astrophysics

study:-conflicting-values-for-hubble-constant-not-due-to-measurement-error

Study: Conflicting values for Hubble Constant not due to measurement error

astrophysics, expansion of the universe, Hubble constant, Science, Webb telescope / /

A long-standing tension —

Something else is influencing the expansion rate of the Universe.

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This image of NGC 5468, a galaxy located about 130 million light-years from Earth, combines data from the Hubble and James Webb space telescopes.

Enlarge / This image of NGC 5468, about 130 million light-years from Earth, combines data from the Hubble and Webb space telescopes.

NASA/ESA/CSA/STScI/A. Riess (JHU)

Astronomers have made new measurements of the Hubble Constant, a measure of how quickly the Universe is expanding, by combining data from the Hubble Space Telescope and the James Webb Space Telescope. Their results confirmed the accuracy of Hubble’s earlier measurement of the Constant’s value, according to their recent paper published in The Astrophysical Journal Letters, with implications for a long-standing discrepancy in values obtained by different observational methods known as the “Hubble tension.”

There was a time when scientists believed the Universe was static, but that changed with Albert Einstein’s general theory of relativity. Alexander Friedmann published a set of equations in 1922 showing that the Universe might actually be expanding, with Georges Lemaitre later making an independent derivation to arrive at that same conclusion. Edwin Hubble confirmed this expansion with observational data in 1929. Prior to this, Einstein had been trying to modify general relativity by adding a cosmological constant in order to get a static universe from his theory; after Hubble’s discovery, legend has it, he referred to that effort as his biggest blunder.

As previously reported, the Hubble Constant is a measure of the Universe’s expansion expressed in units of kilometers per second per megaparsec. So, each second, every megaparsec of the Universe expands by a certain number of kilometers. Another way to think of this is in terms of a relatively stationary object a megaparsec away: Each second, it gets a number of kilometers more distant.

How many kilometers? That’s the problem here. There are basically three methods scientists use to measure the Hubble Constant: looking at nearby objects to see how fast they are moving, gravitational waves produced by colliding black holes or neutron stars, and measuring tiny deviations in the afterglow of the Big Bang known as the Cosmic Microwave Background (CMB). However, the various methods have come up with different values. For instance, tracking distant supernovae produced a value of 73 km/s Mpc, while measurements of the CMB using the Planck satellite produced a value of 67 km/s Mpc.

Just last year, researchers made a third independent measure of the Universe’s expansion by tracking the behavior of a gravitationally lensed supernova, where the distortion in space-time caused by a massive object acts as a lens to magnify an object in the background. The best fits of those models all ended up slightly below the value of the Hubble Constant derived from the CMB, with the difference being within the statistical error. Values closer to those derived from measurements of other supernovae were a considerably worse fit for the data. The method is new, with considerable uncertainties, but it did provide an independent means of getting at the Hubble Constant.

Comparison of Hubble and Webb views of a Cepheid variable star.

Enlarge / Comparison of Hubble and Webb views of a Cepheid variable star.

NASA/ESA/CSA/STScI/A. Riess (JHU)

“We’ve measured it using information in the cosmic microwave background and gotten one value,” Ars Science Editor John Timmer wrote. “And we’ve measured it using the apparent distance to objects in the present-day Universe and gotten a value that differs by about 10 percent. As far as anyone can tell, there’s nothing wrong with either measurement, and there’s no obvious way to get them to agree.” One hypothesis is that the early Universe briefly experienced some kind of “kick” from repulsive gravity (akin to the notion of dark energy) that then mysteriously turned off and vanished. But it remains a speculative idea, albeit a potentially exciting one for physicists.

This latest measurement builds on last year’s confirmation based on Webb data that Hubble’s measurements of the expansion rate were accurate, at least for the first few “rungs” of the “cosmic distance ladder.” But there was still the possibility of as-yet-undetected errors that might increase the deeper (and hence further back in time) one looked into the Universe, particularly for brightness measurements of more distant stars.

So a new team made additional observations of Cepheid variable stars—a total of 1,000 in five host galaxies as far out as 130 million light-years—and correlated them with the Hubble data. The Webb telescope is able to see past the interstellar dust that has made Hubble’s own images of those stars more blurry and overlapping, so astronomers could more easily distinguish between individual stars.

The results further confirmed the accuracy of the Hubble data. “We’ve now spanned the whole range of what Hubble observed, and we can rule out a measurement error as the cause of the Hubble Tension with very high confidence,” said co-author and team leader Adam Riess, a physicist at Johns Hopkins University. “Combining Webb and Hubble gives us the best of both worlds. We find that the Hubble measurements remain reliable as we climb farther along the cosmic distance ladder. With measurement errors negated, what remains is the real and exciting possibility that we have misunderstood the Universe.”

The Astrophysical Journal Letters, 2024. DOI: 10.3847/2041-8213/ad1ddd  (About DOIs).

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A giant meteorite has been lost in the desert since 1916—here’s how we might find it

astrophysics, Chinguetti meteorite, geophysics, meteorites, Physics, Science / /

“This story has everything…” —

A tale of “sand dunes, a guy named Gaston, secret aeromagnetic surveys, and camel drivers.”

–

Chinguetti slice at the National Museum of Natural History

Enlarge / Chinguetti slice at the National Museum of Natural History. A larger meteorite reported in 1916 hasn’t been spotted since.

In 1916, a French consular official reported finding a giant “iron hill” deep in the Sahara desert, roughly 45 kilometers (28 miles) from Chinguetti, Mauritania—purportedly a meteorite (technically a mesosiderite) some 40 meters (130 feet) tall and 100 meters (330 feet) long. He brought back a small fragment, but the meteorite hasn’t been found again since, despite the efforts of multiple expeditions, calling its very existence into question.

Three British researchers have conducted their own analysis and proposed a means of determining once and for all whether the Chinguetti meteorite really exists, detailing their findings in a new preprint posted to the physics arXiv. They contend that they have narrowed down the likely locations where the meteorite might be buried under high sand dunes and are currently awaiting access to data from a magnetometer survey of the region in hopes of either finding the mysterious missing meteorite or confirming that it likely never existed.

Captain Gaston Ripert was in charge of the Chinguetti camel corps. One day he overheard a conversation among the chameliers (camel drivers) about an unusual iron hill in the desert. He convinced a local chief to guide him there one night, taking Ripert on a 10-hour camel ride along a “disorienting” route, making a few detours along the way. He may even have been literally blindfolded, depending on how one interprets the French phrase en aveugle, which can mean either “blind” (i.e. without a compass) or “blindfolded.” The 4-kilogram fragment Ripert collected was later analyzed by noted geologist Alfred Lacroix, who considered it a significant discovery. But when others failed to locate the larger Chinguetti meteorite, people started to doubt Ripert’s story.

“I know that the general opinion is that the stone does not exist; that to some, I am purely and simply an imposter who picked up a metallic specimen,” Ripert wrote to French naturalist Theodore Monod in 1934. “That to others, I am a simpleton who mistook a sandstone outcrop for an enormous meteorite. I shall do nothing to disabuse them, I know only what I saw.”

Encouraged by a separate report of local blacksmiths claiming to recover iron from a giant block somewhere east or southeast of Chinguetti, Monod intermittently searched for the meteorite several times over the ensuing decades, to no avail. A pilot named Jacques Gallouédec thought he spotted a dark silhouette in the Saharan dunes in the 1980s. But neither Monod nor a second expedition in the late 1990s—documented by the UK’s Channel 4—could find anything. Monod concluded in 1989 that Ripert had likely mistakenly identified a sedimentary rock “with no trace of metal” as a meteorite.

Still, as Rutgers University physicist Matt Buckley noted on Bluesky, “This story has everything: giant unexplained meteorites, sand dunes, a guy named Gaston, ductile nickel needles, secret aeromagnetic surveys, and camel drivers.” So naturally, it intrigued Stephen Warren of Imperial College London, Oxford University’s Ekaterini Protopapa, and Robert Warren, who began their own search for the mysterious missing meteorite in 2020.

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Newly spotted black hole has mass of 17 billion Suns, adding another daily

accretion disk, astronomy, astrophysics, black hole, quasar, Science, supermassive black hole / /

Feeding frenzy —

An accretion disk 7 light-years across powers an exceptionally bright galaxy.

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Artist's view of a tilted orange disk with a black object at its center.

Quasars initially confused astronomers when they were discovered. First identified as sources of radio-frequency radiation, later observations showed that the objects had optical counterparts that looked like stars. But the spectrum of these ostensible stars showed lots of emissions at wavelengths that didn’t seem to correspond to any atoms we knew about.

Eventually, we figured out these were spectral lines of normal atoms but heavily redshifted by immense distances. This means that to appear like stars at these distances, these objects had to be brighter than an entire galaxy. Eventually, we discovered that quasars are the light produced by an actively feeding supermassive black hole at the center of a galaxy.

But finding new examples has remained difficult because, in most images, they continue to look just like stars—you still need to obtain a spectrum and figure out their distance to know you’re looking at a quasar. Because of that, there might be some unusual quasars we’ve ignored because we didn’t realize they were quasars. That’s the case with an object named J0529−4351, which turned out to be the brightest quasar we’ve ever observed.

That’s no star!

J0529−4351 had been observed a number of times, but its nature wasn’t recognized until a survey went hunting for quasars and recognized it was one. At the time of the 2023 paper that described the survey, the researchers behind it suggested that it had either been magnified through gravitational lensing, or it was the brightest quasar we’ve ever identified.

In this week’s Nature Astronomy, they confirmed: It’s not lensed, it really is that bright. Gravitational lensing tends to distort objects or create multiple images of them. But J0529−4351 is undistorted, and nothing nearby looks like it. And there’s nothing in the foreground that has enough mass to create a lens.

So, how do you take an instance of an incredibly bright object and make it even brighter? The light from a quasar is produced by an accretion disk. While accretion disks can form around black holes with masses similar to stars, quasars require a supermassive black hole like the ones found at the center of galaxies. These disks are formed of material that has been captured by the gravity of the black hole and is in orbit before falling inward and crossing the event horizon. Light is created as the material is heated by collisions of its constituent particles and gives up gravitational energy as it falls inward.

Getting more light out of an accretion disk is pretty simple: You either put more material in it or make it bigger. But there’s a limit to how much material you can cram into one. At some point, the accretion disk will produce so much radiation that it drives off any additional material that’s falling inward, essentially choking off its own food supply. Called the Eddington limit, this sets ceilings on how bright an accretion disk can be and how quickly a black hole can grow.

Factors like the mass of the black hole and its spin help set the Eddington limit. Plus, the amount of material falling inward can drop below the Eddington limit, leading to a bit less light being produced. Trying various combinations of these factors and checking them against observational data, the researchers came up with several estimates for the properties of the supermassive black hole and its accretion disk.

Extremely bright

For the supermassive black hole’s size, the researchers propose two possible estimates: one at 17 billion solar masses, and the other at 19 billion solar masses. That’s not the most massive one known, but there are only about a dozen thought to be larger. (For comparison, the one at the center of the Milky Way is “only” about 4 million solar masses.) The data is best fit by a moderate spin, with us viewing it from about 45 degrees off the pole of the black hole. The accretion disk would be roughly seven light-years across. Meaning, if the system were centered on our Sun, several nearby stars would be within the disk.

The accretion rate needed to power the brightness is just below the Eddington limit and works out to roughly 370 solar masses of material per year. Or, about a Sun a day. At that rate, it would take about 30 million years to double in size.

But it’s rare to have that much material around for one to feed that long. And a look through archival images shows that the brightness of J0529−4351 can vary by as much as 15 percent, so it’s not likely to be pushing the Eddington limit the entire time.

Even so, it’s difficult to understand how that much material can be driven into the center of a galaxy for any considerable length of time. The researchers suggest that the ALMA telescope array might be able to pick up anything unusual there. “If extreme quasars were caused by unusual host galaxy gas flows, ALMA should see this,” they write. “If nothing unusual was found in the host gas, then this would sharpen the well-known puzzle of how to sustain high accretion rates for long enough to form such extreme supermassive black holes.”

The whole accretion disk is also large enough that it should be possible to image it with the Very Large Telescope, which would allow us to track the disk’s rotation and estimate the black hole’s mass.

The system’s extreme nature, then, may actually help us figure out its details despite its immense distance. Meanwhile, the researchers wonder whether other unusual systems might remain undiscovered simply because we haven’t considered that an object might be a quasar instead of a star.

Nature Astronomy, 2024. DOI: 10.1038/s41550-024-02195-x  (About DOIs).

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Explaining why a black hole produces light when ripping apart a star

astronomy, astrophysics, black holes, Science, tidal disruption / /
Image of a multi-colored curve, with two inset images of actual astronomical objects.

Enlarge / A model of a tidal disruption, along with some observations of one.

Supermassive black holes appear to be present at the core of nearly every galaxy. Every now and again, a star wanders too close to one of these monsters and experiences what’s called a tidal disruption event. The black hole’s gravity rips the star to shreds, resulting in a huge burst of radiation. We’ve observed this happening several times now.

But we don’t entirely know why it happens—”it” specifically referring to the burst of radiation. After all, stars produce radiation through fusion, and the tidal disruption results in the spaghettification of the star, effectively pulling the plug on the fusion reactions. Black holes brighten when they’re feeding on material, but that process doesn’t look like the sudden burst of radiation from a tidal disruption event.

It turns out that we don’t entirely know how the radiation is produced. There are several competing ideas, but we’ve not been able to figure out which one of them fits the data best. However, scientists have taken advantage of an updated software package to model a tidal disruption event and show that their improved model fits our observations pretty well.

Spaghettification simulation

As mentioned above, we’re not entirely sure about the radiation source in tidal disruption events. Yes, they’re big and catastrophic, and so a bit of radiation isn’t much of a surprise. But explaining the details of that radiation—what wavelengths predominate, how quickly its intensity rises and falls, etc.—can tell us something about the physics that dominates these events.

Ideally, software should act as a bridge between the physics of a tidal disruption and our observations of the radiation they produce. If we simulate a realistic disruption and have the physics right, then the software should produce a burst of radiation that is a decent match for our observations of these events. Unfortunately, so far, the software has let us down; to keep things computationally manageable, we’ve had to take a lot of shortcuts that have raised questions about the realism of our simulations.

The new work, done by Elad Steinberg and Nicholas Stone of The Hebrew University, relies on a software package called RICH that can track the motion of fluids (technically called hydrodynamics). And, while a star’s remains aren’t fluid in the sense of the liquids we’re familiar with here on Earth, their behavior is primarily dictated by fluid mechanics. RICH was recently updated to better model radiation emission and absorption by the materials in the fluid, which made it a better fit for modeling tidal disruptions.

The researchers still had to take a few shortcuts to ensure that the computations could be completed in a realistic amount of time. The version of gravity used in the simulation isn’t fully relativistic, and it’s only approximated in the area closest to the black hole. But that sped up computations enough that the researchers could track the remains of the star from spaghettification to the peak of the event’s radiation output, a period of nearly 70 days.

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Astronomers found ultra-hot, Earth-sized exoplanet with a lava hemisphere

astronomy, astrophysics, exoplanets, lava worlds, Physics, Science, Transiting Exoplanet Survey Satellite / /
Like Kepler-10 b, illustrated above, the exoplanet HD 63433 d is a small, rocky planet in a tight orbit of its star.

Enlarge / Like Kepler-10 b, illustrated above, newly discovered exoplanet HD 63433 d is a small, rocky planet in a tight orbit of its star.

NASA/Ames/JPL-Caltech/T. Pyle

Astronomers have discovered an unusual Earth-sized exoplanet they believe has a hemisphere of molten lava, with its other hemisphere tidally locked in perpetual darkness. Co-authors and study leaders Benjamin Capistrant (University of Florida) and Melinda Soares-Furtado (University of Wisconsin-Madison) presented the details yesterday at a meeting of the American Astronomical Society in New Orleans. An associated paper has just been published in The Astronomical Journal. Another paper published today in the journal Astronomy and Astrophysics by a different group described the discovery of a rare small, cold exoplanet with a massive outer companion 100 times the mass of Jupiter.

As previously reported, thanks to the massive trove of exoplanets discovered by the Kepler mission, we now have a good idea of what kinds of planets are out there, where they orbit, and how common the different types are. What we lack is a good sense of what that implies in terms of the conditions on the planets themselves. Kepler can tell us how big a planet is, but it doesn’t know what the planet is made of. And planets in the “habitable zone” around stars could be consistent with anything from a blazing hell to a frozen rock.

The Transiting Exoplanet Survey Satellite (TESS) was launched with the intention of helping us figure out what exoplanets are actually like. TESS is designed to identify planets orbiting bright stars relatively close to Earth, conditions that should allow follow-up observations to figure out their compositions and potentially those of their atmospheres.

Both Kepler and TESS identify planets using what’s called the transit method. This works for systems in which the planets orbit in a plane that takes them between their host star and Earth. As this occurs, the planet blocks a small fraction of the starlight that we see from Earth (or nearby orbits). If these dips in light occur with regularity, they’re diagnostic of something orbiting the star.

This tells us something about the planet. The frequency of the dips in the star’s light tells us how long an orbit takes, which tells us how far the planet is from its host star. That, combined with the host star’s brightness, tells us how much incoming light the planet receives, which will influence its temperature. (The range of distances at which temperatures are consistent with liquid water is called the habitable zone.) And we can use that, along with how much light is being blocked, to figure out how big the planet is.

But to really understand other planets and their potential to support life, we have to understand what they’re made of and what their atmosphere looks like. While TESS doesn’t answer those questions, it’s designed to find planets with other instruments that could answer them.

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Astronomers think they finally know origin of enormous “cosmic smoke rings“

astronomy, astrophysics, galactic winds, Odd Radio Circles, Physics, Science / /

Space oddity —

Massive stars burn out quickly. When they die, they expel their gas as outflowing winds.

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Odd radio circles, like ORC 1 pictured above, are large enough to contain galaxies in their centers and reach hundreds of thousands of light years across.

Enlarge / Odd radio circles are large enough to contain galaxies in their centers and reach hundreds of thousands of light years across.

Jayanne English / University of Manitoba

The discovery of so-called “odd radio circles” several years ago had astronomers scrambling to find an explanation for these enormous regions of radio waves so far-reaching that they have galaxies at their centers. Scientists at the University of California, San Diego, think they have found the answer: outflowing galactic winds from exploding stars in so-called “starburst” galaxies. They described their findings in a new paper published in the journal Nature.

“These galaxies are really interesting,” said Alison Coil of the University of California, San Diego. “They occur when two big galaxies collide. The merger pushes all the gas into a very small region, which causes an intense burst of star formation. Massive stars burn out quickly, and when they die, they expel their gas as outflowing winds.”

As reported previously, the discovery arose from the Evolutionary Map of the Universe (EMU) project, which aims to take a census of radio sources in the sky. Several years ago, Ray Norris, an astronomer at Western Sydney University and CSIRO in Australia, predicted the EMU project would make unexpected discoveries. He dubbed them “WTFs.” Anna Kapinska, an astronomer at the National Radio Astronomy Observatory (NRAO) was browsing through radio astronomy data collected by CSIRO’s Australian Square Kilometer Array Pathfinder (ASKAP) telescope when she noticed several strange shapes that didn’t seem to resemble any known type of object. Following Norris’ nomenclature, she labeled them as possible WTFs. One of those was a picture of a ghostly circle of radio emission, “hanging out in space like a cosmic smoke ring.”

Other team members soon found two more weird round blobs, which they dubbed “odd radio circles” (ORCs). A fourth ORC was identified in archival data from India’s Giant MetreWave Radio Telescope, and a fifth was discovered in fresh ASKAP data in 2021. There are several more objects that might also be ORCs. Based on this, the team estimates there could be as many as 1,000 ORCs in all.

While Norris et al. initially assumed the blobs were just imaging artifacts, data from other radio telescopes confirmed they were a new class of astronomical object. They don’t show up in standard optical telescopes or in infrared and X-ray telescopes—only in the radio spectrum. Astronomers suspect the radio emissions are due to clouds of electrons. But that wouldn’t explain why ORCs don’t show up in other wavelengths. All of the confirmed ORCs thus far have a galaxy at the center, suggesting this might be a relevant factor in how they form. And they are enormous, measuring about a million light-years across, which is larger than our Milky Way.

As for what caused the explosions that led to the formation of ORCs, new data reported in 2022 was sufficient to rule out all but three possibilities. The first is that ORCs are the result of a shockwave from the center of a galaxy, perhaps arising from the merging of two supermassive black holes. Alternatively, they could be the result of radio jets spewing particles from active galactic nuclei. Finally, ORCs may be shells caused by starburst events (“termination shock”), which would produce a spherical shock wave as hot gas blasted out from a galactic center.

A simulation of starburst-driven winds at three different time periods, starting at 181 million years. The top half of each image shows gas temperature, while the lower half shows the radial velocity.

Enlarge / A simulation of starburst-driven winds at three different time periods, starting at 181 million years. The top half of each image shows gas temperature, while the lower half shows the radial velocity.

Cassandra Lochhaas / Space Telescope Science Institute

Coil et al. were intrigued by the discovery of ORCs. They had been studying starburst galaxies, which are noteworthy for their very high rate of star formation, making them appear bright blue. The team thought the later stages of those starburst galaxies might explain the origin of ORCs, but they needed more than radio data to prove it. So the team used the integral field spectrograph at the W.M. Keck Observatory in Hawaii to take a closer look at ORC 4, the first radio circle observable from the Northern Hemisphere. That revealed a much higher amount of bright, heated, compressed gas than one would see in an average galaxy. Additional optical and infrared imaging data revealed that the stars in the ORC 4 galaxy are about 6 billion years old. New star formation seems to have ended some billion years ago.

The next step was to run computer simulations of the odd radio circle itself spanning the course of 750 million years. Those simulations showed an initial 200-million-year period with powerful outflowing galactic winds, followed by a shock wave that propelled very hot gas out of the galaxy to create a radio ring. Meanwhile, a reverse shock wave sent cooler gas back into the central galaxy.

“To make this work, you need a high-mass outflow rate, meaning it’s ejecting a lot of material very quickly. And the surrounding gas just outside the galaxy has to be low density, otherwise the shock stalls. These are the two key factors,” said Coil. “It turns out the galaxies we’ve been studying have these high-mass outflow rates. They’re rare, but they do exist. I really do think this points to ORCs originating from some kind of outflowing galactic winds.” She also thinks that ORCs could help astronomers understand more about galactic outflowing winds since it enables them to “see” those winds through radio data and spectrometry.

Nature, 2024. DOI: 10.1038/s41586-023-06752-8  (About DOIs).

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Galaxy-scale winds spotted in the distant Universe

astronomy, astrophysics, cosmology, Science, Space / /

Out in the wind —

These winds can drive gas out of galaxies, shaping their future evolution.

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Image of a galaxy with a purple blob superimposed on its center.

Enlarge / X-ray emissions (purple) superimposed on a visible light image of a galaxy shows the galaxy winds being launched. CREDIT: X-ray: NASA/CXC/Ohio StateH-alpha and Optical: NSF/NOIRLab/AURA/KPNO/CTIO; Infrared: NASA/JPL-Caltech/Spitzer/ Optical: ESO/La Silla Observatory.

One of the ways massive stars, those at least 10-times bigger than the Sun, reach their end is in a supernova—an enormous explosion caused by the star’s core running out of fuel.

One consequence of a supernova is the production of galactic winds, which play a key role in regulating star formation. Although galactic winds have already been observed in several nearby galaxies, a team of scientists has now made the first direct observations of this phenomenon in a large population of galaxies in the distant Universe, at a time when galaxies are in their early stages of formation.

Feedback

According to the study’s lead author, Yucheng Guo, of the Centre de Recherche Astrophysique de Lyon, galactic winds are an important part of the galaxy evolution models.

“It was assumed there should be galactic winds that can regulate galaxies’ growth. However, it was very difficult to directly observe these winds. With our study, we show that at the early stage of the Universe, every normal galaxy had such winds,” Guo said.

According to Guo, galactic winds form a key part of the so-called feedback process that is important in our understanding of galaxy evolution. “Galactic winds originate as a result of star formation activity. These winds inject a lot of energy and momentum into the gas, resulting in it [being] expelled from the galaxy. If there is not enough gas in the galaxy, the star formation stops. This is called the feedback process,” he said.

According to Guo, galactic winds also enable exchange of matter between galaxies and their surroundings. “Each galaxy is surrounded by a gas halo. Galaxies can breathe out as well as breathe in gas,” Guo said.

Hard to see

He said that traditionally it has been very difficult to observe galactic winds, because the gas halos are almost transparent.

Guo and his team overcame this hurdle by using the Multi-Unit Spectroscopic Explorer (MUSE) instrument on the Very Large Telescope. “The instrument is able to observe the galaxies at redshift z ≈ 1, which corresponds to 7 billion years of the cosmic evolution.” Guo said at that wavelength, the MUSE instrument is able to detect and directly observe the emission from magnesium atoms in the galactic winds.

He said the other important feature of the research is that they managed to observe the galactic winds in more than 100 galaxies. “We also managed to detect the average shape of these winds, which is like an ice cream cone,” he said.

Guo said the direct observation of the galactic winds outside the local Universe was the first step of their research. “We still don’t know about their physical properties such as size, power, and also how they change with time and in different kinds of galaxies.”

Nature, 2023. DOI: 10.1038/s41586-023-06718-w


Dhananjay Khadilkar is a journalist based in Paris.

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