The timing couldn’t be better. A new supernova, named PTF11kly, which was discovered on August. 24, 2011 is continuing to brighten and should be visible to backyard astronomers this weekend using just a pair of binoculars. It’s not quite naked-eye material but this is an exciting opportunity for amateurs (as well as the pros!) to view a supernova first-hand. Of course, if your backyard is full of light, the best option is to go to an area with darker skies, and you’ll be able to see it much better. Astronomers say PTF11kly will likely continue to shine for some time, and be at its brightest on about Sept. 9, 2011.
In this video Peter Nugent, an astrophysicist from Lawrence Berkeley National Labs explains just how to find this star that exploded about 21 million light years away.
Supernova PTF11kly in M101 on August 24, 2011. Credit: BJ Fulton, LCOGT.
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Literally an event of stellar proportions, a new Type Ia supernova has been identified in a spiral galaxy 25 million light-years away! Spotted by Caltech’s Palomar Transit Factory project, this supernova, categorized as PTF11kly, is located 58″.6 west and 270″.7 south of the center of M101. It was first seen yesterday, August 24, 2011.
According to AAVSO Special Notice #250 P. Nugent et al. reported in Astronomical Telegram #3581 that a possible Type-Ia supernova has been discovered by the Palomar Transient Factory shortly after eruption in the galaxy M101 and has been designated “PTF11kly”. The object is currently at a magnitude of 17.2, but may well rise by several magnitudes. The object is well placed within M101 for good photometry, and observations of this potential bright SNIa are strongly encouraged.
There are currently no comparison stars available in VSP for this field; please indicate clearly the comparison stars that you use for photometry when reporting observations to AAVSO. Please retain your images and/or photometry for recalibration when comparison star magnitudes are available.
Need coordinates? The (J2000) coordinates reported for the object are RA: 14:03:05.81 , Dec: +54:16:25.4. Messier 101 is located in the constellation of Ursa Major at RA: 14h 03m 12.6s Dec: +54 20′ 57″
Charts for PTF11kly may be plotted with AAVSO VSP. You should select the DSS option when plotting, as the galaxy will not appear on standard charts. This object has been assigned the name “PTF11kly” for use with AAVSO VSP and WebObs; please use this name when reporting observations until it is conclusively classified as a supernova and a proper SN name is assigned.
Image of M101 and PTF11kly by Joseph Brimacombe.
Type Ia supernovae are the result of a binary pair of mismatched stars, the smaller, denser one feeding on material drawn off its larger companion until it can no longer take in any more material. It then explodes in a catastrophic event that outshines the brightness of its entire galaxy! Astronomers believe that Type Ia supernovae occur in pretty much the same fashion every time and thus, being visible across vast distances, have become invaluable benchmarks for measuring distance in the Universe and gauging its rate of expansion.
The fact that this supernova was spotted literally within a day of its occurrence – visibly speaking, of course, since M101 is 25 million light-years away and thus 25 million years in our past – will be extremely handy for astronomers who will have the opportunity to study the event from beginning to end and learn more about some of the less-understood processes involved in Type Ia events.
“We caught this supernova earlier than we’ve ever discovered a supernova of this type. On Tuesday, it wasn’t there. Then, on Wednesday, boom! There it was – caught within hours of the explosion. As soon as I saw the discovery image I knew we were onto something big.”
– Andy Howell, staff scientist at Las Cumbres Observatory Global Telescope
It’s a big Universe and there are a lot of stars and therefore a lot of supernovae, but getting a chance to study one occurring so recently in a galaxy so relatively close to our own is something that is getting many astronomers very excited.
So, get those CCD camera out and best of luck!
Keep up with the latest news on PTF11kly on the rochesterastronomy.org site, and check out Phil Plait’s informative article on his BadAstronomy blog. Also read the press release from the University of California here.
Tammy Plotner also contributed to this article.
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Jason Major is a graphic designer, photo enthusiast and space blogger. Visit his website Lights in the Dark and follow him on Twitter @JPMajor and on Facebook for more astronomy news and images!
A new supernova (exploding star) has been discovered in the famous Whirlpool Galaxy, M51.
M51, The Whirlpool galaxy is a galaxy found in the constellation of Canes Venatici, very near the star Alkaid in the handle of the saucepan asterism of the big dipper. Easily found with binoculars or a small telescope.
The discovery was made on June 2nd by French astronomers and the supernova is reported to be around magnitude 14. More information (In French) can be found here or translated version here.
Image by BBC Sky at Night Presenter Pete Lawrence
The supernova will be quite tricky to spot visually and you may need a good sized dobsonian or similar telescope to spot it, but it will be a easy target for those interested in astro imaging.
The whirlpool galaxy was the first galaxy discovered with a spiral structure and is one of the most recognisable and famous objects in the sky.
A before and after animation of Supernova 2010lt. Credit: Dave Lane
A ten-year old girl from Canada has discovered a supernova, making her the youngest person ever to find a stellar explosion. The Royal Astronomical Society of Canada announced the discovery by Kathryn Aurora Gray of Fredericton, New Brunswick, (wonderful middle name!) who was assisted by astronomers Paul Gray and David Lane. Supernova 2010lt is a magnitude 17 supernova in galaxy UGC 3378 in the constellation of Camelopardalis, as reported on IAU Electronic Telegram 2618. The galaxy was imaged on New Year’s Eve 2010, and the supernova was discovered on January 2, 2011 by Kathryn and her father Paul.
NGC 1058. Image credit: Bob Ferguson and Richard Desruisseau/Adam Block/NOAO/AURA/NSF
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Up there in the sky! It’s a supernova! It’s a Luminous Blue Variable eruption! It’s…. well, we’re not sure….
In July of 1961, a star in the spiral galaxy NGC 1058 blew up, but in a very odd fashion. The time to reach its peak brightness was several months as well as a slow decline including a three year plateau. Narrow spectral lines revealed a slow expansion velocity of 2,000 km sec-1. Some proposed it was an unusual supernova. Others claimed it was an especially energetic eruption of a Luminous Blue Variable (LBV) star like Eta Carinae. The infamous Fritz Zwicky called it a “Type V Supernova” which meant a supernova in name only, but could be anything as it was simply an “impostor”. For nearly 50 years, astronomers have been trying to sort out what this supernova impostor truly was.
One front on which much of the effort has focused is on the nature of the star before the explosion. The host galaxy is a beautiful face on spiral galaxy and was a tempting target for many observations well before the eruption. This has allowed astronomers to use archival images to determine properties of the parent star. And what a whopper it was. The star had an absolute magnitude near -12! Even Eta Carinae, one of the most massive stars currently known, only has an absolute magnitude of around -5.5. This extreme luminosity led astronomers towards early estimates for its mass to be as much as a staggering 2,000 M☉! While this is certainly incorrect, it still reveals just how massive SN 1961V’s progenitor truly was. Most estimates now put it in the range of 100 – 200 M☉.
A key difference between a supernova and an eruption is the remnant. In the case of a supernova, it is expected that the result would be a neutron star or black hole. If the object were an eruption, even a large one, the star would remain intact. In this vein, many astronomers have also attempted to inspect the remnant. However, due to the shell of gas and dust created in either scenario, imaging the objects has proven to be a challenge. While prior to the event, the culprit stuck out like a sore thumb, the remnant is lost in a haze of other stars.
Numerous telescopes have been aimed at the region to attempt to ferret out the leftovers including the powerful Hubble, but many attempts have remained inconclusive. Recently, the Spitzer Space telescope was employed to study the region, and although not intended for studying individual stars, its infrared vision can allow it to pierce the veil of dust and potentially find the source responsible. If there is still an intense IR source, it would mean the star survived, and the supernova truly was an impostor.
This attempt at identification was recently undertaken by a team of astronomers from Ohio State University, led by Christopher Kochanek. Upon inspection, the team was unable to conclusively identify a source with sufficient intensity as to be a survivor of the SN 1961V event. As such, the team concluded that the event Zwicky defined as a “supernova impostor” was a “‘supernova impostor’ impostor”.
The team compared it to another recent supernova, SN 2005gl, which also had a supermassive progenitor and was observed prior to detonation. Previous studies of this supernova suggested that, just prior to the explosion itself, the star underwent a heavy phase of mass loss. If a similar scenario occurred in 1961V, it could explain the unusual expansion velocity. During this time, the star may quake ferociously, imitating LBV eruptions which could explain the pre-nova plateau.
While this comparison relies on a single strongly similar case, it underscores the need “that studies of SN progenitors should evolve from simple attempts to obtain a single snapshot of the star to monitoring their behavior over their final years.” Hopefully, future studies and observations will provide better theoretical simulations and the numerous large surveys will provide sufficient data on stars prior to eruption to better constrain the behavior of these monsters.
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A supernova is the explosion of a star. In an instant, a star with many times the mass of our own Sun can detonate with the energy of a billion suns. And then, within just a few hours or days, it dims down again. Some explode into a spray of gas and dust, while others become exotic objects like neutron stars or black holes.
Astronomers have classified supernovae into two broad classifications: Type I and Type II. Type I supernovae occur in binary systems, where one star pulls off mass from a second star until it reaches a certain amount of mass. This causes it to explode as a supernova. Type II supernovae are the explosions of massive stars which have reached the end of their lives.
All of the elements heavier than iron were created in supernova explosions. As a massive star runs out of hydrogen fuel, it starts to fuse together heavier and heavier elements. Helium into carbon and oxygen. And then oxygen into heavier elements. It goes up the periodic table this way, fusing heavier elements until it reaches iron. Once a star reaches iron, it’s no longer able to extract energy from the fusion process. The core collapses down into a black hole, and the material around it is fused together into the elements heavier than iron. If you’re wearing any gold jewelry, that was created in a supernova.
In 1054 Chinese astronomers saw a supernova explosion that was so bright it was visible in the middle of the day. The explosion of gas and dust is now visible as the Crab Nebula (that’s the picture at the top of this article). The most recent powerful supernova explosion occurred in 1987, when a star exploded in the Large Magellanic Cloud.
Astronomers use Type I supernovae to judge distances in the Universe. This is because they always explode with approximately the same amount of energy. When a white dwarf star collected approximately 1.4 times the mass of the Sun, it can’t support its mass and collapses. This amount is called the Chandrasekhar Limit. When an astronomer sees a Type I supernova, they know how bright it is, and so they can measure how far away it is.
A Chandra X-ray Observatory image of the supernova remnant Cassiopeia A. Credit: NASA/CXC
Supernova remnant Cassiopeia A (Cas A) has always been an enigma. While the explosion that created this supernova was obviously a powerful event, the visual brightness of the outburst that occurred over 300 years ago was much less than a normal supernova, — and in fact, was overlooked in the 1600’s — and astronomers don’t know why. Another mystery is whether the explosion that produced Cas A left behind a neutron star, black hole, or nothing at all. But in 1999, astronomers discovered an unknown bright object at the core of Cas A. Now, new observations with the Chandra X-Ray Observatory show this object is a neutron star. But the enigmas don’t end there: this neutron star has a carbon atmosphere. This is the first time this type of atmosphere has been detected around such a small, dense object.
A Chandra X-ray Observatory image of the supernova remnant Cassiopeia A, with an artist's impression of the neutron star at the center of the remnant. The discovery of a carbon atmosphere on this neutron star resolves a ten-year old mystery surrounding this object. Credit: Chandra image: NASA/CXC/Southampton/W.Ho; illustration: NASA/CXC/M.Weiss
The object at the core is very small – only about 20 km wide, which was key to identifying it as a neutron star, said Craig Heinke from the University of Alberta. Heinke is co-author with Wynn Ho of the University of Southampton, UK on a paper which appears in the Nov. 5 edition of Nature.
“The only two kinds of stars that we know of that are this small are neutron stars and black holes,” Heinke told Universe Today. “We can rule out that this is a black hole, because no light can escape from black holes, so any X-rays we see from black holes are actually from material falling down into the black hole. Such X-rays would be highly variable, since you never see the same material twice, but we don’t see any fluctuations in the brightness of this object.”
Heinke said the Chandra X-ray Observatory is the only telescope that has sharp enough vision to observe this object inside such a bright supernova remnant.
But the most unusual aspect of this neutron star is its carbon atmosphere. Neutron stars are mostly made of neutrons, but they have a thin layer of normal matter on the surface, including a thin–10 cm–very hot atmosphere. Previously studied neutron stars all have hydrogen atmospheres, which is expected, as the intense gravity of the neutron star stratifies the atmosphere, putting the lightest element, hydrogen, on top.
But not so with this object in Cas A.
“We were able to produce models for the X-ray radiation of a neutron star with several different possible atmospheres,” Heinke said in an email interview. “Only the carbon atmosphere can explain all the data we see, so we are pretty sure this neutron star has a carbon atmosphere, the first time we’ve seen a different atmosphere on a neutron star.” An artist's impression of the neutron star in Cas A showing the tiny extent of the carbon atmosphere. The Earth's atmosphere is shown at the same scale as the neutron star. Credit: NASA/CXC/M.Weiss An artist’s impression of the neutron star in Cas A showing the tiny extent of the carbon atmosphere. The Earth’s atmosphere is shown at the same scale as the neutron star. Credit: NASA/CXC/M.Weiss
So how does Heinke and his team explain the lack of hydrogen and helium on this neutron star? Think of Cas A as being a baby.
“We think we understand that as due to the really young age of this object–we see it at the tender age of only 330 years old, compared to other neutron stars that are thousands of years old,” he said. “During the supernova explosion that created this neutron star (as the core of the star collapses down to a city-sized object, with an incredibly high density higher than atomic nuclei), the neutron star was heated to high temperatures, up to a billion degrees. It’s now cooled down to a few million degrees, but we think its high temperatures were sufficient to produce nuclear fusion on the neutron star surface, fusing the hydrogen and helium to carbon.”
Because of this discovery, researchers now have access to the complete life cycle of a supernova, and will learn more about the role exploding stars play in the makeup of the universe. For example, most minerals found on Earth are the products of supernovae.
“This discovery helps us understand how neutron stars are born in violent supernova explosions,” said Heinke.
The Crab Nebula; at its core is a long dead star. Did early massive stars die in supernova explosions like this? Image credit: NASA, ESA, J. Hester and A. Loll (Arizona State University)
The Crab Nebula, or M1 (the first object in Messier’s famous catalog), is a supernova remnant and pulsar wind nebula. The name – Crab Nebula – is due to the Earl of Rosse, who thought it looked like a crab; it’s not in the constellation Cancer (the Crab), rather Taurus (the Bull).
The supernova which gave rise to the Crab Nebula was seen widely here on Earth in 1054 (and so it’s called SN 1054 by astronomers); it is perhaps the most famous of the historical supernovae. It is certainly one of the brightest (estimated to be –7 at peak), partly because it is so close (only 6,300 light-years away), and partly because it’s not hidden by dust clouds. The expansion of the nebula – as in seen-to-be-getting-bigger, rather than the-gas-is-moving-very-fast – was first confirmed in 1930.
As it was a core collapse supernova (a massive star which ran out of fuel), it left behind a neutron star; by chance, we are in line with its ‘lighthouse beam’, so we see it as a pulsar (all young neutron stars are pulsars, but not all of them have beams which point to us in one part of the cycle). It’s a pretty fast pulsar; the neutron star rotates once every 33 milliseconds. Because it’s so young and so close, the Crab Nebula pulsar was the first to be detected in the visual waveband, and also in x-rays and gamma rays. Being the source of the tremendous output of energy, from both the pulsar wind nebula and the pulsar itself, and as energy is conserved, the pulsar is slowing down, at a rate of 15 microseconds per year.
The inner part of the Crab Nebula, the pulsar wind nebula, contains lots of really hot (‘relativistic’) electrons spiraling around magnetic fields; this creates the eerie blue glow … synchrotron radiation. This makes the Crab Nebula one of the brightest objects in the x-ray and gamma ray region of the electromagnetic spectrum, and as it is a relatively steady source (unlike most high energy objects) it has given its name to a new astronomical unit, the Crab. For example, a new x-ray source may be 2 mCrab (milli-Crab), meaning 0.002 times as strong an x-ray source as the Crab Nebula.
This SEDS page has a lot more information on the Crab Nebula, both historical and contemporary.
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The first supernova in 1987 (that’s what the “A” means) was the brightest supernova in several centuries (and the first observed since the invention of the telescope), the first (and so far only) one to be detected by its neutrino emissions, and the only one in the LMC (Large Magellanic Cloud) observed directly.
Ian Shelton, then a research assistant with the University of Toronto, working at the university’s Las Campanas station, and Oscar Duhalde, a telescope operator at Las Campanas Observatory, were the first to spot it, on the night of 23/24 February 1987 (around midnight actually); over the next 24 hours several others also independently discovered it.
The IAU’s CBAT went wild! That’s the International Astronomical Union’s Central Bureau for Astronomical Telegrams, the clearing house for astronomers for breaking news. You can read the historic IAUC (C for Circular) 4416 here.
Once the discovery of SN 1987A became known, physicists examined the records from various neutrino detectors … and found three, independent, clear signals of a burst of neutrinos several hours before visual discovery, just as predicted by astrophysical models! Champagne flowed.
Not long afterwards, the star which blew up so spectacularly – the progenitor – was identified as Sanduleak -69° 202a, a blue supergiant. This was not what was expected for a Type II supernova (the models said red supergiants), but an explanation was quickly found (Sanduleak -69° 202a had a lower-than-modelled oxygen abundance, affecting the transparency of its outer envelope).
The iconic Hubble Space Telescope image (above) of SN 1987A shows the inner ring, where the debris from the explosion is colliding with matter expelled from the progenitor about 20,000 years ago; more from the Hubble here.
AAVSO (American Association of Variable Star Observers) has a nice write-up of SN 1987A.
Subrahmanyan Chandrasekhar (credit: University of Chicago Press)
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When a human puts on too much weight, there is an increased risk of heart attack; when a white dwarf star puts on too much weight (i.e. adds mass), there is the mother of all fatal heart attacks, a supernova explosion. The greatest mass a white dwarf star can have before it goes supernova is called the Chandrasekhar limit, after astrophysicist Subrahmanyan Chandrasekhar, who worked it out in the 1930s. Its value is approx 1.4 sols, or 1.4 times the mass of our Sun (the exact value depends somewhat on the white dwarf’s composition how fast it’s spinning, etc).
White dwarfs are the end of the road for most stars; once they have used up all their available hydrogen ‘fuel’, low mass stars shed their outermost shells to form planetary nebulae, leaving a high density core of carbon, oxygen, and nitrogen (that’s a summary, it’s actually a bit more complicated). The star can’t collapse further because of electron degeneracy pressure, a quantum effect that comes from the fact that electrons are fermions (technically, only two fermions can occupy a given energy state, one spin up and one spin down).
So what happens in the core of a massive star, one whose core weighs in at more than 1.4 sols? As long as the star is still ‘burning’ nuclear fuel – helium, then carbon etc, then neon, then … – the core will not collapse because it is very hot (electron degeneracy pressure won’t hold it up ’cause it’s too massive). But once the core gets to iron, no more burning is possible, and the core will collapse, spectacularly, producing a core collapse supernova.
There is a way a white dwarf can go out with a bang rather than a whimper; by getting a little help from a friend. If the white dwarf has a close binary companion, and if that companion is a giant star, some of the hydrogen in its outer shell may end up on the white dwarf’s surface (there are several ways this can happen). The white dwarf thus adds mass, and every so often the thin hydrogen envelope blows up, and we see a nova. One day, though, the extra mass may put it over the limit, the Chandrasekhar limit … the temperature in its center gets high enough that the carbon ‘ignites’, the ‘flame’ spreads throughout the star, and it becomes a special kind of supernova, a Ia supernova.
