Ina
The Living Force
The solar winds are maybe phenomena occurring in the Sun's tail. Incidentally, our Solar System could be a 'companion' to a huge comet, that is our Sun.
Rising fluxes of cosmic rays inside the solar system
- Thread starter Laura
- Start date
XPan
The Living Force
Auroras on Jupiter
At Spaceweather.com images of Jupiter were published, taken with the new James Webb Space Telescope (JWST)
Image credit: JWST's Near-Infrared Camera (NIRCam). The camera's F360M filter picked up the 3.3 - 3.6 micron glow of excited H3+ in Jupiter's auroral zone.
Above: This JWST image of Jupiter and its surroundings uses a different color table, so the auroras look blue. They are still infra-red.
At Spaceweather.com images of Jupiter were published, taken with the new James Webb Space Telescope (JWST)
Image credit: JWST's Near-Infrared Camera (NIRCam). The camera's F360M filter picked up the 3.3 - 3.6 micron glow of excited H3+ in Jupiter's auroral zone.
Above: This JWST image of Jupiter and its surroundings uses a different color table, so the auroras look blue. They are still infra-red.
dennis
Jedi Council Member
Just speculating, but what about the sound or vibrational frequencies of the planets? Venus in the above depiction with the flaring tail looks like it is shaped as a tuning fork. Places like Stonehenge could have been cosmic surround sound theaters built to listen to/bath in the EM frequencies.
What does all this mean for Stonehenge?
Various pieces of evidence suggest that Stonehenge began its career around 3000 BC as a combined solar and lunar site. It also came to serve as a place ofinterment of cremated remains. The centerline of the northeastern entrance had a declination of +27º, close to that of the major lunar standstill.5
...
Using the geometry of a diffraction grating,7 the builders arranged the tall sarsens of the Trilithon Horseshoe symmetrically around the main northeast-southwest axis in an arc representing the arc formed by Comet Venus’ body and twin tails (plan by Anthony Johnson, Wikimedia Commons). A parallel arc concept can be found in the original version of the Chinese myth of Archer Yi and his vermilion bow
Venus, Skeleton Key to Stonehenge - Scientia Press
www.scientiapress.com
XPan
The Living Force
Dung Beetles navigate using the Milky Way (article here)
I am really not sure where I should put this fascinating (Spaceweather.com) article about the Dung Beetles who navigate with help of using the Milky way. So, moderators, please feel free to put it into any thread where it could belong better (if there is such thread)
Here it goes:
A nocturnal dung beetle at work. Photo credit: Chris Collingridge © 2017
DUNG BEETLES NAVIGATE USING THE MILKY WAY:
When you hear the words "dung beetle" you probably think of poop. After you read this article, a different picture may come to mind: The Milky Way.
In 2009, entomologists made an astonishing discovery. Nocturnal dung beetles (Scarabaeus satyrus) can navigate using the Milky Way. Although the compound eyes of beetles cannot resolve individual stars, this species can see the Milky Way as a stripe across the sky and perhaps even sense features within it such as the galactic center and lanes of stardust.
"Currently, dung beetles are the only animals we know of that use the Milky Way for reliable orientation," says James Foster of the University of Konstanz in Germany. "They are excellent little astronomers."
A quick review of dung beetles: They are nature's sanitation crew. Whenever a pile of brown material is dumped in the forest, dung beetles converge to clean up the mess. Each beetle sculpts a dung ball, which they roll away in a straight line. Far from the pile, the ball will be buried and eaten, and sometimes used as bedding for dung beetle eggs.
It sounds simple, but there's a problem. Dung beetles are combative. If two beetles leaving the pile bump into one other, they can get into a brutal wrestling match often ending with overhead judo-style full body throws. Wandering around in circles (like lost humans do) boosts the odds of a fight even more. Dung beetles have therefore evolved the ability to navigate to safety in quick straight lines.
During the day they steer by the sun. Dung beetles can see polarization patterns in the daytime sky, and use these patterns to hold course. A single patch of blue sky is sufficient. The trick works at night, too. Dung beetles are the only known creatures who can see the polarization of moonlight, which is 100 million times weaker than daylight polarization. Studies show* that dung beetles walk straight as accurately at night as during the day, even when the Moon is a faint crescent.
* the study
pubmed.ncbi.nlm.nih.gov
Dung beetle vision blurs the Milky Way, but no one is certain how much. These are four models used in the experiments of James Foster.
But what happens when there's no sun or Moon?
In the early 2000s, this question troubled two pioneers of dung beetle research, Eric Warrant and Marie Dacke of Lund University in Sweden. To find the answer, they took some beetles to the planetarium at the University of the Witwatersrand in Johannesburg, South Africa, and projected the Milky Way onto the domed ceiling. The beetles saw it, and navigated.
Their discovery prompted a veritable explosion in dung beetle research. James Foster is a leader in the field, publishing new results every few years.
Foster and colleagues have built a rudimentary planetarium just for dung beetles. It uses LED lights to mimic the Milky Way as beetles see it through their compound eyes. In 2017 they found that dung beetles were able to distinguish between north and south arms of the Milky Way, sensing intensity contrasts as low as 13%. This threshold puts features such as the galactic center in Sagittarius and the Great Rift in Cygnus theoretically within range of beetle senses.
Next they added city lights to their experiment--and the results were not good. "Light pollution may be forcing beetles to abandon the Milky Way as their compass," worries Foster.
Researcher Claudia Tocco observes the behavior of a dung beetle surrounded by urban lights. Photo credit Marcus Byrne.
In a paper** published July 2021, Foster's team described how urban lights wipe out the Milky Way, reduce the polarization of moonlight by 60% to 70%, and "create anthropogenic celestial cues." The last item is worst of all. Spotlights and brightly lit buildings mesmerize beetles who suddenly ignore the sky and make a beeline for manmade bulbs.
"These beacons draw beetles towards the most hostile regions of their environments," says Foster. "After rolling their balls some distance, beetles need to find a patch of soft sand where they can dig in. They are unlikely to find that in the immediate vicinity of bright artificial lights, whether in cities or the countryside, since these are usually associated with concrete and tarmac."
Dung beetles aren't the only ones. Researchers believe they are only scratching the surface of this field with potentially thousands of species watching the stars. Everything from simple light bulbs to sophisticated satellite megaconstellations may be affecting these members of our ecosystem.
"Dung beetle!" What are you thinking of now?
Taken by Ruslan Merzlyakov on May 31, 2022 @ Gran Canaria, Spain
**) the study/paper July 2001
I am really not sure where I should put this fascinating (Spaceweather.com) article about the Dung Beetles who navigate with help of using the Milky way. So, moderators, please feel free to put it into any thread where it could belong better (if there is such thread)
Here it goes:
A nocturnal dung beetle at work. Photo credit: Chris Collingridge © 2017
DUNG BEETLES NAVIGATE USING THE MILKY WAY:
When you hear the words "dung beetle" you probably think of poop. After you read this article, a different picture may come to mind: The Milky Way.
In 2009, entomologists made an astonishing discovery. Nocturnal dung beetles (Scarabaeus satyrus) can navigate using the Milky Way. Although the compound eyes of beetles cannot resolve individual stars, this species can see the Milky Way as a stripe across the sky and perhaps even sense features within it such as the galactic center and lanes of stardust.
"Currently, dung beetles are the only animals we know of that use the Milky Way for reliable orientation," says James Foster of the University of Konstanz in Germany. "They are excellent little astronomers."
A quick review of dung beetles: They are nature's sanitation crew. Whenever a pile of brown material is dumped in the forest, dung beetles converge to clean up the mess. Each beetle sculpts a dung ball, which they roll away in a straight line. Far from the pile, the ball will be buried and eaten, and sometimes used as bedding for dung beetle eggs.
It sounds simple, but there's a problem. Dung beetles are combative. If two beetles leaving the pile bump into one other, they can get into a brutal wrestling match often ending with overhead judo-style full body throws. Wandering around in circles (like lost humans do) boosts the odds of a fight even more. Dung beetles have therefore evolved the ability to navigate to safety in quick straight lines.
During the day they steer by the sun. Dung beetles can see polarization patterns in the daytime sky, and use these patterns to hold course. A single patch of blue sky is sufficient. The trick works at night, too. Dung beetles are the only known creatures who can see the polarization of moonlight, which is 100 million times weaker than daylight polarization. Studies show* that dung beetles walk straight as accurately at night as during the day, even when the Moon is a faint crescent.
* the study
How dim is dim? Precision of the celestial compass in moonlight and sunlight - PubMed
Prominent in the sky, but not visible to humans, is a pattern of polarized skylight formed around both the Sun and the Moon. Dung beetles are, at present, the only animal group known to use the much dimmer polarization pattern formed around the Moon as a compass cue for maintaining travel...
pubmed.ncbi.nlm.nih.gov
Dung beetle vision blurs the Milky Way, but no one is certain how much. These are four models used in the experiments of James Foster.
But what happens when there's no sun or Moon?
In the early 2000s, this question troubled two pioneers of dung beetle research, Eric Warrant and Marie Dacke of Lund University in Sweden. To find the answer, they took some beetles to the planetarium at the University of the Witwatersrand in Johannesburg, South Africa, and projected the Milky Way onto the domed ceiling. The beetles saw it, and navigated.
Their discovery prompted a veritable explosion in dung beetle research. James Foster is a leader in the field, publishing new results every few years.
Foster and colleagues have built a rudimentary planetarium just for dung beetles. It uses LED lights to mimic the Milky Way as beetles see it through their compound eyes. In 2017 they found that dung beetles were able to distinguish between north and south arms of the Milky Way, sensing intensity contrasts as low as 13%. This threshold puts features such as the galactic center in Sagittarius and the Great Rift in Cygnus theoretically within range of beetle senses.
Next they added city lights to their experiment--and the results were not good. "Light pollution may be forcing beetles to abandon the Milky Way as their compass," worries Foster.
Researcher Claudia Tocco observes the behavior of a dung beetle surrounded by urban lights. Photo credit Marcus Byrne.
In a paper** published July 2021, Foster's team described how urban lights wipe out the Milky Way, reduce the polarization of moonlight by 60% to 70%, and "create anthropogenic celestial cues." The last item is worst of all. Spotlights and brightly lit buildings mesmerize beetles who suddenly ignore the sky and make a beeline for manmade bulbs.
"These beacons draw beetles towards the most hostile regions of their environments," says Foster. "After rolling their balls some distance, beetles need to find a patch of soft sand where they can dig in. They are unlikely to find that in the immediate vicinity of bright artificial lights, whether in cities or the countryside, since these are usually associated with concrete and tarmac."
Dung beetles aren't the only ones. Researchers believe they are only scratching the surface of this field with potentially thousands of species watching the stars. Everything from simple light bulbs to sophisticated satellite megaconstellations may be affecting these members of our ecosystem.
"Dung beetle!" What are you thinking of now?
Taken by Ruslan Merzlyakov on May 31, 2022 @ Gran Canaria, Spain
**) the study/paper July 2001
Light pollution forces a change in dung beetle orientation behavior
Light pollution illuminating the night sky can obscure the visual compass cues on which many animals rely. In simultaneous experiments at light-polluted and dark-sky sites, Foster et al. show that light pollution forces nocturnal dung beetles to abandon celestial cues, instead moving toward...
www.cell.com
XPan
The Living Force
Planet Neptune Rings
An interesting note about the rings of Neptune being photographed, which hasn't happened since the Voyager 2 flyby back in 1998 years ago - the James Webb Space Telescope showed off its capabilities.
www.nasa.gov
What do we see in Webb's latest image of the ice giant Neptune? Webb captured seven of Neptune’s 14 known moons: Galatea, Naiad, Thalassa, Despina, Proteus, Larissa, and Triton. Neptune’s large and unusual moon, Triton, dominates this Webb portrait of Neptune as a very bright point of light sporting the signature diffraction spikes seen in many of Webb’s images. Credits: NASA, ESA, CSA, STScI
Images of Neptune (and its moons) • 1998 Voyager flyby
One Image of Neptune by Hubble
hubblesite.org
An interesting note about the rings of Neptune being photographed, which hasn't happened since the Voyager 2 flyby back in 1998 years ago - the James Webb Space Telescope showed off its capabilities.
New Webb Image Captures Clearest View of Neptune’s Rings in Decades
NASA’s James Webb Space Telescope shows off its capabilities closer to home with its first image of Neptune.
What do we see in Webb's latest image of the ice giant Neptune? Webb captured seven of Neptune’s 14 known moons: Galatea, Naiad, Thalassa, Despina, Proteus, Larissa, and Triton. Neptune’s large and unusual moon, Triton, dominates this Webb portrait of Neptune as a very bright point of light sporting the signature diffraction spikes seen in many of Webb’s images. Credits: NASA, ESA, CSA, STScI
Images of Neptune (and its moons) • 1998 Voyager flyby
Voyager - Images Voyager Took of Neptune
voyager.jpl.nasa.gov
One Image of Neptune by Hubble
Neptune
hubblesite.org
dennis
Jedi Council Member
Jupiter news:
Planetary-scale 'heat wave' discovered in Jupiter's atmosphere
An unexpected "heat wave" of 700 degrees Celsius, extending 130,000 kilometers (10 Earth diameters) in Jupiter's atmosphere, has been discovered.
...
Just like the Earth, Jupiter experiences auroras around its poles as an effect of the solar wind. However, while Earth's auroras are transient and only occur when solar activity is intense, auroras at Jupiter are permanent and have a variable intensity. The powerful auroras can heat the region around the poles to over 700 degrees Celsius, and global winds can redistribute the heat globally around Jupiter.
Planetary-scale 'heat wave' discovered in Jupiter's atmosphere
An unexpected "heat wave" of 700 degrees Celsius, extending 130,000 kilometers (10 Earth diameters) in Jupiter's atmosphere, has been discovered. James O'Donoghue, of the Japanese Aerospace Exploration Agency (JAXA), has presented the results this week at the Europlanet Science Congress (EPSC)...phys.org
XPan
The Living Force
Jupiter Moon Europa
29 Sep 2022
Spaceweather.com had an interesting photo of the Jupiter moon Europa at very close range of 352 km / 219 miles, made by the spacecraft Juno on 29 Sep 2022
www.missionjuno.swri.edu
29 Sep 2022
Spaceweather.com had an interesting photo of the Jupiter moon Europa at very close range of 352 km / 219 miles, made by the spacecraft Juno on 29 Sep 2022
JunoCam : Processing - Mission Juno
Download raw imagery from JunoCam and upload your processed imagery to the gallery!
www.missionjuno.swri.edu
dennis
Jedi Council Member
Very big GRB happening on October 9. Would be interesting to plot its location, its in the plane of the Milky Way but extra galactic.
Scientists have spotted an “unprecedented” explosion of energy in space, known as a gamma ray burst (GRB), which appears brighter at some wavelengths than any event of this kind observed so far.
...
In an email to Motherboard, Evans emphasized that the discovery is so fresh that it will take a while to unpack its significance, but he noted that the burst is “clearly the brightest GRB we’ve seen in X-rays, at least at the time after the initial explosion that we’ve observed it.”
“The new GRB 221009A is something around 1,000 times brighter than the typical GRB and a few hundred times brighter than the brightest ones seen before—but this is only true in X-rays,” Evans said. “In gamma-rays it is one of the brightest seen (according to the report from the Fermi telescope team).”
...
“GRBs are also the most luminous events in the Universe,” he continued. “This one could have an intrinsic brightness of 10^22 times that of the Sun, or around a trillion times the entire energy output of all the stars in the Milky Way combined over that short period that the GRB was on if I have the numbers right.”
Scientists Have Detected a ‘Completely Unprecedented’ Burst of Energy in Space
The gamma ray burst is the brightest ever detected in X-rays, according to scientists, and could shed light on the most energetic phenomena in space.www.vice.com
Olivierlejardinier
Jedi Council Member
dennis
Jedi Council Member
POWERFUL GAMMA-RAY BURST MADE CURRENTS FLOW IN THE EARTH: Astronomers have never seen anything like it. On Oct. 9, 2022, Earth-orbiting satellites detected the strongest gamma-ray burst (GRB) in modern history: GRB221009A. How strong was it? It caused electrical currents to flow through the surface of our planet. Dr. Andrew Klekociuk in Tasmania recorded the effect using an Earth Probe Antenna:
The blue curve is a signal from Klekociuk's antenna, which was sensing VLF (very low frequency) currents in the soil at the time of the blast. The orange curve shows the gamma-ray burst recorded by the STIX telescope on Europe's Solar Orbiter spacecraft, one of many spacecraft that detected the event. The waveforms are a nearly perfect match.
"I am a climate scientist at the Australian Antarctic Division--that's my day job," says Klekociuk. "VLF is my hobby. I started doing VLF radio measurements in the 1970's when I was in high school. This is the first time I have detected a gamma-ray burst."
Klekociuk's unusual "ham rig" uses Earth itself as a giant antenna. In his back garden there are two metal spikes stuck into the ground 75 meters apart. They are connected to a receiver via buried wires. In recent years amateur radio operators have been experimenting with this weird kind of antenna to detect VLF radio signals circling our planet in the Earth-ionosphere waveguide. Earth's crust forms one of the waveguide's walls, allowing Earth Probe Antennas to detect distant transmitters.
"During the gamma-ray burst I detected flickering from multiple stations," says Klekociuk, who made this map showing transmission paths illuminated by the GRB:
Researchers have known since 1983 that gamma-ray bursts can ionize Earth's atmosphere and, thus, disturb the great waveguide. This appears to be the first time anyone has recorded the effect using an Earth Probe Antenna.
The outburst on Oct. 9th shocked astronomers. Consider this tweet from Phil Evans of the University of Leicester: "It's bright. Really bright. Like, stupidly really bright." Evans works with data from NASA's Swift gamma-ray observatory, and the overflowing signal had apparently broken some of his plotting software.
Data from NASA spacecraft have since pinpointed the burst. It came from a dusty galaxy 2.4 billion light years away, almost certainly triggered by a supernova explosion giving birth to a black hole. This is actually the closest GRB ever recorded, thus accounting for its extreme intensity.
The blue curve is a signal from Klekociuk's antenna, which was sensing VLF (very low frequency) currents in the soil at the time of the blast. The orange curve shows the gamma-ray burst recorded by the STIX telescope on Europe's Solar Orbiter spacecraft, one of many spacecraft that detected the event. The waveforms are a nearly perfect match.
"I am a climate scientist at the Australian Antarctic Division--that's my day job," says Klekociuk. "VLF is my hobby. I started doing VLF radio measurements in the 1970's when I was in high school. This is the first time I have detected a gamma-ray burst."
Klekociuk's unusual "ham rig" uses Earth itself as a giant antenna. In his back garden there are two metal spikes stuck into the ground 75 meters apart. They are connected to a receiver via buried wires. In recent years amateur radio operators have been experimenting with this weird kind of antenna to detect VLF radio signals circling our planet in the Earth-ionosphere waveguide. Earth's crust forms one of the waveguide's walls, allowing Earth Probe Antennas to detect distant transmitters.
"During the gamma-ray burst I detected flickering from multiple stations," says Klekociuk, who made this map showing transmission paths illuminated by the GRB:
Researchers have known since 1983 that gamma-ray bursts can ionize Earth's atmosphere and, thus, disturb the great waveguide. This appears to be the first time anyone has recorded the effect using an Earth Probe Antenna.
The outburst on Oct. 9th shocked astronomers. Consider this tweet from Phil Evans of the University of Leicester: "It's bright. Really bright. Like, stupidly really bright." Evans works with data from NASA's Swift gamma-ray observatory, and the overflowing signal had apparently broken some of his plotting software.
Data from NASA spacecraft have since pinpointed the burst. It came from a dusty galaxy 2.4 billion light years away, almost certainly triggered by a supernova explosion giving birth to a black hole. This is actually the closest GRB ever recorded, thus accounting for its extreme intensity.
Spaceweather.com Time Machine
www.spaceweather.com
dennis
Jedi Council Member
On the same date October 9 in 1604
SN 1604, also known as Kepler's Supernova, Kepler's Nova or Kepler's Star, was a Type Ia supernova[1][2] that occurred in the Milky Way, in the constellation Ophiuchus. Appearing in 1604, it is the most recent supernova in the Milky Way galaxy to have been unquestionably observed by the naked eye,[3] occurring no farther than 6 kiloparsecs (20,000 light-years) from Earth.
...
It was the second supernova to be observed in a generation (after SN 1572 seen by Tycho Brahe in Cassiopeia). No further supernovae have since been observed with certainty in the Milky Way, though many others outside the galaxy have been seen since S Andromedae in 1885.
...
Astronomers of the time (including Kepler) were concerned with observing the conjunction of Mars and Jupiter, which they saw in terms of an auspicious conjunction linked in their minds to the Star of Bethlehem. However, cloudy weather prevented Kepler from making any celestial observations. Nevertheless, his fellow astronomers Wilhelm Fabry, Michael Maestlin, and Helisaeus Roeslin were able to make observations on 9 October but did not record the supernova.[9] The first recorded observation in Europe was by Lodovico delle Colombe in northern Italy on 9 October 1604.[10] Kepler was only able to begin his observations on 17 October while working at the imperial court in Prague for Emperor Rudolf II.[11] The supernova was subsequently named after him, even though he was not its first observer, as his observations tracked the object for an entire year. These observations were described in his book De Stella nova in pede Serpentarii ("On the new star in Ophiuchus's foot", Prague 1606).
Kepler's Supernova - Wikipedia
en.wikipedia.org
"Impact Winter Triggered by the Younger Dryas Cosmic Impact" according to Magnetic Reversal News.
Also other related and dated information.
Opinion
Magnetic Reversal News
physics.aps.org
September 16, 2020
New results from the Pierre Auger Observatory could narrow down the search for the origin of ultrahigh-energy cosmic rays
Figure 1: The latest data from the Pierre Auger Observatory suggest that ultrahigh-energy cosmic rays are a mix of nuclei that arrive from a large collection of galaxies spread evenly over the sky. APS/Alan Stonebraker (galaxy images from NASA)
phys.org
January 13, 2021 Video
Also other related and dated information.
Opinion
The Anatomy of Ultrahigh-Energy Cosmic Rays
New results from the Pierre Auger Observatory could narrow down the search for the origin of ultrahigh-energy cosmic rays.
New results from the Pierre Auger Observatory could narrow down the search for the origin of ultrahigh-energy cosmic rays
Ultrahigh-energy cosmic rays (UHECRs) at energies 1018eV and above are the most energetic subatomic particles in nature. To get an idea of their energy, the most energetic of these particles carries the same punch ( 1020eV) as a tennis ball coming off a racket with a speed of 100 km/h. For comparison, the Large Hadron Collider (LHC) at CERN can accelerate protons to only about 1013eV. The tremendous energy of UHECRs naturally begs questions of how and where they are produced. Although discovered almost 60 years ago [1], the origin and chemical composition of UHECRs are still unknown. The latest data from the Pierre Auger Observatory—collected over more than a decade—provide the largest sample to date of UHECRs, with over 215,000 events [2]. The observations reveal a new feature—a steepening in the spectrum that joins other spectral features like the “knee” and the “ankle.” The data also show that UHECRs arrive uniformly over the sky. Together, these results suggest that energetic star factories, called starburst galaxies, might be the most promising sources for UHECRs.The Pierre Auger Observatory [3] in Argentina and the Telescope Array (TA) [4] in the US are the two largest cosmic-ray detectors currently operational, covering 3000 and 700 square kilometers of instrumented areas, respectively. Such huge areas are required to detect UHECRs, which reach Earth with a flux of only about a hundred per square kilometer per year (Fig. 1). At ultrahigh energies, cosmic rays break up in the atmosphere by interacting with the air molecules, creating approximately a billion or more secondary particles, which shower down on Earth’s surface. Such an event is aptly called an extended air shower (EAS). An array of surface detectors can reconstruct the energy and direction of the primary UHECR by detecting the EAS particles (mostly muons) that reach the ground. The accuracy of measurements increases significantly by using telescopes at night to observe fluorescence light from the EAS particles exciting the nitrogen molecules in the air. Both the Auger and TA employ this hybrid technique to detect UHECRs.
One of the most hotly debated issues in the cosmic-ray community is the chemical composition of UHECRs. At lower energies, satellite and balloon-borne experiments directly measure the primary cosmic rays, allowing them to determine the composition as predominantly protons and nuclei with heavier masses like that of iron. At higher energies, ground-based arrays must use computer simulations to decipher which primary particle likely produced an EAS. For example, previous work using Auger data suggested that protons dominate the cosmic-ray composition at energies of 5×1018eV
, the location of the so-called ankle where the UHECR spectrum flattens out briefly. Toward higher energies, the simulations infer that the composition becomes progressively heavier, going through helium, carbon, nitrogen, oxygen, silicon, and (perhaps) iron nuclei. However, these sorts of simulations rely on models of hadronic (quark-containing) interactions, which are only verified up to 1017-eV
lab energy using LHC measurements. Extrapolations to higher energies are uncertain, and small changes in the models can result in a “proton-only” interpretation of the shower data [5]. Furthermore, observations from the Auger and TA are not fully compatible with each other, as simulations based on TA data prefer a predominantly light composition consisting of mostly protons and helium nuclei [6].
Figure 2: The UHECR spectrum compiled from the latest Auger data is shown here in terms of the energy density. The observations reveal a new feature at 13×1018eV, where the spectrum steepens slightly. This break in the power-law fit occurs between two other br... Show more APS/Alan Stonebraker; adapted from Ref. [2].
The latest Auger data could help clear up the issue [2]. The collaboration has compiled all their events above 2.5×1018eV
into a spectrum, which they find is better characterized by a four-component power-law fit than the previously used three-component fit [7]. The new feature is a steepening—or softening—of the spectrum at an energy of 13×1018eV. This break occurs between the ankle at 5×1018eV and the toe at 46×1018eV, where the spectrum steepens very sharply (Fig. 2). The softening of the spectrum in this intermediate region could be a hint that the mass composition of UHECRs is changing from light to heavy. Such an interpretation assumes that the UHECR spectrum is dominated by different elements at different energies. This type of model requires that the UHECR sources accelerate particles with an extremely hard (or flat) spectrum [8], and that the number of these sources either remains the same over cosmic time or was even fewer at earlier times [9]. However, both of these requirements are at odds with our knowledge of luminous astrophysical sources from observations in radio to gamma rays.
A more profound result from the latest Auger data is the near independence of the spectral shape on the angle with respect to the celestial equator [2]. This lack of anisotropy in the arrival directions severely disfavors models that assume that all the UHECRs are produced by a few bright and nearby sources. Instead, the data favor a uniform spatial distribution of UHECR sources, which implies they are extragalactic. To account for the observed UHECR flux, these sources must be injecting energy into the Universe at a rate of approximately 6×1044ergMpc−3yr−1
. Observations in gamma rays with energies above 100 MeV suggest only a few source classes that can supply that much energy, namely, radio galaxies of Fanaroff–Riley type-I, BL Lac objects, and starburst galaxies [10]. The first two are high-energy subclasses of active galactic nuclei (AGN) that have strong jets for possibly accelerating particles. But if indeed the UHECRs are rich in heavy nuclei, then this poses a challenge for AGN scenarios. First, it is not clear how an AGN can produce heavy nuclei in its jet, and second, it is hard to see how those nuclei might be accelerated without breaking up in interactions with the radiation field that surrounds the AGN. By contrast, it is relatively easy to find an environment within starburst galaxies that is rich in heavy elements and has bursting sources that can accelerate these nuclei to ultrahigh energies [11].
To establish this overall picture of starburst galaxies as sources, we will need further evidence that heavy nuclei make up the dominant fraction of the UHECRs above the ankle. Such confirmation will require further observations of the sky and also a better understanding of particle physics interactions seen in collider experiments. The field of UHECRs has now entered into an era of precision measurements that are challenging our knowledge in both physics and astrophysics.
Correction (2 November 2020): An earlier version stated that models of hadronic interactions were verified up to 1017-eV center-of-mass energy, when in fact this value corresponds to the lab energy.
Rare star's giant gamma-ray burst GRB 200415A captured close to our home galaxy
Earth gets blasted by mild short gamma-ray bursts (GRBs) most days. But sometimes, a giant flare like GRB 200415A arrives at our galaxy, sweeping along energy that dwarfs our sun. In fact, the most powerful explosions in the universe are gamma-ray bursts.
