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Tag: Radio astronomy

  • Radio Signal Crushes Alien Theory About Interstellar Comet 3I/ATLAS

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    Ever since astronomers first detected interstellar comet 3I/ATLAS in July, speculation about its true nature has run wild. Some experts speculate it isn’t a comet at all but rather an extraterrestrial spacecraft sent to sniff around our solar system.

    New evidence has dumped cold water on this provocative hypothesis. MeerKAT, a radio telescope operated by the South African Radio Astronomy Observatory, recently detected a radio signal from 3I/ATLAS. Before you get excited, this isn’t a technological radio signal used for transmission. It’s a natural radio emission and some of the strongest evidence yet that 3I/ATLAS is a naturally occurring comet.

    The astronomers who identified the signal posted a brief description of their findings on The Astronomer’s Telegram, a website where researchers announce new astronomical discoveries. They explain that MeerKAT detected lines of radio absorption by hydroxyl radicals (OH) at two different frequencies: 1,665 megahertz and 1,667 megahertz. This indicates that 3I/ATLAS was behaving like a normal comet as it zipped around the Sun last month.

    D.J. Pisano, a researcher and professor of extragalactic multi-wavelength astronomy at the University of Cape Town, reported the findings alongside several collaborators. The findings have not yet been peer reviewed.

    What MeerKAT’s discovery means

    Between July and October, astronomers kept a close eye on 3I/ATLAS as it approached the Sun. MeerKAT observed the comet on October 24—just five days before 3I/ATLAS reached its closest point to our home star, also known as perihelion.

    The closer a comet is to perihelion, the faster it sublimates due to increasing solar radiation. This is when ice on the comet’s surface rapidly transitions from a solid to a gas without entering an intermediate liquid state. It’s also what gives comets their signature comas and tails.

    During sublimation, each frozen water molecule (H2O) on the comet’s surface splits into a hydroxyl radical (OH) and a hydrogen atom (H). Thus, hydroxyl radicals are a product—and therefore an indicator—of cometary sublimation.

    If 3I/ATLAS were a metal spacecraft, telescopes wouldn’t detect these molecules. Previous failed attempts to spot them helped fuel speculation that this interstellar object could be technological—a hypothesis first proposed by Harvard astronomer Avi Loeb and colleagues. In a blog post about MeerKAT’s new findings, Loeb acknowledged the new findings and the apparent natural cometary phenomena at play but still did not explicitly rule out a technological explanation.

    Not just a comet

    Just because 3I/ATLAS is almost definitely a natural comet, that doesn’t mean it isn’t extraordinary. It’s only the third interstellar object ever discovered by astronomers, and its highly unusual characteristics offer a glimpse of the far-off solar system it hails from.

    Astronomers have found evidence to suggest that 3I/ATLAS contains one of the highest carbon dioxide to water ratios ever seen in a comet and that it could be older than our solar system. Another preprint study shows that 3I/ATLAS exhibits “extreme negative polarization” that suggests it is a completely new type of comet—unlike any observed before.

    3I/ATLAS is now departing our solar system, but astronomers—and several deep-space probes—will still have opportunities to study it before it disappears. The more information scientists gather about this interstellar visitor, the more it seems to surprise us.

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    Ellyn Lapointe

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  • Citizen Scientists Spot a Perfect Extragalactic Venn Diagram

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    For lovers of cool astronomy and math, this finding is a real treat. Citizen astronomers stumbled upon not one but two rings of extragalactic radio signals crossing each other to form a near-perfect Venn diagram.

    A paper published October 2 in Monthly Notices of the Royal Astronomical Society identifies this strangely geometric object as an “odd radio circle” (ORC), vast rings of magnetized plasma. These rings, only visible at radio wavelengths, emit non-thermal synchrotron radiation. They’re also gigantic, typically spanning hundreds of thousands of light-years. Astronomers have only documented a small handful of cases, but this particular pair of rings is reportedly the most distant and most powerful so far.

    What’s more, the researchers found two more powerful radio signals that offer valuable information about the dynamics of ORCs, first discovered six years ago.

    “ORCs are among the most bizarre and beautiful cosmic structures we’ve ever seen—and they may hold vital clues about how galaxies and black holes co-evolve, hand-in-hand,” said Ananda Hota, study lead author and founder of the RAD@home Astronomy Collaboratory for citizen science research, in a statement.

    An ongoing puzzle

    As the name suggests, odd radio circles are only visible to radio telescopes, which operate at comparatively low frequencies. At other frequencies, or wavelengths, they become invisible—one reason they only recently came into view, owing to advances in radio astronomy.

    Given their novelty, astronomers have yet to pinpoint an exact cause for odd radio circles. The handful of detections so far have suggested they could be shockwaves from merging galaxies or black holes, or even the remnants of supernovas. Either way, ORCs almost always materialize near large galaxies, hinting there should be some correlation between the two.

    The new discovery raises another possibility. What if these rings are the product of “superwinds” compressing dormant radio lobes? Galactic superwinds can emerge from a variety of powerful extragalactic events, which could explain why past ORC observations had conflicting sources.

    Many moving parts

    The other two radio signals that the researchers found nearby also support this hypothesis. Specifically, these were two gigantic galaxies in a crowded galaxy cluster that were blasting out powerful jets of plasma and radio emissions. Their activity, coupled with the local environment, likely helped shape the rings, the researchers said.

    Optical RGB image from the Legacy Surveys, overlaid with radio emission in red from the LOFAR Two-Metre Sky Survey (LoTSS), showing the ‘odd radio circle’ (ORC) RAD J131346.9+500320. Credit: Rad@home Astronomy Collaboratory

    “These discoveries show that ORCs and radio rings are not isolated curiosities,” noted Pratik Dabhade, study co-author and an astronomer at the National Centre for Nuclear Research in Poland, in the statement. “They are part of a broader family of exotic plasma structures shaped by black hole jets, winds, and their environments.”

    The signals were first detected by citizen scientists using the Low Frequency Array, a sensitive radio telescope based in Europe. Professional scientists associated with the RAD@home Astronomy Collaboratory helped assess and confirm the validity of their findings.

    “The fact that citizen scientists uncovered them highlights the continued importance of human pattern recognition, even in the age of machine learning,” Dabhade added.

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    Gayoung Lee

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  • Daylight Savings Time Is So Bad, It’s Messing With Our View of the Cosmos

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    Tracking gravitational waves—invisible ripples in space-time from intense astronomical events—pushes the limits of what astronomers must do to reduce unwanted noise. Scientists have been getting increasingly better at doing just that, but new research warns that something rather unexpected might be getting in the way: daylight savings time.

    In a preprint titled “Can LIGO Detect Daylight Savings Time?,” Reed Essick, former LIGO member and now a physicist at the University of Toronto, gives a simple answer to the paper’s title: “Yes, it can.” The paper, which has yet to be peer-reviewed, was recently uploaded to arXiv.

    That might seem like an odd connection. It’s true that observational astronomy must contend with noise from light pollution, satellites, and communication signals. But these are tangible sources of noise that scientists can sink their teeth into, whereas daylight savings time is considerably more nebulous and abstract as a potential problem.

    To be clear, and as the paper points out, daylight savings time does not influence actual signals from merging black holes billions of light-years away—which, as far as we know, don’t operate on daylight savings time. The “detection” here refers to the “non-trivial” changes in human activity having to do with the researchers involved in this kind of work, among other work- and process-related factors tied to the sudden shift in time.

    The presence of individuals—whether through operational workflows or even their physical activity at the observatories—has a measurable impact on the data collected by LIGO and its sister institutions, Virgo in Italy and KAGRA in Japan, the new paper argues.

    We ripple in space

    To see why this might be the case, consider again the definition of gravitational waves: ripples in space-time. A very broad interpretation of this definition implies that any object in space-time affected by gravity can cause ripples, like a researcher opening a door or the rumble of a car moving across the LIGO parking lot.

    Of course, these ripples are so tiny and insignificant that LIGO doesn’t register them as gravitational waves. But continued exposure to various seismic and human vibrations does have some effect on the detector—which, again, engineers and physicists have attempted to account for.

    What they forgot to consider, however, were the irregular shifts in daily activity as researchers moved back and forth from daylight savings time. The bi-annual time adjustment shifted LIGO’s expected sensitivity pattern by roughly 75 minutes, the paper noted. Weekends, and even the time of day, also influenced the integrity of the collected data, but these factors had been raised by the community in the past.

    “[Gravitational wave] interferometers are not uniformly sensitive to signals coming from different relative directions and orientations,” Essick wrote in the paper. This inconsistency, in tandem with changes in Earth’s rotations and known noise factors, could “easily create non-trivial selections” and a “systemic bias” in gravitational wave astronomy, he added.

    No clear path forward

    A solution to this problem won’t come easily. What’s more, the new research suggests “other hidden selections might be present within gravitational wave observations,” Essick remarked.

    That said, the analysis is more of a reminder that our data could be biased in unexpected ways, he added. Gravitational wave astronomy is a growing field, and as we collect more data, the influence of these subtle effects will grow in scale.

    Multi-messenger astronomy—using different techniques to cross-check the same phenomenon—could help verify results. Space-based observatories with zero human presence could eliminate this problem altogether. The lesson is to just “retain healthy skepticism,” Essick wrote.

    And really, that’s a prudent stance to have for scientific pursuits in general.

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    Gayoung Lee

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  • Jaw-Dropping Report Reveals Causes of Arecibo Telescope Collapse

    Jaw-Dropping Report Reveals Causes of Arecibo Telescope Collapse

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    The famous Arecibo Observatory in Puerto Rico collapsed due to a combination of decayed zinc in the telescope’s cable sockets and previous damage from Hurricane Maria, according to a report published by the National Academies of Sciences, Engineering, and Medicine.

    The massive radio telescope’s collapse in December 2020 marked the end of a prolific source of radio astronomy data. According to the recent report, the root cause of the telescope’s collapse was “unprecedented and accelerated long-term zinc creep induced failure.” That failure occurred in the telescope’s cable sockets—crucial bits of infrastructure for supporting the telescope’s 900-ton platform, which hung above the radio dish.

    The cables began to fail before the collapse. The NSF decided to demolish the dish before it fell, but the weakened infrastructure beat them to the punch. The Academies’ Committee on Analysis of Causes of Failure and Collapse of the 305-Meter Telescope at the Arecibo Observatory published the aptly titled report. The committee analyzed data and investigations collected and performed by the University of Central Florida and the National Science Foundation (NSF). You can read the report online here.

    The telescope’s collapse in 2020 was dramatic as it was swift. The cables suspending the telescope’s platform above the its 1,000-foot (304.8-meter) dish snapped, causing the platform to plummet down through the radio dish. The catastrophic collapse took less than 10 seconds, thus ending the venerated observatory’s 57 years of operation in northern Puerto Rico. The Arecibo Observatory discovered new exoplanets, created maps of other worlds, observed fast radio bursts, and aided in humankind’s search for life beyond Earth.

    “The lack of documented concern from the contracted engineers about the inconsequentiality of cable pullouts or the safety factors between Hurricane Maria in 2017 and the failure is alarming.”

    However, the report found the collapse began well before the fateful day in December 2020. The committee concluded that the “failure sequence” took 39 months and began with the effects of Hurricane Maria in September 2017. Inspections following the storm found evidence of cable slippage, according to the report, but wasn’t investigated further or addressed by anyone. “The lack of documented concern from the contracted engineers about the inconsequentiality of cable pullouts or the safety factors between Hurricane Maria in 2017 and the failure is alarming,” the committee wrote.

    But that’s not all. As the committee noted, “in over a century of successful use prior to the Arecibo Telescope’s collapse, all the forensic investigations agreed that such a spelter socket failure had never been reported.” The report went on: “The only hypothesis the committee could develop that provides a plausible but unprovable answer … is that the socket zinc creep was unexpectedly accelerated in the Arecibo Telescope’s uniquely powerful electromagnetic radiation environment.” In other words, the sockets’ role in suspending such a powerful radio transmitter somehow contributed to the 2020 catastrophe.

    In October 2022, the National Science Foundation announced that the site would be remade into a STEM-focused education center, with a slated opening of 2023. But in June 2023, the observatory officially scaled back the succession plans. In September 2023, NSF announced their institutional partners to manage the transition of the observatory site into an education center. The site may never again collect radio data, but it will—in some form—continue its legacy as an epicenter of astronomical discovery.

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    Isaac Schultz

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  • Breakthrough Image of Milky Way Black Hole Is Flawed, New Analysis Suggests

    Breakthrough Image of Milky Way Black Hole Is Flawed, New Analysis Suggests

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    A team of researchers from Japan’s National Astronomical Observatory (NAOJ) is claiming that the groundbreaking image of the supermassive black hole at the center of our galaxy is not accurate.

    The original image of Sagittarius A* was constructed from data taken by the Event Horizon Telescope Collaboration, which revealed the picture to the public in May 2022. It showed our galaxy’s central black hole as an ominous black cloud surrounded by a ring of light—the hole’s accretion disk. In its paper, the recent team suggests that the the object is more likely to have an elongated disk. The team published its proposed black hole structure in the Monthly Notices of the Royal Astronomical Society.

    The 2022 image of the black hole depicts a four-million-solar-mass behemoth called Sagittarius A*. It is the first image of the object at our galaxy’s core and the Event Horizon Telescope (or EHT)’s second black hole image. The EHT’s first black hole image—the first-ever—depicted the black hole Messier 87 (M87), and published in 2019.

    Black holes are regions of spacetime with gravitational fields so intense that not even light can escape them at a certain distance. That distance is the black hole’s event horizon. There is a field of glowing superheated matter around the event horizon: the accretion disk. The team’s recent paper focused on the accretion disk of Sagittarius A*, which they claim has a different shape than previously thought.

    The EHT is a large radio observatory made up of a network of radio telescopes. EHT data reveal the black hole—an inherently invisible object, because light does not escape the event horizon—in its silhouette against a backdrop of its accretion disk.

    “We hypothesise that the ring image resulted from errors during EHT’s imaging analysis and that part of it was an artefact, rather than the actual astronomical structure,” said Miyoshi Makoto, an astronomer at the NAOJ and co-author of the paper, in a Royal Astronomical Society release.

    In its study, the team analyzed the same 2017 data on which the EHT Collaboration built its black hole image. But the team used a different method of analysis than the collaboration, indicating an elongated accretion disk compared to the doughnut structure seen in the 2022 image.

    A radio image of Sagittarius A* according to the recent team. Image: Miyoshi et al.

    The recent team contends that the black hole’s accretion disk is elongated. In other words, it has a different structure than the ring-like disk imaged in 2022. The M87 black hole also appears to have a ring-like shape in the EHT image, which a later team developed into a polarized image of the object, complete with the structure of its magnetic fields.

    In August, the EHT published a new method by which they improved the telescope’s resolution, hinting at sharper images of black holes in the near future. Should they follow through, future observations could clarify the actual structure of Sagittarius A*.

    Even further down the road, a space-based mission to improve the sharpness of EHT images may launch. The mission concept describes a $300 million investigation of black holes’ photon rings—is called the Event Horizon Explorer.

    Improving our understanding of the cosmos’ most extreme environments—the environments that foster black holes, neutron stars, and collisions of those two objects—will yield insights into the gravitational universe, as well as the core of our own galaxy.

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    Isaac Schultz

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