test runs without any software errors.

Crew preps JAXA investigation for initiation

Spaceflight brings an extreme environment with unique stressors. Exposure to cosmic radiation increases intracellular oxidative stresses, which can lead to DNA damage and cell death. Microgravity provokes cellular mechanical stresses and perturbs cellular signaling, leading to reduction of muscle and bone density. To overcome these space stresses, one of the promising strategies is to activate Nuclear Factor-like 2 (Nrf2), a master regulator of antioxidant pathway. Mouse Stress Defense, a JAXA investigation, tests genetically modified loss-of-Nrf2-function and gain-of-Nrf2-function in mice in the space environment and examines how Nrf2 contributes to effective prevention against the space-originated stresses.

Space to Ground: A Learning Doubleheader: 04/06/2018

This week, crew members prepped and transferred the investigation from the Dragon capsule.

Other work was done on these investigations: Crew Earth Observations, CBEF, Polar, Veg-03, STP-H5 ICE, METEOR, MSG, Food Acceptability, EarthKAM, HDEV, METEOR, HDEV, SCAN Testbed, Metabolic Tracking, HRF-2, SPHERES Tether Slosh and Lighting Effects.

Related links:

SpaceX-14 Dragon: https://www.nasa.gov/mission_pages/station/research/SpX-14_research_launch_feature

Invitrobone: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7355

Multi-use Variable-g Platform (MVP): https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=1777

Fruit Fly Lab-3: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1774

NanoRacks-NDC-CCSJ-Beta-Amyloid Peptide: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7497

Tangolab Payload Card-6: http://www.spacetango.com/blog/2018/4/1/whats-flying-a-look-at-space-tango-crs-14-payloads

Microbial Tracking-2: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1663

Minus Eighty Degree Celsius Laboratory Freezer for ISS (MELFI): https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=56

Advanced Combustion Microgravity Experiment (ACME): https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1651

Combustion Integration Rack (CIR): https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=317

E-Fields Flame: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=2058

Crew Earth Observations: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=84

CBEF: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=333

Polar: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=1092

Veg-03: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1159

STP-H5 ICE: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1749

METEOR: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1174

MSG: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=341

Food Acceptability: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7562

EarthKAM: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=87

HDEV: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=892

SCAN Testbed: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=156

Metabolic Tracking: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7517

HRF-2: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7517

SPHERES Tether Slosh: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7381

Lighting Effects: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=2013

Expedition 55: https://www.nasa.gov/sites/default/files/atoms/files/exp-55-summary.pdf

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), Animation (mentioned), Video, Text, Credits: NASA/Michael Johnson/Yuri Guinart-Ramirez, Lead Increment Scientist Expeditions 55 & 56.

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