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After analyzing the temperature data from 2023, NASA has concluded that it was the hottest year on record. This will surprise almost nobody. If you live in one of the regions stricken by drought, forest fires, or unusually powerful weather, you don’t need NASA to confirm that the planet is warming.

NASA’s Goddard Institute for Space Studies produced the analysis that led to this conclusion. They looked at temperature anomalies rather than strictly at temperatures. Temperature anomalies show how much hotter or colder than normal it is at a specific place and time. In this case, normal means the average over a 30-year period between 1951 and 1980 for a time and place.

The analysis, which makes use of extensive satellite data, showed that 2023 was the hottest year on record. In fact, every month from June to December 2023 was the hottest month compared to the same months in previous years. Not only that, but July was the hottest month ever recorded.

This image shows the global temperature anomalies for July 2023. Image Credit: NASA’s Scientific Visualization Studio

How much hotter was 2023? “Global temperatures in 2023 were around 2 degrees Fahrenheit (1.1 degrees Celsius) above the average for NASA’s baseline period (1951-1980),” NASA’s Goddard Institute for Space Studies (GISS) said.

Anyone who follows news from around the world knows the world is facing more severe weather. In the USA, a mega-drought meant that parts of the Southwest suffered from a water shortage. Reservoirs were reduced to historically low levels.

In Canada, massive, numerous, and stubborn forest fires dominated the summer, with smoke moving south and enshrouding some of America’s largest cities for days. Many of those fires are still burning as zombie fires that will spring back to life after this winter.

The Donnie Creek fire of 2023 in British Columbia, Canada, was the largest-ever fire in that province. It covered over 600,000 hectares. Image Credit: BC Wildfire Service.

In Asia, a record-breaking heat wave struck India, China, Vietnam, and other countries. In India, major cities exceeded 45 Celsius, schools and other places were shutdown, and rolling blackouts, triggered by air conditioner use, made things even worse.

In the desert kingdom of Saudi Arabia, the temperatures reached 49 C in some places. In Europe, the Cerberus Heatwave brought temperatures above 40 C to many countries, including Spain, where temperatures reached 45 C.

Hundreds of millions of us faced extreme temperatures during the summer of 2023. Millions of us watched helplessly as forest fire smoke clouded our skies and damaged our lungs. Farmers struggled, and food prices rose.

But climate change isn’t just about heat, smoke, and fire. It’s also about extreme rainfall, flooding, and hurricanes. Whatever the consequences, it’s not something humanity has seen before.

“The exceptional warming that we’re experiencing is not something we’ve seen before as a species,” said Gavin Schmidt, director of GISS. “It’s driven primarily by our fossil fuel emissions, and we’re seeing the impacts in heat waves, intense rainfall, and coastal flooding.”

Most of what the Earth is going through is due to human-caused climate change. But other things still contribute to the climate, like El Nino and El Nina. Climate scientists consider all these things when trying to understand what’s happening.

This image shows how the El Niño Southern Oscillation (ENSO) affects global temperatures. There are three phases in the South Pacific’s ENSO: El Niño, La Niña, and neutral, or average. El Nino is a weakening of trade winds that blow from east to west in the South Pacific, allowing the sea surface to warm up and rise. La Nina is the opposite: the winds become stronger, and sea temperatures become cooler than normal. La Nina can help offset some of the effects of climate change, but only temporarily. Image Credit: NASA

But we have no control over El Nino. Our carbon emissions are the only thing we have control over. Vegetation and the oceans only absorb about 50% of our emissions, and the rest persists in the atmosphere.

This visualization shows the atmosphere in three dimensions and highlights the accumulation of CO2 during a single calendar year.

It’s not just Earth’s atmosphere that warms. Our oceans absorb most of the heat trapped by greenhouse gases, about 90% of it. The oceans are a gigantic heat sink, and they’ll continue to warm as the atmosphere does. That changes the biochemistry and the overall health of the oceans and also accelerates the melting of our major ice sheets.

“Just like global temperatures, ocean temperatures are on the rise,” said Josh Willis, a climate scientist at NASA’s Jet Propulsion Laboratory. “They have been rising for the last century or more, and they are not slowing down. If anything, they are speeding up.”

This image shows anomalies in the sea surface temperature. These temperatures reached new record highs in 2023. Image Credit: NASA.

The world will keep warming for the next several decades or more, no matter what changes we make today. But the future is still in play. Scientists still need as much detailed climate data as we can gather, even though we know we’re responsible for the warming world. We can still prepare for the worst of it while developing and implementing solutions.

“We are very interested in the weather and extremes of any particular year because those are the things that impact us,” said GISS Director Schmidt. “But the key difference between this decade and the ones before is that the temperatures keep rising because of our activities, principally the burning of fossil fuels.”

NASA’s results show the future we face. More heatwaves, more devastating forest fires, more pressure on agriculture and food prices, and a bleak future for some of the world’s poorest people.

But it’s not foreordained. There are solutions, and they’re being implemented. Renewable energy use is on the rise, for example, and people around the world are demanding that governments implement more changes. And while arcane scientific arguments about atmospheric chemistry and physics are not that impactful for many people, extreme heat is a much more effective alarm bell. So are the things that extreme heat brings, like flooding, fire, smoke, heat waves, rising sea levels, and higher food prices.

Let’s hope the next generations and the politicians that accompany them don’t keep pressing the snooze button like we have.

The post NASA Confirms that 2023 was the Hottest Year on Record appeared first on Universe Today.

We have all been there, had that one stubborn jar of jam that we just can’t open. Maybe you grab a rubber band or run it under warm water and its an easy fix but just imagine when the jar is a module from a $1.16 billion interplanetary probe! That’s what happened to NASA engineers when they were trying to recover samples from the OSIRIS-REx module  when they discovered the clamps had cold welded shut! 

OSIRIS-REx is a NASA mission to retrieve a sample from asteroid Bennu and return it to Earth. The probe launched in September 2016 in what was a complex and audatious mission. In order to collect the samples the probe ‘kissed’ the surface at just the right trajectory and velocity so not to be destroyed and to return them, OSIRIS-REx completed a flyby manouvre of Earth and dropped them off before continuing on to a new destination. Impressive stuff.

An artist’s illustration of NASA’s OSIRIS-REx spacecraft approaching asteroid Bennu with its sampling instrument extended. Image Credit: NASA/Goddard/University of Arizona

The samples were successfully returned to Earth on 24 September 2023 having been deployed high above the Earth’s atmosphere. The capsule then gracefully floated down under a parachute to the Department of Defense’s Utah Test and Training Range. The samples that were contained within will help us to better understand how the planets formed, how life began and to improve our knowledge of asteroids and just how we might be able to defend ourselves from future potential impacts. 

Having successfully completed the sample collection and recovery, it seems that getting the samples out of the capsule was destined to be the more challenging aspect.  When the engineers tried to open the sample head of the Touch and Go Sample Acquisition Mechanism they quickly learned that two of the 35 fastenings had cold welded themselves shut!

Unfortunately, the team did not have any ready made tools for such a situation so they had to improvise and created their own new tool from a special non-magnetic stainless steel. If this wasn’t hard enough, the team’s challenge was exaserbated because of the lack of space in the container that the samples and the capsule were stored within. This process was a laborious one though as the team had to test and refine the tool and instrument many times to minimise risk of damage and contamination.

Success was limited as the team were only able to recover 70 grams of the asteroid sample although this was in excess of the target 60 grams. The science teams are now working with some of the samples and have hermetically sealed the rest for future studies.

Source : NASA’s OSIRIS-REx Team Clears Hurdle to Access Remaining Bennu Sample

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Planning large astronomical missions is a long process. In some cases, such as the now functional James Webb Space Telescope, it can literally take decades. Part of that learning process is understanding what the mission will be designed to look for. Coming up with a list of what it should look for is a process, and on larger missions, teams of scientists work together to determine what they think will be best for the mission. In that vein, a team of researchers from UC Berkeley and UC Riverside have released a paper describing a database of exoplanets that could be worth the time of NASA’s new planned habitable planet survey, the Habitable Worlds Observatory HWO.

Astronomy’s decadal surveys are the starting point for many ambitious projects, and the Astro2020 Decadal Survey didn’t disappoint. It called for NASA to develop a 6-meter space telescope capable of high-contrast observations in optical, infrared, and ultraviolet wavelengths. 

That project became known as the HWO; its primary mission is to observe 25 different exoplanets in their parent star’s habitable zones and look for biosignatures on them. Essentially, it will be humanity’s best alien finder. While not searching biosignatures, it can also do general astronomy, but knowing what planets to look at is critical to its mission.

The first in a series of lectures leading up to the advent of the HWO.
Credit – STScI Research YouTube Channel

To tackle that part of the project, a NASA project known as the Exoplanet Exploration Program developed a list of 164 candidate exoplanets “whose [hypothetical] exo-Earths would be the most accessible” for the HWO. Mainly, that accessibility had to do with the characteristics of the planet’s parent star, but its separation from that star was also considered. 

While those are helpful characteristics to consider, there are plenty more factors that we believe go into whether a planet is habitable or not. These include the frequency of flares and the abundance of certain elements in the star itself. That is precisely the kind of information the new catalog contains.

Specifically, the measurements the authors collected can be broken down into five categories: stellar element abundance, photometric values, flare rates, variability estimates, and X-ray emissions. However, each of those categories has plenty of nuance in it. For example, the researchers collected 1700 stellar measurements of elemental abundance for 14 different elements. However, they could only find X-ray emission data for 41 of the 168 stars in the catalog.

Fraser discusses what exoplanet hunting will look like in the future.

The lack of data isn’t surprising, as they were simply collecting data from other publicly available sources. Some of those sources focused on thousands of stars and weren’t paying close attention to the ones needed from this data set. Data came from various places, including the Gaia, TESS, and WISE.  

Even the database itself was modeled on a similar one, known as ExEP Mission Star List (EMSL), that was originally developed for two other Great Observatories, LUVOIR and HabEx. Each has its own specialization, and while there is some overlap with HWO, the data defining those missions wasn’t complete enough to help define HWO.

As such, there is still work to do in drawing up a project definition and finalizing the scientific and technical goals for HWO. The authors pointed out that this paper was only the first of a series of precursor papers that would help flesh out what this new observatory would be able to do. Luckily, the catalog they have created is freely available, so any interested party can explore the data they’ve collected and potentially contribute to some of the future work defined at the end of the paper. There’s always more science to be done.

Learn More:
Harada et al. – Setting the stage for the search for life with the Habitable Worlds Observatory: Properties of 164 promising planet survey targets
UT – Planning is Underway for NASA’s Next Big Flagship Space Telescope
UT – An Ambitious New Technology Might be Needed to See Other Earths
NASA Science – Habitable Worlds Observatory

Lead Image:
Artist’s illustration of exoplanets

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There’s a galaxy out there without apparent stars but largely chock full of dark matter. What’s that you say? A galaxy without stars? Isn’t that an impossibility? Not necessarily, according to the astronomers who found it and are trying to explain why it appears starless. “What we do know is that it’s an incredibly gas-rich galaxy,” said Green Bank Observatory’s Karen O’Neil, an astronomer studying this primordial galactic object. “It’s not demonstrating star formation like we’d expect, probably because its gas is too diffuse.”

O’Neil and a team of colleagues found this odd, seemingly starless object called J0613+52, while they were doing a sky survey. Their target was a set of so-called “Low Surface Brightness” galaxies (LSBG) They used the Green Bank Telescope, the Arecibo Telescope (before its untimely end), and the Nançay Radio Telescope to look at 350 of these dim, diffuse objects. The idea was to survey them and determine their gas content and dynamic masses.

J0613+52 wasn’t one of the team’s original targets. Instead, they stumbled across it while trying to figure out why some of the data from Green Bank and Nançay didn’t match, according to O’Neil. “The GBT was accidentally pointed to the wrong coordinates and found this object,” she explained, noting that this galaxy was new and unknown. There are no galaxies within 112 parsecs, making it a pretty isolated target. Interestingly, based on their observations, the team found that J0613+52 has about the same characteristics of mass and gas content as a normal spiral. Yet, it has no stars. That poses a mystery they’d like to solve.

What’s a Low Surface Brightness Galaxy?

The type of galaxy represented by J0613+52 is an odd one when you compare it to the more familiar types such as the star-filled spirals and ellipticals. For one thing, it’s a dwarf galaxy with an irregular shape. Without any obvious stars, it’s quite dim. The most unusual thing about objects like this one is that dark matter appears to dominate their compositions. If J0613+52 is like others, it could have up to 95 percent dark matter constraining the neutral gaseous hydrogen that we can detect.

So, why no stars in J0613+52? O’Neil describes it as an “unevolved” dwarf. That’s because the neutral hydrogen gas component is too diffuse, and too spread out. LSBG generally have less gravity and that makes it tough to form stars on their own. So, they evolve very gradually. If they do start to convert gas to stars, it takes a long time for that to happen. Some astronomers suggest that LSBG are late-forming objects in cosmic time. That might explain the presence of this one in relatively “modern” times.

In addition, J0613+52 lies too far from any neighboring galaxies to interact with them gravitationally. That means they can’t trigger star formation through any possible mergers or collisions. “J0613+52 appears to be both undisturbed and underdeveloped,” she said. “This could be our first discovery of a nearby galaxy made up of primordial gas.” That means its gas content is largely unchanged over time.

J0613+52 and Dark Matter

J0613+52 is fascinating on its own, but it also has something to say about dark matter. We can’t see this unknown “stuff” but we can measure its gravitational effects. It seems to dominate in regions where these dwarf LSBG form and that gives astronomers insight into how this stuff is distributed in the Universe.

Dark matter content may also explain why galaxies like J0613+52 don’t easily interact with others. Dark matter “halos” act like gatekeepers to keep them apart. That lack of “contact” may kept it from forming giant stars as a result of collisions. Those kinds of stars are among the first to form. They ultimately die in supernova explosions and seed their environments with the heavy elements needed for ongoing star and planet formation. J0613+52 and others don’t have those heavy elements, which is another clue that stars aren’t forming inside them.

Any Other Ones Like this Dark Matter Galaxy?

It’s not the first time someone has stumbled across a “dark” galaxy like this one. There are certainly other candidates. Astronomers found what a dark galaxy called VIRGOH1 21 in 2005 in the Virgo Cluster. One consensus is that it’s made largely of dark matter. That describes J0613+52 as well. VIRGOH1 21 was found using radio telescopes, too, looking for the vibrations of hydrogen gas molecules. Since its discovery, however, some astronomers have suggested that this dark galaxy could be part of a tidal tail of gas and debris generated by a long-ago galactic collision. That uncertainty is why further observations of J0613+52 will be crucial.

A radio view tracing out gas in the so-called “dark matter galaxy” VIRGOH121. Made from data collected by the Arecibo Radio Telescope.

In her presentation at AAS, O’Neil pointed out that it will take high-sensitivity instruments to explore J0613+52 and understand its characteristics. There is a new one about to be installed at Green Bank, called ALPACA (Advanced L-Band Phased Array Camera for Astronomy). Once it’s up and running, ALPACA will extend the field of view of the telescope, allowing astronomers to probe further into J0613+52 and other low surface brightness galaxies like it.

For More Information

Astronomers Accidentally Discover Dark Primordial Galaxy
Low Surface Brightness Galaxies

Green Bank Observatory: Technology in the Next Decade

The post A Primordial Dark Matter Galaxy Found Without Stars appeared first on Universe Today.

The surface of Mars is hostile and unforgiving. But put a few meters of regolith between you and the Martian sky, and the place becomes a little more habitable. Cave entrances from collapsed lava tubes could be some of the most interesting places to explore on Mars, since not only would they provide shelter for future human explorers, but they could also be a great place to find biosignatures of microbial life on Mars.

But cave entrances are difficult to spot, especially from orbit, as they blend in with the dusty background. A new machine learning algorithm has been developed to quickly scan images of the Martian surface, searching for potential cave entrances.

Researchers Thomas Watson and James Baldini from Durham University in the UK used a convolutional neural network (CNN), trained to identify potential cave entrances (PCEs) from images of the Martian surface to locate new potential caves. It was able to identify 61 new cave entrances from images in four different regions on Mars.  

Previously, most detections of Martian PCEs have come from a manual review of visible satellite imagery, with images taken by the Mars Reconnaissance Orbiter’s (MRO) Context Camera (CTX) and High-Resolution Imaging Science Experiment (HiRISE) cameras. A database from that manual review called the Mars Global Candidate Cave Catalogue (MGC3) contains the coordinates and brief descriptions of over one thousand identified PCEs on Mars.

The circular black features in this 2007 figure are caves formed by the collapse of lava tubes on Mars. Image credit: NASA/JPL-Caltech/ASU/USGS

“Manual review of satellite imagery for Martian cave detection is far from efficient on a planet-wide scale,” wrote Watson and Baldini in their paper, published in the journal Icarus, “due to the time constraints associated with reviewing such a large dataset. Machine learning presents an intriguing solution to this problem, reducing the dataset to only include imagery computationally determined to contain a PCE.”

The caves on Mars are created by lava tubes, which were formed by flowing lava on ancient Mars. As the outside of the flowing lava cooled and solidified into a ceiling and walls, the interior stayed molten and kept flowing. Eventually, the lava flowed out of the tube in a downslope direction, leaving the tube intact and open. Sometimes these lava tubes are apparent from linear pit chains on the surface – many of which are likely connected linearly underground. But more commonly, they are found by locating a “skylight” or collapsed lava tube ceiling in an orbital image. That skylight provides an entrance to the underground cave.

This is a collapsed ceiling of a Martian lava tube. It measures 50 meters (150 ft) across, much larger than any Earth lava tubes. Image Credit: NASA/JPL/University of Arizona

Lava tubes can be found on Earth, the Moon, and Mars. Even though Earth is larger than Mars, some incredibly large lava tubes have been found on Mars, bigger than those found on Earth. On Earth, lava tubes are usually only as large as 14–15 meters (46–49 ft) wide – and typically much narrower. In 2020, the HiRISE (High-Resolution Imaging Science Experiment) camera on NASA’s Mars Reconnaissance Orbiter (MRO) took a picture of a collapsed lava tube ceiling that is pit crater is 50 m (150 ft) across. The subsurface lava tube cave is likely larger than that.

Regular neural networks are commonly used for natural language processing and speech recognition. But CNNs or ConvNets are more often utilized for classification and computer vision tasks. CNNs can recognize patterns in images and provide image classification and object recognition to projects both large and small. For example, in a previous study, CNNs were trained to recognize Martian surface features, such as craters, and achieved accuracies of more 90%

Watson and Baldini created and trained their CNN model, called CaveFinder by having it look at images from the MGC3 catalog from the Tharsis and Elysium regions on Mars, which has the highest concentrations of volcanoes.

Elevation map of Martian surface with five survey regions highlighted. The Tharsis and Elysium Bulges and the Hellas Basin are also highlighted. Map created using MOLA Shaded relief/ colorized digital elevation map from JMARS. Credit: Watson and Baldini/Icarus.

After the training period, CaveFinder achieved a test accuracy of 77%. It found four PCEs that Watson and Baldini highlighted for having specific qualities that make them interesting for further research, including one PCE nicknamed Marvin, which was the largest PCE identified, as well as another they called Emily, whose low altitude could enable surveyance by drone. Additionally, CaveFinder identified twelve regions that appear to have multiple PCEs, which the authors say be a great place to explore multiple caves with a future mission, due to the proximity and abundance of PCEs.

But the researchers say that CaveFinder needs more work before being used on a large, planet-wide database. It had a large number of false positives, and it appears to have a limited ability to identify “lone small cave types, such as skylights and pinholes.”

“CaveFinder is still not considered appropriate for detection on a planet-wide scale, due to the high number of false positive outputs requiring manual assessment,” Watson and Baldini wrote. “However, it could prove effective in smaller regions perhaps already known to contain PCEs.”

For future tests, they plan to increase the size of the training dataset used. Other ideas for improving CaveFinder’s accuracy is to use thermal imagery alongside the visible data. Higher resolution images from a future Mars orbiter would also be beneficial for CaveFinder’s increased detection and accuracy.

“Overall, this survey’s findings indicate that, with these additions, machine learning has a great potential to advance remote cave detection, which is key to future Martian exploration,” the researchers concluded.

The post Machine Learning Could Find all the Martian Caves We Could Ever Want appeared first on Universe Today.

In the search for potentially life-supporting exoplanets, liquid water is the key indicator. Life on Earth requires liquid water, and scientists strongly believe the same is true elsewhere. But from a great distance, it’s difficult to tell what worlds have oceans of water. Some of them can have lava oceans instead, and getting the two confused is a barrier to understanding exoplanets, water, and habitability more clearly.

This brings us to K2-18b, a mini-Neptune orbiting a red dwarf (M dwarf) star about 134 light-years away. The Kepler Space Telescope found it in 2015. NASA’s Exoplanet Catalog describes it as a potentially rocky world almost nine times more massive than Earth. It takes about 30 days to complete one orbit and is about 0.1429 AU from its star.

When it was confirmed as a planet, the authors of the paper presenting the results wrote that “The planet orbiting K2-18 may be an interesting target for atmospheric studies of transiting exoplanets.”

Prophetic words, and when the JWST examined K2-18b’s atmosphere in 2023, it found the carbon-bearing molecules methane and carbon dioxide. “Webb’s discovery adds to recent studies suggesting that K2-18 b could be a Hycean exoplanet, one which has the potential to possess a hydrogen-rich atmosphere and a water ocean-covered surface,” a NASA press release said.

Planetary scientists are very interested in Hycean exoplanets. As things stand now, they’re purely hypothetical. But if scientists could confirm the existence of one of these ocean-bearing planets, the outlook for life elsewhere in our galaxy would change considerably. (If they’re not subject to the runaway greenhouse effect.) If we could reliably find a population of Hycean worlds spread out among the stars, surely that would constitute a powerful signal that life is not confined to Earth.

But there’s a lot of uncertainty regarding Hycean worlds. Do they exist? Can they hold onto their oceans, or are they too hot? Could something else explain the JWST’s atmospheric findings? Why is there a discrepancy between observation and climate modelling? The authors of a new paper point out that, observationally, K2-18b is the archetypal Hycean world. As such, it’s a good place to try to answer some of our scientific questions. The authors say that K2-13b could indeed be an ocean planet, but an ocean of lava rather than water.

The new paper is “Distinguishing oceans of water from magma on mini-Neptune K2-18b.” The lead author is Oliver Shorttle, who studies planetary chemistry at the Institute of Astronomy at Cambridge University. The paper is in pre-print and hasn’t been peer-reviewed yet.

“We propose a solution to this discrepancy between observation and climate modelling by investigating the effect of a magma ocean on the atmospheric chemistry of mini-Neptunes,” the authors write.

K2-18b is a puzzle. Its density is in between Neptune’s and Earth’s, meaning its composition is uncertain. Its density covers a range of possible compositions. JWST observations show that it has a carbon-rich atmosphere and an ammonia-poor atmosphere. These observations are both indicators of an ocean world with a thick H/He atmosphere.

Spectra of K2-18 b, obtained with Webb’s NIRISS (Near-Infrared Imager and Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrograph), display an abundance of methane and carbon dioxide in the exoplanet’s atmosphere. The detection of methane and carbon dioxide and the shortage of ammonia support the hypothesis that there may be a water ocean underneath a hydrogen-rich atmosphere in K2-18 b. Image Credit: NASA, CSA, ESA, R. Crawford (STScI), J. Olmsted (STScI), Science: N. Madhusudhan (Cambridge University)

But there’s another possible explanation: a magma ocean. “We demonstrate that atmospheric NH3 depletion is a natural consequence of the high solubility of nitrogen species in magma at reducing conditions, precisely the conditions prevailing where a thick hydrogen envelope is in communication with a molten planetary surface,” the authors write.

As is so often the case when it comes to atmospheres, the availability of oxygen plays an enormous role. Oxygen is a swinger; it likes to bond with almost anything. Its presence dictates a lot of what happens in an atmosphere.

“How oxidizing a magma is has a profound effect on the solubility of nitrogen,” the authors. Nitrogen is necessary for ammonia to form since ammonia is NH3. So when the JWST found no ammonia in K2-18b’s atmosphere, it may not indicate a Hycean world after all. Instead, it may indicate a magma ocean.

The researchers used models and simulations to try to determine what the JWST observations mean for K2-18b.

This figure from the study shows the relationship between oxygen fugacity and how much nitrogen can stay in the atmosphere of a magma ocean planet. “As oxygen fugacity is decreased, nitrogen’s increased solubility depletes the atmosphere by orders of magnitude,” the authors explain. (Each coloured circle represents a model run for a given set of parameters.) Image Credit: Shorttle et al. 2024.

The researchers found that some of their modelled results of a magma ocean world agree with what the JWST found. “A set of the resulting atmospheres in the magma ocean scenario are consistent with the full transmission spectrum of K2-18b observed by JWST,” they write, adding that “this self-consistent magma ocean model can produce a qualitatively similar transmission spectrum to that observed for K2-18b, and those hypothesized for Hycean planets generally.”

If Shorttle and his colleagues are correct, then a dearth of ammonia can no longer be used to indicate the presence of an ocean on a Hycean world. Ammonia’s profile in an atmosphere can be attributed to both the magma ocean scenario and the water-world scenario. They’re not exclusive.

Artist’s depiction of a waterworld. So far, they’re only hypothetical and can be confused with magma ocean worlds. We need a way to tell them apart. Credit: David A. Aguilar (CfA)

What’s the solution?

“Thus, alternative mutually exclusive chemical tracers of the presence of a water ocean versus a magma ocean should be sought so that future observations can distinguish these potential scenarios,” the researchers write.

The authors think they may have found a chemical tracer that can do the job. They say that finding both CO2 and CO in an exoplanet atmosphere could contra-indicate a magma ocean. “One such possible tracer, and source of potential misfit of the magma ocean scenario with the observed spectrum of K2-18b, is the co-existence of CO2 and CO,” they explain. The problem is that the presence of any CO in K2-18b’s atmosphere is uncertain.

The researchers have shown that we can’t rely on the detection of carbon and the non-detection of ammonia to indicate a Hycean world because, in some circumstances, a magma ocean can produce the same atmospheric chemical profile. What can be done?

Better data and more research, of course.

“Developing clear disambiguating atmospheric tracers for the presence of liquid water versus magma
oceans is key in our quest of finding potentially habitable worlds amongst the exoplanet population,” they conclude.

The post Is K2-18b Covered in Oceans of Water or Oceans of Lava? appeared first on Universe Today.

Random physical fluctuations – or noise – can be a source of errors for conventional computers, but for a prototype "thermodynamic computer" they can be harnessed to run calculations

Perhaps the greatest and most frustrating mystery in cosmology is the Hubble tension problem. Put simply, all the observational evidence we have points to a Universe that began in a hot, dense state, and then expanded at an ever-increasing rate to become the Universe we see today. Every measurement of that expansion agrees with this, but where they don’t agree is on what that rate exactly is. We can measure expansion in lots of different ways, and while they are in the same general ballpark, their uncertainties are so small now that they don’t overlap. There is no value for the Hubble parameter that falls within the uncertainty of all measurements, hence the problem.

Of course, most of the results depend on a long chain of observational results. When we measure cosmic expansion using distant supernovae, for example, the result depends on the derived distances of these supernovae as found through the cosmic distance ladder, where ever greater distances are determined based on the distance of closer things. So, from parallax we measure nearby stellar distances, use that to calibrate a type of variable star known as Cepheid variables, use Cepheids to measure galactic distances in our local group, use that to standardize the brightness of Type Ia supernovae, and finally use those supernovae to measure the most distant galaxies.

Each step in the cosmic distance ladder has a certain amount of uncertainty and this carries on to the next level. So, if one kind of distance measure happens to be really off, that would throw off our measure of cosmic expansion for any method that depends upon the distance ladder. As a result, astronomers have started to take a very close look at various ladder steps, looking for an error that would solve the tension problem. Much of that has focused on Cepheid variable stars.

Cepheid variables are a type of variable star that varies in brightness at a rate proportional to its overall luminosity. This period-luminosity relation was first discovered by Henrietta Leavitt in the 1800s, and has been central to cosmology ever since. If you measure the period of a Cepheid, you know its actual brightness and compare it to its apparent brightness to determine its distance. Cepheids were used by Edwin Hubble to discover cosmic expansion in the first place, and the method has proven quite reliable.

But over the years we found that Leavitt’s period-luminosity relation is a bit more subtle than originally thought. For example, we now know that the period of a Cepheid is slightly different based upon its metallicity and other factors. Perhaps there’s some variation in the data we’ve missed.

Comparison of Cepheid period-luminosity relations used to measure distances. The red points are from Webb and the gray points are from Hubble. Credit: NASA, ESA, CSA, J. Kang (STScI)

A few years ago Cepheid observations from Hubble were used to see if adjustments in the period-luminosity relation could account for the Hubble tension, but the results didn’t look promising. Now a study using JWST observations has been released. One advantage of JWST over Hubble is that Webb observes Cepheids in infrared light, which penetrates interstellar dust more readily. The Webb observations are also better at addressing the issue of “crowding,” where light from the Cepheid can be overwhelmed a bit by the light of stars in the same cluster. So these latest results are the most accurate Cepheid observations we have. In this new study, the team looked at more than a thousand Cepheid variables and was able to pinpoint the distance relation for Cepheids with extreme precision. From this, they proved that Cepheid variable error can’t account for the Hubble tension.

The Cepheid solution to the tension problem is ruled out at a statistical level of 8-sigma. In science, a 5-sigma result is considered “certain,” so the Hubble tension is very, very real. Whether it’s spacetime structure, dark energy, or something we haven’t yet discovered, there is something we simply don’t understand about cosmic expansion.

Reference: Riess, Adam G., et al. “JWST Observations Reject Unrecognized Crowding of Cepheid Photometry as an Explanation for the Hubble Tension at 8 sigma Confidence.” arXiv preprint arXiv:2401.04773 (2024).

The post Astronomers Rule Out One Explanation for the Hubble Tension appeared first on Universe Today.

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