Latest city-level emission accounting in China: cities are on the track toward net-zero emissions and 38 have achieved emission peak

Peer-Reviewed Publication

SCIENCE CHINA PRESS

 

IMAGE: 38 CITIES HAVE PROACTIVELY PEAKED THEIR EMISSIONS FOR AT LEAST FIVE YEARS AND 21 CITIES HAVE REDUCED EMISSIONS PASSIVELY. ANOTHER 20 CITIES ARE AT A PLATEAU PHASE OF EMISSIONS. THE REMAINING 139 CITIES ARE STILL INCREASING THEIR EMISSIONS. view more 

CREDIT: ©SCIENCE CHINA PRESS

This study is led by Assoc. Prof. Yuli Shan (University of Birmingham / University of Groningen), Yuru Guan (PhD researcher, University of Groningen), Prof. Dabo Guan (Tsinghua University), Prof Klaus Hubacek (University of Groningen) and 5 other researchers. The study presents the most comprehensive and long-reaching time series (2001 to 2019) of CO2 emission inventories of 287 Chinese cities, covering 98%+ of China’s population, 99%+ of GDP, and 97%+ of CO2 emissions (compared to the national emissions from EDGAR) in 2014.

The emission inventories were compiled for 47 economic sectors and included energy-related emissions for 17 types of fossil fuels and process-related emissions from cement production. The inventories capture all direct emissions from human economic activities within the city boundary based on the administrative-territorial accounting approach recommended by the Intergovernmental Panel on Climate Change (IPCC). Dr Shan tells us “This accounting approach has been widely used for designing low-carbon policies and allocating responsibility for global climate change targets”. “It's also worth mentioning that the emission factors of fossil fuels we used were collected from our previous studies, which are based on a wide survey of over 4,243 state-owned Chinese coal mines in China”, Dr Shan emphasizes.

Prof. Guan mentions that “this city-level emission estimates are consistent with our CEADs team’s previous accounting of national and provincial emissions in terms of methods, scope, and data sources. So, we are now able to compare emissions across scales”. Prof. Guan and Dr. Shan have established an open-access dataset called CEADs (Carbon Emission Accounts and Datasets for Emerging Economies) since 2016. CEADs team works on the emission accounting methods and applications for China and other emerging economies. Dr Shan is the subject leader in environmental accounting and Prof. Guan is the founder of CEADs.

Based on the long time-series city-level emission data, Dr Shan and his colleagues tested the status of the emissions peak in 287 Chinese cities based on several conditional functions, the Mann-Kendall (MK) trend test, and cities’ decoupling of emissions and social development indexes (e.g., level of economic development and size of the population). The MK trend test is a nonparametric statistical method recommended by the World Meteorological Organization (WMO) and has been widely used to detect time-series trends of climate sequences.

They found that 38 Chinese cities have proactively peaked their emissions (i.e., cities reduced emissions significantly for at least five years while economy and population kept increasing), 21 cities have passively declined their emissions (i.e., cities have achieved emission decline for more than five years but their economy or population also decreased during the same period), 20 cities are at a plateau phase (i.e., emissions declined for more than five years but might rebound to a higher level afterward), and the remaining 139 cities are still increasing their emissions or reduced emissions temporarily for less than five years. Looking into the emission drivers in each city, Dr Shan found that proactively peaked cities have achieved emission decline mainly due to efficiency improvements and structural changes in energy use, while passively emission declined cities have an economic recession or population loss as one possible reason for emission decline.

This study provides policy recommendations for achieving emission peaks and carbon neutrality in different types of cities. “It is not easy to reduce every ton of emissions”, Dr Shan says, “the reduction strategy cannot be designed with one-size-fits-all mitigation policies for all cities, but has to be individualized, considering cities’ resource endowment, industrialization level, socio-economic characteristics, and development goals.” Prof. Hubacek says that “emission peaked cities should provide successful models for other non-peaked cities. Super emitters with laggard technologies and production efficiency should have more stringent policies and targets for emission reduction, while less developed regions could have more emission space for economic development.”

This study also suggests that passively emission declined cities need to face up to the reasons that caused the emission to decline, and fully exploit the opportunities provided by industrial innovation and green investment brought by the low-carbon targets to achieve economic recovery and carbon mitigation goals. The proactively peaked cities need to seek strategies to maintain the downward trend in emissions and avoid an emission rebound.

The latest emission inventories of Chinese cities are now freely available (for non-commercial use only) to the public and the scientific community from CEADs dataset website (https://ceads.net/data/city/). Please cite the following papers when using the data.

1. Shan et al. City-level emission peak and drivers in China (2022) Science Bulletin.
2. Shan et al. City-level climate change mitigation in China (2018) Science Advances’
3. Shan et al. Methodology and applications of city level CO2 emission accounts in China.  (2017) Journal of Cleaner Production
4. Shan et al. An emissions-socioeconomic inventory of Chinese cities (2019) Scientific Data

See the article:

Shan et al. City-level emission peak and drivers in China (2022) Science Bulletin.

https://doi.org/10.1016/j.scib.2022.08.024

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JOURNAL

Science Bulletin

DOI

10.1016/j.scib.2022.08.024 

Researchers of the Human Brain Project identify seven new areas in the insular cortex

Peer-Reviewed Publication

HUMAN BRAIN PROJECT

 

IMAGE: PROBABILITY MAPS OF THE SEVEN NEWLY DISCOVERED AREAS OF THE INSULAR CORTEX view more 

CREDIT: IMAGE FROM QUABS ET AL. 2022 (CC BY 4.0) HTTPS://WWW.SCIENCEDIRECT.COM/SCIENCE/ARTICLE/PII/S1053811922005699?VIA%3DIHUB

All newly detected areas are now available as 3D probability maps in the Julich Brain Atlas, and can be openly accessed via the HBP’s EBRAINS infrastructure. Their findings, published in NeuroImage, provide new insights into the structural organisation of this complex and multifunctional region of the human neocortex.

The human insular cortex, or simply “insula”, has gained the attention from researchers since the early 19th century. But a 3D cytoarchitectonic map of the insula that could be linked to neuroimaging studies addressing different cognitive tasks was thus far not available.
 
The HBP team from the University of Düsseldorf and Forschungszentrum Jülich analysed images of the middle posterior and dorsal anterior insula of ten human brains and used statistical mapping to calculate 3D-probability maps of seven new areas. The probability maps reflect the interindividual variability and localisation of the areas in a three-dimensional space.

Brain areas with differences in their cytoarchitecture - or the organisation of their cellular composition - also likely differ in function. Based on this hypothesis, the researchers aimed to better understand the differences in the microstructure of the insula, and to identify areas that may correlate with its diverse and complex multifunctionality. 

CAPTION

Maximum probability map of seven newly discovered areas of the human insula

CREDIT

Image from Quabs et al. 2022 (CC BY 4.0) https://www.sciencedirect.com/science/article/pii/S1053811922005699?via%3Dihub

The team found that the microstructure of the insula has a remarkable diversity and a broad range of cytoarchitectonic features, which might be the basis for the complex functional organisation in this brain region.

A cluster analysis based on cytoarchitecture resulted in the identification of three superordinate microstructural clusters in the insular cortex. The clusters revealed significant differences in the microstructure of the anterior and posterior insula, reflecting systematic functional differences between both entities. 

The new maps are now openly available in the Human Brain Project’s Multilevel Human Brain Atlas on EBRAINS to support future studies addressing relations between structure and function in the human insula.

Text by Helen Mendes

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JOURNAL

NeuroImage

DOI

10.1016/j.neuroimage.2022.119453 

ARTICLE TITLE

Cytoarchitecture, probability maps and segregation of the human insula

How light and temperature work together to affect plant growth

The findings may help scientists develop more resilient plants to help withstand climate change

Peer-Reviewed Publication

SALK INSTITUTE

 

IMAGE: ARABIDOPSIS THALIANA CELLS (TOP) AND SEEDLINGS (BOTTOM) IN DIFFERENT LIGHT AND TEMPERATURE CONDITIONS. THE SEEDLINGS PICTURED ON THE FAR RIGHT SHOW ACCELERATED GROWTH IN RESPONSE TO SHADE AND WARM TEMPERATURES. view more 

CREDIT: SALK INSTITUTE COURTESY OF NATURE COMMUNICATIONS

LA JOLLA—(August 29, 2022) Plants lengthen and bend to secure access to sunlight. Despite observing this phenomenon for centuries, scientists do not fully understand it. Now, Salk scientists have discovered that two plant factors—the protein PIF7 and the growth hormone auxin—are the triggers that accelerate growth when plants are shaded by canopy and exposed to warm temperatures at the same time.

The findings, published in Nature Communications on August 29, 2022, will help scientists predict how plants will respond to climate change—and increase crop productivity despite the yield-harming global temperature rise.

“Right now, we grow crops in certain densities, but our findings indicate that we will need to lower these densities to optimize growth as our climate changes,” says senior author Professor Joanne Chory, director of Salk’s Plant Molecular and Cellular Biology Laboratory and Howard Hughes Medical Institute investigator. “Understanding the molecular basis of how plants respond to light and temperature will allow us to fine-tune crop density in a specific way that leads to the best yields.”

During sprouting, seedlings rapidly elongate their stems to break through the covering soil to capture sunlight as fast as possible. Normally, the stem slows down its growth after exposure to sunlight. But the stem can lengthen rapidly again if the plant is competing with surrounding plants for sunlight, or in response to warm temperatures to increase distance between the hot ground and the plant’s leaves. While both environmental conditions—canopy shade and warm temperatures—induce stem growth, they also reduce yield.

In this study, the scientists compared plants growing in canopy shade and warm temperatures at the same time—a condition that mimics high crop density and climate change. The scientists used the model plant Arabidopsis thaliana, as well as tomato and a close relative of tobacco, because they were interested to see if all three plant species were affected similarly by this environmental condition.

Across all three species, the team found that the plants grew extremely tall when simultaneously trying to avoid the shade created by neighboring plants and being exposed to warmer temperatures. On a molecular level, the researchers discovered that transcription factor PIF7, a protein that helps turn genes “on” and “off,” was the dominant player driving the increased rapid growth. They also found that the growth hormone auxin increased when the crops detected neighboring plants, which fostered growth in response to simultaneous warmer temperatures. This synergistic PIF7-auxin pathway allowed the plants to respond to their environments and adapt to seek the best growing conditions

A related transcription factor, PIF4, also stimulated stem elongation during warm temperatures. However, when shade and increased temperatures were combined, this factor no longer played an important role.

“We were surprised to find that PIF4 did not play a major role because prior studies have shown the importance of this factor in related growth situations,” says first author Yogev Burko, a Salk staff researcher and assistant professor at the Agriculture Research Organization at the Volcani Institute in Israel. “The fact that PIF7 is the dominant driving force behind this plant growth was a real surprise. With this new knowledge, we hope to fine-tune this growth response in different crop plants to help them adapt to climate change.”

The researchers believe that there is another player, yet to be discovered, that is boosting the effect of PIF7 and auxin. They hope to explore this unknown factor in future studies. Burko’s lab will also be studying how this pathway can be optimized in crop plants.

“Global temperatures are increasing, so we need food crops that can thrive in these new conditions,” says Chory, who co-directs Salk’s Harnessing Plants Initiative and holds the Howard H. and Maryam R. Newman Chair in Plant Biology. “We’ve identified key factors that regulate plant growth during warm temperatures, which will help us to develop better-performing crops to feed future generations.”

Other authors included Björn Christopher Willige and Adam Seluzicki of Salk; Ondřej Novák of Palacký University and Institute of Experimental Botany at The Czech Academy of Sciences; and Karin Ljung of the Swedish University of Agricultural Sciences.

The work was funded by the National Institutes of Health (5R35GM122604-05_05), Howard Hughes Medical Institute, Knut and Alice Wallenberg Foundation (KAW 2016.0341 and KAW 2016.0352), Swedish Governmental Agency for Innovation Systems (VINNOVA 2016-00504), EMBO Fellowships (ALTF 785-2013 and ALTF 1514-2012), BARD (FI-488-13), Human Frontier Science Program (LT000222/2013-L) and Salk’s Pioneer Postdoctoral Endowment Fund.

About the Salk Institute for Biological Studies:

Every cure has a starting point. The Salk Institute embodies Jonas Salk’s mission to dare to make dreams into reality. Its internationally renowned and award-winning scientists explore the very foundations of life, seeking new understandings in neuroscience, genetics, immunology, plant biology and more. The Institute is an independent nonprofit organization and architectural landmark: small by choice, intimate by nature and fearless in the face of any challenge. Be it cancer or Alzheimer’s, aging or diabetes, Salk is where cures begin. Learn more at salk.edu.

JOURNAL

Nature Communications

DOI

10.1038/s41467-022-32585-6 

ARTICLE TITLE

PIF7 is a master regulator of thermomorphogenesis in shade

ARTICLE PUBLICATION DATE

29-Aug-2022

Chinese scientists reported the thermophysical properties of lunar farside regolith with the first in-situ temperature measurement by Chang’E-4 mission

Peer-Reviewed Publication

SCIENCE CHINA PRESS

 

IMAGE: (A) THE COLORED SCATTER PLOTS REPRESENT THE REGOLITH TEMPERATURE MEASUREMENT BY THE CE-4 TEMPERATURE PROBES. (B) THE TEMPERATURE MEASURED NEAR THE LUNAR NOON. view more 

CREDIT: ©SCIENCE CHINA PRESS

Lunar regolith is a layer of loosely-packed rocky grains deposited on the lunar surface, whose physical and chemical properties are important for deciphering the geologic history and lunar spacecraft design. Probing the thermal conductivity of the lunar regolith has drawn a lot of attention since the Apollo era. Early measurements focused on the Apollo regolith samples, but the experimental data were available only at a few landing sites at the nearside.

The CE-4 spacecraft landed at 45.4446°S, 177.5991°E, on the floor of Von Kármán crater, on January 3rd, 2019. After landing, the Yutu-2 rover was released via the deployed two rails. Four temperature probes beneath the terminals of the rails began to measure the temperature of the local regolith every 900 seconds. “It was awesome to have contact temperature measurements of the far side regolith for the first time (Figure 1)”, says Dr. Jun Huang from China University of Geosciences in Wuhan, one of the leaders of this study.

The team found the particle size of the lunar regolith at the CE-4 landing site to be ~15 μm on average over depth, which indicates an immature regolith below the surface. In addition, the conductive component of thermal conductivity is measured as ~1.53×10-3 W m-1 K-1 on the surface and ~8.48×10-3 W m-1 K-1 at 1-m depth. The average bulk density is ~471 kg m-3 on the surface and ~824 kg m-3 in the upper 30 cm of lunar regolith (Figure 2).

“These results will provide important additional ‘ground truth’ for the future analysis and interpretation of global temperature observations. It will also shed lights on the design for future in-situ temperature and heat flux probes” Huang says.

Mr. Xiao Xiao, a PhD candidate at China University of Geosciences, and Dr. Shuoran Yu from Macau University of Science and Technology, together with Dr. Jun Huang, made the plan to analyze the temperature measurements. The study lasted over 2 years from 2020, interrupted several times by the Covid pandemic. “It was a difficult time to build the thermal model, but I enjoyed it,” says Xiao. It is very time-consuming to run the thermal model even with the high-performance cluster in Planetary Science Institute of China University of Geosciences, Wuhan.

Xiao and Yu processed the data and carried out the thermophysical modelling. Ms. He Zhang is the Executive Director of the Chang’E-4 (CE-4) mission and Dr. Youwei Zhang is the principal investigator of the temperature measurement system. Ms. Zhang and Dr. Zhang provide the temperature data and important information of the temperature probes. All the authors contributed to the writing of the manuscript.

CAPTION

(a) The minimum, average and maximum temperature profile from the surface to the depth of 1 m with a surface pressure of 80 Pa. (b) The bulk density profile from the surface to the depth of 1 m corresponding to the minimum, average and maximum temperature in (a) without surface pressure. (c) The conductive component of thermal conductivity profile from the surface to the depth of 1 m corresponding to the minimum, average and maximum temperature in (a) without surface pressure.

CREDIT

©Science China Press

See the article:

Thermophysical properties of the regolith on the lunar farside revealed by the in-situ temperature probing of Chang’E-4 mission

https://doi.org/10.1093/nsr/nwac175

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JOURNAL

National Science Review

DOI

10.1093/nsr/nwac175 

Discovery of the oldest visible planetary nebula hosted by a 500 million year old galactic cluster – a rare beauty with a hot blue heart

Peer-Reviewed Publication

THE UNIVERSITY OF HONG KONG

 

IMAGE: A CONTRAST ENHANCED 30°Ø30 ARCMINUTE QUOTIENT (HΑ−R BAND) IPHAS (DREW ET AL. 2005) MOSAIC CENTRED ON THE CORE OF GALACTIC OPEN CLUSTER M 37 (NGC 2099). THE LOW SURFACE BRIGHTNESS BIPOLAR PN (IPHASX J055226.2+323724) IS ENCOMPASSED BY A RED CIRCLE WITH A DIAMETER OF 445 X 10 ARCSECONDS (THE NEBULAR MAJOR AXIS) WHILE THE BLUE CIRCLE INDICATES THE FULL ∼ 30 ARCMINUTE EXTENT OF THE CLUSTER. THE PN IS WELL WITHIN THE CLUSTER TIDAL RADIUS WITH THE BLUE CSPN AT ALMOST THE PRECISE GEOMETRIC CENTRE OF THE PN. THE CSPN IS ITSELF ONLY ∼280 ARCSECONDS FROM THE PUBLISHED CLUSTER CENTER POSITION. view more 

CREDIT: THE UNIVERSITY OF HONG KONG

An international team of astronomers led by members of the Laboratory for Space Research (LSR) and Department of Physics at The University of Hong Kong (HKU), have discovered a rare celestial jewel–a so-called Planetary Nebula (PN) inside a 500 million-year-old Galactic Open Cluster (OC) called M37 (also known as NGC2099). This is a very rare finding of high astrophysical value. Their findings have just been published in the prestigious open-access paper Astrophysical Journal Letters.

PNe are the ejected, glowing shrouds of dying stars that shine with a rich emission line spectrum and display, as a result, their distinct colours and shapes that make them photogenic magnets for public interest. It was no coincidence that one of the first James Webb Space Telescope (the largest optical telescope in space) images released to the public was a PN!

The PN, with the rather ungainly name of “IPHASX J055226.2+323724”, is only the 3rd example of an association between a PN and an OC out of the ~4,000 PNe known in our Galaxy. It also appears to be the oldest PN ever found. The small team led by Professor Quentin PARKER, Director of the HKU LSR, have determined some interesting properties for their discovery: the authors found the PN has a “kinematic age” of 70,000 years. This estimate is based on how fast the nebula is expanding, as determined from the PN emission lines, and assuming this speed has remained effectively the same since the beginning, and is the time elapsed since the nebular shell was first ejected by the host, a dying star. This compares to typical PN ages of 5,000-25,000 years. It is truly a grand old dame in PN terms but of course a mere “blink of the eye” in terms of the life of the original star itself that runs to hundreds of millions of years.

Because this “grand old dame” lives in a stellar cluster, this environment enables the team to determine powerful additional parameters not possible for the general Galactic PN population. These include estimating the mass of the PN’s progenitor star when it turned off the stellar main sequence, as derived from the observed properties of the thousands of stars in the cluster when plotted in a so-called colour-magnitude diagram. The team can also estimate the residual mass of the central star that ejected the PNe via theoretical isochrones and observed properties of the hot, blue central star. As a result, they figured how massive the star was that ejected the PN gaseous shell when it was born and how much mass is now left in its residual, contracting hot core (which is already a so-called ‘White Dwarf’ star). Fresh “Gaia” data for the hot blue, PN central star also provide a good distance estimate allowing the PN’s actual size at this extreme age to be determined as 3.2pc (parsec, an astronomical unit of measure for interstellar space with 1pc equals to 3.26 light-years) in diameter – unsurprisingly perhaps also at the extreme end of known PN physical sizes.

Former HKU PhD student Dr Vasiliki FRAGKOU, the first author of the study stated, “I am so excited to be able to work on these fascinating rare cases of OC-PN associations because they keep turning up important science results, like all three cases we have found are butterfly (bi-polar) PN in terms of shape, all are very faint and highly evolved, and all have Type-I chemistry according to their emission lines, and of course all have intermediate to high progenitor masses.”

Corresponding author Professor Quentin Parker said, “This is only the third example of a PN found in a Galactic open star cluster, and my group has found all three confirmed examples. They are incredibly rare but also very important as these beautiful objects allow us to independently determine points on the so called initial to final mass relation (IFMR) for stars – an important astrophysical relation –  independent of the traditional method of using white dwarfs in clusters.  Intriguingly, all our points lie just below the empirical IFMR trend currently established but add to the “kink” in this relation found recently in the 2-3 Solar mass range for the original progenitor mass by Marigo et al in the Nature Astronomy journal. Our OC-PN points fortuitously are found in currently sparsely populated regions of the IFMR, making them even more valuable.”

Co-author Professor Albert ZILJSTRA, Hung Hing Ying Distinguished Visiting Professor in Science and Technology at HKU LSR from the University of Manchester commented on the PN visibility lifetimes which have previously been much shorter in the general Galaxy. “This new result implies that the location of a PN in an OC provides an environment suitable for allowing the PNe to expand and fade without disruption by the ambient ISM (which is typically much weaker in an OC) and not as would be the case in the Galaxy.”

The journal paper can be access from here: https://doi.org/10.3847/2041-8213/ac88c1.

About LSR:
The LSR is well situated in a dynamic region of Asia to foster links with the astrophysics, space and planetary sciences community in China and globally. The LSR’s interdisciplinary research launches various bids to exploit and access the emerging Mainland funding and research environment. We have developed multilateral and strategic partnerships with world-leading universities, space science institutes and participate in large, international, high-impact space missions. Website: www.lsr.hku.hk

Image download and caption: https://www.scifac.hku.hk/press

For media enquiries, please contact Ms Casey To, External Relations Officer (tel: 3917 4948; email: caseyto@hku.hk / Ms Cindy Chan, Assistant Director of Communications of HKU, Faculty of Science (tel: 3917 5286; email: cindycst@hku.hk).

CAPTION

Fig. 2a left panel: An enhanced 6.5 x.5 arcminute colour-composite RGB image of PN IPHASX J055226.2+323724 from the IPHAS survey (Drew et al. 2005) that we confirm as a physical member of the Galactic open cluster M37. Red = Hα, Green = broad band red and Blue = broad band ‘i’. The CSPN is circled in blue; Fig. 2b right panel: 190 x145 arcsecond RGB image created from SDSS with red = i, green = r and blue = g-band. These data clearly shows the faint CSPN (arrowed) at the centre. North is top and East is to the left in both images.

CREDIT

The University of Hong Kong

CAPTION

A combined 1-d continuum subtracted example PN spectrum from March 4th 2022 for IFU pointings a, b, c and d from the paper. The 5 visible PN emission lines are labeled.

CREDIT

The University of Hong Kong

CAPTION

Cluster Gaia DR3 CMD (B versus B-R) diagram fitted with a Padova theoretical isochrone (Bressan et al. (2012), Marigo et al. (2013) for adopted cluster parameters (age = 470 +/- 50 Myrs, reddening E(B−V ) = 0.26 +/-0.04, distance = 1.49 +/- 0.13 kpc and metallicity [Fe/H] = 0.03 +/- 0.28). The CSPN is indicated by the red filled symbol. Stars with >80% probability (Cantat-Gaudin et al. 2018) of being a cluster member, where cross-correlated with Gaia DR3 and are plotted as green dots. The CMD includes all stars with pmRA =0 to 4 and pmDec = −8 to −2 mas/yr (most probable cluster members based on mean proper motions) within 15 arcminutes from the cluster’s apparent center.

CREDIT

The University of Hong Kong

CAPTION

A plot from the known sample of cluster white dwarfs for the latest IFMR estimates and semi-empirical ‘PARSEC’ fit (Cummings et al. 2018) together with our estimated point for PN IPHAS J055226.2+323724 plotted as a red circle. The other two points from known open-cluster PNe are plotted as a yellow circle (PHR 1315-6555 (Fragkou et al. 2019a) and (Parker et al. 2011)) and green circle (BMP J1613-5406 - Fragkou et al. (2019c)). The errors attached to our point reflect the errors in the adopted cluster parameters and the spread of the estimated central-star magnitudes.

CREDIT

The University of Hong Kong

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JOURNAL

The Astrophysical Journal Letters

DOI

10.3847/2041-8213/ac88c1 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

The Planetary Nebula in the 500 Myr Old Open Cluster M37

X-shaped radio galaxies might form more simply than expected

Simple simulation accidentally leads to X-shaped galaxy for first time

Peer-Reviewed Publication

NORTHWESTERN UNIVERSITY

 

IMAGE: A STILL IMAGE TAKEN FROM THE 3D SIMULATION OF THE NATURAL DEVELOPMENT OF AN X-SHAPED JET. THE GAS (BRIGHT RED) FALLS INTO THE BLACK HOLE, WHICH LAUNCHES A PAIR OF RELATIVISTIC JETS (LIGHT BLUE). THE JETS PROPAGATE VERTICALLY AND SHOCK THE AMBIENT GAS (DARK RED) THE OLDER CAVITIES (DARK BLUE) BUOYANTLY RISE AT AN ANGLE TO THE VERTICALLY PROPAGATING JETS TO FORM THE X-SHAPE. view more 

CREDIT: ARETAIOS LALAKOS/NORTHWESTERN UNIVERSITY

When astronomers use radio telescopes to gaze into the night sky, they typically see elliptical-shaped galaxies, with twin jets blasting from either side of their central supermassive black hole. But every once in a while — less than 10% of the time — astronomers might spot something special and rare: An X-shaped radio galaxy, with four jets extending far into space.

Although these mysterious X-shaped radio galaxies have confounded astrophysicists for two decades, a new Northwestern University study sheds new insight into how they form — and its surprisingly simple. The study also found that X-shaped radio galaxies might be more common than previously thought.

The study will be published on Aug. 29 in the Astrophysical Journal Letters. It marks the first large-scale galaxy accretion simulation that tracks the galactic gas far from the supermassive black hole all the way toward it.

Simple conditions lead to messy result

Using new simulations, the Northwestern astrophysicists implemented simple conditions to model the feeding of a supermassive black hole and the organic formation of its jets and accretion disk. When the researchers ran the simulation, the simple conditions organically and unexpectedly led to the formation of an X-shaped radio galaxy. 

Surprisingly, the researchers found that the galaxy’s characteristic X-shape resulted from the interaction between the jets and the gas falling into the black hole. Early in the simulation, the infalling gas deflected the newly formed jets, which turned on and off, erratically wobbled and inflated pairs of cavities in different directions to resemble an X-shape. Eventually, however, the jets became strong enough to push through the gas. At this point, the jets stabilized, stopped wobbling and propagated along one axis.

“We found that even with simple symmetric initial conditions, you can have quite a messy result,” said Northwestern’s Aretaios Lalakos, who led the study. “A popular explanation of X-shaped radio galaxies is that two galaxies collide, causing their supermassive black holes to merge, which changes the spin of the remnant black hole and the direction of the jet. Another idea is that the jet’s shape is altered as it interacts with large-scale gas enveloping an isolated supermassive black hole. Now, we have revealed, for the first time, that X-shaped radio galaxies can, in fact, be formed in a much simpler way.”

Lalakos is a graduate student in Northwestern’s Weinberg College of Arts and Sciences and a member of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). He is co-advised by paper coauthor Sasha Tchekhovskoy, an assistant professor of physics and astronomy at Northwestern and key member of CIERA, and Ore Gottlieb, a CIERA postdoctoral fellow.

An accidental X-shape

Although radio galaxies emit visible light, they also encompass large regions of radio emission. Perhaps the most famous radio galaxy is M87, one of the most massive galaxies in the universe, which was further popularized in 2019 when the Event Horizon Telescope imaged its central supermassive blackhole. First coined in 1992, X-shaped radio galaxies make up less than 10% of all radio galaxies.

When Lalakos set out to model a black hole, he did not expect to simulate an X-shaped galaxy. Instead, he aimed to measure the amount of mass eaten by a black hole. He inputted simple astronomical conditions into the simulation and let it run. Lalakos did not initially recognize the importance of the emerging X-shape, but Tchekhovskoy reacted with enthusiastic fervor.

“He said, ‘Dude, this is very important! This is an X-shape!’” Lalakos said. “He told me that astronomers have observed this in real life and didn’t know how they formed. We created it in a way that no one had even speculated before.”

In previous simulations, other astrophysicists have attempted to create X-shaped structures artificially in order study how they arise. But Lalakos’ simulation organically led to the X-shape.

“In my simulation, I tried to assume nothing,” Lalakos said. “Usually, researchers put a black hole in the middle of a simulation grid and place a large, already-formed gaseous disk around it, and then they may add ambient gas outside the disk. In this study, the simulation starts without a disk, but soon one forms as the rotating gas gets closer to the black hole. This disk then feeds the black hole and creates jets. I made the simplest assumptions possible, so the whole outcome was a surprise. This is the first time anyone has seen X-shaped morphology in simulations from very simple initial conditions.”

‘Not lucky enough to see them’

Because the X-shape only emerged early in the simulation — until the jets strengthened and stabilized — Lalakos believes X-shaped radio galaxies might appear more frequently, but last a very short time, in the universe than previously thought.

“They might arise every time the black hole gets new gas and starts eating again,” he said. “So they might be happening frequently, but we might not be lucky enough to see them because they only happen for as long as the power of the jet is too weak to push the gas away.”

Next, Lalakos plans to continue running simulations to better understand how these X-shapes arise. He looks forward to experimenting with the size of the accretion disks and spins of central black holes. In other simulations, Lalakos included accretion disks that were almost non-existent all the way up to extremely large — none led to the elusive X-shape.

“For most of the universe, it’s impossible to zoom in right at the center and see what’s happening very near a black hole,” Lalakos said. “And even the things we can observe, we are constrained by time. If the supermassive black hole is already formed, we cannot observe its evolution because human lifetime is too short. In most cases, we rely on simulations to understand what happens near a black hole.”

The study, “Bridging the Bondi and Event Horizon Scales: 3D GRMHD simulations reveal X-shaped radio galaxy morphology,” was supported by the National Science Foundation (grant numbers AST-2107839, AST-1815304, AST-1911080 and OAC-2031997).

Simulation of X-shaped radio galaxy (VIDEO)

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JOURNAL

The Astrophysical Journal Letters

METHOD OF RESEARCH

Computational simulation/modeling

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Bridging the Bondi and Event Horizon Scales: 3D GRMHD simulations reveal X-shaped radio galaxy morphology

ARTICLE PUBLICATION DATE

29-Aug-2022

V'GER
An alien hunting radio telescope has picked up humanity’s most distant creation
Jon Kelvey -

PIA21740~medium.jpg© Nasa

An alien-hunting telescope has picked up a faint and interesting signal — but it’s not from aliens.

Instead, the recently refurbished Allen Telescope Array in California on 9 July picked up the signal of Voyager 1, the most distant object created by humans.

Launched on 5 September 1977, Nasa’s Voyager 1 mission provided stunning images of the outer Solar System before passing beyond the orbit of Neptune. Voyager has continued flying away from us at more than 38,000 miles per hour and has crossed into interstellar space: the spacecraft is currently about 14.5bn miles from Earth.

That’s more than 150 times the distance of the Earth to the Sun. Nevertheless, the distant probe still makes regular contact with the Deep Space Network, a series of antennas around the globe Nasa uses for keeping in touch with spacecraft in deep space.

The 42 antenna dishes of the Allen Telescope Array were also able to detect Voyager 1’s signal and record about a quarter-hour of data from the space probe, which continues to beam back information about the properties of the “interstellar medium,” the space outside the immediate electromagnetic influence of the Sun.

“The detection of Voyager 1, the farthest human-made object, with the refurbished Allen Telescope Array is an excellent display of the telescope’s capabilities and strengths, and a representation of the outstanding hard work put by the ATA team since the start of the refurbishment program in 201,” Wael Farah, a postdoctoral researcher at the Seti institute wrote in a statement.

EXPLAINER: Pakistan fatal flooding has hallmarks of warming


The familiar ingredients of a warming world were in place: searing temperatures, hotter air holding more moisture, extreme weather getting wilder, melting glaciers, people living in harm’s way, and poverty. They combined in vulnerable Pakistan to create unrelenting rain and deadly flooding.


EXPLAINER: Pakistan fatal flooding has hallmarks of warming© Provided by The Canadian Press

The flooding has all the hallmarks of a catastrophe juiced by climate change, but it is too early to formally assign blame to global warming, several scientists tell The Associated Press. It occurred in a country that did little to cause the warming, but keeps getting hit, just like the relentless rain.

“This year Pakistan has received the highest rainfall in at least three decades. So far this year the rain is running at more than 780% above average levels,” said Abid Qaiyum Suleri, executive director of the Sustainable Development Policy Institute and a member of Pakistan’s Climate Change Council. “Extreme weather patterns are turning more frequent in the region and Pakistan is not a exception.”

Climate Minister Sherry Rehman said “it’s been a catastrophe of unprecedented proportions.”

Pakistan “is considered the eighth most vulnerable country to climate change,” said Moshin Hafeez, a Lahore-based climate scientist at the International Water Management Institute. Its rain, heat and melting glaciers are all climate change factors scientists warned repeatedly about.

While scientists point out these classic climate change fingerprints, they have not yet finished intricate calculations that compare what happened in Pakistan to what would happen in a world without warming. That study, expected in a few weeks, will formally determine how much climate change is a factor, if at all.

The “recent flood in Pakistan is actually an outcome of the climate catastrophe ... that was looming very large,” said Anjal Prakash, a research director at India’s Bharti Institute of Public Policy. “The kind of incessant rainfall that has happened ... has been unprecedented."

Pakistan is used to monsoons and downpours, but “we do expect them spread out, usually over three months or two months,” said the country's climate minister Rehman.

There are usually breaks, she said, and not as much rain -- 37.5 centimeters (14.8 inches) falls in one day, nearly three times higher than the national average for the past three decades. “Neither is it so prolonged. ... It’s been eight weeks and we are told we might see another downpour in September.”

“Clearly, it’s being juiced by climate change,” said Jennifer Francis, a climate scientist at the Woodwell Climate Research Center in Massachusetts.

There’s been a 400% increase in average rainfall in areas like Baluchistan and Sindh, which led to the extreme flooding, Hafeez said. At least 20 dams have been breached.

The heat has been as relentless as the rain. In May, Pakistan consistently saw temperatures above 45 degrees Celsius (113 Fahrenheit). Scorching temperatures higher than 50 degrees Celsius (122 Fahrenheit) were recorded in places like Jacobabad and Dadu.

WION Climate Tracker: Floods wreak havoc in Pakistan, over a million people affected by rains  View on Watch   Duration 2:29

Warmer air holds more moisture -- about 7% more per degree Celsius (4% per degree Fahrenheit) — and that eventually comes down, in this case in torrents.

Across the world “intense rain storms are getting more intense,” said Princeton University climate scientist Michael Oppenheimer. And he said mountains, like those in Pakistan, help wring extra moisture out as the clouds pass.

Instead of just swollen rivers flooding from extra rain, Pakistan is hit with another source of flash flooding: The extreme heat accelerates the long-term glacier melting then water speeds down from the Himalayas to Pakistan in a dangerous phenomena called glacial lake outburst floods.

“We have the largest number of glaciers outside the polar region, and this affects us,” climate minister Rehman said. “Instead of keeping their majesty and preserving them for posterity and nature. We are seeing them melt.”

Not all of the problem is climate change.

Pakistan saw similar flooding and devastation in 2010 that killed nearly 2,000 people. But the government didn’t implement plans to prevent future flooding by preventing construction and homes in flood prone areas and river beds, said Suleri of the country's Climate Change Council.

The disaster is hitting a poor country that has contributed relatively little to the world's climate problem, scientists and officials said. Since 1959, Pakistan has emitted about 0.4% of heat-trapping carbon dioxide, compared to 21.5% by the United States and 16.4% by China.

“Those countries that have developed or gotten rich on the back of fossil fuels, which are the problem really,” Rehman said. “They’re going to have to make a critical decision that the world is coming to a tipping point. We certainly have already reached that point because of our geographical location.”

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Borenstein reported from Kensington, Maryland, and Arasu from New Delhi. AP journalists Munir Ahmed in Islamabad, Pakistan, and Aniruddha Ghosal in New Delhi contributed to this report.

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Follow AP’s climate and environment coverage at https://apnews.com/hub/climate-and-environment

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Follow Seth Borenstein on Twitter at @borenbears and Sibi Arasu at @sibi123.

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Associated Press climate and environmental coverage receives support from several private foundations. See more about AP’s climate initiative here. The AP is solely responsible for all content.

Seth Borenstein And Sibi Arasu, The Associated Press