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More Strange Cosmic Threads Discovered Outside Our Galaxy, And They’re Huge : ScienceAlert

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We’re getting closer to resolving the strange mystery presented by hundreds of enormous filaments dangling through the heart of the Milky Way.

For the first time, these long, magnetized filaments glowing in radio waves have been observed emerging from other galaxies. Not only are they no longer unique to the Milky Way, the range of environments in which they can be found is allowing scientists to narrow down the mechanisms that create them.

Astrophysicist Farhad Yusuf-Zadeh of Northwestern University in the US first discovered the Milky Way’s filaments in the 1980s, and has been puzzling over them ever since.

According to Yusuf-Zadeh, there are two possible explanations. The first is an interaction between galactic winds and large clouds; the second is turbulence within weak magnetic fields stirred by the motion of galaxies.

“We know a lot about the filaments in our own Galactic Center, and now filaments in outside galaxies are beginning to show up as a new population of extragalactic filaments,” Yusuf-Zadeh says.

“The underlying physical mechanisms for both populations of filaments are similar despite the vastly different environments. The objects are part of the same family, but the filaments outside the Milky Way are older, distant cousins – and I mean very distant (in time and space) cousins.”

Around 1,000 of the filaments, measuring up to 150 light-years in length and hanging in strangely neat and orderly arrangements like harp strings, have been discovered in the Milky Way to date, most recently thanks to the MeerKAT radio telescope in South Africa.

The telescope’s sensitive observations of the galactic center – penetrating through the thick dust and gas that obscures much of what’s inside – expanded the number of filaments known previously by a factor of ten. These radio observations also revealed that the filaments contain cosmic ray electrons spinning around in magnetic fields at close to the speed of light, and that magnetic fields are amplified along the entire length of all the filaments.

Some of the newly discovered filaments, from a galaxy 246 million light-years away. (Yusuf-Zadeh et al.)

Without more information, figuring out why they’re there, just quietly hanging out in the galactic center, was going to be tricky. The discovery of more filaments, in four different galaxy clusters ranging between 163 million and 652 million light-years away, is a huge breakthrough.

“After studying filaments in our own Galactic Center for all these years, I was extremely excited to see these tremendously beautiful structures,” Yusuf-Zadeh says. “Because we found these filaments elsewhere in the Universe, it hints that something universal is happening.”

The newly discovered filaments outside of the Milky Way are different from our galaxy’s thread-like structures in several pretty important ways. They’re associated with jets and lobes of radio galaxies – huge structures that erupt from the galactic center, extending vast distances on either side of the galactic plane. The filaments that extend from these jets and lobes are also far larger than the structures seen in the Milky Way’s center – between 100 and 1,000 times larger.

“Some of them have amazing length, up to 200 kiloparsecs,” Yusuf-Zadeh says.

“That is about four or five times bigger than the size of our entire Milky Way. What’s remarkable is that their electrons stay together on such a long scale. If an electron traveled at the speed of light along the filament’s length, it would take it 700,000 years. And they don’t travel at the speed of light.”

Filaments extending at roughly right-angles from the jet of a radio galaxy. (Rudnick et al.)

They’re also older, and their magnetic fields are weaker. And, of course, they extend out into intergalactic space, often at right-angles to the jets. The Milky Way’s filaments appear to be centered on the galactic disk.

On the other hand, the similarities are strong. The galactic and extragalactic filaments have the same length-to-width ratio, and the cosmic ray transport mechanism is the same. If the same mechanism produces all the filaments, it needs to be something that works on different scales.

Winds could be one such mechanism. Active supermassive black holes and rampant star formation can generate galactic winds that gust out into intergalactic space. These winds could push into the tenuous clouds of gas and dust that drift through interstellar and intergalactic space, pushing the material together to create filamentary structures.

Simulations suggested another possibility: turbulence in the medium, generated by gravitational disturbances. This turbulence can create eddies in the intergalactic medium, around which weak magnetic fields get snagged, folded, and ultimately stretched out into filaments with strong magnetic fields.

It’s not a definitive answer – yet. We don’t even know for sure if the same mechanism is responsible for both kinds of filaments, or if vastly different phenomena create structures that look uncannily alike.

“All of these filaments outside our galaxy are very old,” Yusuf-Zadeh says.

“They are almost from a different era of our Universe and yet signaling the Milky Way inhabitants that a common origin exists for the formation of the filaments. I think this is remarkable.”

The research has been published in The Astrophysical Journal Letters.

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A cosmic hourglass: Webb captures image of protostar swathed in dark clouds

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The protostar L1527 is embedded within a cloud of material that is feeding its growth.

Just last month, the James Webb Telescope gifted us a spectacular new image of the Pillars of Creation—arguably the most famous image taken by Webb’s predecessor, the Hubble Space Telescope, in 1995. Now the telescope is giving astronomers clues about the formation of a new star, with a stunning image of an hourglass-shaped dark cloud surrounding a protostar, an object known as L1527.

As we’ve reported previously, the James Webb Space Telescope launched in December 2021 and, after a suspenseful sunshield and mirror deployment over several months, began capturing stunning images. First, there was the deep field image of the Universe, released in July. This was followed by images of exoplanet atmospheres, the Southern Ring Nebula, a cluster of interacting galaxies called Stephan’s Quintet, and the Carina Nebula, a star-forming region about 7,600 light-years away.

In August, we received gorgeous images of Jupiter, including the auroras at both poles that result from Jupiter’s powerful magnetic field, as well as its thin rings and two of the gas giant’s small moons. This was followed a month later by a mosaic image showing a panorama of star formation stretching across a staggering 340 light-years in the Tarantula Nebula—so named because of its long, dusty filaments. We also were treated to spectacular images of Neptune and its rings, which have not been directly observed since Voyager 2 flew by the planet in 1989, and, as already mentioned, the Pillars of Creation.

This latest image is courtesy of Webb’s primary imager, the Near-Infrared Camera (MIRCam). To capture images of very faint objects, NIRCam’s coronagraphs block any light coming from brighter objects in the vicinity, similar to how shielding one’s eyes from bright sunlight helps us focus on the scene in front of us. The dark clouds of L1527 are only visible in the infrared, and NIRCam was able to capture features that had previously been hidden from view. Check it out:

Enlarge / Material ejected from the star has cleared out cavities above and below it, whose boundaries glow orange and blue in this infrared view.

NASA/ESA/CSA/STScI/J. DePasquale

Back in 2012, astronomers used the Submillimeter Array—a collection of eight radio telescopes arranged into an interferometer that is also part of the Event Horizon Telescope—to study the accretion disk around L1527 and measure its properties, including the rotation. They found that the disk exhibited Keplerian motion, much like the planets in our Solar System, which enabled them to determine the mass of the protostar. So learning more about L1527 could teach us more about what our own Sun and Solar System were like in their infancy.

Protostars are the earliest stage in stellar evolution, typically lasting about 500,000 years. The process begins when a fragment of a molecular cloud of dense dust and gas gains sufficient mass from the surrounding cloud to collapse under the force of its own gravity, forming a pressure-supported core. The nascent protostar continues to draw mass to itself, and the in-falling material spirals around the center to create an accretion disk.

The protostar within L1527 is only 100,000 years and thus doesn’t generate its own energy from nuclear fusion that turns hydrogen into helium, like a full-fledged star. Rather, its energy comes from the radiation released by shockwaves on the surface of the protostar and its accretion disk. Right now, it’s basically a sphere-shaped puffy clump of gas between 20–40 percent the mass of our Sun. As the protostar continues to gain mass and compress further, its core will continue to heat up. Eventually it will get hot enough to trigger nuclear fusion, and a star will be born.

The Webb image above shows how material ejected from L1527’s protostar has created empty cavities above and below; the glowing orange and blue regions represent the boundaries outlining those regions. (The blue region’s color is because it has less dust, compared to the orange regions above it, which trap more blue light in the thick dust so it can’t escape.) The accretion disk appears as a dark band. There are also filaments of molecular hydrogen in the image, the result of shocks from the protostar ejecting material.

Listing image by NASA/ESA/CSA/STScI/J. DePasquale

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James Webb Space Telescope reveals birth of a star in a cosmic hourglass

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The cosmic chaos caused by a very young star has been captured in the latest enchanting image from NASA’s James Webb Space Telescope.

The protostar the image centers around is hidden from view in the neck of a dark, hourglass-shape cloud of gas and dust. The dark line across the middle of the neck is a protoplanetary disc — dense gas and dust that could form a planet in the future — about the size of our solar system. Light from the protostar spreads above and below this disc, according to a news release.

It has a long way to go until it becomes a full-fledged star. L1527, as the protostar and its cloud are known, is only about 100,000 years old — a relatively young celestial body compared with our sun, which is about 4.6 billion years old.

The blue and orange clouds in the image outline cavities created as material shoots away from the protostar and collides with the surrounding matter, the release noted.

The nebula’s vibrant colors are only visible in infrared light detected by Webb’s Near-Infrared Camera, or NIRCam. Infrared light is invisible to the human eye, making Webb particularly essential to revealing otherwise hidden aspects of the universe.

The blue areas are where the dust is thinnest. The thicker the layer of dust, the less blue light is able to escape, creating pockets of orange.

“Shocks and turbulence inhibit the formation of new stars, which would otherwise form throughout the cloud. As a result, the protostar dominates the space, taking much of the material for itself,” according to the news release.

The protostar doesn’t yet generate its own energy through nuclear fusion of hydrogen, an essential characteristic of stars. Its shape — a puffy clump of hot gas somewhere between 20% and 40% of the mass of our sun — is also unstable.

The image provides context for what our sun and solar system looked like in their infancy.

Webb, which first began sharing new perspectives on the universe in July, is an international partnership between NASA, the European Space Agency and the Canadian Space Agency.

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Neutron Stars Are Basically Giant Cosmic Pralines, Astrophysicists Say

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An illustration showing the internal workings of heavier (left) and lighter (right) neutron stars, imagined as pralines.
Illustration: Peter Kiefer & Luciano Rezzolla

Astrophysicists modeling the insides of neutron stars have found that the extremely compact objects have different internal structures, depending on their mass. They suggest thinking of the stars as different types of chocolate praline, a delicious treat—but that’s where the similarities end, at least as far as we know.

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Neutron stars are the extraordinarily dense corpses of massive stars that imploded; they’re second only to black holes in terms of their density. Neutron stars are so-named because their gravitational force causes their atoms’ electrons to collapse onto the protons, creating an object that is almost entirely composed of neutrons.

Neutron stars’ gravitational fields are super intense. If a human observer went near one, they’d be torn apart at an atomic level. Their gravitations fields are so strong that a “mountain” on a neutron star would stand less than a millimeter tall.

The recent research team constructed millions of models to try to discern the internal workings of these stars, which are remarkably difficult to study and, as a result, are more the domain of theory than observation.

The researchers found that lighter neutron stars—those with masses about 1.7 times that of our Sun and under—should have soft mantles and stiff cores. Heavier neutron stars have the opposite, according to the team’s findings, which were published today in The Astrophysical Journal Letters.

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Luciano Rezzolla, an astrophysicist at the Institute of Theoretical Physics and who led the research, likened the stars’ structure to chocolate pralines.

“Light stars resemble those chocolates that have a hazelnut in their centre surrounded by soft chocolate, whereas heavy stars can be considered more like those chocolates where a hard layer contains a soft filling,” Rezzolla said in a Goethe University Frankfurt release.

The researchers modeled over a million possible scenarios for neutron star makeup, based on expectations for the star’s mass, pressure, volume, and temperature, as well as astronomical observations of the objects.

Modeling is a crucial means of interrogating neutron stars, because only a few contraptions on Earth—CERN’s Large Hadron Collider and SLAC’s Matter in Extreme Conditions instrument, for two—are capable of mimicking such intense physics.

To determine the consistencies of the stars, the researchers modeled how the speed of sound would travel through the objects. Sound waves are also used to understand the internal structure of planets, as the InSight lander has intrepidly done on Mars.

“What we have shown, by constructing millions of equation of state models (from which the sound speed can be computed), is that maximally massive neutron stars have a lower sound speed in the core region than in their outer layers,” said Christian Ecker, an astrophysicist at Goethe University, in an email to Gizmodo.

“This hints to some material change in their cores, like for example a transition from baryonic to quark matter,” Ecker added.

The researchers also found that all neutron stars are probably about 7.46 miles (12 km) across, regardless of their mass. That measurement is less than half that of a 2020 finding that the typical neutron star was about 13.6 miles (22 km) across. Despite that size, the average neutron star mass is around half a million Earths. There’s dense, and then there’s dense.

While the findings offer some insight about the diversity of neutron stars in terms of their consistency, the researchers did not investigate the stars’ ingredients or how they fit together. (If you’ve gotten this far, neutron stars are not actually made of chocolate.) Some suspect that neutron stars are neutrons all the way down; others believe that the centers of the stars are factories for exotic, hitherto unidentified particles.

But for the most part, these superdense enigmas remain just that. Thankfully, there are observatories set up to collect more direct data. Mergers (i.e. violent collisions) between neutron stars and with black holes can reveal the mass of the involved objects, as well as the nature of neutron star material.

Projects like NICER, NANOGrav, the CHIME radio telescope, and the LIGO and Virgo scientific collaborations are all teaching physicists about neutron star size and structure.

More observational data can be fed into models for better estimates of the stars’ aspects. Ecker added that very massive neutron stars (in the ballpark of two solar masses) would be particularly helpful in better constraining expectations of the physical characteristics of these extreme objects.

With any luck, we may soon get more details of the exact ingredients of these giant cosmic pralines—and how their recipes may differ depending on their size.

More: Extremely Massive Neutron Star May Be the Largest Ever Spotted

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Cosmic chocolate pralines? General neutron star structure revealed

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The study of the sound speed has revealed that heavy neutron stars have a stiff mantle and a soft core, while light neutron stars have a soft mantle and a stiff core—much like different chocolate pralines. Credit: Peter Kiefer & Luciano Rezzolla

So far, little is known about the interior of neutron stars, those extremely compact objects that can form after the death of a star. The mass of our sun or even more is compressed into a sphere with the diameter of a large city. Since their discovery more than 60 years ago, scientists have been trying to decipher their structure.

The greatest challenge is to simulate the extreme conditions inside neutron stars, as they can hardly be recreated on Earth in the laboratory. There are therefore many models in which various properties—from density and temperature—are described with the help of so-called equations of state. These equations attempt to describe the structure of neutron stars from the stellar surface to the inner core.

Now, physicists at Goethe University Frankfurt have succeeded in adding further crucial pieces to the puzzle. The working group, led by Prof. Luciano Rezzolla at the Institute of Theoretical Physics, has developed more than a million different equations of state that satisfy the constraints set by data obtained from theoretical nuclear physics on the one hand, and by astronomical observations on the other. Their work is published in The Astrophysical Journal Letters.

When evaluating the equations of state, the working group made a surprising discovery: “Light” neutron stars (with masses smaller than about 1.7 solar masses) seem to have a soft mantle and a stiff core, whereas “heavy” neutron stars (with masses larger than 1.7 solar masses) instead have a stiff mantle and a soft core.

“This result is very interesting because it gives us a direct measure of how compressible the center of neutron stars can be,” says Prof. Luciano Rezzolla, “Neutron stars apparently behave a bit like chocolate pralines: Light stars resemble those chocolates that have a hazelnut in their center surrounded by soft chocolate, whereas heavy stars can be considered more like those chocolates where a hard layer contains a soft filling.”

Crucial to this insight was the speed of sound, a study focus of Bachelor’s student Sinan Altiparmak. This quantity measure describes how fast sound waves propagate within an object and depends on how stiff or soft matter is. Here on Earth, the speed of sound is used to explore the interior of the planet and discover oil deposits.

By modeling the equations of state, the physicists were also able to uncover other previously unexplained properties of neutron stars. For example, regardless of their mass, they very probably have a radius of only 12 km. Thus, they are just as large in diameter as Goethe University’s hometown of Frankfurt.

Study author Dr. Christian Ecker explains, “Our extensive numerical study not only allows us to make predictions for the radii and maximum masses of neutron stars, but also to set new limits on their deformability in binary systems, that is, how strongly they distort each other through their gravitational fields. These insights will become particularly important to pinpoint the unknown equation of state with future astronomical observations and detections of gravitational waves from merging stars.”

More information:
On the Sound Speed in Neutron Stars, The Astrophysical Journal Letters (2022). DOI: 10.3847/2041-8213/ac9b2a

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Goethe University Frankfurt am Main

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Cosmic chocolate pralines? General neutron star structure revealed (2022, November 15)
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Scientists Tested Einstein’s Relativity on a Cosmic Scale, And Found Something Odd : ScienceAlert

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Everything in the Universe has gravity – and feels it too. Yet this most common of all fundamental forces is also the one that presents the biggest challenges to physicists.

Albert Einstein’s theory of general relativity has been remarkably successful in describing the gravity of stars and planets, but it doesn’t seem to apply perfectly on all scales.

General relativity has passed many years of observational tests, from Eddington’s measurement of the deflection of starlight by the Sun in 1919 to the recent detection of gravitational waves.

However, gaps in our understanding start to appear when we try to apply it to extremely small distances, where the laws of quantum mechanics operate, or when we try to describe the entire universe.

Our new study, published in Nature Astronomy, has now tested Einstein’s theory on the largest of scales.

We believe our approach may one day help resolve some of the biggest mysteries in cosmology, and the results hint that the theory of general relativity may need to be tweaked on this scale.

Faulty model?

Quantum theory predicts that empty space, the vacuum, is packed with energy. We do not notice its presence because our devices can only measure changes in energy rather than its total amount.

However, according to Einstein, the vacuum energy has a repulsive gravity – it pushes the empty space apart. Interestingly, in 1998, it was discovered that the expansion of the Universe is in fact accelerating (a finding awarded with the 2011 Nobel Prize in physics).

However, the amount of vacuum energy, or dark energy as it has been called, necessary to explain the acceleration is many orders of magnitude smaller than what quantum theory predicts.

Hence the big question, dubbed “the old cosmological constant problem”, is whether the vacuum energy actually gravitates – exerting a gravitational force and changing the expansion of the universe.

If yes, then why is its gravity so much weaker than predicted? If the vacuum does not gravitate at all, what is causing the cosmic acceleration?

We don’t know what dark energy is, but we need to assume it exists in order to explain the Universe’s expansion.

Similarly, we also need to assume there is a type of invisible matter presence, dubbed dark matter, to explain how galaxies and clusters evolved to be the way we observe them today.

These assumptions are baked into scientists’ standard cosmological theory, called the lambda cold dark matter (LCDM) model – suggesting there is 70 percent dark energy, 25 percent dark matter, and 5 percent ordinary matter in the cosmos. And this model has been remarkably successful in fitting all the data collected by cosmologists over the past 20 years.

But the fact that most of the Universe is made up of dark forces and substances, taking odd values that don’t make sense, has prompted many physicists to wonder if Einstein’s theory of gravity needs modification to describe the entire universe.

A new twist appeared a few years ago when it became apparent that different ways of measuring the rate of cosmic expansion, dubbed the Hubble constant, give different answers – a problem known as the Hubble tension.

The disagreement, or tension, is between two values of the Hubble constant.

One is the number predicted by the LCDM cosmological model, which has been developed to match the light left over from the Big Bang (the cosmic microwave background radiation).

The other is the expansion rate measured by observing exploding stars known as supernovas in distant galaxies.

Many theoretical ideas have been proposed for ways of modifying LCDM to explain the Hubble tension. Among them are alternative gravity theories.

Digging for answers

We can design tests to check if the universe obeys the rules of Einstein’s theory.

General relativity describes gravity as the curving or warping of space and time, bending the pathways along which light and matter travel. Importantly, it predicts that the trajectories of light rays and matter should be bent by gravity in the same way.

Together with a team of cosmologists, we put the basic laws of general relativity to test. We also explored whether modifying Einstein’s theory could help resolve some of the open problems of cosmology, such as the Hubble tension.

To find out whether general relativity is correct on large scales, we set out, for the first time, to simultaneously investigate three aspects of it. These were the expansion of the Universe, the effects of gravity on light, and the effects of gravity on matter.

Using a statistical method known as the Bayesian inference, we reconstructed the gravity of the Universe through cosmic history in a computer model based on these three parameters.

We could estimate the parameters using the cosmic microwave background data from the Planck satellite, supernova catalogs as well as observations of the shapes and distribution of distant galaxies by the SDSS and DES telescopes.

We then compared our reconstruction to the prediction of the LCDM model (essentially Einstein’s model).

We found interesting hints of a possible mismatch with Einstein’s prediction, albeit with rather low statistical significance.

This means that there is nevertheless a possibility that gravity works differently on large scales, and that the theory of general relativity may need to be tweaked.

Our study also found that it is very difficult to solve the Hubble tension problem by only changing the theory of gravity.

The full solution would probably require a new ingredient in the cosmological model, present before the time when protons and electrons first combined to form hydrogen just after the Big Bang, such as a special form of dark matter, an early type of dark energy, or primordial magnetic fields.

Or, perhaps, there’s a yet unknown systematic error in the data.

That said, our study has demonstrated that it is possible to test the validity of general relativity over cosmological distances using observational data. While we haven’t yet solved the Hubble problem, we will have a lot more data from new probes in a few years.

This means that we will be able to use these statistical methods to continue tweaking general relativity, exploring the limits of modifications, to pave the way to resolving some of the open challenges in cosmology.

Kazuya Koyama, Professor of Cosmology, University of Portsmouth and Levon Pogosian, Professor of Physics, Simon Fraser University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Astronomers Discover Closest Black Hole to Earth – In Our Cosmic Backyard

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Astronomers using the International Gemini Observatory, have uncovered the closest-known black hole to Earth. It is also the first unambiguous detection of a dormant stellar-mass black hole in the Milky Way. Its close proximity to Earth, a mere 1600 light-years away, offers an intriguing target of study to advance our understanding of the evolution of binary systems. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/J. da Silva/Spaceengine/M. Zamani

Gemini North telescope on Hawai‘i reveals the first dormant, stellar-mass

“Take the Solar System, put a black hole where the Sun is, and the Sun where the Earth is, and you get this system.” — Kareem El-Badry

Black holes are the most extreme objects in the Universe. It is believed that supermassive versions of these unimaginably dense objects reside at the centers of all large galaxies. Stellar-mass black holes — which weigh approximately five to 100 times the mass of the Sun — are much more common. In fact, there are an estimated 100 million stellar-mass black holes in the Milky Way alone. However, only a handful have been confirmed to date, and nearly all of these are ‘active’. This means that they shine brightly in X-rays as they consume material from a nearby stellar companion, unlike dormant black holes which do not.

Astronomers have now discovered the closest black hole to Earth, which the researchers have dubbed Gaia BH1. To find it, they used the Gemini North telescope in Hawai‘i, one of the twin telescopes of the International Gemini Observatory, operated by NSF’s NOIRLab.

Gaia BH1 is a dormant black hole that is about 10 times more massive than the Sun and is located about 1600 light-years away in the constellation Ophiuchus. This means it is three times closer to Earth than the previous record holder, an X-ray binary in the constellation of Monoceros. The new discovery was made possible by making exquisite observations of the motion of the black hole’s companion, a Sun-like star that orbits the black hole at about the same distance as the Earth orbits the Sun.


This animation shows a Sun-like star orbiting Gaia BH1, the closest black hole to Earth, located about 1600 light-years away. Observations by Gemini North, one of the twin telescopes of the International Gemini Observatory, operated by NSF’s NOIRLab, were crucial to constraining the orbital motion and hence masses of the two components in the binary system, allowing the team to identify the central body as a black hole roughly 10 times as massive as our Sun. Credit: T. Müller (MPIA), PanSTARRS DR1 (K. C. Chambers et al. 2016), ESA/Gaia/DPAC

“Take the Solar System, put a black hole where the Sun is, and the Sun where the Earth is, and you get this system,” explained Kareem El-Badry, an astrophysicist at the Center for Astrophysics | Harvard & Smithsonian and the Max Planck Institute for Astronomy, and the lead author of the paper describing this discovery that was published on November 2 in Monthly Notices of the Royal Astronomical Society.

“While there have been many claimed detections of systems like this, almost all these discoveries have subsequently been refuted. This is the first unambiguous detection of a Sun-like star in a wide orbit around a stellar-mass black hole in our Galaxy.”

Though there are likely millions of stellar-mass black holes roaming the Milky Way Galaxy, those few that have been detected were uncovered by their energetic interactions with a companion star. As material from a nearby star spirals in toward the black hole, it becomes superheated and generates powerful X-rays and jets of material. If a black hole is not actively feeding (i.e., it is dormant) it simply blends in with its surroundings.

“I’ve been searching for dormant black holes for the last four years using a wide range of datasets and methods,” said El-Badry. “My previous attempts — as well as those of others — turned up a menagerie of binary systems that masquerade as black holes, but this is the first time the search has borne fruit.”

“While this potentially augurs future discoveries of the predicted dormant black hole population in our Galaxy, the observations also leave a mystery to be solved — despite a shared history with its exotic neighbor, why is the companion star in this binary system so normal?” — Martin Still

The team originally identified the system as potentially hosting a black hole by analyzing data from the European Space Agency’s Gaia spacecraft. Gaia captured the minute irregularities in the star’s motion caused by the gravity of an unseen massive object. To explore the system in more detail, El-Badry and his team turned to the Gemini Multi-Object Spectrograph instrument on Gemini North, which measured the velocity of the companion star as it orbited the black hole and provided precise measurement of its orbital period. The Gemini follow-up observations were crucial to constraining the orbital motion and hence masses of the two components in the binary system, allowing the team to identify the central body as a black hole roughly 10 times as massive as our Sun.

“Our Gemini follow-up observations confirmed beyond reasonable doubt that the binary contains a normal star and at least one dormant black hole,” elaborated El-Badry. “We could find no plausible astrophysical scenario that can explain the observed orbit of the system that doesn’t involve at least one black hole.”

The team relied not only on Gemini North’s superb observational capabilities but also on Gemini’s ability to provide data on a tight deadline, as the team had only a short window in which to perform their follow-up observations.

“When we had the first indications that the system contained a black hole, we only had one week before the two objects were at the closest separation in their orbits. Measurements at this point are essential to make accurate mass estimates in a binary system,” said El-Badry. “Gemini’s ability to provide observations on a short timescale was critical to the project’s success. If we’d missed that narrow window, we would have had to wait another year.”

Astronomers’ current models of the evolution of binary systems are hard-pressed to explain how the peculiar configuration of Gaia BH1 system could have arisen. Specifically, the progenitor star that later turned into the newly detected black hole would have been at least 20 times as massive as our Sun. This means it would have lived only a few million years. If both stars formed at the same time, this massive star would have quickly turned into a supergiant, puffing up and engulfing the other star before it had time to become a proper, hydrogen-burning, main-sequence star like our Sun.

It is not at all clear how the solar-mass star could have survived that episode, ending up as an apparently normal star, as the observations of the black hole binary indicate. Theoretical models that do allow for survival all predict that the solar-mass star should have ended up on a much tighter orbit than what is actually observed.

This could indicate that there are important gaps in our understanding of how black holes form and evolve in binary systems, and also suggests the existence of an as-yet-unexplored population of dormant black holes in binaries.

“It is interesting that this system is not easily accommodated by standard binary evolution models,” concluded El-Badry. “It poses many questions about how this binary system was formed, as well as how many of these dormant black holes there are out there.”

“As part of a network of space- and ground-based observatories, Gemini North has not only provided strong evidence for the nearest black hole to date but also the first pristine black hole system, uncluttered by the usual hot gas interacting with the black hole,” said NSF Gemini Program Officer Martin Still. “While this potentially augurs future discoveries of the predicted dormant black hole population in our Galaxy, the observations also leave a mystery to be solved — despite a shared history with its exotic neighbor, why is the companion star in this binary system so normal?”

Reference: “A Sun-like star orbiting a black hole” by Kareem El-Badry, Hans-Walter Rix, Eliot Quataert, Andrew W Howard, Howard Isaacson, Jim Fuller, Keith Hawkins, Katelyn Breivik, Kaze W K Wong, Antonio C Rodriguez, Charlie Conroy, Sahar Shahaf, Tsevi Mazeh, Frédéric Arenou, Kevin B Burdge, Dolev Bashi, Simchon Faigler, Daniel R Weisz, Rhys Seeburger, Silvia Almada Monter and Jennifer Wojno, 2 November 2022, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stac3140

Gemini North observations were made as part of a director’s discretionary time program (program id: GN-2022B-DD-202).

The International Gemini Observatory is operated by a partnership of six countries, including the United States through the National Science Foundation, Canada through the National Research Council of Canada, Chile through the Agencia Nacional de Investigación y Desarrollo, Brazil through the Ministério da Ciência, Tecnologia e Inovações, Argentina through the Ministerio de Ciencia, Tecnología e Innovación, and Korea through the Korea Astronomy and Space Science Institute. These Participants and the University of Hawaii, which has regular access to Gemini, each maintain a “National Gemini Office” to support their local users.



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IceCube neutrino analysis pegs possible galactic source for cosmic rays

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Enlarge / Artist’s representation of a cosmic neutrino source shining above the IceCube Observatory at the South Pole. Beneath the ice are photodetectors that pick up the neutrino signals.

IceCube/NSF

Ever since French physicist Pierre Auger proposed in 1939 that cosmic rays must carry incredible amounts of energy, scientists have puzzled over what could be producing these powerful clusters of protons and neutrons raining down onto Earth’s atmosphere. One possible means for identifying such sources is to backtrack the paths that high-energy cosmic neutrinos traveled on their way to Earth, since they are created by cosmic rays colliding with matter or radiation, producing particles that then decay into neutrinos and gamma rays.

Scientists with the IceCube neutrino observatory at the South Pole have now analyzed a decade’s worth of such neutrino detections and discovered evidence that an active galaxy called Messier 77 (aka the Squid Galaxy) is a strong candidate for one such high-energy neutrino emitter, according to a new paper published in the journal Science. It brings astrophysicists one step closer to resolving the mystery of the origin of high-energy cosmic rays.

“This observation marks the dawn of being able to really do neutrino astronomy,” IceCube member Janet Conrad of MIT told APS Physics. “We’ve struggled for so long to see potential cosmic neutrino sources at very high significance and now we’ve seen one. We’ve broken a barrier.”

As we’ve previously reported, neutrinos travel near the speed of light. John Updike’s 1959 poem, “Cosmic Gall,” pays tribute to the two most defining features of neutrinos: they have no charge and, for decades, physicists believed they had no mass (they actually have a teeny bit of mass). Neutrinos are the most abundant subatomic particle in the universe, but they very rarely interact with any type of matter. We are constantly being bombarded every second by millions of these tiny particles, yet they pass right through us without our even noticing. That’s why Isaac Asimov dubbed them “ghost particles.”

Enlarge / When a neutrino interacts with molecules in the clear Antarctic ice, it produces secondary particles that leave a trace of blue light as they travel through the IceCube detector.

Nicolle R. Fuller, IceCube/NSF

That low rate of interaction makes neutrinos extremely difficult to detect, but because they are so light, they can escape unimpeded (and thus largely unchanged) by collisions with other particles of matter. This means they can provide valuable clues to astronomers about distant systems, further augmented by what can be learned with telescopes across the electromagnetic spectrum, as well as gravitational waves. Together, these different sources of information have been dubbed “multimessenger” astronomy.

Most neutrino hunters bury their experiments deep underground, the better to cancel out noisy interference from other sources. In the case of IceCube, the collaboration features arrays of basketball-sized optical sensors buried deep within the Antarctic ice. On those rare occasions when a passing neutrino interacts with the nucleus of an atom in the ice, the collision produces charged particles that emit UV and blue photons. Those are picked up by the sensors.

So IceCube is well-positioned to help scientists advance their knowledge of the origin of high-energy cosmic rays. As Natalie Wolchover cogently explained at Quanta in 2021:

A cosmic ray is just an atomic nucleus—a proton or a cluster of protons and neutrons. Yet the rare ones known as “ultrahigh-energy” cosmic rays have as much energy as professionally served tennis balls. They’re millions of times more energetic than the protons that hurtle around the circular tunnel of the Large Hadron Collider in Europe at 99.9999991% of the speed of light. In fact, the most energetic cosmic ray ever detected, nicknamed the “Oh-My-God particle,” struck the sky in 1991 going something like 99.99999999999999999999951 percent of the speed of light, giving it roughly the energy of a bowling ball dropped from shoulder height onto a toe.

But where do such powerful cosmic rays originate? One strong possibility is active galactic nuclei (AGNs), found at the center of some galaxies. Their energy arises from supermassive black holes at the center of the galaxy, and/or from the black hole’s spin.

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Astronomers spy the ghost of a star and cosmic cobwebs

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 — 

Colorful, ghostly remnants drift in space where a massive star exploded 11,000 years ago.

The Vela supernova remnant, named after the Vela constellation, is all that remains after the star reached the end of its life.

Pink and orange gas clouds mark the spot 800 light-years away from Earth, making it one of the closest known features. (A light-year is about 6 trillion miles.)

When the star went supernova, shock waves moved through the surrounding layers of gas released by the star.

The energetic waves compressed the gas and created threadlike filaments that resemble wispy cobwebs.

In a new image of the Vela supernova remnant, captured by the VLT Survey Telescope at the European Southern Observatory in Chile, the glowing threads of gas appear to shine due to heat from the shock waves.

The eerily beautiful sight where the star died was fittingly released on Halloween.

Within the remnant is a dense neutron star, or pulsar, which rapidly spins and releases beams of light like a celestial lighthouse — but it’s located just outside of the region shown in the image.

Nine full moons could fit within the detailed perspective, and the image only reflects part of the giant cloud.

The European Southern Observatory also shared detailed views of intriguing features within the mosaic. The 12 highlights zoom in on different aspects of the bright stars and gas clouds within the region.

The image, which contains 554 million pixels, was captured by the wide-field OmegaCAM on the telescope. The 268 million-pixel camera is capable of capturing images using several different filters that allow for varied wavelengths of light and colors — hence the magenta, blue, green and red colors in the image.

The VLT Survey Telescope is one of the largest telescopes that surveys the night sky using visible light, helping astronomers unlock the secrets of star formation and death.

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Hubble telescope peeks through ‘cosmic keyhole’ in stunning photo

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It’s not everyday that you can peek through a keyhole in the cosmos, but Hubble did just that — and it didn’t even realize it.

A new photo of the reflection nebula NGC 1999 taken by the Hubble Space Telescope and released by NASA and the European Space Agency (ESA) on Oct. 24 shows a “peculiar portrait” of the swirling cloud of gas and dust. The nebula is a relic of a star’s formation, V380 Orion, which can be seen in the center of the image, according to an ESA statement (opens in new tab) that accompanied the image.

The most distinctive feature of the photo, however, is the dark void in the heart of the nebula shaped like a keyhole.

Related: Hubble Space Telescope shows Webb a thing or two with spectacular new photo

When the nebula was first imaged by Hubble in 1999, it was believed that the dark central region was something known as a “Bok globule.” These globules are cold clouds of gas, dust, and other molecules that are so dense that they block any light from passing through. It was only after subsequent observations of the nebula that astronomers learned that the dark region was actually empty space. At the moment, the origin of this keyhole feature isn’t known.

The nebula is illuminated from the inside by the newborn star V380 Orion, and the nebula itself is actually the leftover material from the star’s formation. The star is white in color owing to the intense heat of its surface — roughly 18,000 degrees Fahrenheit (10,000 degrees Celsius), or twice the temperature of the sun — and it is estimated at 3.5 stellar masses.

The nebula is close to the Orion Nebula, located about 1,500 light-years away, in an active star-forming region of the Milky Way. It is also famous for its proximity to the first Herbig-Haro object ever discovered, which is just outside of the image frame, according to the space agencies. (Herbig-Haro objects are relatively short-lived jets of ionized gas shot out from very young stars.)

This peculiar portrait from the NASA/ESA Hubble Space Telescope showcases NGC 1999, a reflection nebula in the constellation Orion.  (Image credit: ESA/Hubble & NASA, ESO, K. Noll)

The new image was created using archival data from Hubble’s Wide Field Planetary Camera 2, which uses a mix of ultraviolet, visible, and near-infrared sensors to create the image of the nebula we see. The infrared sensor is arguably the most important when looking at nebulae, since Hubble’s other sensors cannot see past the clouds of dust to the stars within or behind the nebula.

This ability for infrared light to pass through clouds of gas and dust is what makes the James Webb Space Telescope such an important instrument, since it’s infrared camera is much more sensitive than Hubble’s, and has already revealed dazzling images of famous nebulae like the Pillars of Creation in the Eagle Nebula.

You can find John on Twitter at @thisdotjohn (opens in new tab). Follow us on Twitter @Spacedotcom (opens in new tab) and on Facebook (opens in new tab).



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