Posted on 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
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.

Posted on by Jason Major

Rare Images of Red Sprites Captured at ESO

Distant sprites (right) captured from ESO's VLT by Photo Ambassador Petr Horálek. (P. Horálek/ESO)

At the ESO’s observatories located high in the Atacama Desert of Chile, amazing images of distant objects in the Universe are captured on a regular basis. But in January 2015, ESO photo ambassador Petr Horálek captured some amazing photos of much closer phenomena: red sprites flashing in the atmosphere high above distant thunderstorms.

The photo above was captured from ESO’s Paranal Observatory. A few days earlier during the early morning hours of Jan. 20 Petr captured another series of sprites from the La Silla site, generated by a storm over Argentina over 310 miles (500 km) away.

Sprites spotted from ESO's La Silla observatory by Petr Horálek
Sprites spotted from ESO’s La Silla observatory by Petr Horálek (left horizon)

So-named because of their elusive nature, sprites appear as clusters of red tendrils above a lighting flash, often extending as high as 55 miles (90 km) into the atmosphere. The brightest region of a sprite is typically seen at altitudes of over 40-45 miles (65-75 km).

Because they occur high above large storms, only last for fractions of a second and emit light in the portion of the spectrum to which our eyes are the least sensitive, observing sprites is notoriously difficult.

Read more: On the Hunt for High-Speed Sprites

These furtive atmospheric features weren’t captured on camera until 1989. Continuing research has since resulted in more images, including some from the International Space Station. When they are spotted, sprites – and their lower-altitude relatives blue jets – can appear as bright as moderate aurorae and have also been found to emit radio noise. It has even been suggested that looking for sprite activity on other planets could help identify alien environments that are conducive to life.

Find out more about sprite research from the University of Alaska Fairbanks, and check out the PBS NOVA program “At the Edge of Space” below about a sprite hunt in the skies over Denver, CO conducted by a team of American scientists and Japanese filmmakers.

Source: ESO

Posted on by Jason Major

What Is This Empty Hole In Space?

The dark nebula LDN 483 imaged by ESO's La Silla Observatory in Chile (ESO)

What may appear at first glance to be an eerie, empty void in an otherwise star-filled scene is really a cloud of cold, dark dust and molecular gas, so dense and opaque that it obscures the distant stars that lie beyond it from our point of view.

Similar to the more well-known Barnard 68, “dark nebula” LDN 483 is seen above in an image taken by the MPG/ESO 2.2-meter telescope’s Wide Field Imager at the La Silla Observatory in Chile.

While it might seem like a cosmic no-man’s-land, no stars were harmed in the making of this image – on the contrary, dark nebulae like LDN 483 are veritable maternity wards for stars. As their cold gas and dust contracts and collapses new stars form inside them, remaining cool until they build up enough density and gravity to ignite fusion within their cores. Then, shining brightly, the young stars will gradually blast away the remaining material with their outpouring wind and radiation to reveal themselves to the galaxy.

The process may take several million years, but that’s just a brief flash in the age of the Universe. Until then, gestating stars within LDN 483 and many other clouds like it remain dim and hidden but keep growing strong.

Wide-field view of the LDN 483 region. (Credit: ESO and Digitized Sky Survey 2)
Wide-field view of the LDN 483 region. (Credit: ESO and Digitized Sky Survey 2)

Located fairly nearby, LDN 483 is about 700 light-years away from Earth in the constellation Serpens.

Source: ESO

Posted on by Matt Williams

VLTI Detects Exozodiacal Light Around Exoplanets

Artist's impression of zodiacal light viewed from the surface of an exoplanet. Credit: ESO/L. Calçada

If you’ve ever stood outside after twilight has passed, or a few hours before the sun rises at dawn,  then chances are you’ve witnessed the phenomenon known as zodiacal light. This effect, which looks like a faint, diffuse white glow in the night sky, is what happens when sunlight is reflected off of tiny particles and appears to extend up from the vicinity of the Sun. This reflected light is not just observed from Earth but can be observed from everywhere in the Solar System.

Using the full power of the Very Large Telescopic Interferometer (VLTI), an international team of astronomers recently discovered that the exozodiacal light – i.e., zodiacal light around other star systems – close to the habitable zones around nine nearby stars was far more extreme. The presence of such large amounts of dust in the inner regions around some stars may pose an obstacle to the direct imaging of Earth-like planets.

The reason for this is simple: even at low levels, exozodiacal dust causes light to become amplified intensely. For example, the light detected in this survey was roughly 1000 times brighter than the zodiacal light seen around the Sun. While this exozodiacal light had been previously detected, this is the first large systematic study of this phenomenon around nearby stars.

The team used the VLTI visitor instrument PIONIER which is able to interferometrically connect all four Auxiliary Telescopes or all four Unit Telescopes of the VLTI at the Paranal Observatory. This led to not only extremely high resolution of the targets but also allowed for a high observing efficiency.

The Very Large Telescoping Interferometer firing it's adaptive optics laser. Credit: ESO/G. Hüdepohl
The Very Large Telescoping Interferometer firing its adaptive optics laser.
Credit: ESO/G. Hüdepohl

In total, the team observed exozodiacal light from hot dust close to the habitable zones of 92 nearby stars and combined the new data with their earlier observations.

In contrast to these earlier observations – which were made with the Center for High Angular Resolution Astronomy (CHARA) array at Georgia State University – the team did not observe dust that will later form into planets, but dust created in collisions between small planets of a few kilometers in size – objects called planetesimals that are similar to the asteroids and comets of the Solar System. Dust of this kind is also the origin of the zodiacal light in the Solar System.

As a by-product, these observations have also led to the discovery of new, unexpected stellar companions orbiting around some of the most massive stars in the sample. “These new companions suggest that we should revise our current understanding of how many of this type of star are actually double,” says Lindsay Marion, lead author of an additional paper dedicated to this complementary work using the same data.

“If we want to study the evolution of Earth-like planets close to the habitable zone, we need to observe the zodiacal dust in this region around other stars,” said Steve Ertel, lead author of the paper, from ESO and the University of Grenoble in France. “Detecting and characterizing this kind of dust around other stars is a way to study the architecture and evolution of planetary systems.”

A portrait of the HR8799 planetary system as imaged by the Hale Telescope. Credit: NASA/JPL-Caltech/Palomar Observatory.
A portrait of the HR8799 planetary system as imaged by the Hale Telescope.
Credit: NASA/JPL-Caltech/Palomar Observatory.

However, the good news is that the number of stars containing zodiacal light at the level of our Solar System is most likely much higher than the numbers found in the survey.

“The high detection rate found at this bright level suggests that there must be a significant number of systems containing fainter dust, undetectable in our survey, but still much brighter than the Solar System’s zodiacal dust,” explains Olivier Absil, co-author of the paper, from the University of Liège. “The presence of such dust in so many systems could therefore become an obstacle for future observations, which aim to make direct images of Earth-like exoplanets.”

Therefore, these observations are only a first step towards more detailed studies of exozodiacal light, and need not dampen our spirits about discovering more Earth-like exoplanets in the near future.

Further Reading: ESO

Posted on by Shannon Hall

ESO’s La Silla Observatory Reveals Beautiful Star Cluster “Laboratory”

In this image from the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile young stars huddle together against a backdrop of clouds of glowing gas and lanes of dust. The star cluster, known as NGC 3293, would have been just a cloud of gas and dust itself about ten million years ago, but as stars began to form it became the bright group we see here. Clusters like this are celestial laboratories that allow astronomers to learn more about how stars evolve. Credit: ESO/G. Beccari

Any human being knows the awe-inspiring wonder of a splash of stars against a dark backdrop. But it takes a skilled someone to truly appreciate a distant object viewed through an eyepiece. Your gut tightens as you realize that the tiny fuzzy blob is really thousands of light-years away.

That wave of amazement is encouraged by understanding and knowledge.

Stunning photographs of the cosmos further convey the beauty that arises from the simple interplay of dust, light and gas on absolutely massive and distant scales. The striking image above from ESO’s La Silla Observatory in Chile is but one example.

Stars are born in enormous clouds of gas and dust. Small pockets in these clouds collapse under the pull of gravity, eventually becoming so hot that they ignite nuclear fusion. The result is a cluster of tens to hundreds of thousands of stars bound together by their mutual gravitational attraction.

Every star in a cluster is roughly the same age and has the same chemical composition. They’re the closest thing astronomers have to a controlled laboratory environment.

This chart shows the location of the bright open star cluster NGC 3293 in the southern constellation of Carina (The Keel). All the stars visible to the naked eye on a clear and dark night are marked, along with the positions of some nebulae and clusters. The location of NGC 3293 is marked with a red circle. This cluster is bright enough to be seen without optical aid in good conditions and is a spectacular sight in a moderate-sized telescope. Credit: ESO, IAU and Sky & Telescope
This chart shows the location of the bright open star cluster NGC 3293 (marked by a red circle) in the southern constellation of Carina. Image Credit: ESO / IAU / Sky & Telescope

The star cluster, NGC 3293, is located 8000 light-years from Earth in the constellation of Carina. It was first spotted by the French astronomer Nicolas-Louis de Lacaille during his stay in South Africa in 1751. Because it stands as one of the brightest clusters in the southern sky, de Lacaille was able to site it in a tiny telescope with an aperture of just 12 millimeters.

The cluster is less than 10 million years old, as can be seen by the abundance of hot, blue stars. Despite some evidence suggesting that there is still some ongoing star formation, it is thought that most, if not all, of the nearly 50 stars were born in one single event.

But even though these stars are all the same age, they do not all have the dazzling appearance of stars in their infancy. Some look positively elderly. The reason is simple: stars of different size, evolve at different speeds. More massive stars speed through their evolution, dying quickly, while less massive stars can live tens of billions of years.

Take the bright orange star at the bottom right of the cluster. Stars initially draw their energy from burning hydrogen into helium deep within their cores. But this star ran out of hydrogen fuel faster than its neighbors, and quickly evolved into a cool and bright, giant star with a contracted core but an extended atmosphere.

It’s now a cool, red giant, in a new stage of evolution, while its neighbors remain hot, young stars.

Eventually the star will collapse under its own gravity, throwing off its outer layers in a supernova explosion, and leaving behind a neutron star or a black hole. The peppering shock waves will likely initiate further star formation in the ever-changing laboratory.

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Source: ESO

Posted on by David Dickinson

Dazzling New Views of a Familiar Cluster

Credit: ESO

Wow. It’s always amazing to get new views of familiar sky targets. And you always know that a “feast for the eyes” is in store when astronomers turn a world-class instrument towards a familiar celestial object.

Such an image was released this morning from the European Southern Observatory (ESO). Astronomers turned ESO’s 2.2-metre telescope towards Messier 7 in the constellation Scorpius recently, and gave us the star-studded view above.

Also known as NGC 6475, Messier 7 (M7) is an open cluster comprised of over 100 stars located about 800 light years distant. Located in the curved “stinger” of the Scorpion, M7 is a fine binocular object shining at a combined magnitude of about +3.3. M7 is physically about 25 light years across and appears about 80 arc minutes – almost the span of three Full Moons – in diameter from our Earthly vantage point.

One of the most prominent open clusters in the sky, M7 lies roughly in the direction of the galactic center in the nearby astronomical constellation of Sagittarius. When you’re looking towards  M7 and the tail of Scorpius you’re looking just south of the galactic plane in the direction of the dusty core of our galaxy. The ESO image reveals the shining jewels of the cluster embedded against the more distant starry background.

Messier 7 is middle-aged as open clusters go, at 200 million years old. Of course, that’s still young for the individual stars themselves, which are just venturing out into the galaxy. The cluster will lose about 10% of its stellar population early on, as more massive stars live their lives fast and die young as supernovae. Our own solar system may have been witness to such nearby cataclysms as it left its unknown “birth cluster” early in its life.

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Other stars in Messier 7 will eventually mature, “join the galactic car pool” in the main sequence as they disperse about the plane of the galaxy.

But beyond just providing a pretty picture, studying a cluster such as Messier 7 is crucial to our understanding stellar evolution. All of the stars in Messier 7 were “born” roughly around the same time, giving researchers a snapshot and a chance to contrast and compare how stars mature over there lives. Each open cluster also has a unique spectral “fingerprint,” a chemical marker that can even be used to identify the pedigree of a star.

For example, there’s controversy that the open cluster Messier 67 may actually be the birth place of our Sun. It is interesting to note that the spectra of stars in this cluster do bear a striking resemblance in terms of metallicity percentage to Sol. Remember, metals in astronomer-speak is any element beyond hydrogen and helium. A chief objection to the Messier 67 “birth-place hypothesis” is the high orbital inclination of the open cluster about the core of our galaxy: our Sun would have had to have undergone a series of improbable stellar encounters to have ended up its current sedate quarter of a billion year orbit about the Milky Way galaxy.

Still, this highlights the value of studying clusters such as Messier 6. It’s also interesting to note that there’s also data in what you can’t see in the above image – dark gaps are thought to be dust lanes and globules in the foreground. Though there is some thought that this dust is debris that may also be related to the cluster and may give us clues as to its overall rotation, its far more likely that these sorts of “dark spirals” related to the cluster have long since dispersed. M7 has completed about one full orbit about the Milky Way since its formation.

Another famous binocular object, the open cluster Messier 6 (M6) also known as the Butterfly Cluster lies nearby. Messier 7 also holds the distinction as being the southernmost object in Messier’s catalog. Compiled from Parisian latitudes, Charles Messier entirely missed southern wonders such as Omega Centauri in his collection of deep sky objects that were not to be mistaken for comets. We also always thought it curious that he included such obvious “non-comets” such as the Pleiades, but missed fine northern sky objects as the Double Cluster in the northern constellation Perseus.

Finding Messier 6: the view from latitude 30 degrees north before dawn in mid-February. Credit: Stellarium.
Finding Messier 6: the view from latitude 30 degrees north before dawn in mid-February. Credit: Stellarium.

Messier 7 is also sometimes called Ptolemy’s Cluster after astronomer Claudius Ptolemy, who first described it in 130 A.D. as the “nebula following the sting of Scorpius.” The season for hunting all of Messier’s objects in an all night marathon is coming right up in March, and Messier 7 is one of the last targets on the list, hanging high due south in the early morning sky.

Interested in catching how Messier 7 will evolve, or might look like up close?  Check out Messier 45 (the Pleiades) and the V-shaped Hyades high in the skies in the constellation Taurus at dusk to see what’s in store as Messier 7 disperses, as well as the Ursa Major Moving Group.

And be sure to enjoy the fine view today of Messier 7 from the ESO!

Got pics of Messier 7 or any other deep sky objects? Send ’em, in to Universe Today!

Posted on by Jason Major

Keeping An Eye On Gaia

ESA's Gaia spacecraft as seen by the VLT (Credit: ESO)

Gaia, ESA’s long-anticipated mission to map the stars of our galaxy (as well as do a slew of other cool science things) is now tucked comfortably in its position in orbit around Earth-Moon L2, a gravitationally stable spot in space 1.5 million km (932,000 miles) away.

Once its mission begins in earnest, Gaia will watch about a billion stars an average of 70 times each over a five-year span… that’s 40 million observations every day. It will measure the position and key physical properties of each star, including its brightness, temperature and chemical composition, and help astronomers create the most detailed 3D map of the Milky Way ever.

But before Gaia can do this, its own position must be precisely determined. And so several of the world’s most high-powered telescopes are trained on Gaia, keeping track daily of exactly where it is up to an accuracy of 150 meters… which, with the ten-meter-wide spacecraft one and a half million kilometers away, isn’t too shabby.

Called GBOT, for Ground Based Orbit Tracking, the campaign to monitor Gaia’s position was first set up in 2008 — long before the mission launched. This allowed participating observatories to practice targeting on other existing spacecraft, like NASA’s WMAP and ESA’s Planck space telescopes.

The image above shows an image of Gaia (circled) as seen by the European Southern Observatory’s Very Large Telescope Survey Telescope (VST) atop Cerro Paranal in Chile, one of the supporting observatories in the GBOT campaign. The images were taken with the 2.6-meter Survey Telescope’s 268-megapixel OmegaCAM on Jan. 23, 6.5 minutes apart. With just the reflected sunlight off its circular sunshield, the distant spacecraft is about a million times fainter than what your eyes could see unaided.

Gaia mapping the stars of the Milky Way. (ESA/ATG medialab; background: ESO/S. Brunier)
Gaia mapping the stars of the Milky Way. (ESA/ATG medialab; background: ESO/S. Brunier)

It’s also one the closest objects ever imaged by the VST.

Currently Gaia is still undergoing calibration for its survey mission. Some problems have been encountered with stray sunlight reaching its detectors, and this may be due to the angle of the sunshield being a few degrees too high relative to the Sun. It could take a few weeks to implement an orientation correction; read more on the Gaia blog here.

Read more: Ghostly Cat’s Eye Nebula Shines In Space Telescope Calibration Image

Of the billion stars Gaia will observe, 99% have never had their distances accurately measured. Gaia will also observe 500,000 distant quasars, search for brown dwarfs and exoplanets, and will conduct experiments testing Einstein’s General Theory of Relativity. Find out more facts about the mission here.

Gaia launched on December 19, 2013, aboard a Soyuz VS06 from ESA’s spaceport in Kourou, French Guiana. Watch the launch here.

Source: ESA

Posted on by Elizabeth Howell

Astronomers Look “Inside” an Asteroid for the First Time

Itokawa, a peanut-shaped asteroid that has different densities in its small body. Credit: ESO/JAXA

From directly inferring the inside of an asteroid for the first time, astronomers have discovered these space rocks can have strange variations in density. The observations of Itokawa — which you may remember from the Japanese Hayabusa mission that landed on the asteroid in 2005 — not only teach us more about how asteroids came to be, but could help protect Earth against stray space rocks in the future, the researchers said.

“This is the first time we have ever been able to to determine what it is like inside an asteroid,” stated Stephen Lowry, a University of Kent scientist who led the research. “We can see that Itokawa has a highly varied structure; this finding is a significant step forward in our understanding of rocky bodies in the solar system.”

It’s not clear why Itokawa has such different densities at opposite sides of its peanut shape; perhaps it was two asteroids that rubbed up against each other and merged. At just shy of six American football fields long, the space rock has density varying from 1.75 to 2.85 grams per cubic centimetre. This precise measurement came courtesy of the European Southern Observatory’s New Technology Telescope in Chile.

The telescope calculated the speed and speed changes of Itokawa’s spin and combined that information with data on how sunlight can affect the spin rate. Asteroids are generally tiny and irregularly shaped sorts of bodies, which means the effect of heat on the body is not evenly distributed. That small difference makes the asteroid’s spin rate change.

This heat effect (more properly called the Yarkovsky-O’Keefe-Radzievskii-Paddack effect) is slowly making Itokawa’s spin rate go faster, at a rate of 0.045 seconds every Earth year. This change, previously unexpected by scientists, is only possible if the peanut bulges have different densities, the scientists said.

“Finding that asteroids don’t have homogeneous interiors has far-reaching implications, particularly for models of binary asteroid formation,” added Lowry.  “It could also help with work on reducing the danger of asteroid collisions with Earth, or with plans for future trips to these rocky bodies.”

More details on the research will be available in the journal Astronomy and Astrophysics.

Source: European Southern Observatory