Posted on by Shannon Hall

Hypervelocity Neutron Stars Crashing Into White Dwarfs — A Scenario for the Loneliest Supernovae?

University of Warwick researchers explain mystery of the loneliest supernovas. Compact binary star systems that have been thrown far from their host galaxy when one star of that pair became a neutron star, go through a second trauma when the remaining white dwarf star is eventually pulled onto the neutron star Credit: Artist’s impression is free to use with story but must include this credit: © Mark A. Garlick / space-art.co.uk / University of Warwick

It’s hard to comprehend the vast emptiness of space. Especially when we detect odd signatures, such as luminous explosions that are neither as bright nor as long as traditional supernovae, originating in the unfathomable emptiness.

But a team of astronomers is now beginning to understand these so-called calcium-rich transients, often referred to as the Universe’s loneliest supernovae, hypothesizing that they’re created by collisions between white dwarf stars and neutron stars — both of which have been thrown out of their galaxy.

“One of the weirdest aspects is that they seem to explode in unusual places. For example, if you look at a galaxy, you expect any explosions to roughly be in line with the underlying light you see from that galaxy, since that is where the stars are” said lead author Joseph Lyman from the University of Warwick in a press release. “However, a large fraction of these are exploding at huge distances from their galaxies, where the number of stellar systems is miniscule.”

The team guessed there could be very faint dwarf galaxies, hiding beneath the limit of detection, but found nothing with our best telescopes, namely the Very Large Telescope in Chile and the Hubble Space Telescope.

“So the question becomes, how did the get there?” pondered Lyman. Roughly a third of these events occur at least 65 thousand light-years away from a potential host galaxy.

We’ve discovered dozens of so-called hypervelocity stars — single stars that escape their home galaxy, traveling rapidly throughout intergalactic space — and even one runaway globular cluster. Nature clearly has a way of kicking systems out of an entire galaxy, likely by an interaction with the supermassive black hole lurking in the center of that galaxy.

So it’s viable that the source of these supernovae was first kicked out of its host galaxy. But the second puzzle wondered what type of system could have caused such an odd explosion.

Previous studies show that calcium comprises up to half of the material thrown off in these transients, compared to only a tiny fraction in normal supernovae. It remained unclear how to explain such a calcium-rich system.

So the research team compared their data to short-duration gamma ray bursts, which are also seen to explode in remote locations with no coincident galaxy detected. We think these enigmatic bursts occur when two neutron stars collide, or when a neutron star merges with a black hole.

Alas, the research team discovered that if a neutron star collided with a white dwarf, the explosion would not only provide enough energy to generate the low luminosity of the calcium rich transients, but it would also produce calcium rich material.

“What we therefore propose is these are systems that have been ejected from their galaxy,” said Lyman. “A good candidate in this scenario is a white dwarf and a neutron star in a binary system. The neutron star is formed when a massive star goes supernova. The mechanism of the supernova explosion causes the neutron star to be ‘kicked’ to very high velocities (100s of km/s). This high velocity system can then escape its galaxy, and if the binary system survives the kick, the white dwarf and neutron star will merge causing the explosive transient.”

Any merger should also produce high-energy gamma-ray bursts, motivating further observations of any new examples.

The paper has been published today in the journal Monthly Notices of the Royal Astronomical Society and is available online.

Posted on by Shannon Hall

New VLT Observations Clear Up Dusty Mystery

The dwarf galaxy UGC 5189A, site of the supernova SN 2010jl. Image Credit: ESO

The Universe is overflowing with cosmic dust. Planets form in swirling clouds of dust around a young star; Dust lanes hide more-distant stars in the Milky Way above us; And molecular hydrogen forms on the dust grains in interstellar space.

Even the soot from a candle is very similar to cosmic carbon dust. Both consist of silicate and amorphous carbon grains, although the size grains in the soot are 10 or more times bigger than typical grain sizes in space.

But where does the cosmic dust come from?

A group of astronomers has been able to follow cosmic dust being created in the aftermath of a supernova explosion. The new research not only shows that dust grains form in these massive explosions, but that they can also survive the subsequent shockwaves.

Stars initially draw their energy by fusing hydrogen into helium deep within their cores. But eventually a star will run out of fuel. After slightly messy physics, the star’s contracted core will begin to fuse helium into carbon, while a shell above the core continues to fuse hydrogen into helium.

The pattern continues for medium to high mass stars, creating layers of different nuclear burning around the star’s core. So the cycle of star birth and death has steadily produced and dispersed more heavy elements throughout cosmic history, providing the substances necessary for cosmic dust.

“The problem has been that even though dust grains composed of heavy elements would form in supernovae, the supernova explosion is so violent that the grains of dust may not survive,” said coauthor Jens Hjorth, head of the Dark Cosmology Center at the Niels Bohr Institute in a press release. “But cosmic grains of significant size do exist, so the mystery has been how they are formed and have survived the subsequent shockwaves.”

The team led by Christa Gall used ESO’s Very Large Telescope at the Paranal Observatory in northern Chile to observe a supernova, dubbed SN2010jl, nine times in the months following the explosion, and for a tenth time 2.5 years after the explosion. They observed the supernova in both visible and near-infrared wavelengths.

SN2010jl was 10 times brighter than the average supernova, making the exploding star 40 times the mass of the Sun.

“By combining the data from the nine early sets of observations we were able to make the first direct measurements of how the dust around a supernova absorbs the different colours of light,” said lead author Christa Gall from Aarhus University. “This allowed us to find out more about the dust than had been possible before.”

The results indicate that dust formation starts soon after the explosion and continues over a long time period.

The dust initially forms in material that the star expelled into space even before it exploded. Then a second wave of dust formation occurs, involving ejected material from the supernova. Here the dust grains are massive — one thousandth of a millimeter in diameter — making them resilient to any following shockwaves.

“When the star explodes, the shockwave hits the dense gas cloud like a brick wall. It is all in gas form and incredibly hot, but when the eruption hits the ‘wall’ the gas gets compressed and cools down to about 2,000 degrees,” said Gall. “At this temperature and density elements can nucleate and form solid particles. We measured dust grains as large as around one micron (a thousandth of a millimeter), which is large for cosmic dust grains. They are so large that they can survive their onward journey out into the galaxy.”

If the dust production in SN2010jl continues to follow the observed trend, by 25 years after the supernova explosion, the total mass of dust will have half the mass of the Sun.

The results have been published in Nature and are available for download here. Niels Bohr Institute’s press release and ESO’s press release are also available.

Posted on by Fraser Cain

Which Star Will Explode Next?

Which Star Will Explode Next?

Come on Betelguese, explode already. Or maybe it’ll be Eta Carinae. Which of the billions of stars in the galaxy can we count on to explode next, and when?

When a new supernova is discovered, we can take that as a reminder that we live in a terribly hostile Universe. Sometimes stars just explode, and devastate a corner of a galaxy. On average, a supernova goes off twice a century in a galaxy the size of the Milky Way. Since there are potentially hundreds of billions of galaxies out there, dozens of supernovae are detonating every second in the observable Universe.

The last bright supernova was SN 1987A, located in the Large Magellanic Cloud, about 168,000 light years away. Even though it was far, it exploded with so much energy it was visible to the unaided eye. That one wasn’t even in our galaxy.

The Milky Way’s most recent supernova that we know of was G1.9+0.3, recently confirmed by the Chandra X-Ray Observatory. It would have been visible from Earth about 100 years ago, but it was located in the dusty regions of the Milky Way and obscured from our view.

The last bright supernova was discovered in 1604 by the astronomer Johannes Kepler. This was a naked-eye supernova, in fact, at its peak, it was brighter than any other star in the night sky and for a few weeks it was even visible during the day.

So, which star is likely to explode next? Can we even know that?

Artist’s impression of the supergiant star Betelgeuse as it was revealed with ESO’s Very Large Telescope. Credit: ESO/L.Calçada
Artist’s impression of the supergiant star Betelgeuse as it was revealed with ESO’s Very Large Telescope. Credit: ESO/L.Calçada

We can, and there are even likely candidates. There’s Betelgeuse, the red supergiant star located in the constellation of Orion, only 640 light-years from Earth. Betelgeuse is massive, and it’s only been around for 10 million years. It will likely explode within a million years. Which, in astronomical time, is just before lunch.

Another candidate is Eta Carinae, located about 8,000 light years from us. This blue supergiant has roughly 120 times the mass of the Sun, and it’s ready to explode in the next few hundred thousand years. Which, from the Universe’s perspective is any moment now.

The closest star that could go supernova is most likely Spica, a short 240 light-years from Earth.
Spica has several times the mass of the Sun, it shouldn’t go off for a few million years yet. According to Phil Plait, the Bad Astronomer, another candidate is the star IK Pegasus A at just 150 light-years away.

Bright Star Spica - Brightest Star in Virgo 16" F4.5 2 minute exposure , 400 ISO
Bright Star Spica – Brightest Star in Virgo by John Chumack

If any of these supernovae do go off, they’ll be incredibly bright. Supernova Betelgeuse would be visible during the day, it might even brighter than the full Moon. It would shine in the sky for weeks, possibly months before fading away.

These explosions are destructive, releasing a torrent of gamma radiation and high energy particles. Fortunately for us, we’re safe. You’d need to be within about 75 light years to really receive a lethal dose. Which means that even the closest supernova candidate is still too far to cause us any real harm.

Which star is set to explode next? Well, in the last second, 30 supernovae just went off, somewhere in the Universe. Here in our galaxy, there should be a supernova in the next 50 years or so, but we still might not be able to see it.
And if we’re really really lucky, Betelgeuse or Eta Carinae will detonate, and we’ll witness one of the most awe inspiring events in the cosmos from the safety of the front porch of our galactic suburban home. Any time now.

Which star would you like to see go supernova? Tell us in the comments below!

Posted on by Shannon Hall

Is Eta Carinae Heading Toward Another Eruption?

Eta Car

Massive stars can devastate their surroundings, unleashing hot winds and blasting radiation. With a mass over 100 times heavier than the Sun and a luminosity a million times brighter than the Sun, Eta Carinae clocks in as one of the biggest and brightest stars in our galaxy.

The enigmatic object walks a thin line between stellar stability and tumultuous explosions. But now a team of international astronomers is growing concerned that it’s leaning toward instability and eruption.

In the 19th Century the star mysteriously threw off unusually bright light for two decades in an event that became known as the “Great Eruption,” the causes of which are still up for debate. John Herschel and others watched as Eta Carinae’s brightness oscillated around that of Vega — rivaling a supernova explosion.

We now know the star ejected material in the form of two big globes. “During the eruption the star threw off more than 10 solar masses, which can now be observed as the surrounding bipolar nebula,” said lead author Dr. Andrea Mehner from the European Southern Observatory. Miraculously the star survived, but the nebula has been expanding into space ever since.

Eta Carinae has been observed at the South African Astronomical Observatory — a 0.75m telescope outside of Cape Town — for more than 40 years, providing a wealth of data. From the start of observations in 1976 until 1998, astronomers saw an increase across the J, H, K and L bands — filters, which allow certain wavelength ranges of infrared light to pass through.

“This data set is unique for its consistency over a timespan of more than 40 years,” Mehner told Universe Today. “It provides us with the opportunity to analyze long-term changes in the system as Eta Carinae still recovers from its Great Eruption.”

In order to understand the longterm overall increase in light we have to look at a more recent discovery noted in 2005 when scientists discovered that Eta Carinae is actually two stars: a massive blue star and a smaller companion. The temperature increased for 15 years until the companion came very close to the massive star, reaching periastron.

This increase in brightness is likely due to an overall increase in temperature of some component of the Eta Carinae system (which includes the massive blue star, its smaller companion, and the shells of gas and dust that now enshroud the system).

After 1998, however, the linear trend changed significantly and the star’s brightness increased much more rapidly in the J and H bands. It’s getting bluer, which in astronomy, typically means it’s getting hotter.

However, it’s unlikely the star itself is getting hotter. Instead we are seeing the effect of dust around the star being destroyed rapidly. Dust absorbs blue light. So if the dust is getting destroyed, more blue light will be able to pass through the nebulous globes surrounding the system. If this is the case, then we’re really seeing the star as it truly is, without dust absorbing certain wavelengths of its light.

While the nebula is slowly expanding and the dust is therefore dissipating, the authors do not think it’s enough to account for the recent brightening. Instead Eta Carinae is likely rotating at a different speed or losing mass at a different rate. “The changes observed may imply that the star is becoming more unstable and may head towards another eruptive phase,” Mehner told Universe Today.

Perhaps Eta Carinae is heading toward another “Great Eruption.” Only time will tell. But in a field where most events occur on a timescale of millions of years, it’s a great opportunity to watch the system evolve on a human time scale. And when Eta Carinae reaches periastron in the middle of this year, tens of telescopes will be collecting its light, hoping to see a sudden turn of events that may help us explain this exotic system.

The paper has been accepted for publication in Astronomy & Astrophysics and is available for download here.

Posted on by Fraser Cain

Will The Sun Explode?

Will The Sun Explode?

All stars die, some more violently than others.

Once our own Sun has consumed all the hydrogen fuel in its core, it too will reach the end of its life. Astronomers estimate this to be a short 7 billion years from now. For a few million years, it will expand into a red giant, puffing away its outer layers. Then it’ll collapse down into a white dwarf and slowly cool down to the background temperature of the Universe.

I’m sure you know that some other stars explode when they die. They also run out of fuel in their core, but instead of becoming a red giant, they detonate in a fraction of a second as a supernova.

So, what’s the big difference between stars like our Sun and the stars that can explode as supernovae?

Mass. That’s it.

Supernova progenitors – these stars capable of becoming supernovae – are extremely massive, at least 8 to 12 times the mass of our Sun. When a star this big runs out of fuel, its core collapses. In a fraction of a second, material falls inward to creating an extremely dense neutron star or even a black hole. This process releases an enormous amount of energy, which we see as a supernova.

If a star has even more mass, beyond 140 times the mass of the Sun, it explodes completely and nothing remains at all. If these other stars can detonate like this, is it possible for our Sun to explode?

Could there be some chain reaction we could set off, some exotic element a rare comet could introduce on impact, or a science fiction doomsday ray we could fire up to make the Sun explode?

Nope, quite simply, it just doesn’t have enough mass. The only way this could ever happen is if it was much, much more massive, bringing it to that lower supernovae limit.

In other words, you would need to crash an equally massive star into our Sun. And then do it again, and again.. and again… another half dozen more times. Then, and only then would you have an object massive enough to detonate as a supernova.

We don't have to worry about our sun exploding into a supernova.
We don’t have to worry about our sun exploding into a supernova.

Now, I’m sure you’re all resting easy knowing that solar detonation is near the bottom of the planetary annihilation list. I’ve got even better news. Not only will this never happen to the Sun, but there are no large stars close enough to cause us any damage if they did explode.
A supernova would need to go off within a distance of 100 light-years to irradiate our planet.

According to Dr. Phil Plait from Bad Astronomy, the closest star that could detonate as a supernova is the 10 solar mass Spica, at a distance of 260 light-years. No where near close enough to cause us any danger.

So don’t worry about our Sun exploding or another nearby star going supernova and wiping us out. You can put your feet up and relax, as it’s just not going to happen.

Posted on by Fraser Cain

Can Stars Collide?

Can Stars Collide?

Imagine a really bad day. Perhaps you’re imagining a day where the Sun crashes into another star, destroying most of the Solar System.

No? Well then, even in your imagination things aren’t so bad… It’s all just matter of perspective.

Fortunately for us, we live in out the boring suburbs of the Milky Way. Out here, distances between stars are so vast that collisions are incredibly rare. There are places in the Milky Way where stars are crowded more densely, like globular clusters, and we get to see the aftermath of these collisions. These clusters are ancient spherical structures that can contain hundreds of thousands of stars, all of which formed together, shortly after the Big Bang.

Within one of these clusters, stars average about a light year apart, and at their core, they can get as close to one another as the radius of our Solar System. With all these stars buzzing around for billions of years, you can imagine they’ve gotten up to some serious mischief.

Within globular clusters there are these mysterious blue straggler stars. They’re large hot stars, and if they had formed with the rest of the cluster, they would have detonated as supernovae billions of years ago. So scientists figure that they must have formed recently.

How? Astronomers think they’re the result of a stellar collision. Perhaps a binary pair of stars merged, or maybe two stars smashed into one another.

Professor Mark Morris of the University of California at Los Angeles in the Department of Physics and Astronomy helps to explain this idea.

“When you see two stars colliding with each other, it depends on how fast they’re moving. If they’re moving at speeds like we see at the center of our galaxy, then the collision is extremely violent. If it’s a head-on collision, the stars get completely splashed to the far corners of the galaxy. If they’re merging at slower velocities than we see at our neck of the woods in our galaxy, then stars are more happy to merge with us and coalesce into one single, more massive object.”

There’s another place in the Milky Way where you’ve got a dense collection of stars, racing around at breakneck speeds… near the supermassive black hole at the center of the galaxy.

This monster black hole contains the mass of 4 million times the Sun, and dominates the region around the center of the Milky Way.

This artist's concept illustrates a supermassive black hole with millions to billions times the mass of our sun. Supermassive black holes are enormously dense objects buried at the hearts of galaxies. Image credit: NASA/JPL-Caltech
Supermassive black holes are enormously dense objects buried at the hearts of galaxies. Image credit: NASA/JPL-Caltech

“The core of the Milky Way is one of those places where you find the extremes of nature. The density of stars there is higher than anywhere else in the galaxy,”Professor Morris continues. “Overall, in the center of our galaxy on scales of hundreds of light years, there is much more gas present than anywhere else in the galaxy. The magnetic field is stronger there than anywhere else in the galaxy, and it has it’s own geometry there. So it’s an unusual place, an energetic place, a violent place, because everything else is moving so much faster there than you see elsewhere.”

“We study the stars in the immediate vicinity of the black hole, and we find that there’s not as many stars as one might have expected, and one of the explanations for that is that stars collide with each other and either eliminate one another or merge, and two stars become one, and both of those processes are probably occurring.”

Stars whip around it, like comets dart around our Sun, and interactions are commonplace.

There’s another scenario that can crash stars together.

The Milky Way mostly has multiple star systems. Several stars can be orbiting a common center of gravity. Many are great distances, but some can have orbits tighter than the planets around our Sun.

When one star reaches the end of its life, expanding into a red giant, It can consume its binary partner. The consumed star then strips away 90% of the mass of the red giant, leaving behind a rapidly pulsating remnant.

What about when galaxies collide? That sounds like a recipe for mayhem.
Surprisingly, not so much.

“That’s actually a very interesting question, because if you imagine two galaxies colliding, you’d imagine that to be an exceptionally violent event,’ Professor Morris explains. “But in fact, the stars in those two galaxies are relatively unaffected. The number of stars that will collide when two galaxies collide is possibly counted on the fingers of one or two hands. Stars are so few and far between that they just aren’t going to meet each other with any significance in a field like that.”

Galaxy mergers, such as the Mice Galaxies will be part of Galaxy Zoo's newest project. Credit: Hubble Space Telescope
The Mice galaxies merging. Credit: Hubble Space Telescope

“What you see when you see two galaxies collide, however, on the large scale, is that the tidal forces of the two galaxies will rip each of the galaxies apart in terms of what it will look like. Streams of stars will be strewn out in various directions depending on the precise history of the interaction between the two galaxies. And so, eventually over time, the galaxies will merge, the whole configuration of stars will settle down into something that looks unlike either of the two initially colliding galaxies. Perhaps something more spheroidal or spherical, and it might look more like an elliptical galaxy than the spiral galaxy that these two galaxies now are.”

Currently, we’re on a collision course with the Andromeda Galaxy, and it’s expected we’ll smash into it in about 4 billion years. The gas and dust will collide and pile up, igniting an era of furious star formation. But the stars themselves? They’ll barely notice. The stars in the two galaxies will just streak past each other, like a swarm of angry bees.

Phew.

So, good news! When you’re imagining a worse day, you won’t have to worry about our Sun colliding with another star. We’re going to be safe and sound for billions of years. But if you live in a globular cluster or near the center of the galaxy, you might want to check out some property here in the burbs.

Thanks to Professor Mark Morris at UCLA – visit their Physics and Astronomy program homepage here.

Posted on by Shannon Hall

How do Hypervelocity Stars End up Breaking The Speed Limit?

An artist's conception of a hypervelocity star that has escaped the Milky Way. Credit: NASA

The Sun is racing through the Galaxy at a speed that is 30 times greater than a space shuttle in orbit (clocking in at 220 km/s with respect to the galactic center). Most stars within the Milky Way travel at a relatively similar speed. But certain stars are definitely breaking the stellar speed limit. About one in a billion stars travel at a speed roughly 3 times greater than our Sun – so fast that they can easily escape the galaxy entirely!

We have discovered dozens of these so-called hypervelocity stars. But how exactly do these stars reach such high speeds? Astronomers from the University of Leicester may have found the answer.

The first clue comes in observing hypervelocity stars, where we can note their speed and direction. From these two measurements, we can trace these stars backward in order to find their origin. Results show that most hypervelocity stars begin moving quickly in the Galactic Center.

We now have a rough idea of where these stars gain their speed, but not how they reach such high velocities. Astronomers think two processes are likely to kick stars to such great speeds. The first process involves an interaction with the supermassive black hole (Sgr A*) at the center of our Galaxy. When a binary star system wanders too close to Sgr A*, one star is likely to be captured, while the other star is likely to be flung away from the black hole at an alarming rate.

The second process involves a supernova explosion in a binary system. Dr. Kastytis Zubovas, lead author on the paper summarized here, told Universe Today, “Supernova explosions in binary systems disrupt those systems and allow the remaining star to fly away, sometimes with enough velocity to escape the Galaxy.”

There is, however, one caveat. Binary stars in the center of our Galaxy will both be orbiting each other and orbiting Sgr A*. They will have two velocities associated with them. “If the velocity of the star around the binary’s center of mass happens to line up closely with the velocity of the center of mass around the supermassive black hole, the combined velocity may be large enough to escape the Galaxy altogether,” explained Zubovas.

In this case, we can’t sit around and wait to observe a supernova explosion breaking up a binary system. We would have to be very lucky to catch that! Instead, astronomers rely on computer modeling to recreate the physics of such an event. They set up multiple calculations in order to determine the statistical probability that the event will occur, and check if the results match observations.

Astronomers from the University of Leicester did just this. Their model includes multiple input parameters, such as the number of binaries, their initial locations, and their orbital parameters. It then calculates when a star might undergo a supernova explosion, and depending on the position of the two stars at that time, the final velocity of the remaining star.

The probability that a supernova disrupts a binary system is greater than 93%. But does the secondary star then escape from the galactic center? Yes, 4 – 25% of the time. Zubovas described, “Even though this is a very rare occurrence, we may expect several tens of such stars to be created over 100 million years.” The final results suggest that this model ejects stars with rates high enough to match the observed number of hypervelocity stars.

Not only do the number of hypervelocity stars match observations but also their distribution throughout space. “Hypervelocity stars produced by our supernova disruption method are not evenly distributed on the sky,” said Dr. Graham Wynn, a co-author on the paper. “They follow a pattern which retains an imprint of the stellar disk they formed in. Observed hypervelocity stars are seen to follow a pattern much like this.”

In the end, the model was very successful at describing the observed properties of hypervelocity stars. Future research will include a more detailed model that will allow astronomers to understand the ultimate fate of hypervelocity stars, the effect that supernova explosions have on their surroundings, and the galactic center itself.

It’s likely that both scenarios – binary systems interacting with the supermassive black hole and one undergoing a supernova explosion – form hypervelocity stars.  Studying both will continue to answer questions about how these speedy stars form.

The results will be published in the Astrophysical Journal (preprint available here)

 

Posted on by Nancy Atkinson

Hubble Telescope Breaks Record in Finding Most Distant Type Ia Supernova

This is a NASA/ESA Hubble Space Telescope view looking long ago and far away at a supernova that exploded over 10 billion years ago — the most distant Type Ia supernova ever detected. The supernova’s light is just arriving at Earth, having travelled more than 10 billion light-years (redshift 1.914) across space. Credit: NASA, ESA, A. Riess (STScI and JHU), and D. Jones and S. Rodney (JHU).

Astronomers just keep honing their skills and refining their techniques to get the most out of their telescopes. Scientists using the Hubble Space Telescope have now broken the record for the most distant Type Ia supernova ever imaged. This supernova is over 10 billion light-years away, with a redshift of 1.914. When this star exploded 10 billion years ago, the Universe was in its early formative years and stars were being born at a rapid rate.

“This new distance record holder opens a window into the early Universe, offering important new insights into how these supernovae form,” said astronomer David O. Jones of The Johns Hopkins University in Baltimore, Md., lead author on the science paper detailing the discovery. “At that epoch, we can test theories about how reliable these detonations are for understanding the evolution of the Universe and its expansion.”

These three frames show the supernova dubbed SN UDS10Wil, or SN Wilson, the most distant Type Ia supernova ever detected. The leftmost frame in this image shows just the supernova’s host galaxy, before the violent explosion. The middle frame shows the galaxy after the supernova had gone off, and the third frame indicates the brightness of the supernova alone. Credit: NASA, ESA, A. Riess (STScI and JHU), and D. Jones and S. Rodney (JHU)
These three frames show the supernova dubbed SN UDS10Wil, or SN Wilson, the most distant Type Ia supernova ever detected. The leftmost frame in this image shows just the supernova’s host galaxy, before the violent explosion. The middle frame shows the galaxy after the supernova had gone off, and the third frame indicates the brightness of the supernova alone. Credit: NASA, ESA, A. Riess (STScI and JHU), and D. Jones and S. Rodney (JHU)

Designated as SN UDS10Wil (and nicknamed SN Wilson after American President Woodrow Wilson (president from 1913-1921), the distant supernova was part of a three-year Hubble program to survey faraway Type Ia supernovae and determine whether they have changed during the 13.8 billion years since the explosive birth of the universe. Since 2010, the CANDELS+CLASH Supernova Project has uncovered more than 100 supernovae of all types that exploded from 2.4 to over 10 billion years ago.

The previous record holder for Type Ia was announced earlier this year, a supernova that exploded around 9 billion years ago and has a redshift of 1.7. Although SN Wilson is only 4 percent more distant than the previous record holder, it pushes roughly 350 million years farther back in time.

The most distant supernovae ever are a pair of super-luminous supernovae, at redshifts of 2.05 and 3.90, announced in November 2012. Read about that discovery here.

Astronomers took advantage of the sharpness and versatility of Hubble’s Wide Field Camera 3 to search for supernovae in near-infrared light and verify their distance with spectroscopy. These bright beacons are prized by astronomers because they can be used as a yardstick for measuring cosmic distances, thereby yielding clues to the nature of dark energy, the mysterious force accelerating the rate of expansion of the Universe.

Additionally, finding remote supernovae provides a powerful method to measure the universe’s accelerating expansion.

“The Type Ia supernovae give us the most precise yardstick ever built, but we’re not quite sure if it always measures exactly a yard,” said team member Steve Rodney of Johns Hopkins University. “The more we understand these supernovae, the more precise our cosmic yardstick will become.”

Read the team’s paper: The Discovery of the Most Distant Known Type Ia Supernova at Redshift 1.914

Sources: NASA, ESA

Posted on by Nancy Atkinson

New Bright and Blue Supernova in NGC 1365

Supernova 2012fr in NGC 1365. It is the bright blue “star” directly below the galaxy core. Credit: Rolf Wahl Olsen. Click the image for larger version.

A very bright supernova has shown up in NGC 1365, the galaxy also known as the Great Barred Spiral Galaxy, visible now for southern hemisphere observers. This already elegant galaxy lies about 56 million light-years away in the constellation Fornax. The supernova, a type Ia, was discovered by Alain Klotz with the TAROT telescope at the La Silla Observatory in Chile on October 27, 2012. “The supernova is a very nice addition to the already highly photogenic galaxy,” said Rolf Wahl Olsen, who took the gorgeous image above. “I’m amazed by how blue it is; it’s really intense.”

Supernova 2012fr is the bright and intensely blue star directly below the galaxy core. Olsen said that as of November 10, 2012 the supernova appeared to be nearing its peak, with an R magnitude of 11.90.

“To get an idea of how bright this event is we can calculate the absolute magnitude M of the supernova using the following formula where m is the apparent magnitude and D the distance in parsecs: M = m – 5(log10(D) – 1),” Olsen wrote. “This gives an absolute magnitude of -19.27 for SN2012fr. This means that if the supernova had occurred at a distance to us similar to Betelgeuse (643 light years), then its apparent magnitude would be -12.80, same as the full Moon!”

Details about Olsen’s image:
Date: 7th and 9th November 2012
Exposure: LRGB: 205:57:56:51m, total 6hrs 9mins @ -30C
Telescope: 10″ Serrurier Truss Newtonian f/5
Camera: QSI 683wsg with Lodestar guider
Filters: Astrodon LRGB E-Series Gen 2
Taken from his observatory in Auckland, New Zealand

See more of Olsen’s astrophotography at his Flickr page.