supernova Archives

August 20, 2016September 26, 2016 by Bob King

A History Of Violence: Iron Found in Fossils Suggests Supernova Role In Mass Dying

These are transmission electron microscope images showing tiny magnetofossils containing iron-60, a form of iron produced during the violent explosion and death of a massive star in a supernova. They were deposited by bacteria in sediments found on the floor of the Pacific Ocean. Click for more details. Credit: courtesy Marianne Hanzlik, Chemie Department, FG Elektronenmikroskopie, Technische Universität München

Space and events that transpire there directly affect our lives and those of our remote ancestors. Credit: Bob King — Space and events that transpire there directly affect our lives and those of our remote ancestors including early humans who walked the planet two million years ago. Credit: Bob King

Outer space touches us in so many ways. Meteors from ancient asteroid collisions and dust spalled from comets slam into our atmosphere every day, most of it unseen. Cosmic rays ionize the atoms in our upper air, while the solar wind finds crafty ways to invade the planetary magnetosphere and set the sky afire with aurora. We can’t even walk outside on a sunny summer day without concern for the Sun’s ultraviolet light burning out skin.

So perhaps you wouldn’t be surprised that over the course of Earth’s history, our planet has also been affected by one of the most cataclysmic events the universe has to offer: the explosion of a supergiant star in a Type II supernova event. After the collapse of the star’s core, the outgoing shock wave blows the star to pieces, both releasing and creating a host of elements. One of those is iron-60. While most of the iron in the universe is iron-56, a stable atom made up of 26 protons and 30 neutrons, iron-60 has four additional neutrons that make it an unstable radioactive isotope.

Crab Nebula from NASA's Hubble Space Telescope — The Crab Nebula, shown here in this image from NASA’s Hubble Space Telescope, is the expanding cloud of gas and dust left after a massive star exploded as a supernova in 1054. Supernovae propel a star’s innards back into space while creating new radioactive isotopes such as iron-60. Credit: NASA, ESA, J. Hester and A. Loll (Arizona State University)

If a supernova occurs sufficiently close to our Solar System, it’s possible for some of the ejecta to make its way all the way to Earth. How might we detect these stellar shards? One way would be to look for traces of unique isotopes that could only have been produced by the explosion. A team of German scientists did just that. In a paper published earlier this month in the Proceedings of the National Academy of Sciences, they report the detection of iron-60 in biologically produced nanocrystals of magnetite in two sediment cores drilled from the Pacific Ocean.

Magnetite is an iron-rich mineral naturally attracted to a magnet just as a compass needle responds to Earth’s magnetic field. Magnetotactic bacteria, a group of bacteria that orient themselves along Earth’s magnetic field lines, contain specialized structures called magnetosomes, where they store tiny magnetic crystals – primarily as magnetite (or greigite, an iron sulfide) in long chains. It’s thought nature went to all this trouble to help the creatures find water with the optimal oxygen concentration for their survival and reproduction. Even after they’re dead, the bacteria continue to align like microscopic compass needles as they settle to the bottom of the ocean.

These are transmission electron microscope images showing tiny magnetofossils left by bacteria about 2.5 million years ago. — These are transmission electron microscope images showing tiny magnetofossils containing iron-60, a form of iron produced during the violent explosion and death of a massive star in a supernova. They were deposited by bacteria in sediments found on the floor of the Pacific Ocean. Click for more details. Credit: courtesy Marianne Hanzlik, Chemie Department, FG Elektronenmikroskopie, Technische Universität München

After the bacteria die, they decay and dissolve away, but the crystals are sturdy enough to be preserved as chains of magnetofossils that resemble beaded garlands on the family Christmas tree. Using a mass spectrometer, which teases one molecule from another with killer accuracy, the team detected “live” iron-60 atoms in the fossilized chains of magnetite crystals produced by the bacteria. Live meaning still fresh. Since the half-life of iron-60 is only 2.6 million years, any primordial iron-60 that seeded the Earth in its formation has long since disappeared. If you go digging around now and find iron-60, you’re likely looking at at a supernova as the smoking gun.

Co-authors Peter Ludwig and Shawn Bishop, along with the team, found that the supernova material arrived at Earth about 2.7 million years ago near the boundary of the Pleistocene and Pliocene epochs and rained down for all of 800,000 years before coming to an end around 1.7 million years ago. If ever a hard rain fell.

Reconstruction of Homo habilis at the Westfälisches Museum für Archäologie. Credit: Lillyundfreya / Wikipedia

The peak concentration occurred about 2.2 million years ago, the same time our early human ancestors, Homo habilis, were chipping tools from stone. Did they witness the appearance of a spectacularly bright “new star” in the night sky? Assuming the supernova wasn’t obscured by cosmic dust, the sight must have brought our bipedal relations to their knees.

There’s even a possibility that an increase in cosmic rays from the event affected our atmosphere and climate and possibly led to a minor die-off at the time. Africa’s climate dried out and repeated cycles of glaciation became common as global temperatures continued their cooling trend from the Pliocene into the Pleistocene.

Cosmic rays strike our atmosphere all the time, but their energy is spent creating showers of secondary, less energetic particles. Credit: Simon Swordy, University of Chicago, NASA — Cosmic rays strike our atmosphere all the time, but their energy is spent striking atoms to create showers of secondary, less energetic particles, a few of which sometimes make it to the ground. Credit: Simon Swordy, University of Chicago, NASA

Cosmic rays, which are extremely fast-moving, high-energy protons and atomic nucleic, rip up molecules in the atmosphere and can even penetrate down to the surface during a nearby supernova explosion, within about 50 light years of the Sun. The high dose of radiation would put life at risk, while at the same time providing a surge in the number of mutations, one of the creative forces driving the diversity of life over the history of our planet. Life — always a story of taking the good with the bad.

The discovery of iron-60 further cements our connection to the universe at large. Indeed, bacteria munching on supernova ash adds a literal twist to the late Carl Sagan’s famous words: “The cosmos is within us. We are made of star-stuff.” Big or small, we owe our lives to the synthesis of elements within the bellies of stars.

August 3, 2016September 26, 2016 by Matt Williams

The Closest Supernova Since 1604 Is Hissing At Us

Artist’s impression of the supernova flare seen in the Large Magellanic Cloud on February 23rd, 1987. Credit: CAASTRO / Mats Björklund (Magipics).

Thirty years ago, a star that went by the designation of SN 1987A collapsed spectacularly, creating a supernova that was visible from Earth. This was the largest supernova to be visible to the naked eye since Kepler’s Supernova in 1604. Today, this supernova remnant (which is located approximately 168,000 light-years away) is being used by astronomers in the Australian Outback to help refine our understanding of stellar explosions.

Led by a student from the University of Sydney, this international research team is observing the remnant at the lowest-ever radio frequencies. Previously, astronomers knew much about the star’s immediate past by studying the effect the star’s collapse had on the neighboring Large Magellanic Cloud. But by detecting the star’s faintest hisses of radio static, the team was able to observe a great deal more of its history.

The team’s findings, which were published yesterday in the journal Monthly Notices of the Royal Astronomical Society, detail how the astronomers were able to look millions of years farther back in time. Prior to this, astronomers could only observe a tiny fraction of the star’s life cycle before it exploded – 20,000 years (or 0.1%) of its multi-million year life span.

*Artist’s impression of the star in its multi-million year long and previously unobservable phase as a large, red supergiant. Credit: CAASTRO / Mats Björklund (Magipics)*

As such, they were only able to see the star when it was in its final, blue supergiant phase. But with the help of the Murchison Widefield Array (MWA) – a low-frequency radio telescope located at the Murchison Radio-astronomy Observatory (MRO) in the West Australian desert – the radio astronomers were able to see all the way back to when the star was still in its long-lasting red supergiant phase.

In so doing, they were able to observe some interesting things about how this star behaved leading up to the final phase in its life. For instance, they found that SN 1987A lost its matter at a slower rate during its red supergiant phase than was previously assumed. They also observed that it generated slower than expected winds during this period, which pushed into its surrounding environment.

Joseph Callingham, a PhD candidate with the University of Sydney and the ARC Center of Excellence for All-Sky Astrophysics (CAASTRO), is the leader of this research effort. As he stated in a recent RAS press release:

“Just like excavating and studying ancient ruins that teach us about the life of a past civilization, my colleagues and I have used low-frequency radio observations as a window into the star’s life. Our new data improves our knowledge of the composition of space in the region of SN 1987A; we can now go back to our simulations and tweak them, to better reconstruct the physics of supernova explosions.”

*Aerial photograph of the core region of the MWA telescope. Credit: mwatelescope.org*

The key to finding this new information was the quiet and (some would say) temperamental conditions that the MWA requires to do its thing. Like all radio telescopes, the MWA is located in a remote area to avoid interference from local radio sources, not to mention a dry and elevated area to avoid interference from atmospheric water vapor.

As Professor Gaensler – the former CAASTRO Director and the supervisor of the project – explained, such methods allow for impressive new views of the Universe. “Nobody knew what was happening at low radio frequencies,” he said, “because the signals from our own earthbound FM radio drown out the faint signals from space. Now, by studying the strength of the radio signal, astronomers for the first time can calculate how dense the surrounding gas is, and thus understand the environment of the star before it died.”

These findings will likely help astronomers to understand the life cycle of stars better, which will come in handy when trying to determine what our Sun has in store for us down the road. Further applications will include the hunt for extra-terrestrial life, with astronomers being able to make more accurate estimates on how stellar evolution could effect the odds of life forming in different star systems.

In addition to being home to the MWA, the Murchison Radio-astronomy Observatory (MRO) is also the planned site of the future Square Kilometer Array (SKA). The MWA is one of three telescopes – along with the South African MeerKAT array and the Australian SKA Pathfinder (ASKAP) array – that are designated as a Precursor for the SKA.

Further Reading: Royal Astronomical Society

April 6, 2016April 14, 2016 by Jason Major

Nearby Supernovas Showered Earth With Iron

Visible, infrared, and X-ray light image of Kepler's supernova remnant (SN 1604) located about 13,000 light-years away. Credit: NASA, ESA, R. Sankrit and W. Blair (Johns Hopkins University).

We all know that we are “made of star-stuff,” with all of the elements necessary for the formation of planets and even life itself having originated inside generations of massive stars, which over billions of years have blasted their creations out into the galaxy at the explosive ends of their lives. Supernovas are some of the most powerful and energetic events in the known Universe, and when a dying star finally explodes you wouldn’t want to be anywhere nearby—fresh elements are nice and all but the energy and radiation from a supernova would roast any planets within tens if not hundreds of light-years in all directions. Luckily for us we’re not in an unsafe range of any supernovas in the foreseeable future, but there was a time geologically not very long ago that these stellar explosions are thought to have occurred in nearby space… and scientists have recently found the “smoking gun” evidence at the bottom of the ocean.

Two independent teams of “deep-sea astronomers”—one led by Dieter Breitschwerdt from the Berlin Institute of Technology and the other by Anton Wallner from the Australian National University—have investigated sediment samples taken from the floors of the Pacific, Atlantic, and Indian oceans. The sediments were found to contain relatively high levels of iron-60, an unstable isotope specifically created during supernovas.

*The Local Bubble is a 300-light-year long region that was carved out of the interstellar medium by supernovas (Source: Science@NASA)*

Watch: How Quickly Does a Supernova Happen?

The teams found that the ages of the iron-60 concentrations (the determination of which was recently perfected by Wallner) centered around two time periods, 1.7 to 3.2 million years ago and 6.5 to 8.7 million years ago. Based on this and the fact that our Solar System currently resides within a peanut-shaped region virtually empty of interstellar gas known as the Local Bubble, the researchers are confident that this provides further evidence that supernovas exploded within a mere 330 light-years of Earth, sending their elemental fallout our way.

“This research essentially proves that certain events happened in the not-too-distant past,” said Adrian Melott, an astrophysicist and professor at the University of Kansas who was not directly involved with the research but published his take on the findings in a letter in Nature. (Source)

The researchers think that two supernova events in particular were responsible for nearly half of the iron-60 concentrations now observed. These are thought to have taken place among a a nearby group of stars known as the Scorpius–Centaurus Association, some 2.3 and 1.5 million years ago. At those same time frames Earth was entering a phase of repeated global glaciation, the end of the last of which led to the rise of modern human civilization.

While supernovas of those sizes and distances wouldn’t have been a direct danger to life here on Earth, could they have played a part in changing the climate?

“Our local research group is working on figuring out what the effects were likely to have been,” Melott said. “We really don’t know. The events weren’t close enough to cause a big mass extinction or severe effects, but not so far away that we can ignore them either. We’re trying to decide if we should expect to have seen any effects on the ground on the Earth.”

Regardless of the correlation, if any, between ice ages and supernovas, it’s important to learn how these events do affect Earth and realize that they may have played an important and perhaps overlooked role in the history of life on our planet.

“Over the past 500 million years there must have been supernovae very nearby with disastrous consequences,” said Melott. “There have been a lot of mass extinctions, but at this point we don’t have enough information to tease out the role of supernovae in them.”

You can find the teams’ papers in Nature here and here.

Sources: IOP PhysicsWorld and the University of Kansas

UPDATE 4/14/16: The presence of iron-60 from the same time periods as those mentioned above has also been found on the Moon by research teams in Germany and the U.S. Read more here.

March 14, 2016February 23, 2017 by Fraser Cain

What are the Different Kinds of Supernovae?

There are a few places in the Universe that defy comprehension. And supernovae have got to be the most extreme places you can imagine. We’re talking about a star with potentially dozens of times the size and mass of our own Sun that violently dies in a faction of a second.

Faster than it take me to say the word supernova, a complete star collapses in on itself, creating a black hole, forming the denser elements in the Universe, and then exploding outward with the energy of millions or even billions of stars.

But not in all cases. In fact, supernovae come in different flavours, starting from different kinds of stars, ending up with different kinds of explosions, and producing different kinds of remnants.

There are two main types of supernovae, the Type I and the Type II. I know this sounds a little counter intuitive, but let’s start with the Type II first.

These are the supernovae produced when massive stars die. We’ve done a whole show about that process, so if you want to watch it now, you can click here.

Our eyes would never see the Crab Nebula as this Hubble image shows it. Image credit: NASA, ESA, J. Hester and A. Loll (Arizona State University)

But here’s the shorter version.

Stars, as you know, convert hydrogen into fusion at their core. This reaction releases energy in the form of photons, and this light pressure pushes against the force of gravity trying to pull the star in on itself.

Our Sun, doesn’t have the mass to support fusion reactions with elements beyond hydrogen or helium. So once all the helium is used up, the fusion reactions stop and the Sun becomes a white dwarf and starts cooling down.

But if you have a star with 8-25 times the mass of the Sun, it can fuse heavier elements at its core. When it runs out of hydrogen, it switches to helium, and then carbon, neon, etc, all the way up the periodic table of elements. When it reaches iron, however, the fusion reaction takes more energy than it produces.

The outer layers of the star collapses inward in a fraction of a second, and then detonates as a Type II supernova. You’re left with an incredibly dense neutron star as a remnant.

But if the original star had more than about 25 times the mass of the Sun, the same core collapse happens. But the force of the material falling inward collapses the core into a black hole.

Extremely massive stars with more than 100 times the mass of the Sun just explode without a trace. In fact, shortly after the Big Bang, there were stars with hundreds, and maybe even thousands of times the mass of the Sun made of pure hydrogen and helium. These monsters would have lived very short lives, detonating with an incomprehensible amount of energy.

Artist's impression of a supernova — Artist’s impression of a supernova

Those are Type II. Type I are a little rarer, and are created when you have a very strange binary star situation.

One star in the pair is a white dwarf, the long dead remnant of a main sequence star like our Sun. The companion can be any other type of star, like a red giant, main sequence star, or even another white dwarf.

What matters is that they’re close enough that the white dwarf can steal matter from its partner, and build it up like a smothering blanket of potential explosiveness. When the stolen amount reaches 1.4 times the mass of the Sun, the white dwarf explodes as a supernova and completely vaporizes.

In a Type Ia supernova, a white dwarf (left) draws matter from a companion star until its mass hits a limit which leads to collapse and then explosion. Credit: NASA

Because of this 1.4 ratio, astronomers use Type Ia supernovae as “standard candles” to measure distances in the Universe. Since they know how much energy it detonated with, astronomers can calculate the distance to the explosion.

There are probably other, even more rare events that can trigger supernovae, and even more powerful hypernovae and gamma ray bursts. These probably involve collisions between stars, white dwarfs and even neutron stars.

As you’ve probably heard, physicists use particle accelerators to create more massive elements on the Periodic Table. Elements like ununseptium and ununtrium. It takes tremendous energy to create these elements in the first place, and they only last for a fraction of a second.

But in supernovae, these elements would be created, and many others. And we know there are no stable elements further up the periodic table because they’re not here today. A supernova is a far better matter cruncher than any particle accelerator we could ever imagine.

Next time you hear a story about a supernova, listen carefully for what kind of supernova it was: Type I or Type II. How much mass did the star have? That’ll help your imagination wrap your brain around this amazing event.

September 17, 2015December 23, 2015 by David Dickinson

Adventures With Starblinker

Observational astronomy is a study in patience. Since the introduction of the telescope over four centuries ago, steely-eyed observers have watched the skies for star-like or fuzzy points of light that appear to move. Astronomers of yore discovered asteroids, comets and even the occasional planet this way. Today, swiftly moving satellites have joined the fray. Still other ‘new stars’ turn out to be variables or novae.

Now, a new and exciting tool named Starblinker promises to place the prospect of discovery in the hands of the backyard observer.

The advent of photography in the late 19^th century upped the game… you’ll recall that Clyde Tombaugh used a blink comparator to discover Pluto from the Lowell Observatory in 1930. Clyde’s mechanical shutter device looked at glass plates in quick sequence. Starblinker takes this idea a step further, allowing astro-imagers to compare two images in rapid sequence in a similar ‘blink comparator’ fashion. You can even quickly compare an image against one online from, say, the SDSS catalog or Wikipedia or an old archival image. Starblinker even automatically orients and aligns the image for you. Heck, this would’ve been handy during a certain Virtual Star Party early last year hosted by Universe Today, making the tale of the ‘supernova in M82 that got away’ turn out very differently…

Often times, a great new program arises simply because astrophotographers find a need where no commercial offering exists. K3CCD Tools, Registax, Orbitron and Deep Sky Stacker are all great examples of DIY programs that filled a critical astronomy need which skilled users built themselves.

“I started to code the software after the mid of last month,” Starblinker creator Marco Lorrai told Universe Today. “I knew there was a plugin for MaximDL to do this job, but nothing for people like me that make photos just with a DSLR… I own a 250mm telescope, and my images go easily down to magnitude +18 so it is not impossible to find something interesting…”

Starblinker is a free application, and features a simple interface. Advanced observers have designed other programs to sift through video and stacks of images in the past, but we have yet to see one with such a straight-forward user interface with an eye toward quick and simple use in the field.

“The idea came to me taking my astrophotos: many images are so rich with stars, why not analyze (them) to check if something has changed?” Lorrai said. “I started to do this check manually, but the task was very thorny, because of differences in scale and rotation between the two images. Also, the ‘blinking’ was done loading two alternating windows containing two different images… not the best! This task could be simplified if someone already has a large set of images for comparison with one old image (taken) with the same instrument… a better method is needed to do this check, and then I started to code Starblinker.”

Why Starblinker

I can see a few immediate applications for Starblinker: possible capture of comets, asteroids, and novae or extragalactic supernovae, to name a few. You can also note the variability of stars in subsequent images. Take images over the span of years, and you might even be able to tease out the proper motion of nearby fast movers such as 61 Cygni, Kapteyn’s or even Barnard’s Star, or the orbits of double stars. Or how about capturing lunar impacts on the dark limb of the Moon? It may sound strange, but it has been done before… and hey, there’s a lunar eclipse coming right up on the night of September 27/28^th. Just be careful to watch for cosmic ray hits, hot pixels, satellite and meteor photobombs, all of which can foil a true discovery.

“A nice feature to add could be the support for FITS images and I think it could be very nice that… the program could retrieve automatically a comparison image, to help amateurs that are just starting (DSLR imaging).” Lorrai said.

And here is our challenge to you, the skilled observing public. What can YOU do with Starblinker? Surprise us… as is often the case with any hot new tech, ya just never know what weird and wonderful things folks will do with it once it’s released in the wild. Hey, discover a comet, and you could be immortalized with a celestial namesake… we promise that any future ‘Comet Dickinson’ will not be an extinction level event, just a good show…

Image credit: Mike Weasner/Cassiopeia observatory

Download Starblinker here.

Think you’ve discovered a comet? Nova? A new asteroid? Inbound alien invasion fleet? OK, that last one might be tweet worthy, otherwise, here’s a handy list of sites to get you started, with the checklist of protocols to report a discovery used by the pros:

–How to Report New Variable Star Discoveries to the American Association of Variable Star Observers (AAVSO)

-The Central Bureau of Astronomical Telegrams (they take emails, too!)

–How to Report a Comet by veteran comet hunter David Levy

–How to Report a Discovery via the International Astronomical Union

-And be sure to send in those Starblinker captures to Universe Today.

May 15, 2015December 23, 2015 by Bob King

Andromeda and Milky Way Might Collide Sooner Than We Think

Andromeda's halo is gargantuan. Extending millions of light years, if we could see in our night sky it would be 100 times the diameter of the Moon or 50 degrees across! Credit: NASA

The merger of the Milky Way and Andromeda galaxy won’t happen for another 4 billion years, but the recent discovery of a massive halo of hot gas around Andromeda may mean our galaxies are already touching. University of Notre Dame astrophysicist Nicholas Lehner led a team of scientists using the Hubble Space Telescope to identify an enormous halo of hot, ionized gas at least 2 million light years in diameter surrounding the galaxy.

The Andromeda Galaxy is the largest member of a ragtag collection of some 54 galaxies, including the Milky Way, called the Local Group. With a trillion stars — twice as many as the Milky Way — it shines 25% brighter and can easily be seen with the naked eye from suburban and rural skies.

Quasars are distant, brilliant sources of light, believed to occur when a massive black hole in the center of a galaxy feeds on gas and stars. As the black hole consumes the material, it emits intense radiation, which is then detected as a quasar. These photos, taken by Hubble, show them as brilliant "stars" in the cores of six different galaxies. Credit: NASA/ESA — Six examples of quasars photographed with the Hubble. Quasars are distant, brilliant sources of light, believed to occur when a massive black hole in the center of a galaxy feeds on gas and stars. As the black hole consumes the material, it emits intense radiation, which is then detected as a quasar. Lehner and team measured Andromeda’s halo by studying how its gas affected the light from 18 different quasars. Credit: NASA/ESA

Think about this for a moment. If the halo extends at least a million light years in our direction, our two galaxies are MUCH closer to touching that previously thought. Granted, we’re only talking halo interactions at first, but the two may be mingling molecules even now if our galaxy is similarly cocooned.

Lehner describes halos as the “gaseous atmospheres of galaxies”. Despite its enormous size, Andromeda’s nimbus is virtually invisible. To find and study the halo, the team sought out quasars, distant star-like objects that radiate tremendous amounts of energy as matter funnels into the supermassive black holes in their cores. The brightest quasar, 3C273 in Virgo, can be seen in a 6-inch telescope! Their brilliant, pinpoint nature make them perfect probes.

To detect Andromeda's halo, Lehner and team studied how the light of 18 quasars (five shown here) was absorbed by the galaxy's gas. Credit: NASA — To detect Andromeda’s halo, Lehner and team studied how the light of 18 quasars (five shown here) was absorbed by the galaxy’s gas. Credit: NASA

“As the light from the quasars travels toward Hubble, the halo’s gas will absorb some of that light and make the quasar appear a little darker in just a very small wavelength range,” said J. Christopher Howk , associate professor of physics at Notre Dame and co-investigator. “By measuring the dip in brightness, we can tell how much halo gas from M31 there is between us and that quasar.”

Astronomers have observed halos around 44 other galaxies but never one as massive as Andromeda where so many quasars are available to clearly define its extent. The previous 44 were all extremely distant galaxies, with only a single quasar or data point to determine halo size and structure.

Andromeda’s close and huge with lots of quasars peppering its periphery. The team drew from about five years’ worth of observations of archived Hubble data to find many of the 18 objects needed for a good sample.

This illustration shows a stage in the predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy, as it will unfold over the next several billion years. In this image, representing Earth's night sky in 3.75 billion years, Andromeda (left) fills the field of view and begins to distort the Milky Way with tidal pull. (Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger) — This illustration shows a stage in the predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy, as it will unfold over the next several billion years. In this image, representing Earth’s night sky in 3.75 billion years, Andromeda (left) fills the field of view and begins to distort the Milky Way with tidal pull. Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger

The halo is estimated to contain half the mass of the stars in the Andromeda galaxy itself, in the form of a hot, diffuse gas. Simulations suggest that it formed at the same time as the rest of the galaxy. Although mostly composed of ionized hydrogen — naked protons and electrons — Andromeda’s aura is also rich in heavier elements, probably supplied by supernovae. They erupt within the visible galaxy and violently blow good stuff like iron, silicon, oxygen and other familiar elements far into space. Over Andromeda’s lifetime, nearly half of all the heavy elements made by its stars have been expelled far beyond the galaxy’s 200,000-light-year-diameter stellar disk.

You might wonder if galactic halos might account for some or much of the still-mysterious dark matter. Probably not. While dark matter still makes up the bulk of the solid material in the universe, astronomers have been trying to account for the lack of visible matter in galaxies as well. Halos now seem a likely contributor.

The next clear night you look up to spy Andromeda, know this: It’s closer than you think!

For more on the topic, here are links to Lehner’s paper in the Astrophysical Journal and the Hubble release.

March 23, 2015December 23, 2015 by Jason Major

As It Turns Out, We Really Are All Starstuff

Hubble image of the Crab Nebula supernova remnant captured with the Wide Field and Planetary Camera 2. Credit: NASA, ESA, J. Hester and A. Loll (Arizona State University)

“The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars,” Carl Sagan famously said in his 1980 series Cosmos. “We are made of starstuff.”

And even today, observations with NASA’s airborne SOFIA observatory are supporting this statement. Measurements taken of the dusty leftovers from an ancient supernova located near the center our galaxy – aka SNR Sagittarius A East – show enough “starstuff” to build our entire planet many thousands of times over.

“Our observations reveal a particular cloud produced by a supernova explosion 10,000 years ago contains enough dust to make 7,000 Earths,” said research leader Ryan Lau of Cornell University in Ithaca, New York – the same school, by the way, where Carl Sagan taught astronomy and space science.

Composite image of SNR Sgr A East showing infrared SOFIA data outlined in white against X-ray and radio observations. (NASA/CXO/Herschel/VLA/Lau et al.)

While it’s long been known that supernovae expel enormous amounts of stellar material into space, it wasn’t understood if clouds of large-scale dust could withstand the immense shockwave forces of the explosion.

NASA's Stratospheric Observatory for Infrared Astronomy 747SP aircraft flies over Southern California's high desert during a test flight in 2010. Credit: NASA/Jim Ross — NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) aircraft (Credit: NASA/Jim Ross)

These observations, made with the joint NASA/DLR-developed Faint Object InfraRed Camera for the SOFIA Telescope (FORCAST) instrument, provide key “missing-link” evidence that dust clouds do in fact survive intact, spreading outward into interstellar space to seed the formation of new systems.

Interstellar dust plays a vital role in the evolution of galaxies and the formation of new stars and protoplanetary discs – the orbiting “pancakes” of material around stars from which planets (and eventually everything on them) form.

The findings may also answer the question of why young galaxies observed in the distant universe possess so much dust; it’s likely the result of frequent supernova explosions from massive early-generation stars.

Winds of Supermassive Black Holes Can Shape Galaxy-Wide Star Formation

An illustration that shows the powerful winds driven by a supermassive black hole at the centre of a galaxy. The schematic figure in the inset depicts the innermost regions of the galaxy where a black hole accretes, that is, consumes, at a very high rate the surrounding matter (light grey) in the form of a disc (darker grey). At the same time, part of that matter is cast away through powerful winds. (Credits: XMM-Newton and NuSTAR Missions; NASA/JPL-Caltech;Insert:ESA)

The combined observations from two generations of X-Ray space telescopes have now revealed a more complete picture of the nature of high-speed winds expelled from super-massive black holes. Scientist analyzing the observations discovered that the winds linked to these black holes can travel in all directions and not just a narrow beam as previously thought. The black holes reside at the center of active galaxies and quasars and are surrounded by accretion discs of matter. Such broad expansive winds have the potential to effect star formation throughout the host galaxy or quasar. The discovery will lead to revisions in the theories and models that more accurately explain the evolution of quasars and galaxies.

This plot of data from NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Space Agency's (ESA's) XMM-Newton determines for the first time the shape of ultra-fast winds from supermassive black holes, or quasars. The winds blow in every direction, in a nearly spherical fashion, coming from both sides of a galaxy (Credit: NASA/JPL-Caltech/Keele Univ.;XMM-Newton and NuSTAR Missions) — This plot of data from NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Space Agency’s (ESA’s) XMM-Newton determines for the first time the shape of ultra-fast winds from supermassive black holes, or quasars. The winds blow in every direction, in a nearly spherical fashion, coming from both sides of a galaxy (Credit: NASA/JPL-Caltech/Keele Univ.;XMM-Newton and NuSTAR Missions, [Ref])

The observations were by the XMM-Newton and NuSTAR x-ray space telescopes of the quasar PDS 456. The observations were combined into the graphic, above. PDS 456 is a bright quasar residing in the constellation Serpens Cauda (near Ophiuchus). The data graph shows both a peak and a trough in the otherwise nominal x-ray emission profile as shown by the NuSTAR data (pink). The peak represents X-Ray emissions directed towards us (i.e.our telescopes) while the trough is X-Ray absorption that indicates that the expulsion of winds from the super-massive black hole is in many directions – effectively a spherical shell. The absorption feature caused by iron in the high speed wind is the new discovery.

X-Rays are the signature of the most energetic events in the Cosmos but also are produced from some of the most docile bodies – comets. The leading edge of a comet such as Rosetta’s P67 generates X-Ray emissions from the interaction of energetic solar ions capturing electrons from neutral particles in the comet’s coma (gas cloud). The observations of a super-massive black hole in a quasar billions of light years away involve the generation of x-rays on a far greater scale, by winds that evidently has influence on a galactic scale.

A diagram of the ESA XMM-Newton X-Ray Telescope. Delivered to orbit by a Ariane 5 launch vehicle in 1999. (Illustration Credit: ESA/XMM-Newton)

The study of star forming regions and the evolution of galaxies has focused on the effects of shock waves from supernova events that occur throughout the lifetime of a galaxy. Such shock waves trigger the collapse of gas clouds and formation of new stars. This new discovery by the combined efforts of two space telescope teams provides astrophysicists new insight into how star and galaxy formation takes place. Super-massive blackholes, at least early in the formation of a galaxy, can influence star formation everywhere.

The NuStar Space Telescope launched into Earth orbit by a Orbital Science Corp. Pegasus rocket, 2012. The Wolter telescope design images throughout a spectral range from 5 to 80 KeV. (Credit: NASA/Caltech-JPL) — The NuStar Space Telescope launched into Earth orbit by a Orbital Science Corp. Pegasus rocket, 2012. The Wolter telescope design – optics in the foreground, 10 meter truss and detectors at back – images throughout a spectral range from 5 to 80 KeV. (Credit: NASA/Caltech-JPL)

Both the ESA built XMM-Newton and the NuSTAR X-Ray space telescope, a SMEX class NASA mission, use grazing incidence optics, not glass (refraction) or mirrors (reflection) as in conventional visible light telescopes. The incidence angle of the X-rays must be very shallow and consequently the optics are extended out on a 10 meter (33 foot) truss in the case of NuSTAR and over a rigid frame on the XMM-Newton.

Diagram of one of three x-ray telescopes of the XMM-Newton design. Only a few of the grazing angle concentric mirrors are shown. Inset: a simplified illustration of how a Wolter telescope works. (Credits: Wikimedia, ESA) [click to enlarge]

The spectral ranges of the XMM-Newton and NuSTAR Telescopes. (Credits: NASA, ESA)

The ESA built XMM-Newton was launched in 1999, an older generation design that used a rigid frame and structure. All the fairing volume and lift capability of the Ariane 5 launch vehicle was needed to put the Newton in orbit. The latest X-Ray telescope – NuSTAR – benefits from tens years of technological advances. The detectors are more efficient and faster and the rigid frame was replaced with a compact truss which required all of 30 minutes to deploy. Consequently, NuSTAR was launched on a Pegasus rocket piggybacked on a L-1011, a significantly smaller and less expensive launch system.

So now these observations are effectively delivered to the theorists and modelers. The data is like a new ingredient in the batter from which a galaxy and stars are formed. The models of galaxy and star formation will improve and will more accurately describe how quasars, with their active super-massive black-holes, transition into more quiescent galaxies such as our own Milky Way.

Reference:

XMM-NEWTON AND NUSTAR SPECTRUM OF THE QUASAR PDS 456

ARTIST’S IMPRESSION OF BLACK-HOLE WIND IN A GALAXY

February 10, 2015December 23, 2015 by Dan Majaess

‘Lopsided’ Supernova Could Be Responsible for Rogue Hypervelocity Stars

Tauris argues that a lopsided supernova explosion may be the source of certain hypervelocity stars (image credit: IsiacDaGraca).

Hypervelocity stars have been observed traversing the Galaxy at extreme velocities (700 km/s), but the mechanisms that give rise to such phenomena are still debated. Astronomer Thomas M. Tauris argues that lopsided supernova explosions can eject lower-mass Solar stars from the Galaxy at speeds up to 1280 km/s. “[This mechanism] can account for the majority (if not all) of the detected G/K-dwarf hypervelocity candidates,” he said.

Several mechanisms have been proposed as the source for hypervelocity stars, and the hypotheses can vary as a function of stellar type. A simplified summary of the hypothesis Tauris favors begins with a higher-mass star in a tight binary system, which finally undergoes a core-collapse supernova explosion. The close proximity of the stars in the system partly ensures that the orbital velocities are exceedingly large. The binary system is disrupted by the supernova explosion, which is lopsided (asymmetric) and imparts a significant kick to the emerging neutron star. The remnants of supernovae with massive progenitors are neutron stars or potentially a more exotic object (i.e., black hole).

Conversely, Tauris noted that the aforementioned binary origin cannot easily explain the observed velocities of all higher-mass hypervelocity stars, namely the B-stars, which are often linked to an ejection mechanism from a binary interaction with the supermassive black hole at the Milky Way’s center. Others have proposed that interactions between multiple stars near the centers of star clusters can give rise to certain hypervelocity candidates.

Certain astronomers argue that hypervelocity stars can stem from interactions in dense star clusters (image credit: Hubble) — Some astronomers argue that certain hypervelocity stars can stem from interactions in dense star clusters (image credit: NASA, ESA, and E. Sabbi (ESA/STScI))

There are several potential compact objects (neutron stars) which feature extreme velocities, such as B2011+38, B2224+65, IGR J11014-6103, and B1508+55, with the latter possibly exhibiting a velocity of 1100 km/s. However, Tauris ends by noting that, “a firm identification of a hypervelocity star being ejected from a binary via a supernova is still missing, although a candidate exists (HD 271791) that’s being debated.”

Tauris is affiliated with the Argelander-Institut für Astronomie and Max-Planck-Institut für Radioastronomie. His findings will be published in the forthcoming March issue of the Monthly Notices of the Royal Astronomical Society.

The interested reader can find a preprint of Tauris’ study on arXiv. Surveys of hypervelocity stars were published by Brown et al. 2014 and Palladino et al. 2014.

February 9, 2015December 23, 2015 by Vanessa Janek

Two Stars On A Death Spiral Set To Detonate As A Supernova

This artist’s impression shows the central part of the planetary nebula Henize 2-428. The core of this unique object consists of two white dwarf stars, each with a mass a little less than that of the Sun. They are expected to slowly draw closer to each other and merge in around 700 million years. This event will create a dazzling supernova of Type Ia and destroy both stars. Credit: ESO/L. Calçada

Two white dwarfs circle around one other, locked in a fatal tango. With an intimate orbit and a hefty combined mass, the pair is ultimately destined to collide, merge, and erupt in a titanic explosion: a Type Ia supernova.

Or so goes the theory behind the infamous “standard candles” of cosmology.

Now, in a paper published in today’s issue of Nature, a team of astronomers have announced observational support for such an arrangement – two massive white dwarf stars that appear to be on track for a very explosive demise.

The astronomers were originally studying variations in planetary nebulae, the glowing clouds of gas that red giant stars throw off as they fizzle into white dwarfs. One of their targets was the planetary nebula Henize 2-428, an oddly lopsided specimen that, the team believed, owed its shape to the existence of two central stars, rather than one. After observing the nebula with the ESO’s Very Large Telescope, the astronomers concluded that they were correct – Henize 2-428 did, in fact, have a binary star system at its heart.

This image of the unusual planetary nebula was obtained using ESO’s Very Large Telescope at the Paranal Observatory in Chile. In the heart of this colourful nebula lies a unique object consisting of two white dwarf stars, each with a mass a little less than that of the Sun. These stars are expected to slowly draw closer to each other and merge in around 700 million years. This event will create a dazzling supernova of Type Ia and destroy both stars. Credit: ESO

“Further observations made with telescopes in the Canary Islands allowed us to determine the orbit of the two stars and deduce both the masses of the two stars and their separation,” said Romano Corradi, a member of the team.

And that is where things get juicy.

In fact, the two stars are whipping around each other once every 4.2 hours, implying a narrow separation that is shrinking with each orbit. Moreover, the system has a combined heft of 1.76 solar masses – larger, by any count, than the restrictive Chandrasekhar limit, the maximum ~1.4 solar masses that a white dwarf can withstand before it detonates. Based on the team’s calculations, Henize 2-428 is likely to be the site of a type Ia supernova within the next 700 million years.

“Until now, the formation of supernovae Type Ia by the merging of two white dwarfs was purely theoretical,” explained David Jones, another of the paper’s coauthors. “The pair of stars in Henize 2-428 is the real thing!”

Check out this simulation, courtesy of the ESO, for a closer look at the fate of the dynamic duo:

Astronomers should be able to use the stars of Henize 2-428 to test and refine their models of type Ia supernovae – essential tools that, as lead author Miguel Santander-García emphasized, “are widely used to measure astronomical distances and were key to the discovery that the expansion of the Universe is accelerating due to dark energy.” This system may also enhance scientists’ understanding of the precursors of other irregular planetary nebulae and supernova remnants.

The team’s work was published in the February 9 issue of Nature. A copy of the paper is available here.