supernova Archives

August 6, 2014December 23, 2015 by Shannon Hall

Hubble Archive Reveals Possible Culprit for Enigmatic Supernova

The white X at the top of the image marks the location of the supernova. The inset panel is a pair of Hubble Space Telescope images of the spiral galaxy NGC 1309 that were taken before and after the appearance of Supernova 2012Z. Credit: NASA, ESA, C. McCully and S. Jha (Rutgers University), R. Foley (University of Illinois), and Z. Levay (STScI)

More than two decades of Hubble observations have produced more than 25 terabytes of data. Thanks to the wealth of information stored in the Hubble data archive, astronomers can easily revisit old images in an effort to better understand new discoveries.

Now, astronomers have used the archive to find the progenitor of a mysterious type of supernova, dubbed Type 1ax, which is less energetic and much fainter than its Type Ia cousin.

A Type 1a supernova occurs when a white dwarf siphons material off a companion star, building an additional layer of hydrogen on its surface that will eventually trigger a runaway reaction that detonates the accumulated gas.

The most popular explanation for Type 1ax supernovae is that they’re created in the same way, except the explosion doesn’t completely tear the white dwarf into pieces. Instead, the white dwarf ejects roughly half of its mass. It becomes battered and bruised, leaving behind a hot core composed of carbon and oxygen.

So far, astronomers have identified more than 30 of these mini-explosions, which occur at one-fifth the rate of Type 1a supernovae.

“Astronomers have been searching for decades for the progenitors of Type Ia’s,” said Saurabh Jha from Rutgers University in a NASA press release. “Type Ia’s are important because they’re used to measure vast cosmic distances and the expansion of the universe. But we have very few constraints on how any white dwarf explodes. The similarities between Type Iax’s and normal Type Ia’s make understanding Type Iax progenitors important, especially because no Type Ia progenitor has been conclusively identified.”

So after the team observed the weak supernova, dubbed SN 2012Z, in the Lick Observatory Supernova Search, they dug through Hubble’s archive. Fortuitously, Hubble had observed the supernova’s host galaxy, NGC 1309, in 2005, 2006, and 2010, before the supernova outburst.

Curtis McCully, a graduate student at Rutgers and lead author on the team’s paper, reprocessed the pre-explosion images to find an object at the supernova’s position.

“I was very surprised to see anything at the supernova’s location,” said McCully. “We expected that the progenitor system would be too faint to see, like in previous searches for normal Type Ia supernova progenitors. It is exciting when nature surprises us.”

The pre-supernova observations reveal a bright, blue source the team calls S1. McCully and colleagues concluded that they were most likely seeing a star that had lost its outer hydrogen envelope, revealing its helium core. But they don’t think it’s a type of star that was about to explode, rather it’s the companion that fed the white dwarf’s outburst.

The most likely explanation involves a binary star system where each star detonates mass to the other over time.

The team acknowledges that they can’t totally rule out other possibilities for the object’s identity, including that it was simply a single, massive star that exploded as a supernova. To settle any uncertainties the team plans to use Hubble again in 2015. Hopefully by then the supernova should fade enough to get a better look at what remains.

The team’s results will appear in the journal Nature tomorrow.

July 22, 2014December 23, 2015 by Elizabeth Howell

Cosmic Fireworks: A Supernova Feast And Google+ Hangout For Chandra’s 15th Anniversary

A collection of images from the Chandra X-Ray Observatory marking its 15th anniversary in space. Top, from left: the crab Nebula, supernova remnant G292.0+1.8 and the Crab Nebula. At bottom, supernova remnant 3C58. Credit: NASA/CXC/SAO

It’s well past the Fourth of July, but you can still easily find fireworks in the sky if you look around. The Chandra X-Ray Observatory has been doing just that for the past 15 years, revealing what the universe looks like in these longer wavelengths that are invisible to human eyes.

Just in time for the birthday, NASA released four pictures that Chandra took of supernova (star explosion) remnants it has observed over the years. The pictures stand as a symbol of what the telescope has shown us so far.

“Chandra changed the way we do astronomy. It showed that precision observation of the X-rays from cosmic sources is critical to understanding what is going on,” stated Paul Hertz, NASA’s Astrophysics Division director, in a press release. “We’re fortunate we’ve had 15 years – so far – to use Chandra to advance our understanding of stars, galaxies, black holes, dark energy, and the origin of the elements necessary for life.”

The telescope launched into space in 1999 aboard the space shuttle and currently works at an altitude as high as 86,500 miles (139,000 miles). It is named after Indian-American astrophysicist Subrahmanyan Chandrasekhar; the name “Chandra” also means “moon” or “luminous” in Sanskrit.

And there’s more to come. You can learn more about Chandra’s greatest discoveries and its future in this Google+ Hangout, which will start at 3 p.m. EDT (7 p.m. EDT) at this link.

June 26, 2014December 23, 2015 by Shannon Hall

Superluminous Supernova Puzzles Astronomers

Before (left) and after (center) images of the region where DES13S2cmm was discovered. On the right is a subtraction of these two images, showing a bright new object at the center -- a supernova. Credit: Dark Energy Survey

Supernovae are surprisingly dependable. These brilliant and powerful explosions that mark the end of massive stars’ lives tend to shine anywhere from one hundred million to a few billion times brighter than the Sun for weeks on end. And their intrinsic brightness is always well known.

But in recent years a rare class of cosmic explosions, which are tens to hundreds of times more luminous than ordinary supernovae, has been discovered. And now one of these odd superluminous supernovae is mystifying astronomers further, with characteristics that simply don’t add up.

The Dark Energy Survey (DES) came online in August 2013 in order to investigate millions of galaxies for the subtle effects of weak lensing, the phenomenon where intervening invisible matter causes distant galaxies to appear minutely sheared and stretched.

The survey started off with a bang; its first images revealed a rare superluminous supernova, dubbed DES13S2cmm, 7.8 billion light-years away.

“Fewer than forty such supernovae have ever been found and I never expected to find one in the first DES images,” said Andreas Papadopoulos from the University of Portsmouth in a press release. “As they are rare, each new discovery brings the potential for greater understanding — or more surprises.”

The problem is this: DES13S2cmm doesn’t easily match the typical characteristics of a superluminous supernova. The stellar explosion could be seen in the data six months later, much longer than most other superluminous supernovae observed to date.

“Its unusual, slow decline was not apparent at first,” said Mark Sullivan from Southampton University. “But as more data came in and the supernova stopped getting fainter, we would look at the light curve and ask ourselves, ‘what is this?’ ”

So Sullivan decided to investigate further. But understanding its origins are proving difficult.

For some supernovae, the optical light we see is actually created by radioactivity. In fact, supernovae tend to create large amounts of radioactive elements, which don’t occur naturally on Earth. Nickel-56, with a half-life of roughly six days, is a common example.

As the nickel decays into cobalt, it releases gamma rays, which are trapped by the other material ejected by the supernova. These trapped rays heat up the surrounding material until it radiates in the optical. In this case, the peak magnitude of the supernova is directly proportional to the amount of nickel-56 created in the explosion.

“We have tried to explain the supernova as a result of the decay of the radioactive isotope nickel-56,” said coauthor Dr Chris D’Andrea of the University of Portsmouth. “But to match the peak brightness, the explosion would need to produce more than three times the mass of our Sun of the element. And even then the behavior of the light curve doesn’t match up.”

So the team is now investigating other explanations. In one intriguing scenario the supernova was relatively normal but created a magnetar — an extremely dense and highly magnetic neutron star that’s millions of times more powerful than the strongest magnets on Earth — whose energy made the explosion exceptionally bright.

But this explanation doesn’t match the data either.

A few months ago a team of astronomers led by Robert Quimby explained a superluminous supernovae, PS1-10afx, by a chance cosmic alignment, where intervening matter worked like a lens to deflect and intensify the background light for a typical Type Ia supernova. D’Andrea, however, doesn’t believe this is the case here.

“DES13S2cmm looks nothing like a normal type of supernova, either in its photometric evolution or its spectroscopy,” D’Andrea told Universe Today. “So while we can never be sure that a very faint but very massive galaxy lies between us and another object and is serendipitously brightening the object, there is no need to adopt that assumption in the case of DES13S2cmm.”

chance cosmic alignment — where intervening matter worked like a lens to deflect and intensify the background light – See more at: http://www.skyandtelescope.com/astronomy-news/stellar-science/mysteriously-bright-supernova-explained/#sthash.m7Z8PJ3k.dpuf

So astronomers are heading back to the drawing board.

“With so few known, it’s hard to really understand their properties in detail,” said Bob Nichol from the University of Portsmouth. “DES should find enough of these objects to allow us to understand superluminous supernovae as a population. But if some of these discoveries prove as difficult to interpret as DES13S2cmm, we’re prepared for the unusual.”

The results will be presented today at the National Astronomy Meeting 2014 in Portsmouth.

May 22, 2014December 23, 2015 by Bob King

New Supernova Pops in Bright Galaxy M106 in the ‘Hunting Dogs’

The new Type II supernova is nestled up to the nucleus of the galaxy in this photo taken May 21 with a 17-inch telescope. Credit: Gianluca Masi, Francesca Nocentini and Patrick Schmeer

A supergiant star exploded 23.5 million years ago in one of the largest and brightest nearby galaxies. This spring we finally got the news. In April, the Katzman Automatic Imaging Telescope (KAIT) as part of the Lick Observatory Supernova Search, photographed a faint “new star” very close to the bright core of M106, a 9th magnitude galaxy in Canes Venatici the Hunting Dogs.

The core of a red or blue supergiant moments before exploding as a supernova looks like an onion with multiple elements "burning" through the fusion process to create the heat to stay the force of gravity. Fusion stops at iron. With no energy pouring from the central core to keep the other elements cooking, the star collapses and the rebounding shock wave tears it apart. — The inner core of a red or blue supergiant moments before exploding as a supernova looks like an onion with multiple elements “burning” through the fusion process to create the heat and pressure that stays the force of gravity. Fusion stops at iron. With no energy pouring from the central core to keep the other elements cooking, the star collapses and the rebounding shock wave tears it apart.

A study of its light curve indicated a Type II supernova – the signature of a rare supergiant star ending its life in the most violent way imaginable. A typical supergiant star is 8 to 12 times more massive than the sun and burns at a much hotter temperature, rapidly using up its available fuel supply as it cooks lighter elements like hydrogen and helium into heavier elements within its core. Supergiant lifetimes are measured in the millions of years (10-100 million) compared to the frugal sun’s 11 billion years. When silicon fuses to create iron, a supergiant reaches the end of the line – iron can’t be fused or cooked into another heavier element – and its internal “furnace” shuts down. Gravity takes over and the whole works collapses in upon itself at speeds up to 45,000 miles per second.

When the outer layers reached the core, they crushed it into a dense ball of subatomic particles and send a powerful shock wave back towards the surface that rips the star to shreds. A supernova is born! Newly-minted radioactive forms of elements like nickel and cobalt are created by the tremendous pressure and heat of the explosion. Their rapid decay into stable forms releases energy that contributes to the supernova’s light.

This Hubble Space Telescope image shows how spectacular M106 truly is. Its spiral arms are dotted with dark lanes of dust, young star clusters rich with hot, blue stars and tufts of pink nebulosity swaddling newborn stars. The galaxy is the 106th entry in the 18th century French astronomer Charles Messier's famous catalog. Credit: NASA / ESA — This Hubble Space Telescope image shows how spectacular M106 truly is. Dark filaments of dust are silhouetted against billions of unresolved suns. Young star clusters rich with hot, blue stars and tufts of pink nebulosity swaddling newborn stars ornament the galaxy’s spiral arms. A supermassive black hole rumbles at the heart of the galaxy. M106 is the 106th entry in Charles Messier’s famous catalog created in the 18th century. It’s located 23.5 million light years away. Credit: NASA / ESA

For two weeks, the supernova in M106 remained pinned at around magnitude +15, too faint to tease out from the galaxy’s bright, compact nucleus for most amateur telescopes. But a photograph taken by Gianluca Masi and team on May 21 indicate it may have brightened somewhat. They estimated its red magnitude – how bright it appears when photographed through a red filter – at +13.5. A spectrum made of the object reveals the ruby emission of hydrogen light, the telltale signature of a Type II supernova event.

At magnitude +9, M106 visible in almost any telescope and easy to find. Start just above the Bowl of the Big Dipper which stands high in the northwestern sky at nightfall in late May. The 5th magnitude stars 5 CVn (5 Canes Venatici) and 3 CVn lie near the galaxy. Star hop from the Bowl to these stars and then over to M106. Stars plotted to mag. +8. Click to enlarge. Stellarium

Visually the supernova will appear fainter because our eyes are more sensitive to light in the middle of the rainbow spectrum (green-yellow) than the reds and purple that bracket either side. I made a tentative observation of the object last night using a 15-inch (37-cm) telescope and hope to see it more clearly tonight from a darker sky. We’ll keep you updated on our new visitor’s brightness as more observations and photographs come in. You can also check Dave Bishop’s Latest Supernovae site for more information and current images.

Even if the supernova never gets bright enough to see in your telescope, stop by M106 anyway. It’s big, easy to find and shows lots of interesting structure. Spanning 80,000 light years in diameter, M106 would be faintly visible with the naked eye were it as close as the Andromeda Galaxy. In smaller scopes the galaxy’s bright nucleus stands out in a mottled haze of pearly light; 8-inch(20-cm) and larger instrument reveal the two most prominent spiral arms. M106 is often passed up for the nearby more famous Whirlpool Galaxy (M51). Next time, take the detour. You won’t be disappointed.

May 21, 2014December 23, 2015 by Elizabeth Howell

New Supernova Likely Arose From Massive Wolf-Rayet Star

M1-67 is the youngest wind-nebula around a Wolf-Rayet star, called WR124, in our Galaxy. Credit: ESO

They’ve been identified as possible causes for supernovae for a while, but until now, there was a lack of evidence linking massive Wolf-Rayet stars to these star explosions. A new study was able to find a “likely” link between this star type and a supernova called SN 2013cu, however.

“When the supernova exploded, it flash ionized its immediate surroundings, giving the astronomers a direct glimpse of the progenitor star’s chemistry. This opportunity lasts only for a day before the supernovablast wave sweeps the ionization away. So it’s crucial to rapidly respond to a young supernova discovery to get the flash spectrum in the nick of time,” the Carnegie Institution for Science wrote in a statement.

“The observations found evidence of composition and shape that aligns with that of a nitrogen-rich Wolf-Rayet star. What’s more, the progenitor star likely experienced an increased loss of mass shortly before the explosion, which is consistent with model predictions for Wolf-Rayet explosions.”

NGC 3199 - Credit: Ken Crawford — NGC 3199 – Credit: Ken Crawford

The star type is known for lacking hydrogen (in comparison to other stars) — which makes it easy to identify spectrally — and being large (upwards of 20 times more massive than our Sun), hot and breezy, with fierce stellar winds that can reach more than 1,000 kilometres per second. This particular supernova was spotted by the Palomar 48-inch telescope in California, and the “likely progenitor” was found about 15 hours after the explosion.

Researchers also noted that the new technique, called “flash spectroscopy”, allows them to look at stars over a range of about 100 megaparsecs or more than 325 million light years — about five times further than what previous observations with the Hubble Space Telescope revealed.

The research was published in Nature. It was led by Avishay Gal-Yam of the Weizmann Institute of Science in Israel.

Source: Carnegie Institution for Science

April 25, 2014December 23, 2015 by Elizabeth Howell

Gallery: Incredible Mirages In Space Show Dark Matter, Supernovas And Galaxies

This artist’s impression of a supernova shows the layers of gas ejected prior to the final deathly explosion of a massive star. Credit: NASA/Swift/Skyworks Digital/Dana Berry

How can an exploding star appear far brighter than expected? This question vexed astronomers since the discovery of PS1-10afx, supernova that was about 30 times more luminous than other Type 1A supernovas. Astronomers have just confirmed in Science that it was likely due to well-known illusion in space.

The mirage is called a gravitational lens that happens when a huge object in the foreground (like a galaxy) bends the light of an object in the background. Astronomers use this trick all the time to spy on galaxies and even to map dark matter, the mysterious substance believed to make up most of the universe.

Check out some spectacular images below of the phenomenon in action.

Canada-France-Hawaii-Telescope (CFHT) image of the field before the supernova PS1-10afx. (Credit: Kavli IPMU / CFHT)

Dark matter in the Bullet Cluster. Otherwise invisible to telescopic views, the dark matter was mapped by observations of gravitational lensing of background galaxies. Credit: X-ray: NASA/CXC/CfA/ M.Markevitch et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/ D.Clowe et al. Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.;

Hubble Space Telescope image shows Einstein ring of one of the SLACS gravitational lenses, with the lensed background galaxy enhanced in blue. A. Bolton (UH/IfA) for SLACS and NASA/ESA.

The image is made from HST data and shows the four lensed images of the dusty red quasar, connected by a gravitational arc of the quasar host galaxy. The lensing galaxy is seen in the centre, between the four lensed images. Credit: John McKean/HST Archive data

The HST WFPC2 image of gravitational lensing in the galaxy cluster Abell 2218, indicating the presence of large amount of dark matter (credit Andrew Fruchter at STScI).

A picture of the object J1000+0221, which demonstrates the most distant gravitational lens ever discovered. This Hubble picture shows a normal galaxy's center region (the glow in the picture), but the object is also aligned with a younger, star-creating galaxy that is in behind. The object in the foreground pulls light from the background galaxy with gravity -- making rings of pictures. Credit: NASA/ESA/A. van der Wel — A picture of the object J1000+0221, which demonstrates the most distant gravitational lens ever discovered. This Hubble picture shows a normal galaxy’s center region (the glow in the picture), but the object is also aligned with a younger, star-creating galaxy that is in behind. The object in the foreground pulls light from the background galaxy with gravity — making rings of pictures. Credit: NASA/ESA/A. van der Wel

April 11, 2014December 23, 2015 by Elizabeth Howell

Supernova Sweeps Away Rubbish In New Composite Image

The supernova remnant G352.7-0.1 in a composite image with X-rays from the Chandra X-Ray Telescope (blue), radio waves from the Very Large Array (pink), infrared information from the Spitzer Space Telescope (orange) and optical data from the Digital Sky Survey (white). Credit: X-ray: NASA/CXC/Morehead State Univ/T.Pannuti et al.; Optical: DSS; Infrared: NASA/JPL-Caltech; Radio: NRAO/VLA/Argentinian Institute of Radioastronomy/G.Dubner

Shining 24,000 light-years from Earth is an expanding leftover of a supernova that is doing a great cleanup job in its neighborhood. As this new composite image from NASA reveals, G352.7-0.1 (G352 for short) is more efficient than expected, picking up debris equivalent to about 45 times the mass of the Sun.

“A recent study suggests that, surprisingly, the X-ray emission in G352 is dominated by the hotter (about 30 million degrees Celsius) debris from the explosion, rather than cooler (about 2 million degrees) emission from surrounding material that has been swept up by the expanding shock wave,” the Chandra X-Ray Observatory’s website stated.

“This is curious because astronomers estimate that G352 exploded about 2,200 years ago, and supernova remnants of this age usually produce X-rays that are dominated by swept-up material. Scientists are still trying to come up with an explanation for this behavior.”

More information about G352 is available in the Astrophysical Journal and also in preprint version on Arxiv.

Source: Chandra X-Ray Telescope

March 13, 2014April 26, 2016 by David Dickinson

“Death Stars” Caught Blasting Proto-Planets

It’s a tough old universe out there. A young star has lots to worry about, as massive stars just beginning to shine can fill a stellar nursery with a gale of solar wind.

No, it’s not a B-movie flick: the “Death Stars of Orion” are real. Such monsters come in the form of young, O-type stars.

And now, for the first time, a team of astronomers from Canada and the United States have caught such stars in the act. The study, published in this month’s edition of The Astrophysical Journal, focused on known protoplanetary disks discovered by the Hubble Space Telescope in the Orion Nebula.

These protoplanetary disks, also known as “tadpoles” or proplyds, are cocoons of dust and gas hosting stars just beginning to shine. Much of this leftover material will go on to aggregate into planets, but nearby massive O-Type stars can cause chaos in a stellar nursery, often disrupting the process.

“O-Type stars, which are really monsters compared to our Sun, emit tremendous amounts of ultraviolet radiation and this can play havoc during the development of young planetary systems,” said astronomer Rita Mann in a recent press release. Mann works for the National Research Council of Canada in Victoria and is lead researcher on the project

Scientists used the Atacama Large Millimeter Array (ALMA) to probe the proplyds of Orion in unprecedented detail. Supporting observations were also made using the Submillimeter Array in Hawaii.

ALMA saw “first light” in 2011, and has already achieved some first rate results.

“ALMA is the world’s most sensitive telescope at high-frequency radio waves (e.g., 100-1000 GHz). Even with only a fraction of its final number of antennas, (with 22 operational out of a total planned 50) we were able to detect with ALMA the disks relatively close to the O-star while previous observatories were unable to spot them,” James Di Francesco of the National Research Council of Canada told Universe Today. “Since the brightness of a disk at these frequencies is proportional to its mass, these detections meant we could measure the masses of the disks and see for sure that they were abnormally low close to the O-type star.”

ALMA also doubled the number of proplyds seen in the region, and was also able to peer within these cocoons and take direct mass measurements. This revealed mass being stripped away by the ultraviolet wind from the suspect O-type stars. Hubble had been witness to such stripping action previous, but ALMA was able to measure the mass within the disks directly for the first time.

And what was discovered doesn’t bode well for planetary formation. Such protostars within about 0.1 light-years of an O-type star are consigned to have their cocoon of gas and dust stripped clean in just a few million years, just a blink of a eye in the game of planetary formation.

With a O-type star’s “burn brightly and die young” credo, this type of event may be fairly typical in nebulae during early star formation.

“O-type stars have relatively short lifespan, say around 1 million years for the brightest O-star in Orion – which is 40 times the mass of our Sun – compared to the 10 billion year lifespan of less massive stars like our Sun,” Di Francesco told Universe Today. “Since these clusters are typically the only places where O-stars form, I’d say that this type of event is indeed typical in nebulae hosting early star formation.”

It’s common for new-born stars to be within close proximity of each other in such stellar nurseries as M42. Researchers in the study found that any proplyds within the extreme-UV envelope of a massive star would have its disk shredded in short order, retaining on average less than 50% the mass of Jupiter total. Beyond the 0.1 light year “kill radius,” however, the chances for these proplyds to retain mass goes up, with researchers observing anywhere from 1 to 80 Jupiter masses of material remaining.

The findings in this study are also crucial in understanding what the early lives of stars are like, and perhaps the pedigree of our own solar system, as well as how common – or rare – our own history might be in the story of the universe.

There’s evidence that our solar system may have been witness to one or more nearby supernovae early in its life, as evidenced by isotopic measurements. We were somewhat lucky to have had such nearby events to “salt” our environment with heavy elements, but not sweep us clean altogether.

“Our own Sun likely formed in a clustered environment similar to that of Orion, so it’s a good thing we didn’t form too close to the O-stars in its parent nebula,” Di Francesco told Universe Today. “When the Sun was very young, it was close enough to a high-mass star so that when it blew up (went supernova) the proto-solar system was seeded with certain isotopes like Al-26 that are only produced in supernova events.”

This is the eventual fate of massive O-type stars in the Orion Nebula, though none of them are old enough yet to explode in this fashion. Indeed, it’s amazing to think that peering into the Orion Nebula, we’re witnessing a drama similar to what gave birth to our Sun and solar system, billions of years ago.

The Orion Nebula is the closest active star forming region to us at about 1,500 light years distant and is just visible to the naked eye as a fuzzy patch in the pommel of the “sword” of Orion the Hunter. Looking at the Orion Nebula at low power through a small telescope, you can just make out a group of four stars known collectively as the Trapezium. These are just such massive hot and luminous O-Type stars, clearing out their local neighborhoods and lighting up the interior of the nebula like a Chinese lantern.

And thus science fact imitates fiction in an ironic twist, as it turns out that “Death Stars” do indeed blast planets – or at least protoplanetary disks – on occasion!

Be sure to check out a great piece on ALMA on a recent episode of CBS 60 Minutes:

Read the abstract and the full (paywalled) paper on ALMA Observations of the Orion Proplyds in The Astrophysical Journal.

March 12, 2014December 23, 2015 by David Dickinson

Astronomers Identify the Largest Yellow “Hypergiant” Star Known

A stellar monster lurks in heart of the Centaur.

A recent analysis of a star in the south hemisphere constellation of Centaurus has highlighted the role that amateurs play in assisting with professional discoveries in astronomy.

The find used of the European Southern Observatory’s Very Large Telescope based in the Atacama Desert in northern Chile — as well as data from observatories around the world — to reveal the nature of a massive yellow “hypergiant” star as one of the largest stars known.

The stats for the star are impressive indeed: dubbed HR 5171 A, the binary system weighs in at a combined 39 solar masses, has a radius of over 1,300 times that of our Sun, and is a million times as luminous. Located 3,600 parsecs or over 11,700 light years distant, the star is 50% larger than the famous red giant Betelgeuse. Plop HR 5171 A down into the center of our own solar system, and it would extend out over 6 astronomical units (A.U.s) past the orbit of Jupiter.

The field around HR 5171 A (the brightest star just below center). Credit: ESO/Digitized Sky Survey 2.

Researchers used observations going back over 60 years – some of which were collected by dedicated amateur astronomers – to pin down the nature of this curious star. A variable star just below naked eye visibility spanning a magnitude range from +6.1 to +7.3, HR 5171 A also has a relatively small companion star orbiting across our line of sight once every 1300 days. Such a system is known as an eclipsing binary. Famous examples of similar systems are the star Algol (Alpha Persei), Epsilon Aurigae and Beta Lyrae. The companion star for HR 5171 is also a large star in its own right at around six solar masses and 400 solar radii in size. The distance from center-to-center for the system is about 10 A.U.s – the distance from Sol to Saturn – and the surface-to-surface distance for the A and B components of the system are “only” about 2.8 A.U.s apart. This all means that these two massive stars are in physical contact, with the expanded outer atmosphere of the bloated primary contacting the secondary, giving the pair a distorted peanut shape.

“The companion we have found is very significant as it can have an influence on the fate of HR 5171 A, for example stripping off its outer layers and modifying its evolution,” said astronomer Olivier Chesneau of the Observatoire de la Côte d’Azur in Nice France in the recent press release.

Knowing the orbital period of a secondary star offers a method to measure the mass of the primary using good old Newtonian mechanics. Coupled with astrometry used to measure its tiny parallax, this allows astronomers to pin down HR 5171 A’s stupendous size and distance.

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Along with luminous blue variables, yellow hypergiants are some of the brightest stars known, with an absolute magnitude of around -9. That’s just 16x times fainter than the apparent visual magnitude of a Full Moon but over 100 times brighter than Venus – if you placed a star like HR 5171 A 32 light years from the Earth, it would easily cast a shadow.

Astronomers used a technique known as interferormetry to study HR 5171 A, which involves linking up several telescopes to create the resolving power of one huge telescope. Researchers also culled through over a decade’s worth data to analyze the star. Though much of what had been collected by the American Association of Variable Star Observers (the AAVSO) had been considered to be too noisy for the purposes of this study, a dataset built from 2000 to 2013 by amateur astronomer Sebastian Otero was of excellent quality and provided a good verification for the VLT data.

The discovery is also crucial as researchers have come to realize that we’re catching HR 5171 A at an exceptional phase in its life. The star has been getting larger and cooling as it grows, and this change can be seen just over the past 40 year span of observations, a rarity in stellar astronomy.

“It’s not a surprise that yellow hypergiants are very instable and lose a lot of mass,” Chesneau told Universe Today. “But the discovery of a companion around such a bright star was a big surprise since any ‘normal’ star should at least be 10,000 times fainter than the hypergiant. Moreover, the hypergiant was much bigger than expected. What we see is not the companion itself, but the regions gravitationally controlled and filled by the wind from the hypergiant. This is a perfect example of the so-called Roche model. This is the first time that such a useful and important model has really been imaged. This hypergiant exemplifies a famous concept!”

Indeed, you can see just such photometric variations as the secondary orbits its host in the VLTI data collected by the AMBER interferometer, backed up by observations from GEMINI’s NICI chronograph:

Credit: ESO/VLT/GEMINI/NICI — Looking at the bizarre system of HR 5171. Credit: Olivier Chesneau/ESO/VLT/GEMINI/NICI

The NIGHTFALL program was also used for modeling the eclipsing binary components.

These latest measurements place HR 5171 A firmly in the “Top 10” for largest stars in terms of size known, as well as the largest yellow hypergiant star known This is due mainly to tidal interactions with its companion. Only eight yellow hypergiants have been identified in our Milky Way galaxy. HR 5171 A is also in a crucial transition phase from a red hypergiant to becoming a luminous blue variable or perhaps even a Wolf-Rayet type star, and will eventually end its life as a supernova.

Enormous stars: From left to right, The Pistol Star, Rho Cassiopeiae, Betelgeuse and VY Canis Majoris compared with the orbits of Jupiter (in red) and Neptune (in blue). Remember, HR 5171 A is 50% larger than Betelgeuse! Credit: Anynobody under a Creative Commons Attribution Share-Alike 3.0 Unported license.

HR 5171 A is also known as HD 119796, HIP 67261, and V766 Centauri. Located at Right Ascension 13 Hours 47’ 11” and declination -62 degrees 35’ 23,” HR 5171 culminates just two degrees above the southern horizon at local midnight as seen from Miami in late March.

HR 5171 A: a finder chart. Click to enlarge. Credit: Stellarium

HR 5171 A is a fine binocular object for southern hemisphere observers.

But the good news is, there’s another yellow hypergiant visible for northern hemisphere observers named Rho Cassiopeiae:

Rho Cass is one of the few naked eye examples of a yellow hypergiant star, and varies from magnitude +4.1 to +6.2 over an irregular period.

It’s amusing read the Burnham’s Celestial Handbook entry on Rho Cass. He notes the lack of parallax and the spectral measurements of the day — the early 1960s — as eluding to a massive star with a “true distance… close to 3,000 light years!” Today we know that Rho Cassiopeiae actually lies farther still, at over 8,000 light years distant. Robert Burnham would’ve been impressed even more by the amazing nature of HR 5171 as revealed today by ESO astronomers!

– The AAVSO is always seeking observations from amateur astronomers of variable stars.

March 3, 2014December 23, 2015 by Jason Major

SOFIA Gives Scientists a First-Class View of a Supernova

This Image of M82 including a supernova at near-infrared wavelengths J, H, and K (1.2, 1.65, and 2.2 microns), made Feb. 20 by the FLITECAM instrument on SOFIA. (NASA/SOFIA/FLITECAM team/S. Shenoy)

Astronomers wanting a closer look at the recent Type Ia supernova that erupted in M82 back in January are in luck. Thanks to NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) near-infrared observations have been made from 43,000 feet — 29,000 feet higher than some of the world’s loftiest ground-based telescopes.

(And, technically, that is closer to M82. If only just a little.)

All sarcasm aside, there really is a benefit from that extra 29,000 feet. Earth’s atmosphere absorbs a lot of wavelengths of the electromagnetic spectrum, especially in the infrared and sub-millimeter ranges. So in order to best see what’s going on in the Universe in these very active wavelengths, observational instruments have to be placed in very high, dry (and thus also very remote) locations, sent entirely out into space, or, in the case of SOFIA, mounted inside a modified 747 where they can simply be flown above 99% of the atmosphere’s absorptive water vapor.

NASA's airborne SOFIA observatory (SOFIA/USRA) — NASA’s airborne SOFIA observatory (SOFIA/USRA)

During a recent 10-hour flight over the Pacific, researchers aboard SOFIA turned their attention to SN2014J, one of the closest Type Ia “standard candle” supernovas that have ever been seen. It appeared suddenly in the relatively nearby Cigar Galaxy (M82) in mid-January and has since been an exciting target of observation for scientists and amateur skywatchers alike.

In addition to getting a bird’s-eye-view of a supernova, they used the opportunity to calibrate and test the FLITECAM (First Light Infrared Test Experiment CAMera) instrument, a near infrared camera with spectrographic capabilities mounted onto SOFIA’s 2.5-meter German-built main telescope.

What they’ve found are the light signatures of heavy metals being ejected by the exploding star. (Rock on, SN2014J.)

“When a Type Ia supernova explodes, the densest, hottest region within the core produces nickel 56,” said Howie Marion from the University of Texas at Austin, a co-investigator aboard the flight. “The radioactive decay of nickel-56 through cobalt-56 to iron-56 produces the light we are observing tonight. At this life phase of the supernova, about one month after we first saw the explosion, the H- and K-band spectra are dominated by lines of ionized cobalt. We plan to study the spectral features produced by these lines over a period of time and see how they change relative to each other. That will help us define the mass of the radioactive core of the supernova.”

Three images of M82 and the supernova SN2014J, including one from the FLITECAM instrument on SOFIA (right). Credit: NASA/SOFIA/FLITECAM team/S. Shenoy

Further observations from SOFIA will help researchers learn more about the evolution of Type Ia supernovas, which in addition to being part of the life cycles of certain binary-pair stars are also valuable tools used by astronomers to determine distances to far-off galaxies.

Researchers work at the FLITECAM instrument station on board SOFIA on Feb. 20 (NASA/SOFIA/N. Veronico)

“To be able to observe the supernova without having to make assumptions about the absorption of the Earth’s atmosphere is great,” said Ian McLean, professor at UCLA and developer of FLITECAM. “You could make these observations from space as well, if there was a suitable infrared spectrograph to make those measurements, but right now there isn’t one. So this observation is something SOFIA can do that is absolutely unique and extremely valuable to the astronomical community.”

Source: SOFIA Science Center, NASA Ames

UPDATE 4 March 2014: The FY 2015 budget request proposed by the White House will effectively shelf the SOFIA mission, redirecting its funding toward planetary missions like Cassini and an upcoming Europa mission. Unfortunately, SOFIA’s flying days are now numbered, unless German partner DLR increases its contribution. Read more here.