Tag Archives: astrophysics

The Beat Goes On…

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The green circle marks the source of FRB 121102. (Rogelio Bernal Andreo/DeepSkyColors.com)

A Mysterious Radio Burst That Keeps Repeating Just Woke Up, Right on Schedule

MICHELLE STARR
24 AUGUST 2020

Earlier this year, astronomers announced a dazzling discovery. A fast radio burst called FRB 121102 wasn’t just repeating – it was repeating on a discernible cycle.

For around 67 days, the source is silent. Then, for around 90 days, it wakes up again, spitting out repeated millisecond radio flares before falling silent, and the whole 157-day cycle repeats.

However, fast radio bursts are extremely mysterious, and there was no guarantee that the cycle would continue. So it’s pretty exciting that the source has flared up again, right on cue – consistent with predictions of its activity cycle.

This suggests that there’s significant value in monitoring known fast radio burst sources – but also in continuing to watch FRB 121102 to try to understand what could be causing the phenomenon.

A quick refresher: fast radio bursts are, as the name suggests, bursts of radio waves that are very fast, just a few milliseconds long, coming from galaxies millions to billions of light-years away. But they’re also extremely powerful; within those milliseconds, they can discharge as much power as hundreds of millions of Suns.

Most of the time, they flare once and we have not heard from them since, making them impossible to predict and very difficult to trace. And we don’t know what causes them, although recent evidence points pretty strongly to a type of neutron star called magnetars.

But a handful of fast radio burst sources have been detected repeating, and these could be one of the keys that helps at least partially solve the mystery.

Before its cycle was discovered by University of Manchester astronomer Kaustubh Rajwade and his team, FRB 121102 was already famous for being the most active fast radio burst discovered yet, spitting out repeated bursts several times since its discovery in 2012.

Because it repeats, astronomers could watch for activity, and trace it to a source galaxy. It was the first fast radio burst to be localised, to a star-forming region in a dwarf galaxy 3 billion light-years away.

The discovery of periodicity in its activity – based on five years’ worth of data – could place some important constraints on what it could be.

For instance, high-mass X-ray binaries in the Milky Way – those that contain neutron stars – can have orbital periods of up to hundreds of days. But there are some types of binary systems with much shorter periods – these could be ruled out for FRB 121102.

And now, periodicity is supported by new sets of observations – although the timing may need revision.

A team led by Marilyn Cruces of the Max Planck Institute for Radio Astronomy detected 36 bursts from FRB 121102 using the Effelsberg 100-m Radio Telescope between September 2017 to June 2020. Combined with the data from Rajwade’s research, the team derived a periodicity of 161 days, in a new preprint paper uploaded to arXiv.

This paper gives dates between 9 July and 14 October 2020 for the source’s active period.

But Cruces and her team aren’t the only ones looking. A team led by Pei Wang of the National Astronomy Observatory of China used the Five-hundred-meter Aperture Spherical radio Telescope to monitor FRB 121102’s location on several dates between March and August 2020.

Between mid-March and late July, they didn’t detect any bursts. But on 17 August, FAST detected at least 12 bursts from FRB 121102 – suggesting the source is once again in an active phase – although the team calculated a different periodicity from both Rajwade’s team and Cruces’ team.

“We combine the bursts collected in Rajwade et al. (2020) and Cruces et al. (2020) with these newly detected by FAST in 2019 and 2020, and obtain a new best-fit period of ~156.1 days,” they wrote in a notice posted to The Astronomer’s Telegram.

According to Wang’s team’s calculations, the active phase is due to end between 31 August and 9 September 2020. If FRB 121102 continues to show activity beyond these dates, this could suggest that either the periodicity isn’t real, or that it has somehow evolved, they noted in their post.

Of course, it’s also possible that the periodicity calculations need to be refined. Which means we should continue to keep an eye on FRB 121102.

“We encourage more follow-up monitoring efforts from other radio observatories,” the researchers wrote.

from:    https://www.sciencealert.com/right-on-schedule-a-repeating-fast-radio-burst-has-woken-up

Unlocking the Secrets of Black Holes

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Black Holes Contain Photon Rings That Record “Movies ” Of Cosmic History

A new paper claims that black holes retain a kind of photon-based record of space-time history that could yield some of the secrets of the universe.

Jake Anderson
Photo by Bryan Goff on Unsplash

 

(TMU) – A new paper claims that black holes retain a kind of photon-based record of space-time history that could yield some of the secrets of the universe.

Astronomers and physicists studying the M87 black hole, recently renamed Pōwehi (which means “embellished dark source of unending creation”), made history earlier this year when they released the first photographic image of a black hole. In their new paper, they argue that the ghostly ring of fire we see could harbor historical records – which some have called “movies” – of the cosmos.

The argument is based on an interferometric study of the vast swirling wreaths of light that are trapped in perpetual orbit around the black hole’s event horizon. This light is comprised of photons, which scientists believe may behave like the rings inside a tree trunk, concentric sequences of information that betray overall age and development.

In the paper, entitled “Universal Interferometric Signatures Of A Black Hole’s Photon Ring,” they write:

“Together, the set of subrings are akin to the frames of a movie, capturing the history of the visible universe as seen from the black hole.”

Studying these rings of photons could help scientists learn more about theories like Einstein’s general relativity.

They could also crack more of the mysteries of black holes, which continue to be one of the most puzzling and monstrous objects predicted by physics. For example, do black holes defy the mandates of quantum mechanics and destroy all information? Do they contain dark matter? Do they curve space-time so severely that matter is sent to the future? Can black holes break the laws of physics by existing in five-dimensional space?

The list goes on and on. Many of the world’s most prominent physicists, including Stephen Hawking and Einstein himself, have spent careers and lifetimes trying to unravel the enigmatic existence of black holes. This has led some thinkers to some very strange theories. For example, mathematical physicist Sir Roger Penrose has suggested that we may actually be able to see the imprints of black holes from alternate universes.

Because of the many related puzzles, the opportunity to study historical records left behind by rings photons inside black holes is tantalizing to scientists.

However, the rings do not exist in perpetuity. Each one is only six days older than its predecessor and is eventually obliterated inside the black hole singularity. So while they cannot be used to peer into the entire history of the universe, “measuring the size, shape, and thickness of the subrings would provide new and powerful probes of a black hole spacetime.” 

Scientists have described the discovery as approaching a “cosmic hall of mirrors, where the black hole’s gravity takes light from all directions, warps it and beams it to us as an infinitely recast image of the hole’s surroundings. The result is an epic movie of the history of the universe, as witnessed by a black hole, playing on a dramatically curved screen tens of billions of kilometres across.”

As we continue to learn more about black holes, what will they whisper to us about the nature of reality and the secrets of the cosmos?

from:    https://themindunleashed.com/2020/07/black-holes-contain-photon-rings-that-record-movies-of-cosmic-history.html

Mysterious Radio Bursts

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‪Not Alone? Four “Mysterious Signals” Captured From Outer Space

A team of scientists headed by Shivani Bhandari, an astronomer with the Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia’s federal agency responsible for scientific research, has made a breakthrough discovery by pinpointing the precise location of four fast radio bursts (FRBs).

FRBs are very mysterious bursts of radio waves coming from somewhere in the universe. The average pulse ranges for a few milliseconds, caused by high-energy sources, which are not entirely understood.

CSIRO’s ASKAP radio telescope in Western Australia detecting FRBs. h/t CSIRO

Bhandari’s new research, published on June 1 in The Astrophysical Journal Letters, reveals that four FRBs came from massive galaxies forming new stars. They said FRBs originated not from the center of galaxies, but rather from the outer edges.

“These precisely localized fast radio bursts came from the outskirts of their home galaxies, removing the possibility that they have anything to do with supermassive black holes,” said Bhandari.

Bhandari’s team found exact locations for FRB 180924, FRB 181112, FRB 190102, and FRB 190608 by using the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope in Western Australia.

Source of FRBs. h/t CSIRO

Bhandari said, “This first detailed study of the galaxies that host fast radio bursts rules out several of the more extreme theories put forward to explain their origins, getting us closer to knowing their true nature.”

Co-author of the study, CSIRO Professor Elaine Sadler said FRBs could not have come from a superluminous stellar explosion or cosmic strings.

“Models such as mergers of compact objects like white dwarfs or neutron stars, or flares from magnetars created by such mergers, are still looking good,” Sadler said.

Dame Jocelyn Bell Burnell, an astrophysicist from Northern Ireland who co-discovered FRBs, said:

“Positioning the sources of fast radio bursts is a huge technical achievement and moves the field on enormously. We may not yet be clear exactly what is going on, but now, at last, options are being ruled out. This is a highly significant paper, thoroughly researched, and well written,” said Burnell.

According to another paper (dated February 3) by a team of astrophysicists in Canada, a “mystery radio signal” was recorded as repeating based on a clearly discernible pattern. “The discovery of a 16.35-day periodicity in a repeating FRB source is an important clue to the nature of this object,” the team said. A summary of some of the key findings are as follows:

“Between September 16, 2018 and October 30, 2019,  detected a pattern in bursts occurring every 16.35 days. Over the course of four days, the signal would release a burst or two each hour. Then, it would go silent for another 12 days.

Spiral galaxy from which repeating signal originates:NSF’s Optical-Infrared Astronomy Research Laboratory/ Gemini Observatory/AURA

“…The signal is a known repeating fast radio burst, FRB 180916.J0158+65. Last year, the CHIME/FRB collaboration detected the sources of eight new repeating fast radio bursts, including this signal. The repeating signal was traced to a massive spiral galaxy around 500 million light-years away.”

Both findings suggest astronomers are one step closer to understanding the source of these mysterious radio signals coming from deep within the universe. Could this mean we’re not alone? 

from:    https://www.zerohedge.com/technology/not-alone-four-mysterious-signals-captured-outer-space

About Black Holes

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The Closest Known Black Hole From Earth Can Be “Seen” With The Naked Eye

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By Mayukh Saha / Truth Theory

European Southern Observatory (ESO) astronomers are astonished to find the closest black hole from Earth. The researchers are saying if you are in the Southern Hemisphere, you can observe this black hole with the naked eye at night. The reason one can so easily view it is that it is only a thousand light-years away from us!

Petr Hadrava is the co-author of the paper published in Astronomy & Astrophysics, which discusses this black hole. He is a scientist at the Academy of Sciences of the Czech Republic, Prague. He explains how the team was surprised to realize that they had found the first stellar system with a black hole that can be observed from Earth unaided.

This relatively dark black hole was rather difficult to spot for the scientists. Black holes are known to flare up when they feed on their companion stars’ matter, which reveals their location to the astronomers. But this particular one did not exhibit such behavior. So it had to be spotted only by tracking its gravitational effect on 2 nearby stars. ESO’s La Silla Observatory in Chile found this black hole with its 2.2-meter telescope.

The researchers were initially observing this HR 6819 system for its 2 very closely spaced stars. One of those stars was orbiting a black every 40 Earth days. So the researchers studied its trajectory to conclude that the black hole was quite big.

“An invisible object with a mass at least 4 times that of the Sun can only be a black hole,” Thomas Rivinius, lead author and ESO scientist, said in the statement.

The handful of black holes discovered in our Milky Way were all discovered with the help of the bright flashes of X-rays they gave away when they were interacting with their environment. But the way our closest black hole was discovered, by studying its gravitational effects, means there are many more such black holes we can now find with this method.

Astronomers are trailing another system LB-1 which they believe also has 3 bodies like the HR 6819. LB-1 is further from Earth than HR 6819 but still relatively close, said another co-author of the paper, Marianne Heida.

Image credit: ESO/L. Calçada

from:   https://truththeory.com/2020/05/13/the-closest-known-black-hole-from-earth-can-be-seen-with-the-naked-eye/

Whole Lotta Untangling to Do

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The Universe May Be Flooded with a Cobweb Network of Invisible Strings

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We may soon find out whether we live in an axiverse

an abstract image of axion strings

(Image: © Shutterstock)

What if I told you that our universe was flooded with hundreds of kinds of nearly invisible particles and that, long ago, these particles formed a network of universe-spanning strings?

It sounds both trippy and awesome, but it’s actually a prediction of string theory, our best (but frustratingly incomplete) attempt at a theory of everything. These bizarre, albeit hypothetical, little particles are known as axions, and if they can be found, that would mean we all live in a vast “axiverse.”

The best part of this theory is that it’s not just some physicist’s armchair hypothesis, with no possibility of testing. This incomprehensibly huge network of strings may be detectable in the near future with microwave telescopes that are actually being built.

If found, the axiverse would give us a major step up in figuring out the puzzle of … well, all of physics.

A symphony of strings

OK, let’s get down to business. First, we need to get to know the axion a little better. The axion, named by physicist (and, later, Nobel laureate) Frank Wilczek in 1978, gets its name because it’s hypothesized to exist from a certain kind of symmetry-breaking. I know, I know — more jargon. Hold on. Physicists love symmetries — when certain patterns appear in mathematics.

There’s one kind of symmetry, called the CP symmetry, that says that matter and antimatter should behave the same when their coordinates are reversed. But this symmetry doesn’t seem to fit naturally into the theory of the strong nuclear force. One solution to this puzzle is to introduce another symmetry in the universe that “corrects” for this misbehavior. However, this new symmetry only appears at extremely high energies. At everyday low energies, this symmetry disappears, and to account for that, and out pops a new particle — the axion.

Now, we need to turn to string theory, which is our attempt (and has been our main attempt for 50-odd years now) to unify all of the forces of nature, especially gravity, in a single theoretical framework. It’s proven to be an especially thorny problem to solve, due to a variety of factors, not the least of which is that, for string theory to work (in other words, for the mathematics to even have a hope of working out), our universe must have more than the usual three dimensions of space and one of time; there have to be extra spatial dimensions.

These spatial dimensions aren’t visible to the naked eye, of course; otherwise, we would’ve noticed that sort of thing. So the extra dimensions have to be teensy-tiny and curled up on themselves at scales so small that they evade normal efforts to spot them.

What makes this hard is that we’re not exactly sure how these extra dimensions curl up on themselves, and there’s somewhere around 10^200 possible ways to do it.

But what these dimensional arrangements appear to have in common is the existence of axions, which, in string theory, are particles that wind themselves around some of the curled-up dimensions and get stuck.

What’s more, string theory doesn’t predict just one axion but potentially hundreds of different kinds, at a variety of masses, including the axion that might appear in the theoretical predictions of the strong nuclear force.

Silly strings

So, we have lots of new kinds of particles with all sorts of masses. Great! Could axions make up dark matter, which seems to be responsible for giving galaxies most of their mass but can’t be detected by ordinary telescopes? Perhaps; it’s an open question. But axions-as-dark-matter have to face some challenging observational tests, so some researchers instead focus on the lighter end of the axion families, exploring ways to find them.

And when those researchers start digging into the predicted behavior of these featherweight axions in the early universe, they find something truly remarkable. In the earliest moments of the history of our cosmos, the universe went through phase transitions, changing its entire character from exotic, high-energy states to regular low-energy states.

During one of these phase transitions (which happened when the universe was less than a second old), the axions of string theory didn’t appear as particles. Instead, they looked like loops and lines — a network of lightweight, nearly invisible strings crisscrossing the cosmos.

This hypothetical axiverse, filled with a variety of lightweight axion strings, is predicted by no other theory of physics but string theory. So, if we determine that we live in an axiverse, it would be a major boon for string theory.

A shift in the light

How can we search for these axion strings? Models predict that axion strings have very low mass, so light won’t bump into an axion and bend, or axions likely wouldn’t mingle with other particles. There could be millions of axion strings floating through the Milky Way right now, and we wouldn’t see them.

But the universe is old and big, and we can use that to our advantage, especially once we recognize that the universe is also backlit.

The cosmic microwave background (CMB) is the oldest light in the universe, emitted when it was just a baby — about 380,000 years old. This light has soaked the universe for all these billions of years, filtering through the cosmos until it finally hits something, like our microwave telescopes.

So, when we look at the CMB, we see it through billions of light-years’ worth of universe. It’s like looking at a flashlight”s glow through a series of cobwebs: If there is a network of axion strings threaded through the cosmos, we could potentially spot them.

In a recent study, published in the arXiv database on Dec. 5, a trio of researchers calculated the effect an axiverse would have on CMB light. They found that, depending on how a bit of light passes near a particular axion string, the polarization of that light could shift. That’s because the CMB light (and all light) is made of waves of electric and magnetic fields, and the polarization of light tells us how the electric fields are oriented — something that changes when the CMB light encounters an axion. We can measure the polarization of the CMB light by passing the signal through specialized filters, allowing us to pick out this effect.

The researchers found that the total effect on the CMB from a universe full of strings introduced a shift in polarization amounting to around 1%, which is right on the verge of what we can detect today. But future CMB mappers, such as the Cosmic Origins Explorer, Lite (Light) satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection (LiteBIRD), and the Primordial Inflation Explorer (PIXIE) , are currently being designed. These futuristic telescopes would be capable of sniffing out an axiverse. And once those mappers come online, we’ll either find that we live in an axiverse or rule out this particular prediction of string theory.

Either way, there’s a lot to untangle.

Paul M. Sutter is an astrophysicist at The Ohio State University, host of Ask a Spaceman and Space Radio, and author of Your Place in the Universe.

from:    https://www.livescience.com/universe-filled-with-axion-strings.html

Maybe We DID Come From Stars

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NASA
Scientists have found a bizarre similarity between human cells and neutron stars

Our link to the stars.

JOSH HRALAFacebook Icon

But, according to new research, we share at least one similarity: the geometry of the matter that makes us.

Researchers have found that the ‘crust’ (or outer layers) of a neutron star has the same shape as our cellular membranes. This could mean that, despite being fundamentally different, both humans and neutron stars are constrained by the same geometry.

“Seeing very similar shapes in such strikingly different systems suggests that the energy of a system may depend on its shape in a simple and universal way,” said one of the researchers, astrophysicist Charles Horowitz, from Indiana University, Bloomington.

To understand this finding, we need to quickly dive into the weird world of nuclear matter, which researchers call ‘nuclear pasta’ because it looks a lot like spaghetti and lasagne. See for yourself:

NuclearPastaD. K. Berry et al.

This nuclear pasta forms in the dense crust of a neutron star thanks to long-range repulsive forces competing with something called the strong force, which is the force that binds quarks together.

In other words, two powerful forces are working against one another, forcing the matter – which consists of various particles – to structure itself in a scaffold-like (pasta) way.

As one of the team, Greg Huber, a biological physicist from the University of California, Santa Barbara, explains:

“When you have a dense collection of protons and neutrons like you do on the surface of a neutron star, the strong nuclear force and the electromagnetic forces conspire to give you phases of matter you wouldn’t be able to predict if you had just looked at those forces operating on small collections of neutrons and protons.”

Now, it turns out that these pasta-like structures look a lot like the structures inside biological cells, even though they are vastly different.

This odd similarity was first discovered in 2014, when Huber was studying the unique shapes on our endoplasmic reticulum (ER) – the little organelle in our cells that makes proteins and lipids.

At first, Huber thought that these structures on the ER – which he called “parking garages”, or more formally, Terasaki ramps – were something that only happened inside soft matter.

But the he saw Horowitz’s models of neutron stars, and was surprised to find that the structures of the ER looked a heck of a lot like the structures inside neutron stars.

“I called Chuck [Horowitz] and asked if he was aware that we had seen these structures in cells and had come up with a model for them,” Huber said. “It was news to him, so I realised then that there could be some fruitful interaction.”

You can see the ER structures (left) compared to the neutron stars (right) below:

NeutronStarsUniversity of California, Santa Barbara

The discovery brought both of the scientists together to compare and contrast the differences between the structures, such as the conditions required for them to form.

Normally, matter is characterised by a phase – sometimes called its state – such as gas, solid, liquid Different phases are usually influenced by a plethora of various conditions, like how hot the matter is, how much pressure it’s under, and how dense it is.

These factors change wildly between soft matter (the stuff inside cells) and neutron stars (nuclear matter). After all, neutron stars form after supernovae explosions, and cells form within living things. With that in mind, it’s quite easy to see that the two things are very different.

“For neutron stars, the strong nuclear force and the electromagnetic force create what is fundamentally a quantum mechanical problem,” Huber said.

“In the interior of cells, the forces that hold together membranes are fundamentally entropic and have to do with the minimisation of the overall free energy of the system. At first glance, these couldn’t be more different.”

While the similarity is cool, and makes us feel connected to the cosmos in a strange way, the differences signify the importance of the discovery, because they hint that two very different things – cells and neutron stars – might be guided by the same geometric rules that we’re only just beginning to understand.

It will take further research to really figure out what’s going on here, but it’s a starting point that could help us understand something fundamental about how matter is structured, and we’re excited to see where that leads.

The team’s work was published in Physical Review C.

from:    http://www.sciencealert.com/scientists-have-found-a-structural-similarity-between-human-cells-and-neutron-stars?utm_source=ScienceAlert+-+Daily+Email+Updates&utm_campaign=e224a761a7-MAILCHIMP_EMAIL_CAMPAIGN&utm_medium=email&utm_term=0_fe5632fb09-e224a761a7-365552945

Of Gamma Ray Bubbles and Dark Matter

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MILKY WAY’S GAMMA RAY BUBBLES SHAPED BY DARK MATTER?

Amy Shira Teitel
Analysis by Amy Shira Teitel
Tue May 8, 2012 11:37 AM ET

Gamma-ray-bubbles

Dark matter, the elusive stuff that makes up a substantial portion of all the mass in the universe, is largely a mystery to astronomers. They’ve tried finding it and creating it, but so far no conclusive proof as to what exactly it is though most theories state that we interact with it through gravity.

But Christoph Weniger, of the Max Planck Institute for Physics in Munich, has a different theory to explain new possible evidence for dark matter. By carrying out statistical analysis of three and a half years worth of publicly available data from NASA’s Fermi Space Telescope, he’s found a gamma ray line across the sky that he says is a clear signature of dark matter.

Astrophysicists generally think that supermassive black holes, like the one at the center of the Milky Way, release jets that interact with surrounding dark matter. This interaction is thought to be the source of high-energy gamma rays that satellites like Fermi can detect. What satellites can see are the photons produced when these jets interact with dark matter.

Weniger looked for signs of such an interaction in about three and a half years worth of gamma-ray observations carried out by the Fermi satellite’s Large Area Telescope (LAT).

To increase his chances of success he only considered data from those regions of the Milky Way that should generate the highest ratios of dark-matter photons to photons from background sources. He was looking specifically for a peak in energy, a sign that a photon was produced by the collision between and annihilation of two particles; the photon left over should have the same mass as one dark matter particle. This energy would theoretically appear as a very narrow peak, a line in gamma-ray spectra, distinct from the broad energy distribution seen across the visible universe.

That’s just what he found — a line in the gamma ray spectrum.

But he’s quick to admit it’s a provisional result. His data points come from about 50 photons and he’ll need a lot more to prove conclusively that his line is related to dark matter. It’s possible the line he observed is from a known, though no less mysterious, astronomical phenomenon: the pair of enormous gamma-ray-emitting bubbles extending outwards from the plane of the Milky Way.

In December 2010, scientists working with the Fermi Space Telescope found two giant lobes extending from the black hole at the center of our galaxy.

Twenty-five thousand light years high, each bubble spans more than half of the visible sky reaching from the constellation Virgo to the constellation Grus and may be relatively young at just a million or so years old.

The bubbles are a recent find, normally masked by the fog of gamma rays that appears throughout the sky that is a result of particles moving near the speed of light interacting with light and interstellar gas in the Milky Way. Scientists only found the bubbles by manipulating the data from the LAT to draw out the striking feature.

The manipulated images show the bubbles have well defined edges, suggesting they were formed as a result of a large and relatively rapid energy release — the source of which is still unknown. Interestingly, the energy cutoff of the bubbles corresponds to the gamma ray line Weniger found, the one he’s associating with a dark matter signature.

It’s possible the bubbles and the line have the same origin. Or, dark matter might be the cause of the bubbles’ defined endpoint.

Whether or not the two observations turn out to be linked — which of course hinges on conclusive proof of Weniger’s gamma ray line — both are very cool and part of the fascinating and mystery nature of our corner of the universe.

Image credit: NASA-Goddard

from:   http://news.discovery.com/space/dark-matter-and-gamma-ray-lobes-light-up-the-visible-universe-120508.html

February Fireballs

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The Fireballs of February

Feb. 22, 2012:  In the middle of the night on February 13th, something disturbed the animal population of rural Portal, Georgia. Cows started mooing anxiously and local dogs howled at the sky. The cause of the commotion was a rock from space.

“At 1:43 AM Eastern, I witnessed an amazing fireball,” reports Portal resident Henry Strickland. “It was very large and lit up half the sky as it fragmented. The event set dogs barking and upset cattle, which began to make excited sounds. I regret I didn’t have a camera; it lasted nearly 6 seconds.”

Strickland witnessed one of the unusual “Fireballs of February.”

February Fireballs (splash, 558 px)

A fireball over north Georgia recorded on Feb. 13th by a NASA all-sky camera in Walker Co., GA. [video]

“This month, some big space rocks have been hitting Earth’s atmosphere,” says Bill Cooke of NASA’s Meteoroid Environment Office. “There have been five or six notable fireballs that might have dropped meteorites around the United States.”

It’s not the number of fireballs that has researchers puzzled. So far, fireball counts in February 2012 are about normal. Instead, it’s the appearance and trajectory of the fireballs that sets them apart.

“These fireballs are particularly slow and penetrating,” explains meteor expert Peter Brown, a physics professor at the University of Western Ontario. “They hit the top of the atmosphere moving slower than 15 km/s, decelerate rapidly, and make it to within 50 km of Earth’s surface.”

The action began on the evening of February 1st when a fireball over central Texas wowed thousands of onlookers in the Dallas-Fort Worth area.

“It was brighter and long-lasting than anything I’ve seen before,” reports eye-witness Daryn Morran. “The fireball took about 8 seconds to cross the sky. I could see the fireball start to slow down; then it exploded like a firecracker artillery shell into several pieces, flickered a few more times and then slowly burned out.” Another observer in Coppell, Texas, reported a loud double boom as “the object broke into two major chunks with many smaller pieces.”

The fireball was bright enough to be seen on NASA cameras located in New Mexico more than 500 miles away. “It was about as bright as the full Moon,” says Cooke. Based on the NASA imagery and other observations, Cooke estimates that the object was 1 to 2 meters in diameter.

So far in February, NASA’s All-Sky Fireball Network has photographed about a half a dozen bright meteors that belong to this oddball category. They range in size from basketballs to buses, and all share the same slow entry speed and deep atmospheric penetration. Cooke has analyzed their orbits and come to a surprising conclusion:

February Fireballs (meteorcam, 200px)

This camera is part of NASA’s All-Sky Fireball Network. [more]

“They all hail from the asteroid belt—but not from a single location in the asteroid belt,” he says. “There is no common source for these fireballs, which is puzzling.”

This isn’t the first time sky watchers have noticed odd fireballs in February. In fact, the “Fireballs of February” are a bit of a legend in meteor circles.

Brown explains: “Back in the 1960s and 70s, amateur astronomers noticed an increase in the number of bright, sound-producing deep-penetrating fireballs during the month of February. The numbers seemed significant, especially when you consider that there are few people outside at night in winter. Follow-up studies in the late 1980s suggested no big increase in the rate of February fireballs. Nevertheless, we’ve always wondered if something was going on.”

Indeed, a 1990 study by astronomer Ian Holliday suggests that the ‘February Fireballs’ are real. He analyzed photographic records of about a thousand fireballs from the 1970s and 80s and found evidence for a fireball stream intersecting Earth’s orbit in February. He also found signs of fireball streams in late summer and fall. The results are controversial, however. Even Halliday recognized some big statistical uncertainties in his results.

NASA’s growing All-Sky Fireball Network could end up solving the mystery. Cooke and colleagues are adding cameras all the time, spreading the network’s coverage across North America for a dense, uninterrupted sampling of the night sky.

“The beauty of our smart multi-camera system,” notes Cooke, “is that it measures orbits almost instantly. We know right away when a fireball flurry is underway—and we can tell where the meteoroids came from.” This kind of instant data is almost unprecedented in meteor science, and promises new insights into the origin of February’s fireballs.

Meanwhile, the month isn’t over yet. “If the cows and dogs start raising a ruckus tonight,” advises Cooke, “go out and take a look.”

from:    http://science.nasa.gov/science-news/science-at-nasa/2012/22feb_februaryfireballs/