It’s official: Australia’s ocean surface was the hottest on record in 2024

Australia’s sea surface temperatures were the warmest on record last year, according to a snapshot of the nation’s climate which underscores the perilous state of the world’s oceans.

The Bureau of Meteorology on Thursday released its annual climate statement for 2024 – the official record of temperature, rainfall, water resources, oceans, atmosphere and notable weather.

Among its many alarming findings were that sea surface temperatures were hotter than ever around the continent last year: a whopping 0.89°C above average.

Oceans cover more than 70% of Earth’s surface, and their warming is gravely concerning. It causes sea levels to rise, coral to bleach and Earth’s ice sheets to melt faster. Hotter oceans also makes weather on land more extreme and damages the marine life which underpins vital ocean ecosystems.

What the snapshot showed

Australia’s climate varies from year to year. That’s due to natural phenomena such as the El Niño and La Niña climate drivers, as well as human-induced climate change.

The bureau confirmed 2024 was Australia’s second-warmest year since national records began in 1910. The national annual average temperature was 1.46°C warmer than the long-term average (1961–90). Heatwaves struck large parts of Australia early in the year, and from September to December.

Average rainfall in Australia was 596 millimetres, 28% above the 30-year average, making last year the eighth-wettest since records began.

And annual sea surface temperatures for the Australian region were the warmest on record. Global sea surface temperatures in 2024 were also the warmest on record.

According to the bureau, Antarctic sea-ice extent was far below average, or close to record-lows, for much of the year but returned to average in December.

What caused the hot oceans?

It’s too early to officially attribute the ocean warming to climate change. But we do know greenhouse gas emissions are heating the Earth’s atmosphere, and oceans absorb 90% of this heat.

So we can expect human-induced climate change played a big role in warming the oceans last year. But shorter-term forces are at play, too.

The rare triple-dip La Niña Australia experienced from 2020 to 2023 brought cooler water from deep in the ocean up to the surface. It was like turning on the ocean’s air-conditioner.

But that pattern ended and Australia entered an El Niño in September 2023. It lasted about seven months, when the oscillation between El Niño and La Niña entered a neutral phase.

The absence of a La Niña meant cool water was no longer being churned up from the deep. Once that masking effect disappeared, the long-term warming trend of the oceans became apparent once more.

Water can store a lot more heat than air. In fact, just the top few metres of the ocean store as much heat as Earth’s entire atmosphere. Oceans take a long time to heat up and a long time to cool.

Heat at the ocean’s surface eventually gets pushed deeper into the water column and spreads across Earth’s surface in currents. The below chart shows how the world’s oceans have heated over the past 70 years. Changes in the world’s ocean heat content since 1955. NOAA/NCEI World Ocean Database

Why should we care about ocean warming?

Rapid warming of Earth’s oceans is setting off a raft of worrying changes.

It can lead to less nutrients in surface waters, which in turn leads to fewer fish. Warmer water can also cause species to move elsewhere. This threatens the food security and livelihoods of millions of people around the world.

Just last week, it was reported that tens of thousands of fish died off northwestern Australia due to a large and prolonged marine heatwave.

Warm water causes coral bleaching, as experienced on the Great Barrier Reef in recent decades. It also makes oceans more acidic, reducing the amount of calcium carbonate available for organisms to build shells and skeletons.

Warming oceans trigger sea level rise – both due to melt water from glaciers and ice sheets, and the fact seawater expands as it warms.

Hotter oceans are also linked to weather extremes, such as more intense cyclones and heavier rainfall. It’s likely the high annual rainfall Australia experienced in 2024 was in part due to warmer ocean temperatures.

What now?

As long as humans keep burning fossil fuels and pumping greenhouse gases into the atmosphere, the oceans will keep warming.

Unfortunately, the world is not doing a good job of shifting its emissions trajectory. As the bureau pointed out in its statement, concentrations of all major long-lived greenhouse gases in the atmosphere increased last year, including carbon dioxide and methane.

Prolonged ocean warming is driving changes in weather patterns and more frequent and intense marine heatwaves. This threatens ecosystems and human livelihoods. To protect our oceans and our way of life, we must transition to clean energy sources and cut carbon emissions.

At the same time, we must urgently expand ocean observing below the ocean’s surface, especially in under-studied regions, to establish crucial baseline data for measuring climate change impacts.

The time to act is now: to reduce emissions, support ocean research and help safeguard the future of our blue planet.The Conversation

Moninya Roughan, Professor in Oceanography, UNSW Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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What’s the difference between climate and weather models? It all comes down to chaos

Weather forecasts help you decide whether to go for a picnic, hang out your washing or ride your bike to work. They also provide warnings for extreme events, and predictions to optimise our power grid.

To achieve this, services such as the Australian Bureau of Meteorology use complex mathematical representations of Earth and its atmosphere – weather and climate models.

The same software is also used by scientists to predict our future climate in the coming decades or even centuries. These predictions allow us to plan for, or avoid, the impacts of future climate change.

Weather and climate models are highly complex. The Australian Community Climate and Earth System Simulator, for example, is comprised of millions of lines of computer code.

Without climate and weather models we would be flying blind, both for short-term weather events and for our long-term future. But how do they work – and how are they different?

The same physical principles

Weather is the short-term behaviour of the atmosphere – the temperature on a given day, the wind, whether it’s raining and how much. Climate is about long-term statistics of weather events – the typical temperature in summer, or how often thunderstorms or floods happen each decade.

The reason we can use the same modelling tools for both weather and climate is because they are both based on the same physical principles.

These models compile a range of factors – the Sun’s radiation, air and water flow, land surface, clouds – into mathematical equations. These equations are solved on a bunch of tiny three-dimensional grid boxes and pieced together to predict the future state.

These boxes are sort of like pixels that come together to make the big picture.

These solutions are calculated on a computer – where using more grid boxes (finer resolution) gives better answers, but takes more computing resources. This is why the best predictions need a supercomputer, such as the National Computational Infrastructure’s Gadi, located in Canberra.

Because weather and climate are governed by the same physical processes, we can use the same software to predict the behaviour of both.

But there most of the similarities end.

The starting point

The main differences between weather and climate come down to a single concept: “initialisation”, or the starting point of a model.

In many cases, the simplest prediction for tomorrow’s weather is the “persistence” forecast: tomorrow’s weather will be similar to today. It means that, irrespective of how good your model is, if you start from the wrong conditions for today, you have no hope of predicting tomorrow.

Persistence forecasts are often quite good for temperature, but they’re less effective for other aspects of weather such as rainfall or wind. Since these are often the most important aspects of weather to predict, meteorologists need more sophisticated methods.

So, weather models use complex mathematics to create models that include weather information (from yesterday and today) and then make a good prediction of tomorrow. These predictions are a big improvement on persistence forecasts, but they won’t be perfect.

In addition, the further ahead you try to predict, the more information you forget about the initial state and the worse your forecast performs. So you need to regularly update and rerun (or, to use modelling parlance, “initialise”) the model to get the best prediction.

Weather services today can reliably predict three to seven days ahead, depending on the region, the season and the type of weather systems involved.

Chaos reigns

If we can only accurately predict weather systems about a week ahead before chaos takes over, climate models have no hope of predicting a specific storm next century.

Instead, climate models use a completely different philosophy. They aim to produce the right type and frequency of weather events, but not a specific forecast of the actual weather.

The cumulative effect of these weather events produces the climate state. This includes factors such as the average temperature and the likelihood of extreme weather events.

So, a climate model doesn’t give us an answer based on weather information from yesterday or today – it is run for centuries to produce its own equilibrium for a simulated Earth.

Because it is run for so long, a climate (also known as Earth system) model will need to account for additional, longer-term processes not factored into weather models, such as ocean circulation, the cryosphere (the frozen portions of the planet), the natural carbon cycle and carbon emissions from human activities.

The additional complexity of these extra processes, combined with the need for century-long simulations, means these models use a lot of computing power. Constraints on computing means that we often include fewer grid boxes (that is, lower resolution) in climate models than weather models.

A machine learning revolution?

Is there a faster way?

Enormous strides have been made in the past couple of years to predict the weather with machine learning. In fact, machine learning-based models can now outperform physics-based models.

But these models need to be trained. And right now, we have insufficient weather observations to train them. This means their training still needs to be supplemented by the output of traditional models.

And despite some encouraging recent attempts, it’s not clear that machine learning models will be able to simulate future climate change. The reason again comes down to training – in particular, global warming will shift the climate system to a different state for which we have no observational data whatsoever to train or verify a predictive machine learning model.

Now more than ever, climate and weather models are crucial digital infrastructure. They are powerful tools for decision makers, as well as research scientists. They provide essential support for agriculture, resource management and disaster response, so understanding how they work is vital.The Conversation

Andy Hogg, Professor and Director of ACCESS-NRI, Australian National University; Aidan Heerdegen, Leader, ACCESS-NRI Model Release Team, Australian National University, and Kelsey Druken, Associate Director (Release Management), ACCESS-NRI, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Not all of nitrogen for plants comes from atmosphere: Study


Davis (California): Contrary to popular belief that all of the nitrogen on Earth available to plants comes from the atmosphere, a study from the University of California, Davis, indicates that more than a quarter comes from Earth's bedrock.

Up to 26 percent of the nitrogen in natural ecosystems is sourced from rocks, with the remaining fraction from the atmosphere. This newly identified source of nitrogen could also feed the carbon cycle on land, allowing ecosystems to pull more emissions out of the atmosphere, the study published in the journal Science said.

"Our study shows that nitrogen weathering is a globally significant source of nutrition to soils and ecosystems worldwide," said co-lead author Ben Houlton, a professor in the UC Davis Department of Land, Air and Water Resources and director of the UC Davis Muir Institute. "This runs counter the centuries-long paradigm that has laid the foundation for the environmental sciences. We think that this nitrogen may allow forests and grasslands to sequester more fossil fuel CO2 emissions than previously thought."

Ecosystems need nitrogen and other nutrients to absorb carbon dioxide pollution, and there is a limited amount of it available from plants and soils. If a large amount of nitrogen comes from rocks, it helps explain how natural ecosystems like boreal forests are capable of taking up high levels of carbon dioxide.

The study also said that large areas of Africa are devoid of nitrogen-rich bedrock while northern latitudes have some of the highest levels of rock nitrogen weathering. Mountainous regions like the Himalayas and Andes are estimated to be significant sources of rock nitrogen weathering, similar to those regions' importance to global weathering rates and climate. Grasslands, tundra, deserts and woodlands also experience sizable rates of rock nitrogen weathering.

Following the discovery the researchers now want the textbooks taught in schools to be changed accordingly. "While there were hints that plants could use rock-derived nitrogen, this discovery shatter the paradigm that the ultimate source of available nitrogen is the atmosphere”, said Kendra McLauchlan, program director in the National Science Foundation's Division of Environmental Biology, which co-sponsored the research.

“Nitrogen is both the most important limiting nutrient on Earth and a dangerous pollutant, so it is important to understand the natural controls on its supply and demand. Humanity currently depends on atmospheric nitrogen to produce enough fertilizer to maintain world food supply. A discovery of this magnitude will open up a new era of research on this essential nutrient”, Kendra McLauchlan added. Source: ummid.com
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Researchers develop novel method to turn footsteps into usable electricity

New York: Researchers at University of Wisconsin-Madison have developed an inexpensive, simple method that allows them to convert footsteps into usable electricity. The method puts to good use a common waste material -- wood pulp.

The pulp, which is already a common component of flooring, is partly made of cellulose nanofibers.

They are tiny fibers that, when chemically treated, produce an electrical charge when they come in contact with untreated nanofibers.

When the nanofibers are embedded within flooring, they are able to produce electricity that can be harnessed to power lights or charge batteries.

And because wood pulp is a cheap, abundant and renewable waste product of several industries, flooring that incorporates the new technology could be as affordable as conventional materials.

While there are existing similar materials for harnessing footstep energy, they are costly, nonrecyclable, and impractical at a large scale.

"We've been working a lot on harvesting energy from human activities. One way is to build something to put on people, and another way is to build something that has constant access to people. The ground is the most-used place," said Xudong Wang, Associate Professor at University of Wisconsin-Madison.

The team's method published in the journal Nano Energy is the latest in a green energy research field called "roadside energy harvesting" that could, in some settings, rival solar power -- and it does not depend on fair weather.

Researchers like Wang who study roadside energy harvesting methods see the ground as holding great renewable energy potential well beyond its limited fossil fuel reserves. Source: ummid.com
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Lightning Longer, Stronger and More Extreme

ASU professor Randy Cerveny credits “huge strides in the detection and monitoring of lightning events.”, Credit; Axel Rouvin/Flickr
It turns out lightning isn’t always a flash, and an Arizona State University (ASU) researcher says a pair of newly classified records for distance and duration reshaping our views of the electric weather phenomena might be just the beginning. The World Meteorological Organization has recently confirmed that a bolt over Oklahoma in 2007 covered a horizontal distance of nearly 200 miles (321 km), and a streak over southern France in 2012 lasted for nearly 8 seconds. “Our weather technology,” said Cerveny, chief rapporteur of climate and weather extremes for the WMO and instructor in the School of Geographical Sciences and Urban Planning, “particularly with regard to lightning, has advanced rapidly in the last few years to now allow us to detect and measure lightning events that we previously had not been able to monitor and evaluate.” Cerveny said this is the first time lightning has been included in the official WMO extreme weather and climate archive, which is maintained by the organization’s Commission for Climatology and documents details of records for heat, cold, wind speed, rainfall and other related events. Full details of the lightning assessments are given in the online issue of the Bulletin of the American Meteorological Society, published Sept. 15. The WMO evaluation committee judged that the world’s longest detected distance for a single lightning bolt occurred over a horizontal distance of 199.5 miles. The event occurred on June 20, 2007, stretching from near Tulsa to near the Texas border. The committee also accepted the world’s longest detected duration for a single shock as a lightning event that lasted continuously for 7.74 seconds on Aug. 30, 2012, over Provence-Alpes-Côte d'Azur, France. Cerveny said researchers gathered their data from networks of sensors that monitor electromagnetic radiation triggered by lightning discharges. “The bursts are similar to the static you hear on an AM radio,” he said. “We can detect the static and its intensity. And through triangulation, we to find where the strike began and where it ended.” Cerveny said that with new technologies, weather researchers are entering a new phase in lightning detection and understanding. “This is the first study to address issues of lightning,” Cerveny said. “Over the next couple of decades I think we will see this field really take off.” He also said the findings highlight the importance of safety. “These extremes point out the need for everybody to be very aware when lightning occurs,” he said. “Lightning can strike far from where a storm is, so this research re-emphasizes the old safety advice that ‘when thunder roars, go indoors.’” 
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How Did Early Earth Stay Warm?

An artist’s depiction of an ice-covered planet in a distant solar system resembles what the early Earth might have looked like if a mysterious mix of greenhouse gases had not warmed the climate, Credit: ESA
A UC Riverside-led astrobiology team discovered that methane, a potent greenhouse gas, was not the climate savior once imagined for the mysterious middle chapter of Earth history For at least a billion years of the distant past, planet Earth should have been frozen over but wasn’t. Scientists thought they knew why, but a new modeling study from the Alternative Earths team of the NASA Astrobiology Institute has fired the lead actor in that long-accepted scenario. Humans worry about greenhouse gases, but between 1.8 billion and 800 million years ago, microscopic ocean dwellers really needed them. The sun was 10 to 15 percent dimmer than it is today—too weak to warm the planet on its own. Earth required a potent mix of heat-trapping gases to keep the oceans liquid and livable. For decades, atmospheric scientists cast methane in the leading role. The thinking was that methane, with 34 times the heat-trapping capacity of carbon dioxide, could have reigned supreme for most of the first 3.5 billion years of Earth history, when oxygen was absent initially and little more than a whiff later on. (Nowadays oxygen is one-fifth of the air we breathe, and it destroys methane in a matter of years.) “A proper accounting of biogeochemical cycles in the oceans reveals that methane has a much more powerful foe than oxygen,” said Stephanie Olson, a graduate student at the University of California, Riverside, a member of the Alternative Earths team and lead author of the new study published September 26 in the Proceedings of the National Academy of Sciences. “You can’t get significant methane out of the ocean once there is sulfate.” Sulfate wasn’t a factor until oxygen appeared in the atmosphere and triggered oxidative weathering of rocks on land. The breakdown of minerals such as pyrite produces sulfate, which then flows down rivers to the oceans. Less oxygen means less sulfate, but even 1 percent of the modern abundance is sufficient to kill methane, Olson said. Stephanie Olson and Tim Lyons next to an image of visualizations of sulfate concentrations (top) and methane destruction (bottom) from their biogeochemical model of Earth’s ocean and atmosphere roughly one billion years ago.
Credit: UC Riverside
Olson and her Alternative Earths coauthors, Chris Reinhard, an assistant professor of earth and atmospheric sciences at Georgia Tech University, and Timothy Lyons, a distinguished professor of biogeochemistry at UC Riverside, assert that during the billion years they assessed, sulfate in the ocean limited atmospheric methane to only 1 to 10 parts per million—a tiny fraction of the copious 300 parts per million touted by some previous models. The fatal flaw of those past climate models and their predictions for atmospheric composition, Olson said, is that they ignore what happens in the oceans, where most methane originates as specialized bacteria decompose organic matter. Seawater sulfate is a problem for methane in two ways: Sulfate destroys methane directly, which limits how much of the gas can escape the oceans and accumulate in the atmosphere. Sulfate also limits the production of methane. Life can extract more energy by reducing sulfate than it can by making methane, so sulfate consumption dominates over methane production in nearly all marine environments. The numerical model used in this study calculated sulfate reduction, methane production, and a broad array of other biogeochemical cycles in the ocean for the billion years between 1.8 billion and 800 million years ago. This model, which divides the ocean into nearly 15,000 three-dimensional regions and calculates the cycles for each region, is by far the highest resolution model ever applied to the ancient Earth. By comparison, other biogeochemical models divide the entire ocean into a two-dimensional grid of no more than five regions. “There really aren’t any comparable models,” says Reinhard, who was lead author on a related paper in Proceedings of the National Academy of Sciences that described the fate of oxygen during the same model runs that revealed sulfate’s deadly relationship with methane. Reinhard notes that oxygen dealt methane an additional blow, based on independent evidence published recently by the Alternative Earths team in the journals Science and Geology. These papers describe geochemical signatures in the rock record that track extremely low oxygen levels in the atmosphere, perhaps much less than 1 percent of modern values, up until about 800 million years ago, when they spiked dramatically. Less oxygen seems like a good thing for methane, since they are incompatible gases, but with oxygen at such extremely low levels, another problem arises. “Free oxygen [O2] in the atmosphere is required to form a protective layer of ozone [O3], which can shield methane from photochemical destruction,” Reinhard said. When the researchers ran their model with the lower oxygen estimates, the ozone shield never formed, leaving the modest puffs of methane that escaped the oceans at the mercy of destructive photochemistry. With methane demoted, scientists face a serious new challenge to determine the greenhouse cocktail that explains our planet’s climate and life story, including a billion years devoid of glaciers, Lyons said. Knowing the right combination other warming agents, such as water vapor, nitrous oxide, and carbon dioxide, will also help us assess habitability of the hundreds of billions of other Earth-like planets estimated to reside in our galaxy. “If we detect methane on an exoplanet, it is one of our best candidates as a biosignature, and methane dominates many conversations in the search for life on Mars,” Lyons said. “Yet methane almost certainly would not have been detected by an alien civilization looking at our planet a billion years ago—despite the likelihood of its biological production over most of Earth history.” 
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NASA video to help ‘see’ sun’s magnetic field

Washington: NASA has created a video to 'see' and understand the sun's invisible magnetic field, that may be crucial for future deep space travel, by combining real time observations and computer simulations to analyse how plasma courses through its corona. The sun is a giant magnetic star, made of material that moves in concert with the laws of electromagnetism. Its magnetic field is responsible for everything from the solar explosions that cause space weather on Earth — such as auroras — to the interplanetary magnetic field and radiation through which our spacecraft journeying around the solar system must travel. “We are not sure exactly where in the sun the magnetic field is created," said Dean Pesnell, a space scientist at NASA's Goddard Space Flight Centre in Greenbelt, Maryland. "It could be close to the solar surface or deep inside the sun — or over a wide range of depths," Pesnell said. To see these invisible fields, scientists observed the material on the sun. The sun is made of plasma, a gas-like state of matter in which electrons and ions have separated, creating a super-hot mix of charged particles. When charged particles move, they naturally create magnetic fields, which in turn have an additional
effect on how the particles move. The plasma in the sun sets up a complicated system of cause and effect in which plasma flows inside the sun — churned up by the enormous heat produced by nuclear fusion at the centre of the sun — create the sun's magnetic fields. This system is known as the solar dynamo, scientists said. Next, they turned to models. They combined their observations — measurements of the magnetic field strength and direction on the solar surface — with an understanding of how solar material moves and magnetism to fill in the gaps. The solar magnetic system is known to drive the approximately 11-year activity cycle on the sun. With every eruption, the sun's magnetic field smoothes out slightly until it reaches its simplest state, researchers said. At that point the sun experiences what is known as solar minimum, when solar explosions are least frequent. From that point, the Sun's magnetic field grows more complicated over time until it peaks at solar maximum, some 11 years after the previous solar maximum. “At solar maximum, the magnetic field has a very complicated shape with lots of small structures throughout – these are the active regions we see," said Pesnell. “At solar minimum, the field is weaker and concentrated at the poles. It is a very smooth structure that does not form sunspots," he said. The researchers were able to see how the magnetic fields change, grew and subsided from January 2011 to July 2014. The magnetic field is much more concentrated near the poles in 2011, three years after solar minimum. By 2014, the magnetic field has become more tangled and disorderly, making conditions ripe for solar events like flares and coronal mass ejections, researchers said. — PTI Source: http://www.tribuneindia.com/
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Superluminous Supernova 20 Times Brighter Than 100 Billion Stars Wows Astronomers

Records are made to be broken, as the expression goes, but rarely are records left so thoroughly in the dust. Stunned astronomers have witnessed a cosmic explosion about 200 times more powerful than a typical supernova--events which already rank amongst the mightiest outbursts in the universe--and more than twice as luminous as the previous record-holding supernova. At its peak intensity, the explosion--called ASASSN-15lh--shone with 570 billion times the brightness of the Sun. If that statistic does not impress, consider that this luminosity level is approximately 20 times the entire output of the 100 billion stars comprising our Milky Way galaxy. The record-breaking blast is thought to be an outstanding example of a "superluminous supernova," a recently discovered, supremely rare variety of explosion unleashed by certain stars when they die. Scientists are frankly at a loss, though, regarding what sorts of stars and stellar scenarios might be responsible for these extreme supernovae. These are pseudo-color images showing the host galaxy before the explosion of ASASSN-15lh taken by the Dark Energy Camera (DECam) [Left], and the supernova by the Las Cumbres Observatory Global Telescope Network (LCOGT) 1-meter telescope network [Right]. As described in a new study published today in Science, ASASSN-15lh
Credit: The Dark Energy Survey, B. Shappee and the ASAS-SN team
is amongst the closest superluminous supernovae ever beheld, at around 3.8 billion light years away. Given its uncanny brightness and closeness, ASASSN-15lh might offer key clues in unlocking the secrets of this baffling class of celestial detonations. "ASASSN-15lh is the most powerful supernova discovered in human history," said study lead author Subo Dong, an astronomer and a Youth Qianren Research Professor at the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University. "The explosion's mechanism and power source remain shrouded in mystery because all known theories meet serious challenges in explaining the immense amount of energy ASASSN-15lh has radiated." ASASSN-15lh was first glimpsed in June 2015 by twin telescopes with 14-centimeter diameter lenses in Cerro Tololo, Chile conducting the All Sky Automated Survey for SuperNovae (ASAS-SN), an international collaboration headquartered at The Ohio State University. (Hence ASASSN-15lh's somewhat menacing moniker.) These two tiny telescopes sweep the skies to detect suddenly appearing objects like ASASSN-15lh that are intrinsically very bright, but are too far away for human observers to notice. "ASAS-SN is the first astronomical project in history to frequently scan the entire optical sky for optical transients," said Krzysztof Stanek, professor of astronomy at the Ohio State University and the co-Principal Investigator of ASAS-SN. "Every time in science we open up a new discovery space, exciting findings should follow. The trick is not to miss them." Dong and colleagues immediately put out word about the sighting of ASASSN-15lh in order for as much data as possible to be gathered. Multiple, far larger ground-based telescopes across the globe, as well as NASA's Swift satellite, have since taken part in an intense observing campaign that continues to this day. In just the first four months after it went kablooie, so much energy beamed out of ASASSN-15lh that it would take our Sun in its current state more than 90 billion years to equal its emissions. By examining this bright, slowly fading afterglow, astronomers have gleaned a few basic clues about the origin of ASASSN-15lh. Using the 2.5-meter du Pont telescope in Chile, Dong's colleagues Ben Shappee and Nidia Morrell at the Carnegie Observatories in the United States took the first spectrum of ASASSN-15lh to identify the signatures of chemical elements scattered by the explosion. This spectrum puzzled the ASAS-SN team members, for it did not resemble any of spectra from the 200 or so supernovae the project had discovered to date. These are two of the 14-centimeter diameter lens telescopes in use for the All Sky Automated Survey for SuperNovae (ASAS-SN) that discovered ASASSN-15lh. Since this photo was taken, two more
Credit: Wayne Rosing
telescopes have been added to the ASAS-SN station in Cerro Tololo, Chile. Inspired by suggestions from Jose Prieto at Universidad Diego Portales and Millennium Institute of Astrophysics in Chile and Stanek, Dong realized that ASASSN-15lh might in fact be a superluminous supernova. Dong found a close spectral match for ASASSN-15lh in a 2010 superluminous supernova, and if they were indeed of a kind, then ASASSN-15lh's distance would be confirmable with additional observations. Nearly 10 days passed as three other telescopes, stymied by bad weather and instrument mishaps, attempted to gather these necessary spectra. Finally, the 10-meter South African Large Telescope (SALT) secured the observations of elemental signatures verifying ASASSN-15lh's distance and extreme potency. "Upon seeing the spectral signatures from SALT and realizing that we had discovered the most powerful supernova yet, I was too excited to sleep the rest of the night," said Dong, who had received word of the SALT results at 2 AM in Beijing on July 1, 2015. The ongoing observations have further revealed that ASASSN-15lh bears certain features consistent with "hydrogen-poor" (Type I) superluminous supernovae, which are one of the two main types of these epic explosions so named for lacking signatures of the chemical element hydrogen in their spectra. ASASSN-15lh has likewise shown a rate of temperature decrease and radius expansion similar to some previously discovered Type I superluminous supernova. Yet in other ways, besides its brute power, ASASSN-15lh stands apart. It is way hotter, and not just brighter, than its apparently nearest of supernova kin. The galaxy it calls home is also without precedent. Type I superluminous supernova seen to date have all burst forth in dim galaxies both smaller in size and that churn out stars much faster than the Milky Way. Noticing the pattern, astronomers hoped this specific sort of galactic environment had something to do with superluminous supernovae, either in the creation of the exotic stars that spawn them or in setting these stars off. Exceptionally, however, ASASSN-15lh's galaxy appears even bigger and brighter than the Milky Way. On the other hand, ASASSN-15lh might in fact reside in an as-yet-unseen, small, faint neighboring galaxy of its presumed, large galactic home. To clear up where exactly ASASSN-15lh is located, as well as numerous other mysteries regarding it and its hyper-kinetic ilk, the research team has been granted valuable time this year on the Hubble Space Telescope. With Hubble, Dong and colleagues will obtain the most detailed views yet of the aftermath of ASASSN-15lh's stunning explosion. Important insights into the true wellspring of its power should then come to light. One of the best hypotheses is that superluminous supernovae's stupendous energy comes from highly magnetized, rapidly spinning neutron stars called magnetars, which are the leftover, hyper-compressed cores of massive, exploded stars. But ASASSN-15lh is so potent that this compelling magnetar scenario just falls short of the required energies. Instead, ASASSN-15lh-esque supernovae might be triggered by the demise of incredibly massive stars that go beyond the top tier of masses most astronomers would speculate are even attainable. "The honest answer is at this point that we do not know what could be the power source for ASASSN-15lh," said Dong. "ASASSN-15lh may lead to new thinking and new observations of the whole class of superluminous supernova, and we look forward to plenty more of both in the years ahead." 
Contacts and sources:  Jim Cohen: The Kavli Institute for Astronomy and Astrophysics (KIAA) 

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