Posted on by Jon Voisey

Homeless Supernovae

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

Posted on 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!

Supernova PTF11kly / SN 2011fe in Messier 101. Credit: Joe Brimacombe

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
Posted on 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

Posted on by Tammy Plotner

Cosmic Collisions – The Astronomical Alchemist

New theoretical models now confirm that it could be forged in the merger events of two neutron stars. Image: Natural gold nuggets from California and Australia; Natural History Museum, London

[/caption]Here on Earth the practice of alchemy once had its era – trying to turn lead into gold. However, somewhere out there in the universal scheme of things, that process is a reality and not a myth. Instead of a scientist desperately looking for a sublime formula, it just might happen when neutron stars merge in a violent collision.

We’re all aware of the nuclear fusion manner in which elements are created from stars. Hydrogen is burned into helium, and so up the line until it reaches iron. It’s just the way stellar physics work and we accept it. To date, science has theorized that heavier elements were the creation of supernovae events, but new studies done by scientists of the Max Planck Institute for Astrophysics (MPA) and affiliated to the Excellence Cluster Universe and of the Free University of Brussels (ULB) indicate they may be able to form during encounters with ejected matter from neutron stars.

”The source of about half of the heaviest elements in the Universe has been a mystery for a long time,“ says Hans-Thomas Janka, senior scientist at the Max Planck Institute for Astrophysics (MPA) and within the Excellence Cluster Universe. ”The most popular idea has been, and may still be, that they originate from supernova explosions that end the lives of massive stars. But newer models do not support this idea.“

Although it might take millions of years for such a tryst to take place, it’s not impossible for two neutron stars in a binary system to eventually meet. Scientists at the MPA and the ULB have now simulated all stages of the processes through computer modeling and taken note at the formation of chemical elements which are the offspring.

”In just a few split seconds after the merger of the two neutron stars, tidal and pressure forces eject extremely hot matter equivalent to several Jupiter masses,“ explains Andreas Bauswein, who carried out the simulations at the MPA. Once this so-called plasma has cooled to less than 10 billion degrees, a multitude of nuclear reactions take place, including radioactive decays, and enable the production of heavy elements. ”The heavy elements are `recycled’ several times in various reaction chains involving the fission of super-heavy nuclei, which makes the final abundance distribution become largely insensitive to the initial conditions provided by the merger model,“ adds Stephane Goriely, ULB researcher and nuclear astrophysics expert of the team.

Their findings agree well with observations of abundance distributions in both the Solar System and old stars. When compared with possible neutron star collisions occurring in the Milky Way, the conclusions are the same – this speculation could very well be the explanation for the distribution of heavier elements. The team plans on continuing their studies while on the look out “for detecting the transient celestial sources that should be associated with the ejection of radioactive matter in neutron star mergers.” Like a supernova event, the heat from the radioactive decay will shine like… well…

Gold in the dark.

Original Story Source: Max Planck Institut News. For Further Reading: R-process nucleosynthesis in dynamically ejected matter of neutron star mergers.

Posted on by Tammy Plotner

Milky Way Harbors “Ticking Time Bombs”

New research shows that some old stars known as white dwarfs might be held up by their rapid spins, and when they slow down, they explode as Type Ia supernovae. Thousands of these "time bombs" could be scattered throughout our Galaxy. In this artist's conception, a supernova explosion is about to obliterate an orbiting Saturn-like planet. Credit: David A. Aguilar (CfA)

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According to new research, the only thing that may be keeping elderly stars from exploding is their rapid spin. In a galaxy filled with old stars, this means we could literally be sitting on a nearby “time bomb”. Or is this just another scare tactic?

“We haven’t found one of these ‘time bomb’ stars yet in the Milky Way, but this research suggests that we’ve been looking for the wrong signs. Our work points to a new way of searching for supernova precursors,” said astrophysicist Rosanne Di Stefano of the Harvard-Smithsonian Center for Astrophysics (CfA).

In light of the two recently discovered supernova events in Messier 51 and Messier 101, it isn’t hard to imagine the Milky Way having more than one candidate for a Type Ia supernova. This is precisely the type of stellar explosion Di Stefano and her colleagues are looking for… and it happens when a white dwarf star goes critical. It has reached Chandrasekhar mass. Add any more weight and it blows itself apart. How does this occur? Some astronomers believe Type Ia supernova are sparked by accretion from a binary companion – or a collision of two similar dwarf stars. However, there hasn’t been much – if any – evidence to support either theory. This has left scientists to look for new answers to old questions. Di Stefano and her colleagues suggest that white dwarf spin might just be what we’re looking for.

“A spin-up/spin-down process would introduce a long delay between the time of accretion and the explosion. As a white dwarf gains mass, it also gains angular momentum, which speeds up its spin. If the white dwarf rotates fast enough, its spin can help support it, allowing it to cross the 1.4-solar-mass barrier and become a super-Chandrasekhar-mass star. Once accretion stops, the white dwarf will gradually slow down. Eventually, the spin isn’t enough to counteract gravity, leading to a Type Ia supernova.” explains Di Stefano. “Our work is new because we show that spin-up and spin-down of the white dwarf have important consequences. Astronomers therefore must take angular momentum of accreting white dwarfs seriously, even though it’s very difficult science.”

Sure. It might take a billion years for the spin down process to happen – but what’s a billion years in cosmic time? In this scenario, it’s enough to allow accretion to have completely stopped and a companion star to age to a white dwarf. In the Milky Way there’s an estimated three Type Ia supernovae every thousand years. If figures are right, a typical super-Chandrasekhar-mass white dwarf takes millions of years to spin down and explode. This means there could be dozens of these “time bomb” systems within a few thousand light-years of Earth. While we’re not able to ascertain their locations now, upcoming wide-field surveys taken with instruments like Pan-STARRS and the Large Synoptic Survey Telescope might give us a clue to their location.

“We don’t know of any super-Chandrasekhar-mass white dwarfs in the Milky Way yet, but we’re looking forward to hunting them out,” said co-author Rasmus Voss of Radboud University Nijmegen, The Netherlands.

And the rest of us hope you don’t find them…

Original Story Source: Harvard Smithsonian Center for Astrophysics News. For Further Reading: Spin-Up/Spin-Down models for Type Ia Supernovae.

Posted on by Nancy Atkinson

How to See a Supernova From Your Backyard This Weekend

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.

Posted on by Jason Major

Shiny New Supernova Spotted in Nearby Galaxy

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!

Posted on by Jon Voisey

Pan-STARRS Discovers two Super Supernovae

Artist illustration of a supernova. Image credit: ESO

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Supernovae are the brightest phenomenon in the current universe. As massive stars die as supernovae, they briefly outshine the rest of the stars in their galaxy and are visible, at least once the light gets there, from across the universe. Until recently, astronomers thought they pretty much had supernovae figured out; they could either form from the direct collapse of a massive core or the tipping over the Chandrasekhar limit as a white dwarf accreted neighbor. These methods seemed to work well until astronomers began to discover “ultra-luminous” supernovae beginning with SN 2005ap. The usual suspects could not produce such bright explosions and astronomers began looking for new methods as well as new ultra-luminous supernovae to help understand these outliers. Recently, the automated sky survey Pan-STARRS netted two more.

Since 2010, the Panoramic Survey Telescope & Rapid Response System (Pan-STARR) has been conducting observations atop Mount Haleakala and is controlled by the University of Hawaii. Its primary mission is to search for objects that may pose a threat to Earth. To do this, it repeatedly scans the northern sky, looking at 10 patches per night and cycling through various color filters. While it has been very successful in this area, the observations can also be used to study objects that change on short timescales such as supernovae.

The first of the two new supernovae, PS1-10ky was already in the process of exploding as Pan-STARRS came into operation, thus, the brightness curve was incomplete since it was discovered near peak brightness and no data exists to catch it as it brightened. However, for the second, PS1-10awh, the team caught while in the process of brightening and have a complete light curve for the object. Combining the two, the team, led by Laura Chomiuk at the Harvard-Smithsonian Center for Astrophysics, was able to get a full picture of just how these titanic supernovae behave. And what’s more, since they were observed with multiple filters, the team was able to understand just how the energy was distributed. Additionally, the team was able to use other instruments, including Gemini, to get spectroscopic information.

The two new supernovae are very similar in many regards to the other ultra-luminous supernovae discovered previously, including SN 2010gx and SCP 06F6. All of these objects have been exceptionally bright with little absorption in their spectra. What little they did have was due to partially ionized carbon, silicon, and magnesium. The average peak brightness was -22.5 magnitudes where as typical core collapse supernovae peak around -19.5. The presence of these lines allowed astronomers to measure the expansion velocity for the new objects as 40,000 km/sec and place a distance to these objects as around 7 billion light years (previous ultra-luminous supernovae like these have been between 2 and 5 billion light years).

But what could power these leviathans? The team considered three scenarios. The first was radioactive decay. The violence of supernovae explosions injects atomic nuclei with additional protons and neutrons creating unstable isotopes which rapidly decay giving off visible light. This process is generally implicated in the fading out of supernovae as this decay process withers out slowly. However, based on the observations, the team concluded that it should not be possible to create sufficient amounts of the radioactive elements necessary to account for the observed brightness.

Another possibility was a rapidly rotating magnetar underwent a rapid change in its rotation. This sudden change would throw off large large chunks of material from the surface which could, in extreme cases, match the observed expansion velocity of these objects.

Lastly, the team considers a more typical supernova expanding into a relatively dense medium. In this case, the shockwave produced by the supernova would interact with the cloud around the star and the kinetic energy would heat the gas, causing it to glow. This too could reproduce many of the observed features of the supernova, but had the requirement that the star shed large amounts of material just before exploding. Some evidence is given for this as being a common occurrence in massive Luminous Blue Variable stars observed in the nearby universe. The team notes that this hypothesis may be tested by searching for radio emission as the shockwave interacted with the gas.

Posted on by Tammy Plotner

Burned Out Stars Do A Deadly Last Dance

Two white dwarfs have been discovered on the brink of a merger. In just 900,000 years, material will start to stream from one star to the other (as shown in this artist's conception), beginning the process that may end with a spectacular supernova explosion. Watching these stars fall in will allow astronomers to test Einstein's general theory of relativity as well as the origin of a special class of supernovae. Credit: David A. Aguilar (CfA)

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“Well, I don’t know, but I’ve been told… You never slow down, you never grow old.” Well, Tom Petty might not ever grow old, but stars do. In this case it’s a pair white dwarf stars and they’re locked in a death dance that has them spiraling around each other in just 13 minutes. Astronomers estimated that in about 900,000 years the pair will merge… and what a party that will be!

Traveling in an orbit that’s currently carrying them at 370 miles per second (600 km/s), these two burnt-out stellar cores are heading towards a supernova ending. Right now the brighter of the pair is about the size of Neptune and carries about one quarter of our Sun’s mass. Its companion contains twice as much mass and is about the size of Earth. What’s peculiar is the incredible speed at which they are converging.

“I nearly fell out of my chair at the telescope when I saw one star change its speed by a staggering 750 miles per second in just a few minutes,” said Smithsonian astronomer Warren Brown, lead author of the paper reporting the find.

Using the MMT telescope at the Whipple Observatory on Mt. Hopkins, Arizona, researchers have been looking for just such eclectic white dwarf pairings. Because of their close proximity, they can only be separated spectroscopically and their relative motions then determined. Fortunately, this unusual set are eclipsing, doing their two-step at a very predictable rate. “If there were aliens living on a planet around this star system, they would see one of their two suns disappear every 6 minutes – a fantastic light show.” said Smithsonian astronomer and co-author Mukremin Kilic.

What’s really cool about this observing project is its implications as related to Einstein’s theories. Their movements should create wrinkles in the fabric space-time. These gravitational waves pull away at the energy – allowing the pair to get closer at each pass and their orbits to accelerate.

“Though we have not yet directly measured gravitational waves with modern instruments, we can test their existence by measuring the change in the separation of these two stars,” said co-author J. J. Hermes, a graduate student at the University of Texas at Austin. “Because they don’t seem to be exchanging mass, this system is an exceptionally clean laboratory to perform such a test.”

Just as soon as the pair emerges from behind the Sun, observing will begin again. Some models predict merging white dwarf pairs of this type could be a rare class of unusually faint stellar explosions called underluminous supernovae – or just the source of many other kinds of supernovae. “If these systems are responsible for underluminous supernovae, we will detect these binary white dwarf systems with the same frequency that we see the supernovae. Our survey isn’t complete, but so far, the numbers agree,” said Brown.

What can we say besides, “Last dance with Mary Jane… One more time to kill the pain… I feel summer creepin’ in.”

Original Story Source: Harvard-Smithsonian Center for Astrophysics.

Posted on by Nancy Atkinson

Where Did Early Cosmic Dust Come From? New Research Says Supernovae

A new study from the University of Edinburgh argues that life could be spread throughout the cosmos by interstellar dust. Credit: ESA/NASA-JPL/UCL/STScI

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From a JPL Press Release:

New observations from the infrared Herschel Space Observatory reveal that an exploding star expelled the equivalent of between 160,000 and 230,000 Earth masses of fresh dust. This enormous quantity suggests that exploding stars, called supernovae, are the answer to the long-standing puzzle of what supplied our early universe with dust.

“This discovery illustrates the power of tackling a problem in astronomy with different wavelengths of light,” said Paul Goldsmith, the NASA Herschel project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., who is not a part of the current study. “Herschel’s eye for longer-wavelength infrared light has given us new tools for addressing a profound cosmic mystery.”

Cosmic dust is made of various elements, such as carbon, oxygen, iron and other atoms heavier than hydrogen and helium. It is the stuff of which planets and people are made, and it is essential for star formation. Stars like our sun churn out flecks of dust as they age, spawning new generations of stars and their orbiting planets.

Astronomers have for decades wondered how dust was made in our early universe. Back then, sun-like stars had not been around long enough to produce the enormous amounts of dust observed in distant, early galaxies. Supernovae, on the other hand, are the explosions of massive stars that do not live long.

The new Herschel observations are the best evidence yet that supernovae are, in fact, the dust-making machines of the early cosmos.

This plot shows energy emitted from a supernova remnant called SN 1987A. Previously, NASA's Spitzer Space Telescope detected warm dust around the object. Image credit: ESA/NASA-JPL/UCL/STScI

“The Earth on which we stand is made almost entirely of material created inside a star,” explained the principal investigator of the survey project, Margaret Meixner of the Space Telescope Science Institute, Baltimore, Md. “Now we have a direct measurement of how supernovae enrich space with the elements that condense into the dust that is needed for stars, planets and life.”

The study, appearing in the July 8 issue of the journal Science, focused on the remains of the most recent supernova to be witnessed with the naked eye from Earth. Called SN 1987A, this remnant is the result of a stellar blast that occurred 170,000 light-years away and was seen on Earth in 1987. As the star blew up, it brightened in the night sky and then slowly faded over the following months. Because astronomers are able to witness the phases of this star’s death over time, SN 1987A is one of the most extensively studied objects in the sky.

A new view from the Hubble Space Telescope shows how supernova 1987A has recently brightened.

Initially, astronomers weren’t sure if the Herschel telescope could even see this supernova remnant. Herschel detects the longest infrared wavelengths, which means it can see very cold objects that emit very little heat, such as dust. But it so happened that SN 1987A was imaged during a Herschel survey of the object’s host galaxy — a small neighboring galaxy called the Large Magellanic Cloud (it’s called large because it’s bigger than its sister galaxy, the Small Magellanic Cloud).

After the scientists retrieved the images from space, they were surprised to see that SN 1987A was aglow with light. Careful calculations revealed that the glow was coming from enormous clouds of dust — consisting of 10,000 times more material than previous estimates. The dust is minus 429 to minus 416 degrees Fahrenheit (about minus 221 to 213 Celsius) — colder than Pluto, which is about minus 400 degrees Fahrenheit (204 degrees Celsius).

“Our Herschel discovery of dust in SN 1987A can make a significant understanding in the dust in the Large Magellanic Cloud,” said Mikako Matsuura of University College London, England, the lead author of the Science paper. “In addition to the puzzle of how dust is made in the early universe, these results give us new clues to mysteries about how the Large Magellanic Cloud and even our own Milky Way became so dusty.”

Previous studies had turned up some evidence that supernovae are capable of producing dust. For example, NASA’s Spitzer Space Telescope, which detects shorter infrared wavelengths than Herschel, found 10,000 Earth-masses worth of fresh dust around the supernova remnant called Cassiopea A. Hershel can see even colder material, and thus the coldest reservoirs of dust. “The discovery of up to 230,000 Earths worth of dust around SN 1987A is the best evidence yet that these monstrous blasts are indeed mighty dust makers,” said Eli Dwek, a co-author at NASA Goddard Space Flight Center in Greenbelt, Md.

Herschel is led by the European Space Agency with important contributions from NASA.

See also the ESA press release on this research.