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I found an article suggesting a supernova injected debris which helped nudge the formation of the Solar System 4.5 billion years ago.
I couldn't find a name for this hypothetical star/supernova after some research. Is there one? What is it?
I couldn't find a name for this hypothetical star/nova after some research.
First off, the existence of this former object is hypothetical. Others working in this field have different hypotheses / conjectures; the science is far from settled. Secondly, if true, this star formed a supernova at the time the solar system was born and hence it no longer exists as a star. Thirdly, what's the point? Naming this hypothetical object would add zero credence to the hypothesis, and arguably would detract as being a bit premature.
Names of stars can serve a variety of purposes. Let's look at the different names and designations of Betelgeuse, for example.
- A star's colloquial name, for lack of a better word, is sometimes chosen to recognize past cultural value. In the case of Betelgeuse, this name is… Betelgeuse. In the case of the hypothetical star, though, there is no name from antiquity, as it was not around in antiquity.
- A star's Bayer designation describes what constellation it is in and its apparent brightness. Betelgeuse appears to us as one of the brightest stars in Orion, so its Bayer designation is $alpha$ Orionis. As we know nothing about the location or absolute magnitude of the hypothetical star (and heck, the constellations wouldn't have been the same 4.6 billion years ago), giving it a Bayer designation would be pointless.
- The name of a star in various catalogs may be arbitrary or may tell you something about its current location in the sky (see for instance the Henry Draper Catalogue. However, as I said above, things change on astronomical timescales, and a star will wander from its celestial coordinates on timeframes of hundreds, thousands, or millions of years. And there's no point in assigning this star an arbitrary number.
Finally, as David Hammen said, the existence of this star is still very much hypothetical. Assuming that the paper he found is the right one (and I think it is), the authors don't claim to identify the supernova progenitor with any supernova remnant, location in the sky, or astronomical object. They simply attempt to support the supernova hypothesis with more modeling, something which itself isn't new in the context of this theory. It's certainly nowhere near compelling enough to name the hypothetical object, nor, I think, is the overall evidence for the theory.
The famous supergiant on Orion’s shoulder has rapidly dimmed, stoking excitement that a supernova may be in the offing.Artist’s impression of the tortured, bubbling photosphere of a dying Betelgeuse. [ESO/L. Calçada]
Do you hear that ticking? Doesn’t it sound like a stellar timer is counting down to the inevitable demise of a massive star? While the excitement may be the amplified construct of social media predictions of the death of Betelgeuse, our stellar neighbor really is close to going supernova.
“Close”, however, is relative. It could be as “human close” as blowing up any minute now… to “galactic close” as blowing up in a hundred thousand years, maybe more.
So, what’s all the fuss about? In a nutshell, the brightest star in the famous constellation of Orion is bright no more. In the past few weeks, Betelgeuse has dimmed noticeably, stoking predictions that it could be about to spectacularly erupt at any time, becoming as bright as a full Moon and casting its own shadows at night.
While this may sound ominous, a Betelgeuse supernova poses no threat to life on Earth. It’s located a safe 600 light-years away, so if it did explode, we’d be treated to a historic cosmic firework display and not doomsday. Any energetic particles spewing from the explosion may reach the solar system in 100,000 years, but would have a minimal impact the heliosphere (our Sun’s extended magnetic “bubble” that encompasses all the planets) would be more than powerful enough to deflect the tenuous gases.
The constellation of Orion, with the ruddy Betelgeuse in the upper left-hand corner on Orion’s “shoulder.” [Photo by Frank Cone from Pexels]
There has always been excitement over Betelgeuse and its explosive potential. It’s a massive star, with a mass 12-times that of our Sun, which has reached the end of its life. But with a lifespan of only eight million years or so, it may sound odd that it’s dying of old age. As a comparison, our Sun—an “average” yellow dwarf star—sounds geriatric in comparison it’s approximately five billion years old. But the strange physics of stellar evolution dictates that the more massive the star, the shorter its lifespan. Betelgeuse is on borrowed time, whereas our Sun is only middle-aged. In other words, Betelgeuse has lived fast and it will die young.
As a star that’s about to die, Betelgeuse is experiencing the final throes of violent processes that signify the conclusion of stellar evolution—a phase that sees a massive star puff up into a red supergiant. In the case of Betelgeuse, while it is 12-times more massive than our Sun, it has expanded into a grotesque, bubbling mess of superheated plasma, puffed up to nearly 1,000-times wider than our Sun. If Betelgeuse were transplanted into the middle of our solar system, it would swallow all the planets out to Saturn. Yes, even Jupiter would be ingested.
A precision observation of Betelgeuse’s asymmetric photosphere, highlighting bright spots and a non-spherical shape, as captured by the Atacama Large Millimeter/submillimeter Array (ALMA).
After guzzling all of its hydrogen fuel long ago, it’s now fusing heavier elements inside its tortured interior to the point where iron is being created. For any massive star, the fusion of iron is the death knell energy is being absorbed, and soon, its immense gravity will cause the whole mess to collapse, generating an almighty shockwave that will, ultimately, rip Betelgeuse apart as a supernova.
As reported by astronomers before Christmas, the observed dimming could be interpreted as a precursor to the anticipated supernova, and for good reason. But Betelgeuse is known to regularly vary in brightness, so astronomers suspect that, while this is an unprecedented dimming event, the famous star will soon return to its “regular” brightness once more, reclaiming its rank as ninth brightest star in the sky.
In short, don’t place any serious money on Betelgeuse exploding soon. While there is a tiny chance that it might have already exploded, the light from the supernova currently galloping across the 600 light-year interstellar divide between us and Betelgeuse, it’s way more likely that it’s just Betelgeuse being Betelgeuse and keeping variable star astronomers on their toes.
That’s not to say the dimming event isn’t exciting, on the contrary. Seeing a prominent star in the night sky fade with your own eyes is something to behold, so when you get clear skies, look for Orion and ponder The Hunter’s missing shoulder.
Supernova Precursor Discovered in Spiral Galaxy NGC 2397
It’s a bit like trying to find a needle in a haystack when looking for a star in a galaxy. Although hard to do, astronomers using images from the Hubble Space Telescope (HST) are doing just that, trying to find stars before they explode as supernovae. In 2006, supernova SN 2006bc was spotted in spiral galaxy NGC 2397, so astronomers got to work, sifting through previous images taken by the HST. They found that star, in the rising stage of brightness as it exploded. Usually we don’t get to see this stage of a supernova, as we can’t predict which star is going to blow. But retracing years of HST observational data, scientists are able to piece together the cosmic forensic evidence and see the star before it died…
SN 2006bc was seen in the spiral galaxy NGC 2397, located nearly 60 million light years from the Milky Way, back in 2006. There was no warning or any indication that that star was going to blow in that galaxy (after all, there’s a lot out there), but Hubble’s Advanced Camera for Surveys (ACS) captured the galaxy after it happened. So astronomers watched the afterglow of the event. While a lot of good science can be done by analysing the remnants of a supernova, wouldn’t it be great to see a star before it explodes? Perhaps then we can analyse the emissions from an unstable star before it dies…
Predicting cosmic events is no new thing, and much effort is being put into various forecasting techniques. A few examples include:
- Solar radiation: The main focus for solar physicists is to predict “space weather” to help protect us against the dangerous onslaught of high energy particles (particularly solar flares).
- Detecting supernova neutrinos: An “early warning” system is already in place to detect the neutrinos that are blasted from a star’s core at the moment of a star’s collapse (leading to a supernova). The SuperNova Early Warning System (SNEWS) has been set up to detect these neutrinos.
- Gamma ray bursts (GRBs): The Polish “Pi of the Sky” GRB detector is an array of cameras looking out for optical flashes (or transients) in the night sky above the Chilean mountains. Combined with NASA’s Swift gamma ray observatory in orbit, the burst is detected, immediately signalling other observatories to watch the event.
The above examples usually detect the sudden event of a solar flare, GRB or surge of neutrinos right at the point of initiation. Fortunately for solar physicists, we have a vast amount of high-spatial and high-temporal resolution data about our closest star. Should a flare be launched, we can “rewind the tape” and see the location of flare initiation and work out the conditions before the flare was launched. From this, we are able to be better informed and possibly predict where the next flare will be launched from. Supernova astronomers aren’t so lucky. The cosmos is a big place after all, only a tiny proportion of the night sky has been observed in any great detail, and the chances that the same region has been imaged more than once at high resolution are few and far between.
Although the chances are slim, researchers from Queen’s University Belfast in Northern Ireland, led by Professor Stephen J. Smartt used Hubble Space Telescope (HST) images to “rewind the tape” before supernova SN 2006bc occurred. By confining their search for “pre-supernova” stars in local galaxies, there was a better chance of studying galaxies that have been imaged at high resolution and imaged more than once in the past. SN 2006bc turned out to be the perfect candidate.
The group has done this before. Of the six precursor stars discovered to date, Smartt’s team found five of them. From their analysis, it is hoped that the characteristics of a star before it dies can be worked out as the conditions for a supernova to occur is poorly understood.
After ten years of surveying, the group presented their discoveries of supernova precursor stars at this year’s National Astronomy Meeting 2008 in Belfast, last week. It appears that stars with masses as low as seven times the size of our Sun can explode as supernovae. They go on to hypothesise that the massive stars may not explode as supernovae and may just die through collapse and form as a black hole. The emission from such an event may be too faint to observe and the most energetic supernovae may be restricted to the smaller stars.
However, six supernova precursor stars are not a large number to make any big conclusions quite yet, but it is a big step in the right direction to better understand the mechanisms at work in a star just about to explode…
SN2015bh—the end of a star or an 'impostor' supernova?
Massive stars end their lives in supernova explosions, highly energetic events that can be as luminous as the entire starlight from their host galaxies. However, there are events called "supernova impostors" which, despite their intensity, are not the end of the star's life. This could very well be the case of SN 2015bh, a star which had suffered at least 21 years of violent eruptions and which, together with a number of other objects, could be a member of a new class.
"Luminous blue variable stars like this one show two different kinds of eruptions: regular outbursts after which the star returns to its original state and giant eruptions which alter the star permanently. A prominent example is Eta Carinae, a star which has already lost mass equivalent to 40 times the mass of our Sun though winds and eruptions," says Christina Thöne, scientist at the Institute for Astrophysics of Andalucia (IAA–CSIC) and head of the HETH group (High energy transients and their hosts) who is leading the study.
Some stars suffer even larger outbursts that very much resemble real supernova explosions. The dividing line between those imposter supernovae and real ones is still a matter of debate. The case of SN 2015bh is a good example for this difficult decision about whether the explosion has ended the life of the star or not.
The turbulent chronology of SN 2015bh
Archival records show that the star had experienced frequent minor eruptions since at least 1994, alternating with quieter periods. On Feb. 10, 2015, an outburst was detected and classified as impostor supernova, which prompted a renewed interest in the star.
In April 2015 a group lead by the Institute of Astrophysics of Andalucia (IAA–CSIC) started weekly observations from different observatories observing this new outburst that started to decay slowly. This later called "precursor event" was followed by an even more intense outburst on May 16 which, instead of declining, was rising in intensity until May 24. The energy released in this so-called "main event" is compatible with the release in a real supernova.
"The vast majority of data were obtained from Spanish telescopes, in particular from the Calar Alto observatory in Almeria, the Gran Telescopio Canarias on La Palma and the Observatory of Sierra Nevada (Granada). In fact, the main event had been detected thanks to the Observatory of Sierra Nevada," says Christina Thöne (IAA-CSIC).
Subsequent observations spanning up to 200 days after the main event, show that the star has lost luminosity, and now shows bluer colors than in previous phases, but are unable to confirm that the star has exploded. In addition, the entire process turns out to be very similar to a few other events for which the death of the star could not be confirmed either until now.
"Now we know already several cases of these luminous blue variables that follow the same pattern: smaller, more or less continuous eruption over several decades and an outburst between 40 and 80 days before the main explosion. In fact, the evolution of SN 2015bh turns out to be basically a carbon copy of SN 2009ip, a famous example of a supernova impostor that took place in 2012 whose fate is still highly debated," explains Christina Thöne (IAA-CSIC).
On a fast track to the Wolf-Rayet phase
In the current theoretical framework, luminous blue variables are massive stars in a transition to a Wolf-Rayet phase, which is supposed to be the last phase of its life. But before they can enter this phase, they have to get rid of their outer envelope and the mechanism for that is still unknown: the stars can lose their envelope though very strong stellar winds, however, these winds might result being very inefficient to achieve the transition to the Wolf-Rayet phase a single giant eruption does not seem to solve the problem either, as we see in Eta Carinae, which has already suffered at least two giant eruptions and still continues as a luminous blue variable star.
Nevertheless, a violent eruption such as SN 2015bh could be a way to fast-track the star's evolution to its last phase. If SN 2015bh and other events with similar pattern have survived this explosion, they could already be on their way to become Wolf-Rayet stars.
"SN 2015bh is not an isolated case and there are possibly many more similar objects out there that have gone unnoticed, but it seems we have encountered a new type of stellar event. Now we need to uncover the mechanism driving those events and find out why the observed cases show such very similar behavior," Christina Thöne (IAA-CSIC) concludes.
The Modern Nebular theory
The planets originate in a dense disk formed from material in the gas and dust cloud that collapses to give us the Sun. The density of this disk had to be sufficient to allow the formation of the planets and yet be thin enough for the residual matter to be blown away by the Sun as its energy output increased.
In 1992 the Hubble Space Telescope obtained the first images of proto-planetary disks in the Orion nebula. They are roughly on the same scale as the Solar System and lend strong support to this theory.
(Dept of Astrophysics, Michigan State University)
Artists rendition of the recurrent nova RS Oph Credit: David Hardy/PPARC
(From Universe Today): Today, two amateur astronomers from Florida detected a rare outburst of the recurrent nova U Scorpii, which set in motion satellite observations by the Hubble Space Telescope, Swift and Spitzer. The last outburst of U Scorpii occurred in February of 1999. Observers around the planet will now be observing this remarkable system intensely for the next few months trying to unlock the mysteries of white dwarfs, interacting binaries, accretion and the progenitors of Type IA supernovae.
One of the remarkable things about this outburst is it was predicted in advance by Dr. Bradley Schaefer, Louisiana State University, so observers of the American Association of Variable Star Observers (AAVSO) have been closely monitoring the star since last February, waiting to detect the first signs of an eruption. This morning, AAVSO observers, Barbara Harris and Shawn Dvorak sent in notification of the outburst, sending astronomers scrambling to get ‘target of opportunity observations’ from satellites and continuous coverage from ground-based observatories. Time is a critical element, since U Sco is known to reach maximum light and start to fade again in one day.
A Superbright Supernova That’s the First of Its Kind
In this schematic illustration of the material ejected from SN 2007bi, the radioactive nickel core (white) decays to cobalt, emitting gamma rays and positrons that excite surrounding layers (textured yellow) rich in heavy elements like iron. The outer layers (dark shadow) are lighter elements such as oxygen and carbon, where any helium must reside, which remain unilluminated and do not contribute to the visible spectrum.
(PhysOrg.com) -- An extraordinarily bright, extraordinarily long-lasting supernova named SN 2007bi, snagged in a search by a robotic telescope, turns out to be the first example of the kind of stars that first populated the Universe. The superbright supernova occurred in a nearby dwarf galaxy, a kind of galaxy that's common but has been little studied until now, and the unusual supernova could be the first of many such events soon to be discovered.
SN 2007bi was found early in 2007 by the international Nearby Supernova Factory (SNfactory) based at the U.S. Department of Energy's Lawrence Berkeley National Laboratory. The supernova's spectrum was unusual, and astronomers at the University of California at Berkeley subsequently obtained a more detailed spectrum. Over the next year and a half the Berkeley scientists participated in a collaboration led by Avishay Gal-Yam of Israel's Weizmann Institute of Science to collect and analyze much more data as the supernova slowly faded away.
The analysis indicated that the supernova's precursor star could only have been a giant weighing at least 200 times the mass of our Sun and initially containing few elements besides hydrogen and helium - a star like the very first stars in the early Universe.
"Because the core alone was some 100 solar masses, the long-hypothesized phenomenon called pair instability must have occurred," says astrophysicist Peter Nugent. A member of the SNfactory, Nugent is the co-leader of the Computational Cosmology Center (C3), a collaboration between Berkeley Lab's Physics Division and Computational Research Division (CRD), where Nugent is a staff scientist. "In the extreme heat of the star's interior, energetic gamma rays created pairs of electrons and positrons, which bled off the pressure that sustained the core against collapse."
"SN 2007bi was the explosion of an exceedingly massive star," says Alex Filippenko, a professor in the Astronomy Department at UC Berkeley whose team helped obtain, analyze, and interpret the data. "But instead of turning into a black hole like many other heavyweight stars, its core went through a nuclear runaway that blew it to shreds. This type of behavior was predicted several decades ago by theorists, but never convincingly observed until now."
SN 2007bi is the first confirmed observation of a pair-instability supernova. The researchers describe their results in the 3 December 2009 issue of Nature.
On the trail of a strange beast
SN 2007bi was recorded on images taken as part of the Palomar-QUEST Survey, an automated search with the wide-field Oschin Telescope at the California Institute of Technology's Palomar Observatory, and was quickly detected and categorized as an unusual supernova by the SNfactory. The SNfactory has so far discovered nearly a thousand supernovae of all types and amassed thousands of spectra, but has focused on those designated Type Ia, the "standard candles" used to study the expansion history of the Universe. SN 2007bi, however, turned out not to be a Type Ia. For one thing, it was at least ten times as bright.
"The thermonuclear runaway experienced by the core of SN 2007bi is reminiscent of that seen in the explosions of white dwarfs as Type Ia supernovae," says Filippenko, "but on a much larger scale and with a far greater amount of power."
"The discovery is a great example of how we can get all the science, in addition to cosmology, out of the SNfactory search," says Greg Aldering, SNfactory project leader, who was not an author of the Nature paper. "Berkeley Lab and Caltech's Astronomy Department agreed that we would split the work, the Lab handling the Type Ia's and Caltech all the other types."
Nugent contacted Gal-Yam, then a Caltech postdoctoral fellow, the lead investigator for the all-other category. "I asked, are you interested? He said, sure!" Nugent then contacted Filippenko, who was about to conduct a night of observation with the 10-meter Keck I telescope on the summit of Mauna Kea in Hawaii. Filippenko immediately set out to obtain an optical spectrum of the unusual supernova.
Caltech researchers subsequently acquired additional spectra with the Keck telescope, as did Paolo Mazzali's team from the Max Planck Institute for Astrophysics in Garching, Germany, using the Very Large Telescope (VLT) in Chile.
Says Mazzali, "The Keck and VLT spectra clearly indicated that an extremely large amount of material was ejected by the explosion, including a record amount of radioactive nickel, which caused the expanding gases to glow very brightly."
Rollin Thomas of CRD, a member of C3 and the SNfactory, aided the early analysis, using the Franklin supercomputer at the National Energy Research Scientific Computing Center (NERSC) to run a code he developed to generate numerous synthetic spectra for comparison with the real spectrum.
"The code uses hundreds of cores to systematically test a large number of simplified model supernovae, searching through the candidates by adjusting parameters until it finds a good fit," says Thomas. "This kind of data-driven approach is key to helping us understand new types of transients for which no reliable theoretical predictions yet exist." The model fit was unambiguous: SN 2007bi was a pair-instability supernova.
"The central part of the huge star had fused to oxygen near the end of its life, and was very hot," Filippenko explains. "Then the most energetic photons of light turned into electron-positron pairs, robbing the core of pressure and causing it to collapse. This led to a nuclear runaway explosion that created a large amount of radioactive nickel, whose decay energized the ejected gas and kept the supernova visible for a long time."
Gal-Yam organized a team of collaborators from many institutions to continue to observe SN 2007bi and obtain data as it slowly faded over a span of 555 days. Says Gal-Yam, "As our follow-up observations started to roll in, I immediately realized this must be something new. And indeed it turned out to be a fantastic example of how we are finding new types of stellar explosions."
Because it had no hydrogen or helium lines, the usual classification scheme would have labeled the supernova a Type Ic. But it was so much brighter than an ordinary Type Ic that it reminded Nugent of only one prior event, a supernova designated SN 1999as, found by the international Supernova Cosmology Project but unfortunately three weeks after its peak brightness.
Understanding a supernova requires a good record of its rise and fall in brightness, or light curve. Although SN 2007bi was detected more than a week after its peak, Nugent delved into years of data compiled by NERSC from the SNfactory and other surveys. He found that the Catalina Sky Survey had recorded SN 2007bi before its peak brightness and could provide enough data to calculate the duration of the rising curve, an extraordinarily long 70 days - more evidence for the pair-instability identification.
A fossil laboratory of the early Universe
"It's significant that the first unambiguous example of a pair-instability supernova was found in a dwarf galaxy," says Nugent. "These are incredibly small, very dim galaxies that contain few elements heavier than hydrogen and helium, so they are models of the early Universe."
Dwarf galaxies are ubiquitous but so faint and dim - "they take only a few pixels on a camera," says Nugent, "and until recently, with the development of wide-field projects like the SNfactory, astronomers had wanted to fill the chip with galaxies" - that they've rarely been studied. SN 2007bi is expected to focus attention on what Gal-Yam and his collaborators call "fossil laboratories to study the early Universe."
Says Filippenko, "In the future, we might end up detecting the very first generation of stars, early in the history of the Universe, through explosions such as that of SN 2007bi - long before we have the capability of directly seeing the pre-explosion stars."
With the advent of the multi-institutional Palomar Transient Factory, a fully automated, wide-field survey to find transients, led by Caltech's Shri Kulkarni, and with the aid of the Deep Sky Survey established by Nugent at NERSC to compile historical data from Palomar-QUEST, the SNfactory, the Near Earth Asteroid Team, and other surveys, the collaborators expect they will soon find many more ultrabright, ultramassive supernovae, revealing the role of these supernovae in creating the Universe as we know it today.
“Our ‘Mother’ Sun was a Supernova”
“Although Earth was originally created from the Sun (as part of the ecliptic plane of debris and dust that circulated around the Sun 4.5 billion years ago), our Sun is barely hot enough to fuse hydrogen to helium, observed physicist Michio Kaku in Parallel Worlds: A Journey through Creation, Higher Dimensions, and the Future of the Cosmos. “This means that our true “mother” sun was actually an unnamed star or collection of stars that died billions of years ago in a supernova, which then seeded nearby nebulae with the higher elements beyond iron that make up our body. Literally, our bodies are made of stardust, from stars that died billions of years ago.”
What If History’s Brightest Supernova Exploded In Earth’s Backyard?
In 2015, the automated telescopes in Ohio State’s ASASSN network saw the peach-fuzz blob of a distant galaxy. By June 2015, that galaxy was gone, all of its stars outshone by a piercing blue point, writes Joshua Sokol in The Atlantic. “The explosion, ASASSN-15lh, at the too-close-for comfort distance of the star Arcturus, is a few hundred times brighter than your garden-variety supernova, and two or three times brighter than the previous record holder. It’s in a class by itself,” says Sokol. In addition to the visible light, the exploded star would hang as a blinding point in our sky, pouring X-rays, gamma rays, and hard ultraviolet radiation into Earth’s atmosphere, obliterating its ozone layer.
In 1996, astronomer Brian Fields and his then adviser listed out the radioactive elements blasted into space by a supernova that you might be able hunt down on Earth, reports Sokol. A supernova close enough to leave a trace, they reasoned, might also have been close enough to pose a serious threat to life. “If we were really lucky we could connect it to a mass extinction,” said Fields, now of the University of Illinois. “That’s sort of the Holy Grail, or the unholy grail, of the field.”
Capable of Wiping Human Civilization Off the Face of the Earth
“We see supernovas in other galaxies all the time. Through a telescope, a galaxy is a tiny smudge. Then, all of a sudden, a star-like object appears, emitting enough light to overshadow an entire solar system, even a galaxy,” says geoscientist Robert Brakenridge, a senior research associate at the Institute of Arctic and Alpine Research (INSTAAR) at the University of Colorado, Boulder about a new study that suggests that a very nearby supernova could be capable of wiping human civilization off the face of the Earth. But even from farther away, these explosions may still take a toll, bathing our planet in dangerous radiation and damaging its protective ozone layer.
Releases as Much Energy as the Sun During its Entire Lifetime
Massive supernova explosions can release as much energy as the sun will during its entire lifetime may have left traces in Earth’s biology and geology. A new study probes the impacts of supernovas, some of the most violent events in the known universe. In the span of just a few months, a single one of these eruptions can release as much energy as the sun will during its entire lifetime spreading life-giving elements –helium, carbon, oxygen, iron, nickel-across the universe.
Searching for Cosmic Fingerprints
To study those possible impacts, Brakenridge searched through the planet’s tree ring records for the fingerprints of these distant, cosmic explosions. Although far from conclusive, his findings suggest that relatively close supernovas could theoretically have triggered at least four disruptions to Earth’s climate over the last 40,000 years. “These are extreme events, and their potential effects seem to match tree ring records.”
Brakenridge’s research, reports the University of Colorado, “hinges on the case of a curious atom, carbon-14, also known as radiocarbon, a carbon isotope that occurs only in tiny amounts on Earth. Trees pick up carbon dioxide and some of that carbon will be radiocarbon.”
Carbon-14 –Radiocarbon Atoms on Earth
Scientists have discovered a handful of cases in which the concentration of this isotope inside tree rings spikes–suddenly and for no apparent earthly reason. Many scientists have hypothesized that these several-year-long spikes could be due to solar flares or huge ejections of energy from the surface of the sun. “We’re seeing terrestrial events that are begging for an explanation,” Brakenridge said. “There are really only two possibilities: A solar flare or a supernova. I think the supernova hypothesis has been dismissed too quickly.”
The Last 40,000 Years
Brakenridge noted that scientists have recorded supernovas in other galaxies that have produced a stupendous amount of gamma radiation–the same kind of radiation that can trigger the formation of radiocarbon atoms on Earth. While these isotopes aren’t dangerous on their own, a spike in their levels could indicate that energy from a distant supernova has traveled hundreds to thousands of light-years to our planet. To test the hypothesis, he assembled a list of supernovas that occurred relatively close to Earth over the last 40,000 years. Scientists can study these events by observing the nebulas they left behind. He then compared the estimated ages of those galactic fireworks to the tree ring record on the ground.
The Vela Supernova Remnant
Of the eight closest supernovas studied, all seemed to be associated with unexplained spikes in the radiocarbon record on Earth. Four of these to be especially promising candidates reports Brackenrige, one of which a former star in the Vela constellation, which once sat about 815 lightyears from Earth, that went supernova roughly 13,000 years ago. Not long after that, radiocarbon levels jumped up by nearly 3% on Earth.
The NASA mosaic at the top of the page is centered on the glowing filaments of the Vela Supernova Remnant, the expanding debris cloud from the death explosion of a massive star. Light from the supernova explosion that created the Vela remnant reached Earth about 11,000 years ago, reports NASA — “In addition to the shocked filaments of glowing gas, the cosmic catastrophe also left behind an incredibly dense, rotating stellar core, the Vela Pulsar. Some 800 light-years distant, the Vela remnant is likely embedded in a larger and older supernova remnant, the Gum Nebula.”
Scientists still have trouble dating past supernovas, making the timing of the Vela explosion uncertain with a possible error of as much as 1,500 years. It’s also not clear what the impacts of such a disruption might have been for plants and animals on Earth at the time. But Brakenridge believes that the question begs for more research.
“What keeps me going is when I look at the terrestrial record and I say, ‘My God, the predicted and modeled effects do appear to be there.'”
Rare Star Explosion Follows A Flash Of Light
A team of European, Japanese and Chinese astrophysicists, including members from CNRS (INSU) and CEA (DAPNIA/Sap) laboratories(1) has just discovered one of the strangest star explosions ever observed. The star that burst was massive &ndash 15 to 25 times greater than the mass of the Sun &ndash and was probably made up exclusively of carbon and oxygen.
A brief flash of light had been observed two years before this rare cataclysm occurred. This precursor signal, which had never been seen before, raises hopes that astronomers will be able to "predict" explosions and observe stars as they enter the very last moments of their existence.
On 9 October 2006, two years after a Japanese amateur astronomer observed a flash of light in the constellation Lynx in UGC4904, the appearance of an object ten times brighter in the same spot attracted the attention of a European consortium, which mobilized a bank of telescopes(2). According to the first observations obtained at the La Palma Observatory in Spain, the explosion was exceptional: not a single trace of hydrogen or helium &ndash the most abundant elements in stars &ndash could be seen in the emitted light. It was only some ten days later that the first traces of helium were detected in the star's spectrum (i.e. the distribution of light according to energy).
These findings were confirmed by observations that followed over a period of nearly three months. The supernova, named SN2006jc(3), reached the maximum luminosity that is characteristic of the most powerful star explosions, more than a billion times brighter than the Sun. Astronomers divide these explosions into two broad categories &ndash supernovae types I and II, which refer to two completely different types of phenomenon. The type I category refers to the disintegration of a small, compact star, known as a white dwarf, which has been made unstable by the accumulation of matter coming from a companion.
The type II category, on the other hand, refers to the explosion of a massive star. In the first case, very little hydrogen and helium is seen in the explosion, whereas in the second type of explosion, these two elements are predominant. SN2006jc does not fit into either category and so has been catalogued in a special sub-category, Ic.
These very rare cases have only been discovered very recently. This rarity can no doubt be explained by the great mass of the star concerned. It is probably a star of 60 to 100 solar masses which has lost a great quantity of mass previously. Here it is only the central part, a core of carbon and oxygen of 15 to 25 solar masses that explodes. Thus, most of the elements in the explosion come from the core of the star, while the helium observed is only found around the edge and comes from the star's envelope, which was ejected earlier.
The flash of light observed in 2004 also leaves many questions unanswered. As with earthquakes, scientists know very few precursor events capable of warning them that a star explosion is imminent. Supernova SN2006jc is the only known example of a star explosion for which a flash of light was observed two years earlier. For this reason, it opens up new horizons for predicting massive star explosions. Eta Carinae could be one example of a star similar to SN2006jc close to our galaxy. It also experienced an outburst of luminosity making it the second brightest star in the sky in 1843. A future outburst could be the sign of an imminent explosion.
Regular monitoring of such objects is a fine example of how small telescopes can be used and makes an excellent programme for collaboration between amateur and professional astronomers. It will no doubt be possible for us now to detect some of the most massive stars just before they break up.
The results will be published in the 14 June 2007 issue of Nature.
1) The observations were made at the Haute-Provence Observatory (1.93m telescope, CNRS, France), the Asiago Observatory (1.82 m Copernico telescope, Italy), the National Astronomical Observatory (2.16 m telescope, BAO, Xinglong Observatory, Beijing, China) and La Palma Observatory (Telescopio Nationale Galileo 3.58 m, Nordic Optical Telescope 2.56 m, Liverpool Telescope 2.0 m and Herschell Telescope 4.2m, Canaries, Spain).
2) Several hundred supernovae are discovered each year. The supernova's name is composed of the year it was discovered, followed by letters indicating its chronological order in the year. Thus, "SN2006a" was the first supernova discovered in 2006, "SN2006aa" the 27th and "SN2006jc" the 263rd of the year.
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Tree rings may hold clues to impacts of distant supernovas on Earth
The remnants of a supernova in the Large Magellanic Cloud, a dwarf galaxy that sits close to the Milky Way. Credit: NASA/ESA/HEIC and The Hubble Heritage Team
Massive explosions of energy happening thousands of light-years from Earth may have left traces in our planet's biology and geology, according to new research by University of Colorado Boulder geoscientist Robert Brakenridge.
The study, published this month in the International Journal of Astrobiology, probes the impacts of supernovas, some of the most violent events in the known universe. In the span of just a few months, a single one of these eruptions can release as much energy as the sun will during its entire lifetime. They're also bright—really bright.
"We see supernovas in other galaxies all the time," said Brakenridge, a senior research associate at the Institute of Arctic and Alpine Research (INSTAAR) at CU Boulder. "Through a telescope, a galaxy is a little misty spot. Then, all of a sudden, a star appears and may be as bright as the rest of the galaxy."
A very nearby supernova could be capable of wiping human civilization off the face of the Earth. But even from farther away, these explosions may still take a toll, Brakenridge said, bathing our planet in dangerous radiation and damaging its protective ozone layer.
To study those possible impacts, Brakenridge searched through the planet's tree ring records for the fingerprints of these distant, cosmic explosions. His findings suggest that relatively close supernovas could theoretically have triggered at least four disruptions to Earth's climate over the last 40,000 years.
The results are far from conclusive, but they offer tantalizing hints that, when it comes to the stability of life on Earth, what happens in space doesn't always stay in space.
"These are extreme events, and their potential effects seem to match tree ring records," Brakenridge said.
His research hinges on the case of a curious atom. Brakenridge explained that carbon-14, also known as radiocarbon, is a carbon isotope that occurs only in tiny amounts on Earth. It's not from around here, either. Radiocarbon is formed when cosmic rays from space bombard our planet's atmosphere on an almost constant basis.
"There's generally a steady amount year after year," Brakenridge said. "Trees pick up carbon dioxide and some of that carbon will be radiocarbon."
Sometimes, however, the amount of radiocarbon that trees pick up isn't steady. Scientists have discovered a handful of cases in which the concentration of this isotope inside tree rings spikes—suddenly and for no apparent earthly reason. Many scientists have hypothesized that these several-year-long spikes could be due to solar flares or huge ejections of energy from the surface of the sun.
Brakenridge and a handful of other researchers have had their eye on events much farther from home.
"We're seeing terrestrial events that are begging for an explanation," Brakenridge said. "There are really only two possibilities: A solar flare or a supernova. I think the supernova hypothesis has been dismissed too quickly."
He noted that scientists have recorded supernovas in other galaxies that have produced a stupendous amount of gamma radiation—the same kind of radiation that can trigger the formation of radiocarbon atoms on Earth. While these isotopes aren't dangerous on their own, a spike in their levels could indicate that energy from a distant supernova has traveled hundreds to thousands of light-years to our planet.
To test the hypothesis, Brakenridge turned to the past. He assembled a list of supernovas that occurred relatively close to Earth over the last 40,000 years. Scientists can study these events by observing the nebulas they left behind. He then compared the estimated ages of those galactic fireworks to the tree ring record on the ground.
He found that of the eight closest supernovas studied, all seemed to be associated with unexplained spikes in the radiocarbon record on Earth. He considers four of these to be especially promising candidates. Take the case of a former star in the Vela constellation. This celestial body, which once sat about 815 lightyears from Earth, went supernova roughly 13,000 years ago. Not long after that, radiocarbon levels jumped up by nearly 3% on Earth—a staggering increase.
The findings aren't anywhere close to a smoking gun, or star, in this case. Scientists still have trouble dating past supernovas, making the timing of the Vela explosion uncertain with a possible error of as much as 1,500 years. It's also not clear what the impacts of such a disruption might have been for plants and animals on Earth at the time. But Brakenridge believes that the question is worth a lot more research.
"What keeps me going is when I look at the terrestrial record and I say, 'My God, the predicted and modeled effects do appear to be there.'"
He hopes that humanity won't have to see those effects for itself anytime soon. Some astronomers think they've picked up signs that Betelgeuse, a red giant star in the constellation Orion, might be on the verge of collapsing and going supernova. And it's only 642.5 light-years from Earth, much closer than Vela.
"We can hope that's not what's about to happen because Betelgeuse is really close," he said said.