Two galaxies seen in a 'joust' preceding a cosmic mega-merger
WASHINGTON : Astronomers have observed two distant galaxies - both possessing roughly as many stars as our Milky Way - careening toward each other before their inevitable merger at a time when the universe was about a fifth its current age, a scene resembling two knights charging in a joust.
The galaxies, observed using two Chile-based telescopes, were seen as they existed about 11.4 billion years ago, approximately 2.4 billion years after the Big Bang event that initiated the universe.
At the heart of one of the galaxies resides a quasar, a highly luminous object powered by gas and other material falling into a supermassive black hole. The intense radiation across the electromagnetic spectrum unleashed by the quasar is seen disrupting clouds of gas and dust, known as molecular clouds, in the other galaxy.
It is molecular clouds that give rise to stars. But the effects of the quasar's radiation turned the clouds in the affected region into "only tiny dense cloudlets that are too small to form stars," said astrophysicist Sergei Balashev of the Ioffe Institute in Saint Petersburg, Russia, co-lead author of the study published on Wednesday in the journal Nature.
This is the first time such a phenomenon has been observed, Balashev said.
Stars form by the slow contraction under gravity of these clouds, with small centers taking shape that heat up and become new stars. But the galaxy affected by the quasar's radiation was left with fewer regions that could serve as such stellar nurseries, undermining its star formation rate.
The interaction between the two galaxies reminded the researchers of a medieval joust.
"Much like jousting knights charging toward one another, these galaxies are rapidly approaching. One of them - the quasar host - emits a powerful beam of radiation that pierces the companion galaxy, like a lance. This radiation 'wounds' its 'opponent' as it disrupts the gas," said astronomer and co-lead author Pasquier Noterdaeme of the Paris Institute of Astrophysics in France.
Supermassive black holes are found at the heart of many galaxies, including the Milky Way. The researchers estimated the mass of the one that serves as the engine of the quasar studied in this research at about 200 million times that of our sun.
The intense gravitational strength of the supermassive black hole pulls gas and other material toward it. As this stuff spirals inward at high speed, it heats up due to friction, forming a disk that emits extremely powerful radiation in two opposite directions, called biconical beams.
The ultraviolet light from one of these beams is what played havoc with the gas in the companion galaxy.
This supermassive black hole is much more massive than the one at the center of the Milky Way - called Sagittarius A*, or Sgr A* - which possesses roughly 4 million times the mass of the sun and is located about 26,000 light-years from Earth. A light-year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km).
The researchers used the Atacama Large Millimeter/submillimeter Array, or ALMA, to characterize the two galaxies and used the European Southern Observatory's Very Large Telescope, or VLT, to probe the quasar as well as the gas in the companion galaxy.
The configuration of the galaxies as viewed from the perspective of Earth enabled the researchers to observe the radiation from the quasar passing directly through the companion galaxy.
Most galactic mergers that have been observed by astronomers occurred later in the history of the universe.
"Galaxies are typically found in groups, and gravitational interactions naturally lead to mergers over cosmic time," Noterdaeme said. "In line with current understanding, these two galaxies will eventually coalesce into a single larger galaxy. The quasar will fade as it exhausts the available fuel."
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Straits Times
18 hours ago
- Straits Times
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The research, which quantified carbon stocks in seagrass ecosystems globally, was done by researchers from academic institutions and organisations across the globe, including the National University of Singapore (NUS) and the Singapore-based International Blue Carbon Institute. Published in research journal Nature in May, the study identified the lagoons and small deltas of the Indo-Pacific as being among the top five regions globally with the highest organic carbon storage potential, alongside the Mediterranean, Colombia, Florida and South Africa. Organic carbon refers to carbon that comes from living things. While seagrass meadows are known to be natural carbon sponges that can soak up planet-warming carbon dioxide, there is still much uncertainty and knowledge gaps about these ecosystems, making their conservation challenging. The aim of the study, said the researchers, was to provide policymakers with greater understanding about the factors that affect the carbon storage potential of seagrass meadows. This could help guide the 'development, integrity and reliability of climate change policy, and financing to support seagrass conservation and restoration', they said. What are seagrasses? Seagrasses are aquatic plants that take in carbon dioxide through photosynthesis. This carbon is locked up in the plants' roots and underground stems, and the soil they grow in. Being anchored to the seafloor by their roots, these habitats can also 'trap' carbon-containing particles, such as bits of dead plants or animal faeces, carried by the currents, said Dr Siti Yaakub, senior director of the International Blue Carbon Institute and a co-author of the paper. As more of these particles eventually settle on the seabed, they get trapped in structures of the seagrass. As these layers accumulate, the carbon gets buried by new layers of sediment and moves deeper into the earth, said Dr Siti. Burrowing animals in the seafloor, such as clams and worms, also help bring the carbon to deeper layers of the sediment, she added. These characteristics make seagrass meadows a promising ally in humanity's fight against climate change. A separate study, also published in Nature in 2021, estimated that seagrasses are 40 times more efficient at capturing organic carbon than land forest soils. However, different environmental conditions and types of seagrass could affect how much carbon is stored at a particular site , resulting in a large variation globally . For example, Dr Siti said seagrass meadows near big rivers tend to contain a higher carbon content in the seabed due to the discharge of river sediment and carbon-rich organic matter. Heavy rain can also affect seagrass growth, as the rainfall could stir up sediment and prevent sunlight from reaching the plant. Similarly, high levels of nutrients in waters can cause algae blooms that reduce water clarity. Nutrient levels can go up when fish feed and waste materials are released from fish farms into the sea. The study is one of the first to map out the potential of seagrass meadows around the world to act as natural sponges that can soak up planet-warming carbon dioxide, Dr Siti said. S'pore's underwater carbon banks Through an analysis of 2,171 soil cores retrieved from seagrass beds around the world, the researchers found that the region's seagrass meadows had one of the world's highest carbon stocks on a per-hectare basis. 'As a region, we do have a slightly higher-than-average carbon stock because there is a lot of seagrass in shallow sheltered coastal waters that are also adjacent to river systems, so there's a good source of allochthonous (external) inputs,' said Dr Siti. 'If we lose all this seagrass with high carbon stocks, we will not be able to recover the carbon that is lost. It will take many decades to restore it.' Singapore is home to 12 of the 72 known species of seagrass globally, with some of the country's largest meadows found at Chek Jawa on Pulau Ubin, Pulau Semakau, Cyrene Reef and Changi Beach, said Dr Siti. Seagrass meadows in the Republic also act as shelters and nursery areas for numerous animals like seahorses, and serve as the primary food source for sea turtles and dugongs. The biggest threats to seagrass meadows in Singapore are coastal development and high sedimentation. Large amounts of sediment in the water can result in low light levels reaching the plant. 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Dr Samantha Lai, deputy director of NParks' National Biodiversity Centre Coastal and Marine branch, said the board has also been working with NUS and NParks volunteers on separate projects that aim to study the health and conservation needs of seagrasses. Moving forward, Dr Siti said that a better understanding of the seasonal growth cycles of seagrass can help with better planning during dredging and reclamation activities to minimise stress on the seagrass population. 'For example, if there is dredging involved, there should be measures taken to contain the sediment plumes so that they don't spread to areas with seagrass and stress them out even more,' Dr Siti said. At the global level, the study provided some insight into the carbon storage potential of seagrass meadows in the region, she added. However, the large variation also shows that countries need to more closely study the quantity of carbon being sequestered in their own meadows. This is especially if they intend to tap the carbon storage abilities of these habitats in their plans to tackle climate change, she said. 'The issue with seagrass is that it's not very well mapped. For example, estimates of seagrass cover in Indonesia range between 300,000ha and three million ha, which is a huge range. This results in big uncertainty in calculating the climate mitigation potential of seagrass with respect to their climate commitments. But there are efforts under way to better understand seagrass cover and map them globally ,' Dr Siti said. Singapore can contribute to deepening this understanding, said local experts. Dr Ow Yan Xiang, a seagrass scientist and senior research fellow at the St John's Island National Marine Laboratory who was not involved in the latest research, said: 'This study shows that Singapore has one of the highest data density and sampling efforts for seagrass carbon stocks. Also, our seagrass population is holding steady, despite the region's seagrass declining at an average of 4.7 per cent per year.' The high data density refers to Singapore contributing a high amount of data, in proportion to its small coastline. Dr Siti said: 'This places Singapore at the forefront of carbon mitigation efforts because one, we have influence in climate negotiations, and two, we have the resources and expertise to facilitate or help other countries deploy natural climate solutions.' Join ST's WhatsApp Channel and get the latest news and must-reads.
CNA
23-05-2025
- CNA
Astronomers spot galaxy shaped like the Milky Way but is far more massive
WASHINGTON :Astronomers have observed a galaxy dating to an earlier epoch in the universe's history that surprisingly is shaped much like our Milky Way - a spiral structure with a straight bar of stars and gas running through its center - but far more massive, offering new insight into galactic formation. The distant galaxy, called J0107a, was observed as it appeared 11.1 billion years ago, when the universe was about a fifth of its current age. The researchers used data from the Chile-based Atacama Large Millimeter/submillimeter Array (ALMA) and NASA's James Webb Space Telescope to study the galaxy. They determined that the galaxy's mass, including its stars and gas, was more than 10 times greater than that of the Milky Way, and it was forming stars at an annual rate approximately 300 times greater. J0107a was more compact than the Milky Way, however. "The galaxy is a monster galaxy with a high star formation rate and plenty of gas, much more than present-day galaxies," said astronomer Shuo Huang of the National Astronomical Observatory of Japan, lead author of the study published this week in the journal Nature. "This discovery," said study co-author Toshiki Saito, an astronomer at Shizuoka University in Japan, "raises the important question: How did such a massive galaxy form in such an early universe?" While a few galaxies that are undergoing star formation at a similar rate to J0107a exist in today's universe, almost all of them are ones that are in the process of a galactic merger or collision. There was no sign of such circumstances involving this galaxy. J0107a and the Milky Way have some commonalities. "They are similarly huge and possess a similar barred structure. However, the Milky Way had plenty of time to form its huge structures, while J0107a didn't," Saito said. In the first few billion years after the Big Bang event 13.8 billion years ago that initiated the universe, galaxies were turbulent entities and were much richer in gas than those existing currently - factors that fostered extreme bursts of star formation. While galaxies with highly organized structures like the barred spiral shape of the Milky Way are common now, that was not the case 11.1 billion years ago. "Compared to other monster galaxies in the distant universe (dating to an earlier cosmic epoch) whose shapes are usually disturbed or irregular, it is unexpected that J0107a looks very similar to present-day spiral galaxies," Huang said. "Theories about the formation of present-day galactic structures may need to be revised," Huang added. The Webb telescope, as it peers across vast distances back to the early universe, has found that galaxies with a spiral shape appeared much earlier than previously known. J0107a is now one of the earliest-known examples of a barred spiral galaxy. About two thirds of spiral galaxies observed in the universe today possess a bar structure. The bar is thought to serve as a form of stellar nursery, bringing gas inward from the galaxy's spiral arms. Some of the gas forms what are called molecular clouds. Gravity causes the contraction of these clouds, with small centers taking shape that heat up and become new stars. The bar that is part of J0107a measures about 50,000 light years in length, Huang said. A light-year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km). The Webb telescope "has been studying the morphology of early massive galaxies intensely recently. However, their dynamics are still poorly understood," Saito said.
CNA
21-05-2025
- CNA
Two galaxies seen in a 'joust' preceding a cosmic mega-merger
WASHINGTON : Astronomers have observed two distant galaxies - both possessing roughly as many stars as our Milky Way - careening toward each other before their inevitable merger at a time when the universe was about a fifth its current age, a scene resembling two knights charging in a joust. The galaxies, observed using two Chile-based telescopes, were seen as they existed about 11.4 billion years ago, approximately 2.4 billion years after the Big Bang event that initiated the universe. At the heart of one of the galaxies resides a quasar, a highly luminous object powered by gas and other material falling into a supermassive black hole. The intense radiation across the electromagnetic spectrum unleashed by the quasar is seen disrupting clouds of gas and dust, known as molecular clouds, in the other galaxy. It is molecular clouds that give rise to stars. But the effects of the quasar's radiation turned the clouds in the affected region into "only tiny dense cloudlets that are too small to form stars," said astrophysicist Sergei Balashev of the Ioffe Institute in Saint Petersburg, Russia, co-lead author of the study published on Wednesday in the journal Nature. This is the first time such a phenomenon has been observed, Balashev said. Stars form by the slow contraction under gravity of these clouds, with small centers taking shape that heat up and become new stars. But the galaxy affected by the quasar's radiation was left with fewer regions that could serve as such stellar nurseries, undermining its star formation rate. The interaction between the two galaxies reminded the researchers of a medieval joust. "Much like jousting knights charging toward one another, these galaxies are rapidly approaching. One of them - the quasar host - emits a powerful beam of radiation that pierces the companion galaxy, like a lance. This radiation 'wounds' its 'opponent' as it disrupts the gas," said astronomer and co-lead author Pasquier Noterdaeme of the Paris Institute of Astrophysics in France. Supermassive black holes are found at the heart of many galaxies, including the Milky Way. The researchers estimated the mass of the one that serves as the engine of the quasar studied in this research at about 200 million times that of our sun. The intense gravitational strength of the supermassive black hole pulls gas and other material toward it. As this stuff spirals inward at high speed, it heats up due to friction, forming a disk that emits extremely powerful radiation in two opposite directions, called biconical beams. The ultraviolet light from one of these beams is what played havoc with the gas in the companion galaxy. This supermassive black hole is much more massive than the one at the center of the Milky Way - called Sagittarius A*, or Sgr A* - which possesses roughly 4 million times the mass of the sun and is located about 26,000 light-years from Earth. A light-year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km). The researchers used the Atacama Large Millimeter/submillimeter Array, or ALMA, to characterize the two galaxies and used the European Southern Observatory's Very Large Telescope, or VLT, to probe the quasar as well as the gas in the companion galaxy. The configuration of the galaxies as viewed from the perspective of Earth enabled the researchers to observe the radiation from the quasar passing directly through the companion galaxy. Most galactic mergers that have been observed by astronomers occurred later in the history of the universe. "Galaxies are typically found in groups, and gravitational interactions naturally lead to mergers over cosmic time," Noterdaeme said. "In line with current understanding, these two galaxies will eventually coalesce into a single larger galaxy. The quasar will fade as it exhausts the available fuel."
