'Lost' world rediscovery is step toward finding habitable planets

Agencies
July 21, 2020

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Washington D.C., Jul 21: The rediscovery of a lost planet could pave the way for the detection of a world within the habitable 'Goldilocks zone' in a distant solar system.

The planet, the size, and mass of Saturn with an orbit of 35 days is among hundreds of 'lost' worlds that University of Warwick astronomers are pioneering a new method to track down and characterise in the hope of finding cooler planets like those in our Solar System and even potentially habitable planets.

Reported in Astrophysical Journal Letters, the planet named NGTS-11b orbits a star 620 light-years away and is located five times closer to its sun than Earth is to our own.

The planet was originally found in a search for planets in 2018 by the Warwick-led team using data from NASA's TESS telescope. This uses the transit method to spot planets, scanning for the telltale dip in light from the star that indicates that an object has passed between the telescope and the star. However, TESS only scans most sections of the sky for 27 days.

This means many of the longer period planets only transit once in the TESS data. And without a second observation the planet is effectively lost. The University of Warwick-led team followed up one of these 'lost' planets using the telescopes at the Next-Generation Transit Survey (NGTS) in Chile and observed the star for seventy-nine nights, eventually catching the planet transiting for a second time nearly a year after the first detected transit.

"By chasing that second transit down we've found a longer period planet. It's the first of hopefully many such finds pushing to longer periods. These discoveries are rare but important since they allow us to find longer period planets than other astronomers are finding. Longer period planets are cooler, more like the planets in our own solar system," said Dr. Samuel Gill from the Department of Physics at the University of Warwick.

"NGTS-11b has a temperature of only 160°C -- cooler than Mercury and Venus. Although this is still too hot to support life as we know it, it is closer to the Goldilocks zone than many previously discovered planets which typically have temperatures above 1,000°C," added Gill.

The Goldilocks zone refers to a range of orbits that would allow a planet or moon to support liquid water: too close to its star and it will be too hot, but too far away and it will be too cold.

"This planet is out at a thirty-five days orbit, which is a much longer period than we usually find them. It is exciting to see the Goldilocks zone within our sights," said Co-author Dr. Daniel Bayliss from the University of Warwick.

"The original transit appeared just once in the TESS data, and it was our team's painstaking detective work that allowed us to find it again a year later with NGTS," said Co-author Professor Pete Wheatley from the University of Warwick.

"NGTS has twelve state-of-the-art telescopes, which means that we can monitor multiple stars for months on end, searching for lost planets. The dip in light from the transit is only 1 percent deep and occurs only once every 35 days, putting it out of reach of other telescopes," added Wheatley.

"There are hundreds of single transits detected by TESS that we will be monitoring using this method. This will allow us to discover cooler exoplanets of all sizes, including planets more like those in our own solar system. Some of these will be small rocky planets in the Goldilocks zone that are cool enough to host liquid water oceans and potentially extraterrestrial life," said Dr. Gill.

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Agencies
September 14,2020

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Washington, Sept 14: The detection more than a decade ago by the Fermi Gamma-ray Space Telescope of an excess of high-energy radiation in the centre of the Milky Way convinced some physicists that they were seeing evidence of the annihilation of dark matter particles, but a team led by a researcher at the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) has ruled out that interpretation.

In a paper published recently in the journal Physical Review D, the Kavli IPMU project researcher Oscar Macias and colleagues at other institutions report that -- through an analysis of the Fermi data and an exhaustive series of modelling exercises -- they were able to determine that the observed gamma rays could not have been produced by what are called weakly interacting massive particles (WIMPS), most popularly theorised as the stuff of dark matter.

"The crucial point of our recent paper is that our approach covers the wide range of astrophysical background models that have been used to infer the existence of the galactic centre excess, and goes beyond them. So, using any of our state-of-the-art background models, we find no need for a dark matter component to be included in our model for this sky region. This allows us to impose very stringent constraints on particle dark matter models," said Macias.

By eliminating these particles, the destruction of which could generate energies of up to 300 giga-electron volts, the paper's authors say, they have put the strongest constraints yet on dark matter properties.

"For 40 years or so, the leading candidate for dark matter among particle physicists was a thermal, weakly interacting and weak-scale particle, and this result for the first time rules out that candidate up to very high-mass particles," said co-author Kevork Abazajian, professor of physics and astronomy at the University of California, Irvine (UCI).

"In many models, this particle ranges from 10 to 1,000 times the mass of a proton, with more massive particles being less attractive theoretically as a dark matter particle," added co-author Manoj Kaplinghat, also a UCI professor of physics and astronomy. "In this paper, we're eliminating dark matter candidates over the favoured range, which is a huge improvement in the constraints we put on the possibilities that these are representative of dark matter."

Abazajian said that dark matter signals could be crowded out by other astrophysical phenomena in the galactic centre -- such as star formation, cosmic ray deflection off molecular gas and, most notably, neutron stars and millisecond pulsars -- as sources of excess gamma rays detected by the Fermi space telescope.

"We looked at all of the different modellings that goes on in the galactic centre, including molecular gas, stellar emissions and high-energy electrons that scatter low-energy photons," said Kavli IPMU's Macias. "We took over three years to pull all of these new, better models together and examine the emissions, finding that there is little room left for dark matter."

Macias, who is also a postdoctoral researcher with the GRAPPA Centre at the University of Amsterdam, added that this result would not have been possible without data and software provided by the Fermi Large Area Telescope collaboration.

The group tested all classes of models used in the galactic centre region for excess emission analyses, and its conclusions remained unchanged. "One would have to craft a diffuse emission model that leaves a big 'hole' in them to relax our constraints, and science doesn't work that way," Macias said.

Kaplinghat noted that physicists have predicted that radiation from dark matter annihilation would be represented in a neat spherical or elliptical shape emanating from the galactic centre, but the gamma-ray excess detected by the Fermi space telescope after its June 2008 deployment shows up as a triaxial, bar-like structure.

"If you peer at the galactic centre, you see that the stars are distributed in a boxy way," he said. "There's a disk of stars, and right in the centre, there's a bulge that's about 10 degrees on the sky, and it's actually a very specific shape -- sort of an asymmetric box -- and this shape leaves very little room for additional dark matter."

Does this research rule out the existence of dark matter in the galaxy? "No," Kaplinghat said. "Our study constrains the kind of particle that dark matter could be. The multiple lines of evidence for dark matter in the galaxy are robust and unaffected by our work."

Far from considering the team's findings to be discouraging, Abazajian said they should encourage physicists to focus on concepts other than the most popular ones.

"There are a lot of alternative dark matter candidates out there," he said. "The search is going to be more like a fishing expedition where you don't already know where the fish are."

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Agencies
September 14,2020

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Washington, Sept 14: A rare molecule -- phosphine -- has been detected in the atmosphere of Venus, an international team of astronomers announced today leading to speculation of life on Earth's nearest planetary neighbour.

On Earth, this gas is only made industrially or by microbes that thrive in oxygen-free environments.

Astronomers have speculated for decades that high clouds on Venus could offer a home for microbes -- floating free of the scorching surface but needing to tolerate very high acidity. The detection of phosphine could point to such extra-terrestrial "aerial" life.
"When we got the first hints of phosphine in Venus's spectrum, it was a shock!," says team leader Jane Greaves of Cardiff University in the UK, who first spotted signs of phosphine in observations from the James Clerk Maxwell Telescope, operated by the East Asian Observatory, in Hawaii.

The study was published today in a new paper in the journal Nature Astronomy

Confirming their discovery required using 45 antennas of the Atacama Large Millimeter/submillimeter Array (ALMA, in Chile, a more sensitive telescope in which the European Southern Observatory (ESO) is a partner. Both facilities observed Venus at a wavelength of about 1 millimetre, much longer than the human eye can see -- only telescopes at high altitude can detect it effectively.

The international team, which includes researchers from the UK, US and Japan, estimates that phosphine exists in Venus's clouds at a small concentration, only about 20 molecules in every billion.

Following their observations, they ran calculations to see whether these amounts could come from natural non-biological processes on the planet. Some ideas included sunlight, minerals blown upwards from the surface, volcanoes, or lightning, but none of these could make anywhere near enough of it. These non-biological sources were found to make at most one 10,000th of the amount of phosphine that the telescopes saw.

To create the observed quantity of phosphine (which consists of hydrogen and phosphorus) on Venus, terrestrial organisms would only need to work at about 10% of their maximum productivity, according to the team. Earth bacteria are known to make phosphine: they take up phosphate from minerals or biological material, add hydrogen, and ultimately expel phosphine. Any organisms on Venus will probably be very different to their Earth cousins, but they too could be the source of phosphine in the atmosphere.
While the discovery of phosphine in Venus's clouds came as a surprise, the researchers are confident in their detection.
"To our great relief, the conditions were good at ALMA for follow-up observations while Venus was at a suitable angle to Earth. Processing the data was tricky, though, as ALMA isn't usually looking for very subtle effects in very bright objects like Venus," says team member Anita Richards of the UK ALMA Regional Centre and the University of Manchester.

"In the end, we found that both observatories had seen the same thing -- faint absorption at the right wavelength to be phosphine gas, where the molecules are backlit by the warmer clouds below," adds Greaves, who led the study.

Another team member, Clara Sousa Silva of the Massachusetts Institute of Technology in the US, has investigated phosphine as a "biosignature" gas of non-oxygen-using life on planets around other stars, because normal chemistry makes so little of it. She comments: "Finding phosphine on Venus was an unexpected bonus! The discovery raises many questions, such as how any organisms could survive. On Earth, some microbes can cope with up to about 5% of acid in their environment -- but the clouds of Venus are almost entirely made of acid."

The team believes their discovery is significant because they can rule out many alternative ways to make phosphine, but they acknowledge that confirming the presence of "life" needs a lot more work. Although the high clouds of Venus have temperatures up to a pleasant 30 degrees Celsius, they are incredibly acidic -- around 90% sulphuric acid -- posing major issues for any microbes trying to survive there.

ESO astronomer and ALMA European Operations Manager Leonardo Testi, who did not participate in the new study, says: "The non-biological production of phosphine on Venus is excluded by our current understanding of phosphine chemistry in rocky planets' atmospheres. Confirming the existence of life on Venus's atmosphere would be a major breakthrough for astrobiology; thus, it is essential to follow-up on this exciting result with theoretical and observational studies to exclude the possibility that phosphine on rocky planets may also have a chemical origin different than on Earth."

More observations of Venus and of rocky planets outside our solar system, including with ESO's forthcoming Extremely Large Telescope, may help gather clues on how phosphine can originate on them and contribute to the search for signs of life beyond Earth. 

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Agencies
September 27,2020

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Washington, Sept 27: To understand how it functions and to shed light on what goes awry in cardiovascular disease, scientists have created a detailed cellular and molecular map of the healthy heart.

Scientists have created a detailed cellular and molecular map of the healthy human heart to understand how this vital organ functions and to shed light on what goes awry in cardiovascular disease.

The work, published in the journal Nature, was led by investigators at Harvard Medical School, Brigham and Women's Hospital, the Wellcome Sanger Institute, Max Delbruck Center for Molecular Medicine (MDC) in Germany, Imperial College London, and their global collaborators.

The team analysed almost a half-million individual cells to build the most extensive cell atlas of the human heart to date.

The atlas shows the huge diversity of cells and reveals heart muscle cell types, cardiac protective immune cells, and an intricate network of blood vessels. It also predicts how the cells communicate to keep the heart working.

The research is part of the Human Cell Atlas initiative to map every cell type in the human body.

The new molecular and cellular knowledge of the heart promises to enable a better understanding of heart disease and guide the development of highly individualized treatments.

The work also sets the stage for therapies based on regenerative medicine in the future, the researchers said.

Over a lifetime, the average human heart delivers more than 2 billion life-sustaining beats to the body. In doing so, it helps deliver oxygen and nutrients to cells, tissues and organs and enables the removal of carbon dioxide and waste products.

Each day, the heart beats around 100,000 times with a one-way flow through four different chambers, varying speed with rest, exercise, and stress. Every beat requires an exquisitely complex but perfect synchronization across various cells in different parts of the heart.

When this complex coordination goes bad, it can result in cardiovascular disease, the leading cause of death worldwide, killing an estimated 17.9 million people each year.

Detailing the molecular processes inside the cells of a healthy heart is critical to understanding how things go awry in heart disease. Such knowledge can lead to more precise, better treatment strategies for various forms of cardiovascular illness.

"Millions of people are undergoing treatments for cardiovascular diseases. Understanding the healthy heart will help us understand interactions between cell types and cell states that can allow lifelong function and how these differ in diseases," said study co-senior author Christine Seidman, professor of medicine in the Blavatnik Institute at Harvard Medical School and a cardiovascular geneticist at Brigham and Women's.

"Ultimately, these fundamental insights may suggest specific targets that can lead to individualized therapies in the future, creating personalized medicines for heart disease and improving the effectiveness of treatments for each patient," Seidman said.

The team studied nearly 500,000 individual cells and cell nuclei from six different regions of the heart obtained from 14 organ donors whose hearts were healthy but unsuitable for transplantation.

Using a combination of single-cell analysis, machine learning and imaging techniques, the team could see exactly which genes were switched on and off in each cell.

The researchers discovered major differences in the cells in different areas of the heart. They also observed that each area of the heart had specific subsets of cells--a finding that points to different developmental origins and suggests that these cells would respond differently to treatments.

"This project marks the beginning of new understandings into how the heart is built from single cells, many with different cell states," said study co-first author Daniel Reichart, research fellow in genetics at Harvard Medical School.

"With knowledge of the regional differences throughout the heart, we can begin to consider the effects of age, exercise and disease and help push the field of cardiology toward the era of precision medicine," added Reichart.

"This is the first time anyone has looked at the single cells of the human heart at this scale, which has only become possible with large-scale single-cell sequencing," said Norbert Hubner, co-senior author and professor at Max Delbruck Center for Molecular Medicine. "This study shows the power of single-cell genomics and international collaboration," he added.

"Knowledge of the full range of cardiac cells and their gene activity is a fundamental necessity to understand how the heart functions and to start to unravel how it responds to stress and disease," added Hubner.

As part of this study, the researchers also looked at blood vessels running through the heart in unprecedented detail. The atlas showed how the cells in these veins and arteries are adapted to the different pressures and locations and how this could help researchers understand what goes wrong in blood vessels during coronary heart disease.

"Our international effort provides an invaluable set of information to the scientific community by illuminating the cellular and molecular details of cardiac cells that work together to pump blood around the body," said co-senior author Michela Noseda of Imperial College, London.

"We mapped the cardiac cells that can be potentially infected by SARS-CoV-2 and found that specialized cells of the small blood vessels are also virus targets. Our datasets are a goldmine of information to understand subtleties of heart disease," she added.

The researchers also focused on understanding cardiac repair, looking at how the immune cells interact and communicate with other cells in the healthy heart and how this differs from skeletal muscle.

Further research will include investigating whether any heart cells could be induced to repair themselves.

"This great collaborative effort is part of the global Human Cell Atlas initiative to create a 'Google map' of the human body," said Sarah Teichmann of the Wellcome Sanger Institute, co-senior author of the study and co-chair of the Human Cell Atlas Organising Committee.

"Openly available to researchers worldwide, the Heart Cell Atlas is a fantastic resource, which will lead to a new understanding of heart health and disease, new treatments and potentially even finding ways of regenerating damaged heart tissue," she added.

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