A newly-discovered amoeba has set the record for the hottest temperature at which complex life can thrive.

The amoeba, found in Lassen Volcanic National Park in California, grows and divides at temperatures up to 145 degrees Fahrenheit (63 degrees Celsius) and can survive brief stints in up to 158 F (70 C) environments, a new study finds. Prior to the discovery, no complex cells were known to replicate at temperatures above 140 F (60 C).

"I was very surprised," study first author Beryl Rappaport, a microbiologist at Syracuse University in New York, told Live Science. "We definitely had to go back and check to make sure that our incubators were calibrated correctly … It really was amazing."

Amoebas are single-celled organisms that move by pulling themselves forward with tendrils of cellular fluid. They are eukaryotes, which means they store their DNA inside a membrane-bound nucleus. Amoebas are neither plants, animals nor fungi, but they are more complex than prokaryotic organisms such as bacteria and archaea, which have no nucleus.

Past research had suggested that amoebas could thrive in warm geothermal springs, Rappaport said, but few of these organisms have been studied in laboratories. To investigate, Rappaport and her colleagues travelled to Lassen Volcanic National Park to collect and study these heat-loving creatures.

The team discovered the newfound amoeba in samples collected along a tributary of Hot Springs Creek inside the park. Dubbed Incendiamoeba cascadensis, or "fire amoeba from the Cascades," the species thrive at temperatures between 131 and 135 F (55 and 57 C). In fact, they stopped growing below 108 F (42 C), indicating that the amoebas need high temperatures to flourish.

Using a heated microscope that kept the amoebas toasty, the scientists watched the cells divide and replicate at temperatures as high as 145 F (63 C) — the highest temperatures known for eukaryotic cells (although prokaryotes have been known to survive temperatures as high as 250 F, or 122 C).

At 158 F (70 C), the amoebas created protective shells around themselves and went dormant. The cells recovered when the researchers left them at 158 F for five minutes, then brought the temperature back down to 140 F. But the amoebas didn't survive heating to 176 F (80 C).

I. cascadensis proteins also have positively charged amino acids, or protein building blocks, on their surface, the team found. Other heat-loving prokaryotes share the same feature. This adaptation may help keep proteins stable at high temperatures, the researchers noted.

The researchers reported their findings on Tuesday (Sept. 22) in the journal Cell.

This is not the first time we have seen specialized eukaryotic life-forms survive in extreme temperatures. For example, some fungi can tolerate temperatures up to 140 F in deserts. However, these figures still pale in comparison to the scorching temperatures that some bacteria can survive, and it's not yet clear what factors prevent eukaryotes from tolerating these higher temperatures, Rappaport told Live Science.

Part of the difference in heat tolerance between heat-loving prokaryotes and eukaryotes comes from their differing ability to genetically adapt to heat stress.

"When you're a bacterium … you can reshuffle your genome" by scooping up DNA from other prokaryotes, Debashish Bhattacharya, an evolutionary biologist at Rutgers University in New Jersey who was not involved in the study, told Live Science. That ability helps prokaryotes adapt relatively quickly to stressful environments.

But because DNA in eukaryotic cells is confined in the nucleus, "eukaryotes are not able to simply grab a bunch of genes and switch their lifestyle," at the same rates as prokaryotes, Bhattacharya said. "It takes far, far more evolutionary change to turn a eukaryote into an extremophile."

In future research, Rappaport plans to study Incendiamoeba's closest relatives to learn how they evolved to tolerate heat. Understanding these adaptations could help scientists grasp the limits of life on Earth as well as where else complex life could exist in the universe, she said.

'> Newfound 'fire amoeba from the Cascades' sets record for the hottest temperature complex life can survive at

Ultrafaint dwarf galaxies (UFDGs) are among the tiniest and faintest galaxies in the universe. These dim little clusters contain at most a few hundred thousand stars, compared with the Milky Way's approximately 100 billion, said Joshua Simon, an astronomer at the Observatories of the Carnegie Institution for Science who was not involved in the new research. Instead, "these galaxies are composed almost entirely of dark matter: 99 to 99.9% of their mass is dark, and only 0.1 to 1% is made up of stars," Simon told Live Science in an email.

Because UFDGs are so small and faint, even ones in the Milky Way's vicinity are difficult to detect. Such dwarf galaxies orbit ours, similar to how Earth orbits the sun. In a 2020 study, scientists estimated that hundreds of these satellite UFDGs may exist. However, only around 60 have been found so far, Aashay Pai, a graduate student in physics at the University of Chicago and a co-author of the new study, told Live Science in an email.

But the Rubin Observatory's supersharp vision is poised to increase that total. The telescope's 3,200-pixel, car-sized camera can detect objects up to 100 million times dimmer than those visible to the naked eye as it takes repeat observations of the night sky every few nights. This makes the observatory well equipped to find UFDGs.

However, the data analyzed in the new study wasn't from the LSST; it came from an earlier test run. This test data, collected between April 2025 and January 2026, was called Early Data Preview 2 (EDP2) and covered roughly 7% of the night sky.

The researchers used computer models on the EDP2 data to identify UFDGs as groups of stars whose brightness and colors suggested they had evolved together. The researchers assumed that these stars were around 13 billion years old, Pai said — nearly as old as the universe itself. This framework allowed them to distinguish UFDGs from stars and other galaxies in front of or behind the observed areas.

With this approach, the researchers detected the previously unseen UFDG. Their findings were published in August in the journal Research Notes of the AAS, which presents non-peer-reviewed work in progress. In the research article, the team states that the newfound UFDG was detected at the eight-sigma significance limit, meaning the chance that this group of stars is a random collection is about 1 in 1.6 quadrillion.

The researchers also verified the galaxy's discovery using older images snapped by the 570-megapixel Dark Energy Camera on the NSF Victor M. Blanco Telescope in Chile; the photos showed faint stars that had been overlooked. Although this analysis had a lower significance limit of six sigma — giving it about a 1-in-100-billion chance of being a random fluke — it still supported the tiny galaxy's existence.

The newly discovered satellite galaxy, which the researchers named Aquarius IV, lies in the direction of the constellation Aquarius. Pai described it as "one of the faintest and most compact UFDGs at a large distance." The analyses suggest that the galaxy lies approximately 359,000 light-years from the Milky Way's center. (For comparison, the Milky Way itself is roughly 100,000 light-years long.)

Pai estimated Aquarius IV's mass at about 1,500 times that of the sun. That makes it lightweight relative to the Milky Way, whose mass equals that of 1.5 trillion suns, according to NASA. Furthermore, the absolute magnitude — or intrinsic brightness — of Aquarius IV is -1.9, making it 14 million times dimmer than the Milky Way.

Simon described the discovery of Aquarius IV as robust. However, Pai cautioned that follow-up observations will be required to confirm the object's identity.

Besides fleshing out our map of the nearby universe, studying UFDGs can reveal more clues about the mysterious nature of dark matter, which makes up about 85% of all matter in the universe but doesn't interact with light. Additionally, "the stars in ultra-faint dwarfs are also extremely old, dating back to just after the Big Bang, so they give us a unique window to the properties of the first galaxies that formed," Simon explained.

Pai noted that the Rubin Observatory is expected to find up to 100 such UFDGs during the LSST survey, which officially began in June. The survey will create the most detailed time-lapse video of the universe ever recorded and is expected to reveal millions of changes in the night sky every night, leading to an untold number of discoveries.

How well do you know our home galaxy? Find out with our Milky Way quiz!

'> Vera C. Rubin Observatory detects one of the smallest and faintest satellite galaxies ever seen humanitarian crisis in some regions.

While El Niño is part of a natural multiyear climate cycle, scientists have noticed that it has been rapidly strengthening like never before, intensified by human-driven climate change, and putting stressed natural systems under extra strain.

In a new update this week, the National Oceanic and Atmospheric Administration's (NOAA) Climate Prediction Center continues to forecast a 75% chance that this El Niño event will be stronger than any previous El Niño since 1950, the earliest year from which NOAA has data to make historical comparisons. Furthermore, this El Niño appears to be going "super" ‪—‬ something that has been expected for weeks.

Weekly NOAA data from the eastern Pacific's El Niño region reveal that sea surface temperatures have reached 3.8 degrees Fahrenheit (2.1 degrees Celsius) above average, hitting the more than 3.6 F (2 C) threshold for a very strong or "super" event. Strictly speaking, NOAA uses three-month averages to categorize strength, as weekly data is more prone to temporary anomalies. But the latest data once again signals where this El Niño is heading, with NOAA forecasting a more than 90% chance of a very strong event emerging in the fall and winter.

How will El Niño impact the U.S.?

During El Niño, warmer waters gather east of the equatorial Pacific, forcing the jet stream south. The patterns associated with El Niño bring exceptionally stormy winter weather and a higher chance of rain and snow across California and Southern states, with Northern states experiencing fewer storms and a milder winter, according to the Climate Prediction Center. El Niño can also increase the risk of high-tide flooding, particularly on the West Coast, according to NOAA.

However, as with climate change in general, El Niño doesn't have the same impacts on all regions. Furthermore, while a more intense El Niño typically increases the certainty of expected impacts, they are not guaranteed.

The last "super" El Niño happened in 2015 and 2016. Associated impacts included a historic hurricane season in the central North Pacific and record drought in the Caribbean, according to Climate.gov. Before that, the last El Niño to go super was in 1997 and 1998. That winter was marked by a variety of extreme weather events, including flooding in the Southeast, an ice storm in the Northeast and tornadoes in Florida, according to a report by the National Climatic Data Center.

Already this year, tropical storms in Hawaii have been attributed to El Niño, with warming in the waters where storms typically form there, CNN reported. Meanwhile, the strengthening of El Niño in the Pacific appears to have left the Atlantic unusually calm. Ars Technica reported that the Atlantic hurricane season passed its traditional peak without a tropical storm or hurricane in what is becoming a historic period of quiet.

What is El Niño?

El Niño affects the whole planet, but it begins with unusually warm waters in the eastern tropical Pacific Ocean. NOAA recognizes El Niño conditions when these waters are at least 0.9 F (0.5 C) warmer than average, while wind, surface pressure and rainfall in the region are also consistent with El Niño conditions. An El Niño is then categorized based on its strength, from weak to very strong. Very strong El Niños (above 3.6 F, or 2 C, warmer than average) are nicknamed "super" El Niños, though this isn't a scientific term.

The European Centre for Medium-Range Weather Forecasts' El Niño models suggest that temperatures are sailing past the 2 C threshold and will exceed 6.3 F (3.5 C) by the end of the year. On Sept. 20, the daily El Niño temperature was 5.5 F (3.06 C), according to The Climate Brink. But while this year's El Niño is certainly supercharged, there's still uncertainty about its impacts.

El Niño forecast

On Sept. 3, the World Meteorological Organization (WMO) released a fresh set of El Niño warnings along with a Global Seasonal Climate Update, which the WMO said offers a more refined picture of expected conditions in the coming months.

"For September-November 2026, WMO multi-model forecasts indicate an increased likelihood of above-normal temperatures across almost all land areas, alongside rainfall patterns showing a pronounced and classic atmospheric response to the strong Pacific El Niño," WMO representatives wrote in a statement.

In other words, much of the world is likely to be hotter than normal, while some areas will experience more rainfall and others will see less. The most severe El Niño impacts will likely be felt outside North America.

Liz Stephens, a professor in climate risks and resilience at the University of Reading in the U.K., recently noted that the Indian monsoon season had seen less rainfall than normal and that satellite data revealed that parts of East Africa, Central America and Southeast Asia are experiencing record-dry conditions. The human impact of such weather can be devastating.

"During the large El Niño event of 1997/1998 the associated flooding in Somalia killed over 2000 people," Stephens said in a statement released Sept. 3. "With a bigger El Niño event on the way, and global temperatures now 0.7°C [1.26 F] higher and capable of holding even more moisture as a result of climate change, scientists are concerned that there is potential for even more severe flooding."

'> US heading for unprecedented El Niño winter: Here's what to expect

The sweet spot was 4.33 billion years ago, although Earth may have become suitable for the RNA World as early as 4.4 billion years ago, given that extreme bombardment by asteroids, comets and other rocky leftovers of planet formation had largely stopped by then, the researchers reported in a study published Tuesday (Sept. 22) in the journal Nature Communications.

The findings give a more precise estimate of the RNA World's onset than previous studies based on geochemical modeling, biomolecular analyses and simulations of early atmospheric chemistry did, study first author Oleg Abramov, a senior scientist at the Arizona-based Planetary Science Institute, told Live Science in an email.

"The timing is consistent with previous estimates of approximately 4.35 billion years ago, but our range of uncertainty is significantly narrower," Abramov explained, adding that "previous ranges included 4.46 to 4.26 billion years ago, and 4.45 to 3.9 billion years ago."

The RNA World is a hypothetical time in Earth's history before the emergence of the Last Universal Common Ancestor (LUCA), the single microbe from which all living things on Earth descend. RNA, or ribonucleic acid, is a single-stranded molecule that is structurally similar to DNA and performs vital functions in living cells. Scientists think the RNA World preceded the emergence of DNA; in that early epoch, RNA would have been the primary replicating substance, carrying genetic information across generations of basic lifeforms by copying itself independently.

RNA evolved into its more chemically stable cousin, DNA, sometime before the emergence of LUCA. Scientists think the RNA World first developed into an RNA-and-protein world, and that DNA then appeared in two distinct stages nicknamed the U-DNA and T-DNA worlds.

While researchers have suggested alternative and hybrid scenarios for the emergence of life on Earth, the RNA World is a leading hypothesis, Abramov said. To determine when it might have existed, he and his colleagues built a computer model of Earth's interior that simulated how giant impacts on the planet's surface between 4.5 billion and 3.5 billion years ago affected conditions in the crust and Earth's overall compatibility with life.

"We constructed an impact bombardment model constrained by observables such as the lunar cratering record," Abramov said. "We examined both detrimental effects of impacts, such as temperature-induced degradation of key biomolecules, and effects conducive to life, such as generation of hydrothermal systems."

The model showed that space rocks measuring hundreds of miles across — an order of magnitude larger than the asteroid that killed the dinosaurs, but far smaller than the impactor that created the moon — went on slamming into Earth and sterilizing its surface until 4.4 billion years ago. Life could not have survived such intense bombardment, which probably triggered widespread melting of the crust, ocean vaporization, extreme temperature gradients in the crust and continuous showers of burning material and rock-vapor rain at the surface, Abramov said.

However, the conditions stabilized after 4.4 billion years ago. And as a result, hydrothermal vent clusters appeared within the near-surface crust that concentrated the ingredients for RNA, including nucleotides, short amino-acid chains called peptides and fat-like compounds known as lipids, Abramov said.

"These criteria point to the Earth becoming suitable for an RNA World between 4.4 and 4.3 billion years ago, with optimal conditions at approximately 4.33 billion years ago," he said.

The results suggest there was a gap of roughly 130 million years between the heyday of the RNA World and the emergence of LUCA, which scientists think lived about 4.2 billion years ago. However, there are still large uncertainties around both events, so the interval could be as big as 240 million years, Abramov noted.

"The duration of the RNA World is highly uncertain, and our study did not explicitly constrain it," he said.

'> Scientists identify 'sweet spot' for early stage of life on Earth that preceded LUCA, the ancestor of all living things