Few space images are as iconic as those of the Horsehead Nebula. Its shape makes it instantly recognizable. Over the decades, a number of telescopes have captured its image, turning it into a sort of test case for a telescope’s power.
The JWST has them all beat.
The Horsehead Nebula is about 1300 light-years away in Orion. It’s part of the much larger Orion Molecular Cloud Complex. Horsehead is visible near the three stars in Orion’s Belt in a zoomed-in image.
The leading image shows JWST’s view of the Horsehead Nebula alongside two other views. The Euclid image was captured in November 2023. Euclid features a wide-angle, 600-megapixel camera, and its primary job is to measure the redshift of galaxies and the Universe’s expansion due to dark energy. It took Euclid about one hour to capture the image, showcasing the telescope’s ability to gather highly detailed images quickly.
The Hubble captured its image in 2013 and was released as the telescope’s 23rd-anniversary featured image. The venerable Hubble does a good job of revealing structures hidden by dust. There’s nothing left to say about the Hubble that hasn’t been said already. It’s the revered elder among telescopes, and if you feel no reverence towards it, its contribution to science, and the people responsible for it, you may have a bad case of ennui.
The third image is a new one from the JWST’s NIRCam instrument. It’s described as the sharpest image of the Horsehead ever taken. It shows a small part of the iconic nebula in detail we don’t usually see. The JWST is so powerful it even shows background galaxies.
The Horsehead Nebula is the result of stellar erosion. The nebula itself was formed by a collapsing cloud of material, and a nearby hot star called Sigma Orionis illuminates the structure. The nebula is denser than its surrounding gas and has resisted the dissipative energy of the star, while the gas that used to surround it is long gone.
This definitely isn’t the last we’ll see of Horsehead. New, powerful telescopes coming online soon, like the Giant Magellan Telescope and the European Extremely Large Telescope will likely take a crack at the nebula. Prepare to be wowed.
There’s no rush. According to astronomers, the Horsehead Nebula will eventually be eroded away, too, but not for another five million years or so.
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It stands to reason that stars formed from the same cloud of material will have the same metallicity. That fact underpins some avenues of astronomical research, like the search for the Sun’s siblings. But for some binary stars, it’s not always true. Their composition can be different despite forming from the same reservoir of material, and the difference extends to their planetary systems.
New research shows that the differences can be traced back to their earliest stages of formation.
Binary stars are the norm, while solitary stars like our Sun are in the minority. Some estimates place the number of binary stars in the Milky Way at up to 85%. These pairs of stars form from the same giant molecular clouds. Each cloud has a certain abundance of metals, and that abundance should be reflected in the stars themselves.
But that’s not always the case.
Sometimes, the metallicity of a pair of binary stars doesn’t agree. Astrophysicists have proposed three explanations for this.
Two explanations involve events occurring later in a star’s life after they’ve left the main sequence. One is atomic diffusion, where chemical elements settle into gradient layers in the star. The layers are determined by a star’s gravity and temperature. The second one involves a nearby planet. As stars age, expand, and become red giants, they engulf nearby planets. The planet would introduce new chemistry into the star, differentiating it from its binary partner.
The third explanation reaches back in time to the binary pair’s formation. This explanation says that the giant molecular cloud that spawned the stars wasn’t homogeneous. Instead, there were regional differences in the cloud’s chemistry, and stars formed in different locations showed noticeable differences in their chemical makeup.
A team of researchers wanted to dig into this third explanation to test its veracity. They used the Gemini South Telescope and its Gemini High-Resolution Optical SpecTrograph (GHOST) to examine the light from a pair of giant binary stars. The observations revealed significant differences in their spectra.
They presented their results in a paper titled “Disentangling the origin of chemical differences using GHOST.” It’s published in the journal Astronomy and Astrophysics. The lead author is Carlos Saffe of the Institute of Astronomical, Earth and Space Sciences (ICATE-CONICET) in Argentina. The researchers examined a pair of giant binary stars called HD 138202 + CD?30 12303.
The three explanations for chemical differences between binary stars all stem from studies of main sequence stars. The main sequence is where stars spend most of their time, reliably fusing hydrogen into helium for billions of years.
But Saffe and his colleagues took a different approach. They used Gemini and GHOST to examine a pair of binary stars that had left the main sequence behind and become giant stars. These stars are different from main sequence stars.
“GHOST’s extremely high-quality spectra offered unprecedented resolution,” said Saffe, “allowing us to measure the stars’ stellar parameters and chemical abundances with the highest possible precision.”
These stars experience dredge-ups. Dredge-ups are when a star’s convection zone extends from the surface all the way down to where fusion is taking place. They’re powerful convective currents that mix fusion products into the star’s surface layer when a main sequence star becomes a red giant.
However, the researchers say that dredge-ups and the atomic diffusion they drive can’t explain the wide difference between stars.
The convection currents would also rule out the second proposed explanation: planetary engulfment. With such strong currents, the chemicals from an engulfed planet would quickly be diluted. “Giant stars are thought to be significantly less sensitive than main-sequence stars to engulfment events,” the authors write.
The authors went further and calculated the amount of planetary material a giant star would need to digest to cause the difference in metallicity between the stars. “We estimate that star A would need to have ingested between 11.0 and 150.0 Jupiter masses of planetary material, depending on the adopted convective envelope mass and metallic content of the ingested planet,” the authors explain. That’s an awful lot of material. They also explain that the planets must have had extremely high metallicity for the low value of 11 Jupiter masses to cause the chemical differences.
That only leaves one explanation: inhomogeneities in the molecular cloud.
“This is the first time astronomers have been able to confirm that differences between binary stars begin at the earliest stages of their formation,” said Saffe.
“Using the precision-measurement capabilities provided by the GHOST instrument, Gemini South is now collecting observations of stars at the end of their lives to reveal the environment in which they were born,” said Martin Still, NSF program director for the International Gemini Observatory. “This gives us the ability to explore how the conditions in which stars form can influence their entire existence over millions or billions of years.”
The results go a long way to explaining why a pair of binary stars can have differing compositions. But they reach even further than that. They also explain why a pair of binary stars can have such different planetary systems. “Different planetary systems could mean very different planets — rocky, Earth-like, ice giants, gas giants — that orbit their host stars at different distances and where the potential to support life might be very different,” said Saffe.
But the results also present a challenge. Astronomers use chemical tagging to identify stars that are associated with one another. Stars from the same stellar nursery are expected to have similar compositions. But that method seems unreliable in light of these findings.
The results also challenge the idea that differences in composition between binary stars can be explained by planet engulfment. Instead, those differences might stem from the stars’ earliest days of formation.
“By showing for the first time that primordial differences really are present and responsible for differences between twin stars, we show that star and planet formation could be more complex than initially thought,” said Saffe. “The Universe loves diversity!”
The only drawback of this study is the sample size of one. Small sample sizes are always cautionary: they can lead to an eventual conclusion but don’t form reliable conclusions independently. The authors know this.
“We strongly encourage the study of giant-giant pairs,” the researchers conclude. “This novel approach might help us to distinguish the origin of the slight chemical differences observed in multiple systems.”
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We go about our daily lives sheltered under an invisible magnetic field generated deep inside Earth. It forms the magnetosphere, a region dominated by the magnetic field. Without that planetary protection shield, we’d experience harmful cosmic radiation and charged particles from the Sun.
Has Earth always had this deflector shield? Probably so, and the evidence is in old rocks. A team of researchers at University of Oxford and MIT found the earliest evidence for its existence in stones found along the coast of Greenland in a region called the Isua Supercrustal Belt.
Geologists have long known that iron particles in rocks “entrain” a print of the magnetic field that was in place when they formed. So, the research team uncovered rocks that formed some 3.7 billion years ago. It’s not an easy task, according to team lead Claire Nichols of the Department of Earth Sciences at Oxford. “Extracting reliable records from rocks this old is extremely challenging,” Nichols pointed out. “It was really exciting to see primary magnetic signals begin to emerge when we analyzed these samples in the lab. This is a really important step forward as we try and determine the role of the ancient magnetic field when life on Earth was first emerging.”
The team’s samples recorded a magnetic field strength of 15 microteslas at the time they formed. Today, Earth’s field strength is closer to 30 microteslas, so it’s obvious that our magnetic field and magnetosphere have been there for billions of years. It’s also clear that the field changes over time. The science team also found that early Earth’s magnetosphere was amazingly similar to the one it has today.
Our planet has a main dynamo at its heart. There are two cores—an inner one and an outer one. Motions in the core regions generate the magnetic field that defines our magnetosphere. Molten iron mixes and moves in the fluid outer core and the inner core solidifies. The two actions together create that dynamo. That’s what’s happening inside our planet today.
However, when Earth was first forming some 4.5 billion years ago, that solid inner core didn’t exist. Without the interaction we see today between the two parts of the core, it’s hard to know how any early magnetic field existed. That’s an open question among geologists and planetary scientists: how did it form and how was it sustained?
Another question relates to how much the planetary magnetic field has varied over time. Answering that one would help geologists understand just when the solid inner core formed. It would also show how much heat has escaped our planet from deep inside over time. Heat escape drives plate tectonics, which uses large “plates” of rock to shift things around on the surface over hundreds of millions of years.
Rocks have a long and complex history. They form as a molten mixture that solidifies, or in the case of sandstones, are laid down in layers that then harden. In the case of molten rocks, they have magnetic field fingerprints entrained at the time of formation. In measuring those fingerprints, geologists account for any heating that could “reset” the magnetic signatures over time. The Greenland rocks are relatively pristine, meaning they haven’t been significantly heated since they formed. That means their magnetic fingerprints haven’t changed since formation.
Rocks also get weathered by wind, temperature changes and erosion, but the Isuan samples seem to be relatively pristine, according to Benjamin Weiss of MIT. “Northern Isua has the oldest known well-preserved rocks on Earth,” Weiss said. “Not only have they not been significantly heated since 3.7 billion years ago but they have also been scraped clean by the Greenland ice sheet.”
The rocks the team studied date back to the Archean Eon—the second-oldest geologic eon in Earth’s history. That period began about 4 billion years ago, and during that time Earth was largely an ocean world with a limited amount of continental surface. Since then, Earth’s surface has changed a great deal, destroying or burying rocks from earlier times. So, finding rocks that date back that far in time is a big deal.
The Isuan rocks are relatively unchanged since they formed, and bear proof of a magnetic field existing less than a billion years after the planet formed. That same early magnetic field could have played a role in the development of our planet’s atmosphere, by assisting in removing xenon gas. Other old rocks may well tell scientists more about the birth of the magnetic field. There are rocks in Canada, Australia and South Africa that could give unique insight into the formation of the field and its role in making Earth habitable for life.
Researchers Find Oldest Undisputed Evidence of Earth’s Magnetic Field
Possible Eoarchean Records of the Geomagnetic Field Preserved in the Isua Supracrustal Belt, Southern West Greenland
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When the first stars in the Universe formed, the only material available was primordial hydrogen and helium from the Big Bang. Astronomers call these original stars Population Three stars, and they were extremely massive, luminous, and hot stars. They’re gone now, and in fact, their existence is hypothetical.
But if they did exist, they should’ve left their fingerprints on nearby gas, and astrophysicists are looking for it.
The hunt for the Universe’s Population 3 (Pop III) stars is important in astrophysics. They were the first to form astronomical metals, elements heavier than hydrogen and helium. Only once these metals were available could rocky planets form. Their metals also fed into the next generation of stars, leading to the higher metallicity we observe in stars like our Sun.
Since Pop III stars were so massive and hot, they didn’t last long. None would have survived to this day. But the powerful JWST can expand the search for these crucial stars by looking back in time for their ancient light. That’s what the JWST-JADES (James Webb Space Telescope Advanced Deep Extragalactic Survey) is all about.
Researchers working with JADES data have found tantalizing evidence of Pop III stars in GN-z11, a high-redshift galaxy that’s one of the furthest galaxies from Earth ever observed. Their findings are in the paper “JWST-JADES. Possible Population III signatures at z=10.6 in the halo of GN-z11.” The lead author is Roberto Maiolino, a professor of Experimental Astrophysics at the Cavendish Laboratory (Department of Physics) and the Kavli Institute for Cosmology at the University of Cambridge. The research will be published in the journal Astronomy and Astrophysics.
“Finding the first generation of stars formed out of pristine gas in the early Universe, known as Population III (Pop III) stars, is one of the most important goals of modern astrophysics,” Maiolino and his colleagues write in their paper. “Recent models have suggested that Pop III stars may form in pockets of pristine gas in the halo of more evolved galaxies.”
GN-z11 is one such galaxy. At a redshift of z = 10.6034, the JWST sees the galaxy as it existed about 13.4 billion years ago, corresponding to about 400 million years after the Big Bang.
Pop III stars were massive and could be as much as 1000 times more massive than the Sun. These massive stars would’ve been exceptionally hot, which can provide a clue to their presence. Astrophysicists think all that heat could’ve doubly ionized nearby helium. So they search for the expected signature of that helium: prominent HeII nebular lines called the HeII?1640 emission line. To indicate the presence of Pop III stars, the HeII lines need to be unaccompanied by any metal lines.
The JWST observed the galaxy with its NIRSpec-IFU (Integrated Field Unit) and found a tentative detection of HeII?1640.
Detecting the doubly-ionized helium line was only the first step. Pop III stars aren’t the only objects that could’ve ionized the helium. To determine if the ancient stars were responsible, the researchers examined the galaxy and isolated several features.
Along with the HeII?1640, they also found Lyman-alpha emissions and CIII, or doubly-ionized carbon.
In the images above, the researchers note several features that are clues to the source of the helium ionization.
The HeII emissions show a plume extending to the west of GN-z11. It could be tracing gas photoionized by the galaxy’s active galactic nucleus (AGN.) Since CIII is so weak there, it could indicate very low metallicity gas photoionized by the AGN.
The image also shows a clump of HeII to the northeast of GN-z11. The researchers call this clump the “most intriguing” feature found. They analyzed the clump in the image below.
So what does this all add up to? Did the researchers find Pop III stars?
The spectral feature in the clump is strong evidence of photoionization by Pop III stars, according to the authors. “This wavelength corresponds to HeII?1640 at z=10.600, and it is fully consistent with the redshift of GN-z11,” they write. The same emission was detected over a larger area to the northeast, possibly with a second, fainter clump.
The authors say that the AGN could’ve photoionized the helium close to the galaxy’s center, but it can’t explain the HeII further away. Pop III stars are the best explanation, according to the authors.
Other evidence for Pop III stars comes from the emissions widths of the HeII lines. The high width suggests photoionization by metal poor Pop III stars rather than by Pop II stars with higher metallicity.
The extent of the ionization also indicates a certain mass for the Pop III stars, and the indicated mass agrees with simulations.
There’s another possibility: a direct collapse black hole (DCBH). “We also considered the alternative possibility of photoionization by a DCBH in the HeII clump,” the authors write. But the emission width should be lower in that scenario, although not by a lot. “Hence, this scenario remains another possible interpretation,” the authors write.
If future observations confirm the presence of Pop III stars in GN-z11, that’s a pretty big deal. But even if we have to wait for that confirmation, this research shows how powerful the JWST is again.
“These results have demonstrated the JWST’s capability to explore the primitive environment around galaxies in the early Universe, revealing fascinating properties,” the researchers conclude.
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On 9 January 2024, the Einstein probe was launched, its mission to study the night sky in X-rays. The first image from the probe that explores the Universe in these energetic wavelengths has just been released. It shows Puppis A, the supernova remnant from a massive star that exploded 4,000 years ago. The image showed the expanding cloud of ejecta from the explosion but now, Einstein will continue to scan the skies for other X-ray events.
The Chinese and European probe was designed to revolutionise our understanding of the Universe in X-rays. Named after none other than Albert Einstein, it houses cutting edge technology that will enable the observation of black holes, neutron stars and other events and phenomena emitting X-ray radiation. To achieve this it has two science instruments on board; the Wide-field X-ray Telescope (WXT) to give large field views of the sky and the Follow-up X-ray Telescope (FXT) which homes in on objects of interest identified by WXT.
The Einstein probe has three main questions it hopes to address focusing on black holes, gravity waves and supernovae. The recent image just released shows the stunning Puppis A supernova remnant. Supernova are a common process that takes place at the end of a massive star’s life. A star like the Sun is fusing hydrogen in its core into helium. The process is known as thermonuclear fusion and it releases heat, light and an outward pressure known as the thermonuclear force. While a star is stable, the thermonuclear force balances the force of gravity which is trying to collapse the star.
Massive stars will continue fusing different elements in the core until an iron core remains. It’s not possible to fuse iron so the thermonuclear force ceases allowing gravity to win. the core collapses and the inward rushing material crashes down onto the core and rebounds into a massive explosion known as a supernova.
Puppis A is one such object that is thought to have exploded 4,000 years ago. It lies about 7,000 light years from us which means the light that the radiation detected by the Einstein probe left about 7,000 years ago.
In the image released from Einstein, the cloud like structure is all that remains of the star that went supernova. It is possible to see a bright dot at the centre of the cloud, this is the core of the star that remains, a neutron star. The FXT image was accompanied by a spectrum to show the distribution of energy to help understand the elements present.
Source : Supernova remnant Puppis A imaged by Einstein Probe
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Anyone familiar with astronomy will know that galaxies come in a fairly limited range of shapes, typically; spiral, elliptical, barred-spiral and irregular. The barred-spiral galaxy has been known to be a feature of the modern universe but a study from astronomers using the Hubble Space Telescope has recently challenged that view. Following on observations using the James Webb Space Telescope has found the bar feature in some spiral galaxies as early as 11 billion years ago suggesting galaxies evolved faster in the early Universe than previously expected.
Our own Galaxy, the Milky Way is a spiral galaxy with a central nucleus and spiral arms emanating out from the centre. Our Solar System lies about 25,000 light years from the centre. Look at the galaxies in the sky though and you will see a real mix but generally they fall under the four main categories. Edwin Hubble tried to bring some structure to the different shapes by developing his galaxy classification scheme to articulate not only the shape but also the sub categories within them.
It has been known for some time that galaxies aren’t static. They move and they evolve and change. Spiral galaxies for example, as they age, they often develop a bar feature. The bar joins up the spiral arms instead of a nucleus connecting them and it is believed they are temporary, forming when a build of gas creates a burst of star formation.
The existence of a bar in a spiral galaxy suggests that the galaxy is fairly stable. Understanding just how the bar feature forms is key to understanding the evolutionary process of the galaxy itself. All previous observations showed that the appearance of the bar significantly reduces from the nearby Universe to redshifts near a value of one. This tells us that the bar seemed to be a modern feature and not present in the early Universe.
In a new paper by lead author Zoe A Le Conte, observations from the more sensitive James Webb Space Telescope report that galaxies to greater redshift are studied for bar features. Data is used from the Cosmic Evolution Early Release Science Survey and the observations from the Public Release Imaging for Extragalactic Research studies. Only the galaxies that also appear in the Cosmic Assembly Near Infra Red Deep Extragalactic Legacy Survey are used giving a sample of 368 face on galaxies.
The team visually searched through the 368 galaxy selection to classify and identify those with bars between redshifts 1 and 2 and then repeated the exercise for those between redshift 2 and 3. As expected, the fraction of bars reduced from around 17.8% between a red shift of 1 and 2 down to 13.8% at the greater red shift of 2 to 3.
The study revealed that JWST’s infra-red sensitivity picked up twice as many barred-spiral galaxies than the HST’s more blue sensitive imaging platform. Le Conte and her team conclude that the evolution of bars in spiral galaxies began to appear at a much earlier epoch, around 11 billion years ago.
Source : A JWST investigation into the bar fraction at redshifts 1 ? z ? 3
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When a spacecraft arrives at its destination, it settles into an orbit for science operations. But after the primary mission is complete, there might be other interesting orbits where scientists would like to explore. Maneuvering to a different orbit requires fuel, limiting a spacecraft’s number of maneuvers.
Researchers have discovered that some orbital paths allow for no-fuel orbital changes. But the figuring out these paths also are computationally expensive. Knot theory has been shown to find these pathways more easily, allowing the most fuel-efficient routes to be plotted. This is similar to how our GPS mapping software plots the most efficient routes for us here on Earth.
In mathematics, knot theory is the study of closed curves in three dimensions. Think of it as looking at a knotted necklace or a tangle of fishing line, and figuring out how to untangle them in the most efficient manner.
In the same way, a spacecraft’s path could be computed in a crowded planetary system – around Jupiter and all its moons, for example – where the best, simplest and least tangled route could be computed mathematically.
According to a new paper in the journal Astrodynamics, “Applications of knot theory to the detection of heteroclinic connections between quasi-periodic orbits,” using knot theory to untangle complicated spacecraft routes would decrease the amount of computer power or just plain guesswork in plotting out changes in spacecraft orbits.
“Previously, when the likes of NASA wanted to plot a route, their calculations relied on either brute force or guesswork,” said Danny Owen, a postgraduate research student in astrodynamics, in a press release from the University of Surrey. “Our new technique neatly reveals all possible routes a spacecraft could take from A to B, as long as both orbits share a common energy level.”
Owen added that this new process makes the task of planning missions much simpler. “We think of it as a tube [subway] map for space,” he said.
Spacecraft navigation is complicated by the fact that nothing in space is a fixed position. Navigators must meet the challenges of calculating the exact speeds and orientations of a rotating Earth, a rotating target destination, as well as a moving spacecraft, while all are simultaneously traveling in their own orbits around the Sun.
Since fuel is a limited resource for most missions, it would be beneficial to require the least amount of fuel possible in making any changes to the course of a spacecraft in orbit.
Spacecraft navigators use something called heteroclinic orbits — often called heteroclinic connections — which are paths that allow a spacecraft to travel from one orbit to another using the most efficient amount of fuel – or sometimes no fuel at all. But this usually takes a large amount of computer power or a lot of time to figure out.
But Owen and co-author Nicola Baresi, a lecturer in Orbital Mechanics at the University of Surrey, wrote that by using knot theory, they have developed “a method of robustly detecting heteroclinic connections,” they wrote in their paper, to quickly generate rough trajectories – which can then be refined. This gives spacecraft navigators a full list of all possible routes from a designated orbit, and the one that best fits the mission can be chosen. They can then choose the one that best suits their mission.
The researchers tested their technique on various planetary systems, including the Moon, and the Galilean moons of Jupiter.
“Spurred on by NASA’s Artemis program, the new Moon race is inspiring mission designers around the world to research fuel-efficient routes that can better and more efficiently explore the vicinity of the Moon,” said Baresi. “Not only does our technique make that cumbersome task more straightforward, but it can also be applied to other planetary systems, such as the icy moons of Saturn and Jupiter.”
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The list of chemicals found in space is growing longer and longer. Astronomers have found amino acids and other building blocks of life on comets, asteroids, and even floating freely in space. Now, researchers have found another complex chemical to add to the list.
The new chemical is known as 2-methoxyethanol (CH3OCH2CH2OH). It’s one of several methoxy molecules that scientists have found in space. But with 13 atoms, it’s one of the largest and most complex ones ever detected.
A team of scientists called the McGuire Group specializes in detecting chemicals in space. The McGuire Group and other researchers from institutions in Florida and France worked together to find 2-methoxyethanol.
The researchers published their findings in The Astrophysical Journal Letters. It’s titled “Rotational Spectrum and First Interstellar Detection of 2-methoxyethanol Using ALMA Observations of NGC 6334I.” The lead author is Zachary Fried, a graduate student in the McGuire Group at MIT.
“There are a number of ‘methoxy’ molecules in space, like dimethyl ether, methoxymethanol, ethyl methyl ether, and methyl formate, but 2-methoxyethanol would be the largest and most complex ever seen,” said lead author Fried.
The researchers didn’t stumble upon the large molecule. It was found as part of a concerted effort to detect new chemicals in space. It all started with machine learning. In 2023, one machine-learning model suggested they look for 2-methoxyethanol. The next step was the lab, where researchers performed experiments that measured and analyzed the molecule’s rotational spectrum here on Earth.
“We do this by looking at the rotational spectra of molecules, the unique patterns of light they give off as they tumble end-over-end in space,” said Fried. “These patterns are fingerprints (barcodes) for molecules. To detect new molecules in space, we first must have an idea of what molecule we want to look for, then we can record its spectrum in the lab here on Earth, and then finally we look for that spectrum in space using telescopes.”
The researchers measured the molecule’s spectrum over a broadband region of frequencies ranging from the microwave to sub-millimetre wave regimes (from about 8 to 500 gigahertz).
With that data in hand, the researchers turned to ALMA, the Atacama Large Millimetre/sub-millimetre Array. ALMA gathered data from two star-forming regions: NGC 6334I and IRAS 16293-2422B. Researchers from the McGuire Group, the National Radio Astronomy Observatory, and the University of Copenhagen all worked on analyzing ALMA’s observations.
“Ultimately, we observed 25 rotational lines of 2-methoxyethanol that lined up with the molecular signal observed toward NGC 6334I (the barcode matched!), thus resulting in a secure detection of 2-methoxyethanol in this source,” said Fried. “This allowed us to then derive physical parameters of the molecule toward NGC 6334I, such as its abundance and excitation temperature. It also enabled an investigation of the possible chemical formation pathways from known interstellar precursors.”
Here on Earth, 2-methoxyethanol is used mostly as a solvent. It’s toxic to bone marrow and testicles. But its status here on Earth isn’t relevant to its discovery.
The large molecule isn’t a building block for life, either. It’s significant because of its size and complexity. Scientists are interested in understanding how chemistry evolves and forms large molecules in regions where stars and planets are forming.
“Our group tries to understand what molecules are present in regions of space where stars and solar systems will eventually take shape,” explained Fried. “This allows us to piece together how chemistry evolves alongside the process of star and planet formation.”
Molecular complexity is the hallmark of life, so, of course, scientists want to understand molecular complexity in space. As of 2021, scientists only found six molecules in space larger than 13 atoms outside our Solar System. McGuire’s team found many of them.
Finding them is the first step. The next step is to figure out how and where they form. Though there are no direct links between 2-methoxyethanol and life, all complex chemistry has something to tell us about complex chemistry in general.
“Continued observations of large molecules and subsequent derivations of their abundances allows us to advance our knowledge of how efficiently large molecules can form and by which specific reactions they may be produced,” said Fried. “Additionally, since we detected this molecule in NGC 6334I but not in IRAS 16293-2422B, we were presented with a unique opportunity to look into how the differing physical conditions of these two sources may be affecting the chemistry that can occur.”
NGC 6334I is a higher-mass star-forming region compared to IRAS 16293-2422B. That means it could have a potentially enhanced radiation field. That enhanced radiation could produce more precursors for 2-methoxyethanol, eventually leading to more of the molecule itself. Warmer dust temperatures may have contributed, too. Warmer dust allows greater dust mobility, leading to chemical fragments being allowed to recombine.
Thanks to ever-improving observational tools and methods, including machine learning, astrochemistry is a blossoming field. If we’re ever going to understand how life on Earth arose and where it may likely rise elsewhere in the galaxy, astrochemistry will play a leading role. Though 2-methoxyethanol isn’t directly related to life, its detection still tells scientists something.
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The JWST is flexing its muscles with its interferometry mode. Researchers used it to study a well-known extrasolar system called PDS 70. The goal? To test the interferometry mode and see how it performs when observing a complex target.
The mode uses the telescope’s NIRISS (Near Infrared Imager and Slitless Spectrograph) as an interferometer. It’s called Aperture Masking Interferometry (AMI) and it allows the JWST to reach its highest level of spatial resolution.
A team of astronomers used the JWST’s AMI to observe the PDS 70 system. PDS 70 is a young T-Tauri star about 5.4 million years old. At that young age, its protoplanetary disk still surrounds it. PDS 70 is a well-studied system that’s caught the attention of astronomers. It’s unique because its two planets, PDS 70 b and c, make it the only multiplanet protoplanetary disk system we know of.
The researchers wanted to determine how easily the AMI would find PDS 70’s two known planets and what else it could observe in the system.
Their research is “The James Webb Interferometer: Space-based interferometric detections of PDS 70 b and c at 4.8 µm.” It’s available on the pre-print site arxiv.org and hasn’t been peer-reviewed yet. The lead author is Dori Blakely from the Department of Physics and Astronomy at the University of Victoria, BC, Canada.
PDS 70 is known for its pair of planets. PDS 70 b is about 3.2 Jupiter masses and follows a 123-year orbital period. PDS 70 c is about 7.5 Jupiter masses and follows a 191-year orbit. One of the most puzzling things about the system is that PDS 70 b appears to have its own accretion disk. The system also shows intriguing evidence of a third body, maybe another star.
The JWST’s interferometry easily detected both planets. In fact, the observations found evidence of circumplanetary disk emissions around PDS 70 b and c. “Our photometry of both PDS 70 b and c provide evidence for circumplanetary disk emission,” the researchers write. That means we can see the star and its protoplanetary disk, where planets form, and the individual circumplanetary disks around each planet. Those disks are where moons form, and seeing them in a system 366 light-years away is very impressive.
The JWST’s AMI observations also found a third point source. Its light is different from the light from the pair of planets and more similar to the light from the star. If it’s another planet, its composition is different from the others. If it’s not another planet, that doesn’t mean it necessarily has to be another star. The JWST could be seeing scattered starlight from another gaseous, dusty structure or clump in the disk. “This indicates that what we observe is not due to a simple inner disk structure, and may hint at a complex inner disk morphology such as a spiral or clumpy features,” the researchers explain.
The unexplained third source could be something more exotic. Previous research also identified the source and suggested that it could be an accretion stream flowing between PDS 70 b and c. “We interpret its signal in the direct vicinity of planet c as tracing the accretion stream feeding its circumplanetary disk,” the authors of the previous research wrote.
Or, perhaps most exciting, the source could be another planet. “Another scenario is that the signal we observe is due to an additional planet interior to the orbit of PDS 70 b,” the authors explain. “Follow-up observations will be needed to determine the nature of this emission,” the authors write.
Part of the observations’ success comes from what it didn’t detect. Protoplanetary disks are dusty and difficult to examine. The JWST has a leg up on it because it can see infrared light. When used in interferometry mode, it’s a powerful tool. The fact that it failed to detect any other planets is progress, though. “Additionally, we place the deepest constraints on additional planets,” in part of the disk. These constraints will help future researchers examine the PDS 70 system and other extrasolar systems.
The results also show another of AMI’s strengths: its ability to see into parts of the parameter space that other telescopes can’t. “Furthermore, our results show that NIRISS/AMI can reliably measure relative astrometry and contrasts of young planets in a part of parameter space (small separations and moderate to high contrasts) that is unique to this observing mode, and inaccessible to all other present facilities at 4.8 µm,” the authors explain.
The JWST has already established its place in the history of astronomy. It’s delivered on its promise and has already significantly contributed to our understanding of the cosmos. The telescope’s observations with its Aperture Masking Interferometry mode will further cement its place in history.
“Here, using the power of the James Webb Interferometer, we detect PDS 70, its outer disk, and its two protoplanets, b and c. These are the first planets detected with space-based interferometry,” the authors write.
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Brown dwarfs span the line between planets and stars. By definition, a star must be massive enough for hydrogen fusion to occur within its core. This puts the minimum mass of a star around 80 Jupiters. Planets, even large gas giants like Jupiter, only produce heat through gravitational collapse or radioactive decay, which is true for worlds up to about 13 Jovian masses. Above that, deuterium can undergo fusion. Brown dwarfs lay between these two extremes. The smallest brown dwarfs resemble gas planets with surface temperatures similar to Jupiter. The largest brown dwarfs have surface temperatures around 3,000 K and look essentially like stars.
Because of this, it can be difficult to study brown dwarfs, particularly ones that don’t orbit other stars. Without much reflected or emitted light, we can’t easily analyze their spectra to determine their composition. Fortunately, some brown dwarfs do emit radio light thanks to their strong magnetic fields.
Planets such as Earth and Jupiter have strong magnetic fields, and this means they can trap ionized particles such as hydrogen. These charged particles then spiral along the magnetic field lines until they collide with the planet’s upper atmosphere, generating glowing aurora. On Earth, we see them as the Northern Lights. For brown dwarfs, we can’t see the visible light of their aurora, but we can detect their radio glow.
Recently a team looked at the auroral light from a brown dwarf known as W1935. It is a cold brown dwarf 47 light-years from Earth with a surface temperature of just 200 °C. Within the spectra the team found light emissions from methane. While the presence of methane was expected in cold brown dwarfs, the fact that the methane emitted light was not. This means the atmosphere of W1935 likely has a thermal inversion, where the upper atmosphere is warmer than the lower layers.
This is true for the atmosphere of Earth but is driven by solar radiance. W1935 doesn’t orbit a star, so how can its upper atmosphere get so warm? One possible explanation is that the brown dwarf has an undetected small companion. This companion could be ejecting material similar to the way Saturn’s moon Enceleadus ejects water vapor. Once ionized in the vacuum of space, it would become trapped by the magnetic fields of W1935, eventually colliding with the brown dwarf’s upper atmosphere and giving it a bit of thermal heating.
This discovery shows that even the smallest brown dwarfs defy easy classification. Though they resemble planets, they may have their own planetary system like a star.
Reference: Faherty, Jacqueline K., et al. “Methane emission from a cool brown dwarf.” Nature 628.8008 (2024): 511-514.
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