Astrophysicists Observe Long-Theorized Quantum Phenomena

At the heart of every white dwarf star - the dense stellar object that remains after a star has burned away its fuel reserve of gases as it nears the end of its life cycle - lies a quantum conundrum: as white dwarfs add mass, they shrink in size, until they become so small and tightly compacted that they cannot sustain themselves, collapsing into a neutron star. This puzzling relationship between a white dwarf's mass and size - called the mass-radius relation - was first theorized by Nobel Prize-winning astrophysicist Subrahmanyan Chandrasekhar in the 1930s. Now, a team of Johns Hopkins astrophysicists has developed a method to observe the phenomenon itself using astronomical data collected by the Sloan Digital Sky Survey and a recent dataset released by the Gaia Space Observatory. The combined datasets provided more than 3,000 white dwarfs for the team to study. A report of their findings, led by Hopkins senior Vedant Chandra, is now in press in the Astrophysical Journal and available online on arXiv. "The mass-radius relation is a spectacular combination of quantum mechanics and gravity, but it's counterintuitive for us - we think that as an object gains mass, it should get bigger," says Nadia Zakamska, an associate professor in the Department of Physics and Astronomy who supervised the student researchers. "The theory has existed for a long time, but what's notable is that the dataset we used is of unprecedented size and unprecedented accuracy. These measurement methods, which in some cases were developed years ago, all of a sudden work so much better and these old theories can finally be probed."

The team obtained their results using a combination of measurements, including primarily the gravitational redshift effect, which is the change of wavelengths of light from blue to red as light moves away from an object. It is a direct result of Einstein's general theory of relativity.

"To me, the beauty of this work is that we all learn these theories about how light will be affected by gravity in school and in textbooks, but now we actually see that relationship in the stars themselves," says fifth-year graduate student Hsiang-Chih Hwang, who proposed the study and first recognized the gravitational redshift effect in the data.

The team also had to account for how a star's movement through space might affect the perception of its gravitational redshift. Similar to how a fire engine siren changes pitch according to its movement in relation to the person listening, light frequencies also change depending on movement of the light-emitting object in relation to the observer. This is called the Doppler effect, and is essentially a distracting "noise" that complicates the measurement of the gravitational redshift effect, says study contributor Sihao Cheng, a fourth-year graduate student.

To account for the variations caused by the Doppler effect, the team classified white dwarfs in their sample set by radius. They then averaged the redshifts of stars of a similar size, effectively determining that no matter where a star itself is located or where it's moving in relation to Earth, it can be expected to have an intrinsic gravitational redshift of a certain value.

Think of it as taking an average measurement of all the pitches of all fire engines moving around in a given area at a given time - you can expect that any fire engine, no matter which direction it's moving, will have an intrinsic pitch of that average value.

These intrinsic gravitational redshift values can be used to study stars that are observed in future datasets. The researchers say that upcoming datasets that are larger and more accurate will allow for further fine-tuning of their measurements, and that this data may contribute to the future analysis of white dwarf chemical composition.

They also say their study represents an exciting advance from theory to observed phenomena.

"Because the star gets smaller as it gets more massive, the gravitational redshift effect also grows with mass," Zakamska says. "And this is a bit easier to comprehend - it's easier to get out of a less dense, bigger object than it is to get out of a more massive, more compact object. And that's exactly what we saw in the data."

The team is even finding captive audiences for their research at home - where they've conducted their work amid the coronavirus pandemic.

"The way I extolled it to my granddad is, you're basically seeing quantum mechanics and Einstein's theory of general relativity coming together to produce this result," Chandra says. "He was very excited when I put it that way."

Universe Is More Homogeneous Than Expected

New results from the Kilo-Degree Survey (KiDS) show that the universe is nearly 10 percent more homogeneous than the standard model of cosmology (Lambda-cold dark matter) predicts. The latest KiDS map was made with the OmegaCAM on ESO's VLT Survey Telescope at Cerro Paranal in Northern Chile. A group of astronomers led from institutes in the Netherlands, Scotland, England and Germany have described the KiDS-1000 result in five articles, the last three of which appeared online last week. They have been submitted for publication in the journal Astronomy and Astrophysics. The new KiDS map covers about 1,000 square degrees, which equates to 5% of the extragalactic sky. 31 million galaxies were used for the analysis. The galaxies are up to 10 billion light-years away, which means their light was emitted when our universe was less than half its present age. KiDS uses the galaxies to map the distribution of matter in the universe. This is done through weak gravitational lensing, where the light from distant galaxies is slightly deflected by the gravitational effect of large amounts of matter, such as galaxy clusters. That effect is used to determine the "clumpiness" of the distribution of the galaxies. This concerns all matter in the universe, of which more than 90 percent consists of invisible dark matter plus invisible tenuous gas.

Over time, the gravity of matter in the universe makes it less and less homogeneous; areas with a little more mass than average attract matter from their surroundings, so increasing the contrast. Meanwhile the expansion of the universe counteracts this growth. Both of these processes are gravity driven and are therefore of great importance for testing the standard model of cosmology, which fairly accurately predicts how density variations increase with the age of the universe.

However, the new KiDS results show a discrepancy: the universe is nearly 10 percent more homogeneous than the standard model predicts.

Dr. Marika Asgari, from the University of Edinburgh, who co-led the analysis, calls the result "intriguing." "The standard model of cosmology relies on rather mysterious physics that we call dark matter and dark energy. Scientists have to test this remarkable model in as many ways as possible, and that is exactly what we are doing."

The KiDS results may indicate small cracks in the standard model, just like another discrepancy in the expansion rate of the universe, the so-called Hubble constant. Dr. Tilman Troster (University of Edinburgh): "The question is whether these can be solved with a small adjustment, for example with a somewhat more complex behavior of dark matter than the simple hypothesis of totally inert 'cold dark matter.'"

Leiden professor and KiDS lead Koen Kuijken cannot say whether this will eventually lead to a fundamentally different theory, for example replacing Einstein's general theory of relativity with a new one. "For now, I consciously try to stay away from possible theoretical interpretations, and focus on the measurements and how to make them as accurate as possible."

Prof. Hendrik Hildebrandt (Ruhr University Bochum) adds: "As an observing cosmologist, you try to remain impartial and make the measurements as accurate as possible without theoretical prejudices. One thing is clear: we live in exciting times!"

The team will need more data to be absolutely sure about the results. "There is a 1 in a 1,000 chance that our findings could be caused by us just having looked at a particularly unusual part of the universe," says Dr. Benjamin Joachimi (University College London)."

In one to two years, the final 'legacy' KiDS map will be published, 30% larger than the current one. It will include all KiDS observations.

Two other projects, one American and one Japanese, are also working on similar analyses from other observatories. From 2022, the baton will be passed on to even more powerful telescopes: the Rubin telescope, which will be more than 60 times as powerful as the VST, and the Euclid satellite, which will take much sharper images from outside the atmosphere than is possible from the ground.

Edinburgh Professor Catherine Heymans, says: "With these two new facilities, we will chart the dark matter across the full sky and confront a wide range of different theoretical models to truly understand the mysterious dark side of our universe."

A European dream team for Mars

European scientists will help select rocks and soil from Mars in the search for life on our planetary neighbour. Five European researchers are part of NASA's Mars 2020 science team to select the most promising martian samples bound for Earth. The mission to Mars launched last week for its seven-month journey to the Red Planet. Once there, the team will guide the Perseverance rover as it hunts for evidence of ancient microbial life. The group is made up of researchers from Belgium, France, Sweden and the UK. "These top scientists from across Europe are experts on how to collect, analyse and read the history of the rocks under our feet. Now they will also have to anticipate the needs and challenges of working with martian samples returned to laboratories back on Earth," says ESA's Mars Sample Return acting programme scientist Gerhard Kminek. For the next three years, the team will be at the core of a wider NASA team. Mark Sephton, Professor of organic geochemistry at Imperial College London in the UK, sees it as "a fantastic opportunity to have some of the finest minds in the world come together to solve one of the biggest questions in the Solar System: was there life on Mars?" Sandra Siljestrom, from Sweden's research institute RISE, dreams of having the "Bring it to me now!" feeling while remotely analysing a rock spotted on Mars at the rover landing site - the Jezero crater. The area contains sediments of an ancient river delta, where evidence of past life could be preserved if it ever existed on the planet.

Once the Perseverance rover retrieves samples of rock and soil from Mars, it will seal them in canisters and drop them on the surface to be collected by a future retrieval mission.

"The Mars 2020 mission is the first step for the ultimate martian challenge: the Mars Sample Return campaign. NASA and ESA aim to deliver the material from the martian surface to Earth by 2031," adds Gerhard.

To bring Mars samples to Earth, three carefully timed missions are required.

NASA will deliver the ESA Sample Fetch Rover to the vicinity of the Mars 2020 landing site. This European rover will autonomously track down and collect up to 36 sample tubes deposited by Perseverance, and take them to NASA's Mars Ascent vehicle.

Better together
The team of European scientists believes the road to Mars and back to Earth is like a long-distance run that is best undertaken together.

"I hope that, as a group of scientists with diverse expertise, we will help maximise the quality, depth and breadth of research possible with the returned samples," says palaeontologist Keyron Hickman-Lewis, who has closely worked with ESA's ExoMars rover team.

No place like Mars
Mars is currently the only planetary body accessible to humans on which scientists expect to find relatively unspoilt geological records from the early history of the Solar System.

Finding traces of life "would represent an incredible discovery and a be a gamechanger for our views on how organisms emerge," says cosmochemist Frederic Moynier.

There is no place quite like Mars to find out whether the conditions for supporting life ever existed beyond Earth.

"The Red Planet is the perfect laboratory to check as the environment has dramatically changed over time," says Vinciane Debaille , geochemist at the Universite Libre de Bruxelles, in Belgium.

Sandra has little doubt, "there will be surprises when we land on Mars". She and her new team cannot wait to receive the first data.

Amazon to invest $10 bn in space-based internet system

Amazon says it will invest $10 billion for its planned space-based internet delivery system after winning US regulatory approval to deploy more than 3,000 low-orbit satellites. The US tech giant said on Thursday it is moving forward with its Project Kuiper, one of several systems planned to bring internet to customers without land-based connections. Project Kuiper aims to deliver satellite-based broadband services in the United States, and eventually around the world, and may offer connectively for wireless carriers and 5G networks. Amazon offer no timetable for the project but said it would begin deployment of its 3,236 satellites after the Federal Communications Commission approved the project. "We have heard so many stories lately about people who are unable to do their job or complete schoolwork because they don't have reliable internet at home," said Amazon senior vice president Dave Limp. "There are still too many places where broadband access is unreliable or where it doesn't exist at all. Kuiper will change that. Our $10 billion investment will create jobs and infrastructure around the United States that will help us close this gap." Project Kuiper seeks to deliver high-speed broadband service to places beyond the reach of traditional fiber or wireless networks, including disaster relief. It will be aimed at individual households, as well as schools, hospitals, businesses and other organizations.

An Amazon statement said the project also aims to "deliver an affordable customer terminal that will make fast, reliable broadband accessible to communities around the world."

Kuiper is one of several projects to deliver internet from space begun over the past decades.

Elon Musk's SpaceX and British-based OneWeb, which filed for bankruptcy earlier this year, are working on similar projects.

New Space satellite pinpoints industrial methane emissions

Methane may not be as abundant in the atmosphere as carbon dioxide, but with a global warming potential many times greater than carbon dioxide, monitoring and controlling industrial emissions of this potent gas is imperative to helping combat climate change. GHGSat is a New Space initiative that draws on Copernicus Sentinel-5P data for mapping methane hotspots - and its Claire satellite has now collected more than 60 000 methane measurements of industrial facilities around the world. Copernicus Sentinel-5P's role is to map a range of atmospheric gases around the globe every 24 hours. Its Tropomi spectrometer delivers data with a resolution as high as 7 km + 5.5 km for methane, but these data can't be used to pinpoint specific facilities responsible for emissions. However, GHGSat's demonstration satellite 'Claire' can, but it is helped with a bit of guidance from Sentinel-5P. Drawing on Sentinel-5P data, the GHGSat tasks Claire to home in on methane point sources. Using this approach, GHGSat has been able to attribute large methane leaks to specific industrial facilities. This is catching the attention of managers responsible for emissions from industries such as oil and gas, waste management, mining, agriculture and power generation. The Climate Investments arm of the Oil and Gas Climate Initiative (OGCI) has taken particular interest, including an investment in GHGSat. Managing Director of Ventures for OGCI Climate Investments, Rhea Hamilton, says, "GHGSat's methane monitoring product has achieved impressive results and is attractive to oil and gas operators.

"The company has identified significant methane leaks and supported operators in understanding the results, prompting corrective action. OGCI Climate Investments looks forward to watching GHGSat grow to serve more operators."

Following on from the Claire demonstrator, GHGSat plans to have a constellation of 10 satellites operating by 2022. The next satellite, Iris, which will be able to spot even smaller methane leaks, is one of the 53 satellites that will be launched on the Vega VV16 flight, scheduled for mid-August.

ESA's Director of Earth Observation Programmes, Josef Aschbacher, commented, "Copernicus Sentinel-5P and Claire working together is a prime example of institutional satellites working hand in hand with commercial satellites, a concept that is taking Earth observation into a new era.

"We are very much looking forward to seeing Iris launch as a next step towards better greenhouse gas monitoring."

Iris will offer a spatial resolution of 25 m compared to Claire's 50 m resolution, therefore allowing methane to be traced even more accurately.

Alongside augmented satellite performance coming from Iris, GHGSat is addressing a growing demand for analytics services and predictive models. For example, dedicated methane analytics and reporting is possible for asset managers and stakeholders responsible for environmental, social and governance (ESG) factors for understanding investment risk and growth opportunity.

GHGSat President and CEO, Stephane Germain, makes analytics a priority to answer specific market needs.

He comments, "GHGSat's analytics are of growing interest for industrial operators in all sectors, as they are accelerating their efforts to mitigate emissions. With this in mind, GHGSat is building on its expertise in Canada and has advanced plans for an international analytics centre delivering for ESG in the financial sector."

In anticipation of the data from Iris, ESA, the Canadian Space Agency and GHGSat have teamed up through an announcement of opportunity to make 5% of Iris data freely available for research purposes.