supernova Archives

November 10, 2011December 24, 2015 by Tammy Plotner

New NASA Mission Hunts Down Zombie Stars

This is an artist's concept of a pulsar (blue-white disk in center) pulling in matter from a nearby star (red disk at upper right). The stellar material forms a disk around the pulsar (multicolored ring) before falling on to the surface at the magnetic poles. The pulsar's intense magnetic field is represented by faint blue outlines surrounding the pulsar. Credit: NASA

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Neutron stars have been classed as “undead”… real zombie stars. Even though technically defunct, the neutron star continues to shine – and occasionally feed on a neighbor if it gets too close. They are born when a massive star collapses under its gravity and its outer layers are blown far and wide, outshining a billion suns, in a supernova event. What’s left is a stellar corpse… a core of inconceivable density… where one teaspoon would weigh about a billion tons on Earth. How would we study such a curiosity? NASA has proposed a mission called the Neutron Star Interior Composition Explorer (NICER) that would detect the zombie and allow us to see into the dark heart of a neutron star.

The core of a neutron star is pretty incredible. Despite the fact that it has blown away most of its exterior and stopped nuclear fusion, it still radiates heat from the explosion and exudes a magnetic field which tips the scales. This intense form of radiation caused by core collapse measures out at over a trillion times stronger than Earth’s magnetic field. If you don’t think that impressive, then think of the size. Originally the star could have been a trillion miles or more in diameter, yet now is compressed to the size of an average city. That makes a neutron star a tiny dynamo – capable of condensing matter into itself at more than 1.4 times the content of the Sun, or at least 460,000 Earths.

“A neutron star is right at the threshold of matter as it can exist – if it gets any denser, it becomes a black hole,” says Dr. Zaven Arzoumanian of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We have no way of creating neutron star interiors on Earth, so what happens to matter under such incredible pressure is a mystery – there are many theories about how it behaves. The closest we come to simulating these conditions is in particle accelerators that smash atoms together at almost the speed of light. However, these collisions are not an exact substitute – they only last a split second, and they generate temperatures that are much higher than what’s inside neutron stars.”

If approved, the NICER mission will be launched by the summer of 2016 and attached robotically to the International Space Station. In September 2011, NASA selected NICER for study as a potential Explorer Mission of Opportunity. The mission will receive $250,000 to conduct an 11-month implementation concept study. Five Mission of Opportunity proposals were selected from 20 submissions. Following the detailed studies, NASA plans to select for development one or more of the five Mission of Opportunity proposals in February 2013.

What will NICER do? First off, an array of 56 telescopes will gather X-ray information from a neutron stars magnetic poles and hotspots. It is from these areas that our zombie stars release X-rays, and as they rotate create a pulse of light – thereby the term “pulsar”. As the neutron star shrinks, it spins faster and the resultant intense gravity can pull in material from a closely orbiting star. Some of these pulsars spin so fast they can reach speeds of several hundred of rotations per second! What scientists are itching to understand is how matter behaves inside a neutron star and “pinning down the correct Equation Of State (EOS) that most accurately describes how matter responds to increasing pressure. Currently, there are many suggested EOSs, each proposing that matter can be compressed by different amounts inside neutron stars. Suppose you held two balls of the same size, but one was made of foam and the other was made of wood. You could squeeze the foam ball down to a smaller size than the wooden one. In the same way, an EOS that says matter is highly compressible will predict a smaller neutron star for a given mass than an EOS that says matter is less compressible.”

Now all NICER will need to do is help us to measure a pulsar’s mass. Once it is determined, we can get a correct EOS and unlock the mystery of how matter behaves under intense gravity. “The problem is that neutron stars are small, and much too far away to allow their sizes to be measured directly,” says NICER Principal Investigator Dr. Keith Gendreau of NASA Goddard. “However, NICER will be the first mission that has enough sensitivity and time-resolution to figure out a neutron star’s size indirectly. The key is to precisely measure how much the brightness of the X-rays changes as the neutron star rotates.”

So what else does our zombie star do that’s impressive? Because of their extreme gravity in such small volume, they distort space/time in accordance with Einstein’s theory of General Relativity. It is this space “warp” that allows astronomers to reveal the presence of a companion star. It also produces effects like an orbital shift called precession, allowing the pair to orbit around each other causing gravitational waves and producing measurable orbital energy. One of the goals of NICER is to detect these effects. The warp itself will allow the team to determine the neutron star’s size. How? Imagine pushing your finger into a stretchy material – then imagine pushing your whole hand against it. The smaller the neutron star, the more it will warp space and light.

Here light curves become very important. When a neutron star’s hotspots are aligned with our observations, the brightness increases as one rotates into view and dims as it rotates away. This results in a light curve with large waves. But, when space is distorted we’re allowed to view around the curve and see the second hotspot – resulting in a light curve with smoother, smaller waves. The team has models that produce “unique light curves for the various sizes predicted by different EOSs. By choosing the light curve that best matches the observed one, they will get the correct EOS and solve the riddle of matter on the edge of oblivion.”

And breathe life into zombie stars…

Original Story Source: NASA Mission News.

November 4, 2011December 24, 2015 by Tammy Plotner

Did A Supernova Shape Our Solar System?

The time evolution of case I. Color coded is the density at t = 0 kyr, t = 4.16 kyr and t = 8.33 kyr. The length scale is given in units of the radius of the initial cold core (R0 = 0.21 pc). Credit: M. Gritschneder (et al)

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Away in space some 4.57 billion years ago, in a galaxy yet to be called the Milky Way, a hydrogen molecular cloud collapsed. From it was born a G-type main sequence star and around it swirled a solar nebula which eventually gelled into a solar system. But just what caused the collapse of the molecular cloud? Astronomers have theorized it may have been triggered by a nearby supernova event… And now new computer modeling confirms that our Solar System was born from the ashes a dead star.

While this may seem like a cold case file, there are still some very active clues – one of which is the study of isoptopes contained within the structure of meteorites. As we are well aware, many meteorites could very well be bits of our primordial solar nebula, left virtually untouched since they formed. This means their isotopic signature could spell out the conditions that existed within the molecular cloud at the time of its collapse. One strong factor in this composition is the amount of aluminium-26 – an element with a radioactive half-life of 700,000 years. In effect, this means it only takes a relatively minor period of time for the ratio between Al-26 and Al-24 to change.

“The time-scale for the formation events of our Solar System can be derived from the decay products of radioactive elements found in meteorites. Short lived radionuclides (SLRs) such as 26Al , 41Ca, 53Mn and 60Fe can be employed as high-precision and high-resolution chronometers due to their short half-lives.” says M. Gritschneder (et al). “These SLRs are found in a wide variety of Solar System materials, including calcium-aluminium-rich inclusions (CAIs) in primitive chondrites.”

However, it would seem that a class of carbonaceous chondrite meteorites known CV-chondrites, have a bit more than their fair share of Al-26 in their structure. Is it the smoking gun of an event which may have enriched the cloud that formed it? Isotope measurements are also indicative of time – and here we have two examples of meteorites which formed within 20,000 years of each other – yet are significantly different. What could have caused the abundance of Al-26 and caused fast formation?

“The general picture we adopt here is that a certain amount of Al-26 is injected in the nascent solar nebula and then gets incorporated into the earliest formed CAIs as soon as the temperature drops below the condensation temperature of CAI minerals. Therefore, the CAIs found in chondrites represent the first known solid objects that crystalized within our Solar System and can be used as an anchor point to determine the formation time-scale of our Solar System.” explains Gritschneder. “The extremely small time-span together with the highly homogeneous mixing of isotopes poses a severe challenge for theoretical models on the formation of our Solar System. Various theoretical scenarios for the formation of the Solar System have been discussed. Shortly after the discovery of SLRs, it was proposed that they were injected by a nearby massive star. This can happen either via a supernova explosion or by the strong winds of a Wolf-Rayet star.”

While these two theories are great, only one problem remains… Distinguishing the difference between the two events. So Matthias Gritschneder of Peking University in Beijing and his colleagues set to work designing a computer simulation. Biased towards the supernova event, the model demonstrates what happens when a shockwave encounters a molecular cloud. The results are an appropriate proportion of Al-26 – and a resultant solar system formation.

“After discussing various scenarios including X-winds, AGB stars and Wolf-Rayet stars, we come to the conclusion that triggering the collapse of a cold cloud core by a nearby supernova is the most promising scenario. We then narrow down the vast parameter space by considering the pre-explosion survivability of such a clump as well as the cross-section necessary for sufficient enrichment.” says Gritschneder. “We employ numerical simulations to address the mixing of the radioactively enriched SN gas with the pre-existing gas and the forced collapse within 20 kyr. We show that a cold clump at a distance of 5 pc can be sufficiently enriched in Al-26 and triggered into collapse fast enough – within 18 kyr after encountering the supernova shock – for a range of different metallicities and progenitor masses, even if the enriched material is assumed to be distributed homogeneously in the entire supernova bubble. In summary, we show that the triggered collapse and formation of the Solar System as well as the required enrichment with radioactive 26Al are possible in this scenario.”

While there are still other isotope ratios yet to be explained and further modeling done, it’s a step toward the future understanding of how solar systems form.

Original Story Source: MIT Technology Review News Release. For Further Reading: The Supernova Triggered Formation And Enrichment Of Our Solar System.

October 25, 2011December 24, 2015 by Nancy Atkinson

Space Telescopes Provide New Look at 2,000 Year Old Supernova

This image combines data from four different space telescopes to create a multi-wavelength view of all that remains of the oldest documented example of a supernova, called RCW 86.

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What caused a huge explosion nearly 2,000 years ago, seen by early Chinese astronomers? Scientists have long known that a “guest star” that had mysteriously appeared in the sky and stayed for about 8 months in the year 185 was the first documented supernova. But now the combined efforts of four space observatories have provided insight into this stellar explosion and why it was so huge – and why its shattered remains — the object known as RCW 86 – is now spread out to great distances.

“This supernova remnant got really big, really fast,” said Brian Williams, an astronomer at North Carolina State University in Raleigh. “It’s two to three times bigger than we would expect for a supernova that was witnessed exploding nearly 2,000 years ago. Now, we’ve been able to finally pinpoint the cause.”

By studying new infrared observations from the Spitzer Space Telescope and data from the Wide-field Infrared Survey Explorer, and previous data from NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton Observatory, astronomers were able to determine that the ancient supernova was a Type Ia supernova. And doing some “forensics” on the stellar remains, the astronomers could piece together that prior to exploding, winds from the white dwarf cleared out a huge “cavity,” a region of very low-density surrounding the system. The explosion into this cavity was able to expand much faster than it otherwise would have. The ejected material would have traveled into the cavity, unimpeded by gas and dust and spread out quickly.

This is the first time that astronomers have been able to deduce that this type of cavity was created, and scientists say the results may have significant implications for theories of white-dwarf binary systems and Type Ia supernovae.

At about 85 light-years in diameter, RCW occupies a region of the sky that is slightly larger than the full moon. It lies in the southern constellation of Circinus.

Source: JPL

October 14, 2011April 26, 2016 by Jon Voisey

Missing Black Holes

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As astronomers began working out how stars die, they expected that the mass of remnants, whether white dwarfs, neutron stars, or black holes, should be essentially continuous. In other words, there should be a smooth distribution of remnant masses from a fraction of a solar mass, up to nearly 100 times the mass of the sun. Yet observations have shown a distinct lack of objects at the borderline of neutron stars and black holes weighing 2-5 solar masses. So where have they all gone and what might this imply about the explosions that create such objects?

The gap was first noted in 1998 and was originally attributed to a lack of observations of black holes at the time. But in the past 13 years, the gap has held up.

In an attempt to explain this, a new study has been conducted by a team of astronomers led by Krzystof Belczynski at Warsaw University. Following the recent observations, the team assumed the paucity was not caused by a lack of observations or selection effect, but rather, there simply weren’t many objects in this mass range.

Instead, the team looked at the engines of supernovae that would create such objects. Stars less than ~20 solar masses are expected to explode into supernovae, leaving behind neutron stars, while ones greater than 40 solar masses should collapse directly into black holes with little to no fanfare. Stars between these ranges were expected to fill this gap of 2-5 solar mass remnants.

The new study proposes that the gap is created by a fickle switch in the supernova explosion process. In general, supernovae occur when the cores are filled with iron which can no longer create energy through fusion. When this happens, the pressure supporting the star’s mass disappears and the outer layers collapse onto the immensely dense core. This creates a shockwave which is reflected by the core and rushes outwards, slamming into more collapsing material and creates a stalemate, where the outwards pressure balances the infalling material. For the supernova to proceed, that outwards shockwave needs an extra boost.

While astronomers disagree on exactly what might cause this revitalization, some suggest that it is generated as the core, superheated to hundreds of billions of degrees, emits neutrinos. Under normal densities, these particles travel right past most matter, but in the superdense regions inside the supernova, many are captured, reheating the material and driving the shockwave back out to create the event we observe as a supernova.

Regardless of what causes it, the team suggests that this point is critical for the final mass of the object. If it explodes, much of the mass of the progenitor will be lost, pushing it towards a neutron star. If it fails to push outwards, the material collapses and enters the event horizon, piling on mass and driving the final mass upwards. It’s an all or nothing moment.

And moment is a good description of how fast this occurs. At most, astronomers suggest that this interplay between the outwards shock and the inwards collapse takes a single second. Other models place the timescale at a tenth of a second. The new study notes that the more quickly the decision takes place, the more pronounced the gap is in the resulting objects. As such, the fact that the gap exists may be taken as evidence for this being a split second decision.

October 7, 2011December 24, 2015 by Tammy Plotner

The Crab Gets Cooked With Gamma Rays

X-ray: NASA/CXC/ASU/J. Hester et al.; Optical: NASA/HST/ASU/J. Hester et al.; Radio: NRAO/AUI/NSF Image of the Crab Nebula combines visible light (green) and radio waves (red) emitted by the remnants of a cataclysmic supernova explosion in the year 1054. and the x-ray nebula (blue) created inside the optical nebula by a pulsar (the collapsed core of the massive star destroyed in the explosion). The pulsar, which is the size of a small city, was discovered only in 1969. The optical data are from the Hubble Space Telescope, and the radio emission from the National Radio Astronomy Observatory, and the X-ray data from the Chandra Observatory.

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It’s one of the most famous sights in the night sky… and 957 years ago it was bright enough to be seen during the day. This supernova event was one of the most spectacular of its kind and it still delights, amazes and even surprises astronomers to this day. Think there’s nothing new to know about M1? Then think again…

An international collaboration of astrophysicists, including a group from the Department of Physics in Arts & Sciences at Washington University in St. Louis, has detected pulsed gamma rays coming from the heart of the “Crab”. Apparently the central neutron star is putting off energies that can’t quite be explained. These pulses between range 100 and 400 billion electronvolts (Gigaelectronvolts, or GeV), far higher than 25 GeV, the most energetic radiation recorded. To give you an example, a 400 GeV photon is almost a trillion times more energetic than a light photon.

“This is the first time very-high-energy gamma rays have been detected from a pulsar – a rapidly spinning neutron star about the size of the city of Ames but with a mass greater than that of the Sun,” said Frank Krennrich, an Iowa State professor of physics and astronomy and a co-author of the paper.

We can thank the Arizona based Very Energetic Radiation Imaging Telescope Array System (VERITAS) array of four 12-meter Cherenkov telescopes covered in 350 mirrors for the findings. It is continually monitoring Earth’s atmosphere for the fleeting signals of gamma-ray radiation. However, findings like these on such a well-known object is nearly unprecedented.

“We presented the results at a conference and the entire community was stunned,” says Henric Krawczynski, PhD, professor of physics at Washington University. The WUSTL group led by James H. Buckley, PhD, professor of physics, and Krawczynski is one of six founding members of the VERITAS consortium.

crabpulsar — An X-ray image of the Crab Nebula and pulsar. Image by the Chandra X-ray Observatory, NASA/CXC/SAO/F. Seward.

We know the Crab’s story and how its pulsar sweeps around like a lighthouse… But Krennrich said such high energies can’t be explained by the current understanding of pulsars. Not even curvature radiation can be at the root of these gamma-ray emissions.

“The pulsar in the center of the nebula had been seen in radio, optical, X-ray and soft gamma-ray wavelengths,” says Matthias Beilicke, PhD, research assistant professor of physics at Washington University. “But we didn’t think it was radiating pulsed emissions above 100 GeV. VERITAS can observe gamma-rays between100 GeV and 30 trillion electronvolts (Teraelectronvolts or TeV).”

Just enough to cook one crab… well done!

Original Story Source: Iowa State University News Release. For Further Reading: Washington University in St. Louis News Release.

October 6, 2011December 24, 2015 by Tammy Plotner

Uncloaking Type Ia Supernovae

This three-color composite of a portion of the Subaru Deep Field shows mostly galaxies with a few stars. The inset shows one of the 10 most distant and ancient Type Ia supernovae discovered by the American, Israeli and Japanese team.

Type Ia supernovae… Right now they are one of the most studied – and most mysterious – of all stellar phenomenon. Their origins are sheer conjecture, but explaining them is only half the story. Taking a look back into almost the very beginnings of our Universe is what it’s all about and a team of Japanese, Israeli, and U.S. astronomers have employed the Subaru Telescope to give us the most up-to-date information on these elementally explosive cosmic players.

By understanding the energy release of a Type Ia supernova, astronomers have been able to measure unfathomable distances and speculate on dark energy expansion. It was popular opinion that what caused them was a white dwarf star pulling in so much matter from a companion that it finally exploded, but new research points in a different direction. According to the latest buzz, it may very well be the merging of two white dwarfs.

“The nature of these events themselves is poorly understood, and there is a fierce debate about how these explosions ignite,” said Dovi Poznanski, one of the main authors of the paper and a post-doctoral fellow at the University of California, Berkeley, and Lawrence Berkeley National Laboratory.

“The main goal of this survey was to measure the statistics of a large population of supernovae at a very early time, to get a look at the possible star systems,” he said. “Two white dwarfs merging can explain well what we are seeing.”

Can you imagine the power behind this theory? The Type Ia unleashed a thermonuclear reaction so strong that it is able to be traced back to nearly the beginning of expansion after the Big Bang. By employing the Subaru telescope and its prime focus camera (Suprime-Cam), the team was able to focus their attention four times on a small area named the Subaru Deep Field. In their imaging they caught 150,000 individual galaxies containing a total of 40 Type Ia supernova events. One of the most incredible parts of these findings is that these events happened about five times more frequently in the early Universe. But no worries… Even though the mechanics behind them are still poorly understood, they still serve as “cosmic distance markers”.

“As long as Type Ias explode in the same way, no matter what their origin, their intrinsic brightnesses should be the same, and the distance calibrations would remain unchanged.” says Alex Filippenko, UC Berkeley professor of astronomy.

Original Story Source: University of Berkeley News Release. For Further Reading: National Astronomical Observatory of Japan: Subaru News Release.

September 26, 2011December 24, 2015 by Jon Voisey

A Magnified Supernova

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Supernovae are among astronomers most important tools for exploring the history of the universe. Their frequency allows us to examine how active star formation was, how heavy elements have developed, and the distance to galaxies across vast distances. Yet even these titanic explosions are only so bright, and there’s an effective limit on how far we can detect them with the current generation of telescopes. However, this limit can be extended with a little help from gravity.

One of the consequences of Einstein’s theory of general relativity is that massive objects can distort space, allowing them to act as a lens. While first postulated in 1924, and proposed for galaxies by Fritz Zwicky in 1937, the effect wasn’t observed until 1979 when a distant quasar, an energetic core of a distant galaxy, was split in two by the gravitational disturbances of an intervening cluster of galaxies.

While lensing can distort images, it also provides the possibility that it may magnify a distant object, increasing the amount of light we receive. This would allow astronomers to probe even more distant regions with supernovae as their tool. But in doing so, astronomers must look for these events in a different manner than most supernova searches. These searches are generally limited to the visible portion of the spectrum, the portion we see with our eyes, but due to the expansion of the universe, the light from these objects is stretched into the near-infrared portion of the spectrum where few surveys to search for supernovae exist.

But one team, led by Rahman Amanullah at Stockholm University in Sweden, has conducted a survey using the Very Large Telescope array in Chile, to search for supernovae lensed by the massive galaxy cluster Abell 1689. This cluster is well known as a source of gravitationally lensed objects, making visible some galaxies that formed shortly after the Big Bang.

In 2009, the team discovered one supernova that was magnified by this cluster that originated 5-6 billion lightyears away. In a new paper, the team reveals details about an even more distant supernova, nearly 10 billion lightyears distant. This event was magnified by a factor of 4 from the effects of the foreground cluster. From the distribution of energy in different portions of the spectrum, the team concludes that the supernova was an implosion of a massive star leading to a core-collapse type of supernova. The distance of this event puts it among the most distant supernovae yet observed. Others at this distance have required extensive time using the Hubble telescope or other large telescopes.

September 26, 2011December 24, 2015 by Jon Voisey

Homeless Supernovae

NGC 1058. Image credit: Bob Ferguson and Richard Desruisseau/Adam Block/NOAO/AURA/NSF

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In a post earlier this month, we looked at a team of astronomers searching for stars that were on ejected from their birthplaces in clusters. These stars could receive the needed kick from a gravitational swing by the core of the cluster to achieve a velocity of a few tens of km/sec. But a similar mechanism can function in the cores of galaxies giving stars a speed of roughly 1,000 km/sec, enough to leave their parent galaxies. a new study asks whether we have ever witnessed any of these stellar cast offs explode as supernovae.

The team, led by Peter-Christian Zinn at Ruhr University in Bochum, Germany, searched through roughly 6,000 supernovae listed in the Sternbarg Astronomical Institute Supernova Catalog, for which no host galaxy was apparent, yet weren’t too distant from any known galaxy. The latter criteria was added because, even at the high velocities, stars still couldn’t get too far before they reached the end of their fuses. The team imposed a rough inner cut off of around 10 kiloparsecs (roughly 1/3 of the width of the disk of the Milky Way). They expected stars should be at least this distance from the cores of the parent galaxy.

The initial list contained five candidate stars, dating back as far as 1969. The first step the team used to determine if the supernova was truly in a galaxy or not, was to take long exposure images of the immediate area, to draw out potential low surface brightness hosts. The team also used archival data in the far ultraviolet as well as the x-ray spectrum to determine whether or not the nearby galaxies from which the supernovae could potentially be ejected had an extended disk, invisible in the visible portion of the spectrum that would have allowed the progenitor star to form in the outskirts of the galaxy. These wavelengths are tracers of ongoing star formation which are sites in which high mass stars that would lead to core-collapse supernovae, would likely be found.

The oldest candidate, SN 1969L, was located near the flocculent spiral NGC 1058. While the deep exposures did not show a host galaxy, the x-ray and UV images both showed some extended structure of the parent galaxy at the distance of the supernova. This led to the conclusion that this supernova, while far removed from its host galaxy, was still gravitationally tied to it.

With the second candidate, SN 1970L, the team again failed to find any faint host galaxy. However, the supernova was situated between two galaxies, NGC 2968 and a faint elliptical, NGC 2970. A 1994 study had revealed a faint bridge of matter connecting the two, implying that they had had an interaction in the past. This interaction would likely have pulled off gas and stars, of which SN 1970L could have been one.

SN 1997C was the third candidate and also lacked a discernible host galaxy, even with long exposures. This one also did not have an indication of an extended disk of which the supernova could have been part. Given the characteristics of the supernova, the team estimated that it had an original mass of 15 times that of the Sun. Given its projected distance and the lifetime of such stars, the team noted that this would correspond to a velocity of some 3,000 km/sec, which is several times the speed of the highest confirmed hypervelocity star. As such, the team expected that this star would have to be ejected in a similar manner to SN 1970L, using an interaction between galaxies. Given that the host galaxy is known to be one in a small cluster and the disk shows some signs of perturbation, they suggested this was likely.

The fourth candidate, SN 2005nc, the team selected because there was no nearby galaxy they could assign as a possible parent. They suggested this was due to an extremely distant host galaxy, too faint to resolve with previous studies. The basis for this assertion was that the supernova came with a gamma ray burst that indicated an origin some 5-6 billion light years distant. Due to the associated GRB, the Hubble telescope swung in to take a look. These archival pictures failed to reveal any objects that could readily be identified as host galaxies leaving the team to presume the host was simply too far away to resolve.

The last candidate was SN 2006bx located near the galaxy UGC 5434. This supernova did not appear to be in a faint background galaxy and did not have hints of being formed in an extended disk. The estimated velocity from the projected distance was ~850 km/sec which placed it in the realm of plausible speeds for stars ejected by gravitational assists from the supermassive black hole at the center of galaxies.

September 20, 2011December 24, 2015 by Ray Sanders

How to See the Brightest Supernova in a Generation

Astrophoto: Supernova PTF11kly in M101 by Rick Johnson — Supernova PTF11kly in M101. Credit: Rick Johnson

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Here at Universe Today, we’ve been providing plenty of coverage on the recent supernova in spiral galaxy M101 (AKA Pinwheel Galaxy). Readers have uploaded their images to our Flickr page and have been asking about the event, weeks after it was detected.

While the supernova has been dimming since its peak brightness, most supernova events brighten quickly, but fade slowly. This supernova is by no means visible with the naked eye, but here’s what you need to know to catch a glimpse of the brightest supernova in the past few decades.

First a short primer on M101: Nicknamed the “Pinwheel Galaxy” for its resemblance to the toy, M101’s distinct spiral arms can be imaged with modest amateur astronomy equipment. M101 is about six megaparsecs ( 1 parsec is just over three and one-quarter light years ) away from our solar system, which is over six times more distant than our closest neighbor, the Andromeda Galaxy. M101 is a galaxy that is much larger than our own galaxy – nearly double the size of the Milky Way.

What made M101 newsworthy as of late was the Type Ia supernova discovered inside the galaxy. Discovered nearly a month ago on August 24th, SN 2011fe (initial designation PTF 11kly) started off at around 17th magnitude and recently peaked around magnitude 10 (magnitude 6-7 is limit of “naked-eye” visibility with dark skies).

Scientists and amateur astronomers alike have scrambled to gather data on SN 2011fe. Some observers have even looked through data collected in late August only to see they captured the supernova without knowing it!

By mid-September, though, SN 2011fe has become too faint for casual observers to see, but experienced amateur astronomers can still see it with telescopes. If you don’t have a good-sized “amateur” telescope, you might consider contacting a local astronomy club to see if they are having a “star party” or observing night in your area. To find an astronomy club, check out NASA’s Night Sky Network.

Viewing M101 and SN 2011fe isn’t terribly challenging, so long as you have a decent view to the North. You can find M101 by using the Big Dipper asterism (Ursa Major for the constellation purists). Look for the last two stars of the Big Dipper’s handle (Mizar and Alkaid). Above the midpoint between the two stars is M101. For those with motorized telescopes, start at Mizar, slew a little to the east and up a little. People who are lucky enough to have a computerized, “Go-To” scope can enter the RA and Dec coordinates of 14:03:05.81 , +54:16:25.4.

This week you’ll want to try viewing M101 in late evenings, otherwise you may find it too close to the horizon and washed out by the waning gibbous Moon. To your eyes, M101 will appear as a fuzzy “smudge” in the eyepiece. If you are at a very dark site and use averted (looking slightly to the side of the object) vision you might see some detail with a 12″ or larger telescope. You can certainly view M101 with a telescope as small as 6″, but you really do want to view M101 with as big of a telescope as possible. Don’t use higher power eyepieces to try and make up for a small telescope. Many galaxies, including M101 are best viewed with mid-to-low power eyepieces.

Below is an image generated by Stellarium. In the image are a few constellations and some guide stars you can use to guide your eyes and telescope to M101.

Clear skies and good luck!

Location of M101 at 9 PM ( 33 Degrees N. ) Image generated with Stellarium

September 9, 2011December 24, 2015 by Tammy Plotner

PTF11kly: Messier 101 Supernova SN 2011fe Update

PTF11kly: Messier 101 Supernova Credit: Joe Brimacombe

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Are you curious about what’s happening with the supernova event in Messier 101? What’s its magnitude and how can you observe it? Then step out here into the back yard with me and let’s discuss some facts.

First off, you’re not going to be able to see the Messier 101 supernova event with your unaided eye. The brightness of celestial objects are categorized by a number that denotes magnitude. A negative number, such as -4 is blazing – like Venus in all its glory. A small number, like 3 is about the average brightness of most of the stars you can see in the urban glow. Higher numbers, like 12, are so faint you’d need a large telescope to see them. And when it comes to just using your eyes, you’ll be lucky to spot a 6 when you’re well dark adapted and in a non-light polluted location.

And right now the brightest the supernova has been so far was two days ago at magnitude 10.

Next up? Right now there’s a light pollution source we simply can’t escape… the Moon. Given absolutely pristine skies and a very, very large telescope you might be able to cut through the normal thin atmospheric haze and catch the supernova. Are you going to see Messier 101? Very doubtful. But here’s where your computerized telescope comes into play. You’ll need to enter the coordinates: RA: 14:03:05.81 , Dec: +54:16:25.4. If you are perfectly polar aligned, this will place the supernova directly in the center of the field of view. Using a light pollution filter will only darken the event as well, so you are best off to use a higher magnification eyepiece to darken the field, but I personally wouldn’t recommend anything stronger than a 10mm unless you’ve got a long focal ratio scope. Now go to the eyepiece and match up star patterns. You’re not going to see the galaxy, but you will see the field stars.

Until the Moon leaves the sky, it’s improbable (but not impossible) that you’ll be able to see SN 2011fe with anything less than around a 12-16″ telescope. Even though your telescope may be rated as reaching a stellar magnitude 13, we simply can’t break the rules of physics. But don’t be discouraged. While it is theorized the supernova event has already reached peak brightness, we just really don’t know, do we? While it will fade in the upcoming days, so will the early evening moonlight. Darker skies mean the ability to catch the supernova with smaller instruments, so be ready when opportunity knocks!

Addendum:

“Skywatchers in the northern hemisphere are being treated to a rare, bright supernova in a nearby galaxy, and observers worldwide have the opportunity to contribute scientific data to our study of this object. This supernova, named SN 2011fe, exploded in the nearby spiral galaxy Messier 101 some time on August 24, 2011, and quickly became bright enough for backyard astronomers to observe with modest-sized telescopes. The supernova belongs to the class of objects called “Type Ia supernovae” that are caused by the explosion of a white dwarf in a binary star system. When these stars explode, they briefly give off as much energy as all of the other stars in the galaxy combined, making them visible from millions and billions of light-years away. SN 2011fe is special because it exploded in a galaxy that’s “only” 20 million light-years from Earth — very close compared to the size of the Universe. This gives astronomers a great opportunity to understand better what Type Ia supernovae are like and how they change over time. This is where backyard astronomers can help.

The American Association of Variable Star Observers, an organization dedicated to collaborative science by amateur and professional astronomers, is one of many groups observing this supernova, and we’ve provided the community with tools to help them make observations and share them with the broader astronomical community. The AAVSO has published star charts and other materials that enable anyone with a modest sized telescope (6 inches/15 centimeters or larger) to measure the brightness of this supernova with their own eyes. We also give observers the ability to report their observations in a way that’s useful for researchers studying this supernova. Observing the supernova is not only fun, but anyone can help astronomers do real science. The AAVSO invites all members of the public, worldwide, to help us to record this special event and to help astronomers improve our understanding of this important phenomenon.”

Learn more about how to observe this supernova and contribute observations to the AAVSO: http://www.aavso.org/sn-2011fe