Astronomers Find Rare 5-Star System


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An illustration of two contacting stars — part of the newly discovered bizarre five-star system.

Scientists have discovered an absolutely bizarre star system about 250 light years away, in the constellation Ursa Major.

The system (officially known as 1SWASP J093010.78+533859.5) features five stars that are all gravitationally bound together. Two orbit each other in what’s called a contact eclipsing binary, meaning they’re so close together that they actually share an atmosphere, with gases flowing between them.

Another two stars also orbit each other, but at a much greater distance — about 1.8 million miles, which is more than twice the diameter of the sun. Another star hangs out near that pair, but doesn’t appear to orbit them.

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Systems that include five stars gravitationally bound together are rare, though not unprecedented (astronomers have actually found systems that include as many as six stars). But this is the first one ever found that includes multiple pairs of stars orbiting each other.

The discoverers of the strange system — a team of astronomers from Open University in the UK and elsewhere — presented all these discoveries in a new paper published in the journal Astronomy & Astrophysics. Thanks to George Dvorsky at io9 for bringing it to our attention.

Source: vox.com

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Our star is five billion years younger than most in the Milky Way


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Our sun is nearly 4.5 billion years — which means it missed the charming initial years of the Milky Way galaxy. If you were standing on a planet nearly about 10 billion years ago, when the Milky Way was pretty young, the night sky would have appeared very different. The image below is an artist’s impression of the night sky on a planet in a relatively young Milky Way-type galaxy, the way our galaxy was 10 billion years ago. You can see “the sky are ablaze with star birth. Pink clouds of gas harbor newborn stars, and bluish-white, young star clusters litter the landscape,” as NASA explains.

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Image Credit: NASA/ESA/Z. Levay (STScI)

A recent study of young galaxies like our own demonstrates that as these galaxies slow down creating stars, they also stop developing as quickly in general. Which is quite logical. NASA explains:

“Astronomers don’t have baby pictures of our Milky Way’s formative years to trace the history of stellar growth so they studied galaxies similar in mass to our Milky Way, found in deep surveys of the universe. The farther into the universe astronomers look, the further back in time they are seeing, because starlight from long ago is just arriving at Earth now. From those surveys, stretching back in time more than 10 billion years, researchers assembled an album of images containing nearly 2,000 snapshots of Milky Way-like galaxies. The new census provides the most complete picture yet of how galaxies like the Milky Way grew over the past 10 billion years into today’s majestic spiral galaxies. The multi-wavelength study spans ultraviolet to far-infrared light, combining observations from NASA’s Hubble and Spitzer space telescopes, the European Space Agency’s Herschel Space Observatory, and ground-based telescopes, including the Magellan Baade Telescope at the Las Campanas Observatory in Chile.”

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Above is a selection of Hubble Space Telescope photos, displaying how galaxies similar to our own developed over time.

Source : Physics-astronomy

Hubble Space Telescope Views Globular Cluster Messier 22


The crammed centre of Messier 22

This newly released Hubble image shows Messier 22, the brightest globular cluster visible from the northern hemisphere.

A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers.

Messier 22 is located in the constellation Sagittarius, approximately 10,400 light-years away.

It was the first globular cluster to be discovered. German astronomer Johann Abraham Ihle found it on August 26, 1665, while observing Saturn.

The cluster, also known as M22 or NGC 6656, has a diameter of about 70 light-years and half a million solar masses.

According to astronomers, Messier 22 orbits the galactic center once every 200 million years.

The cluster is an easy object for the naked eye to see. Despite its relative proximity to us, the light from the cluster’s stars is not as bright as it should be as it is dimmed by dust and gas located between us and Messier 22.

As they are leftovers from the early Universe, globular clusters are popular study objects for astronomers.

Messier 22 has fascinating additional features: six planet-sized objects that are not orbiting a star have been detected in the cluster; it seems to host two black holes.

The cluster is one of only three ever found to host a planetary nebula – a short-lived gaseous shells ejected by massive stars at the ends of their lives.

Source : Sci-news

‘Perfect Storm’ Suffocating Star Formation around a Supermassive Black Hole


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High-energy jets powered by supermassive black holes can blast away a galaxy’s star-forming fuel — resulting in so-called “red and dead” galaxies: those brimming with ancient red stars yet little or no hydrogen gas available to create new ones.

Now astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered that black holes don’t have to be nearly so powerful to shut down star formation. By observing the dust and gas at the center NGC 1266, a nearby lenticular galaxy with a relatively modest central black hole, the astronomers have detected a “perfect storm” of turbulence that is squelching star formation in a region that would otherwise be an ideal star factory.

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Fig 1. Artist impression of the central region of NGC 1266. The jets from the central black hole are creating turbulence in the surrounding molecular gas, suppressing star formation in an otherwise ideal environment to form new stars. Credit: B. Saxton (NRAO/AUI/NSF)

This turbulence is stirred up by jets from the galaxy’s central black hole slamming into an incredibly dense envelope of gas. This dense region, which may be the result of a recent merger with another smaller galaxy, blocks nearly 98 percent of material propelled by the jets from escaping the galactic center.

“Like an unstoppable force meeting an immovable object, the molecules in these jets meet so much resistance when they hit the surrounding dense gas that they are almost completely stopped in their tracks,” said Katherine Alatalo, an astronomer with the California Institute of Technology in Pasadena and lead author on a paper published in the Astrophysical Journal. This energetic collision produces powerful turbulence in the surrounding gas, disrupting the first critical stage of star formation. “So what we see is the most intense suppression of star formation ever observed,” noted Alatalo.

Previous observations of NGC 1266 revealed a broad outflow of gas from the galactic center traveling up to 400 kilometers per second. Alatalo and her colleagues estimate that this outflow is as forceful as the simultaneous supernova explosion of 10,000 stars. The jets, though powerful enough to stir the gas, are not powerful enough to give it the velocity it needs to escape from the system.

Continue reading ‘Perfect Storm’ Suffocating Star Formation around a Supermassive Black Hole

ALMA Identifies Gas Spirals as a Nursery of Twin Stars


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With new Atacama Large Millimeter/submillimeter Array (ALMA) observations, astronomers led by Shigehisa Takakuwa, Associate Research Fellow at the Institute of Astronomy and Astrophysics, Academia Sinica (ASIAA), Taiwan, have found spiral arms of molecular gas and dust around “baby twin” stars. Gas motions supplying materials to the twin were also identified. These results unveil for the first time, the mechanism of the birth and growth of binary stars, which are ubiquitous throughout the Universe. The study was published on November 20 in The Astrophysical Journal.

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Fig 1. Gas and dust disks around L1551 NE spotted by ALMA. Credit: ALMA (ESO/NAOJ/NRAO) / Takakuwa et al.

Stars form in interstellar clouds of molecular gas and dust. Previous studies of star formation focused primarily on single stars like the Sun, and a standard picture of single star formation has been established. According to this picture, a dense gas condensation in an interstellar cloud collapses gravitationally to form a single protostar at the center. Previous observations have found such collapsing gas motions feeding material toward the central protostars.

Compared to single star formation, our understanding of binary star formation has been limited, even though more than half of stars with a mass similar to that of the Sun are known to be binaries. It is thus crucial to observe the physical mechanism of binary formation to obtain a more comprehensive understanding of star formation. Theory suggests that a disk surrounding a young binary will feed material to the central “baby twin” in order for them to grow. While recent observations have found such disks (known as “circumbinary disks”), it was not possible to image the structure and gas motions because of the insufficient imaging resolution and sensitivity.

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Fig 2. Comparison of the disks in simulation and observation. The right panel shows the disk image simulated with ATERUI, and the left panel the real ALMA image. Credit: ALMA (ESO/NAOJ/NRAO)/ Takakuwa et al.

Continue reading ALMA Identifies Gas Spirals as a Nursery of Twin Stars

The Fastest Stars in the Universe May Approach Light Speed


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Our sun orbits the Milky Way’s center at an impressive 450,000 mph. Recently, scientists have discovered stars hurtling out of our galaxy at a couple million miles per hour. Could there be stars moving even faster somewhere out there?

After doing some calculations, Harvard University astrophysicists Avi Loeb and James Guillochon realized that yes, stars could go faster. Much faster. According to their analysis, which they describe in two papers recently posted online, stars can approach light speed. The results are theoretical, so no one will know definitively if this happens until astronomers detect such stellar speedsters—which, Loeb says, will be possible using next-generation telescopes.

But it’s not just speed these astronomers are after. If these superfast stars are found, they could help astronomers understand the evolution of the universe. In particular, they give scientists another tool to measure how fast the cosmos is expanding. Moreover, Loeb says, if the conditions are right, planets could orbit the stars, tagging along for an intergalactic ride. And if those planets happen to have life, he speculates, such stars could be a way to carry life from one galaxy to another.

It all started in 2005 when a star was discovered speeding away from our galaxyfast enough to escape the gravitational grasp of the Milky Way. Over the next few years, astronomers would find several more of what became known as hypervelocity stars. Such stars were cast out by the supermassive black hole at the center of the Milky Way. When a pair of stars orbiting each other gets close to the central black hole, which weighs about four million times as much as the sun, the three objects engage in a brief gravitational dance that ejects one of the stars. The other remains in orbit around the black hole.

Loeb and Guillochon realized that if instead you had two supermassive black holes on the verge of colliding, with a star orbiting around one of the black holes, the gravitational interactions could catapult the star into intergalactic space at speeds reaching hundreds of times those of hypervelocity stars.

This appears to be the most likely scenario that would produce the fastest stars in the universe, Loeb says. After all, supermassive black holes collide more often than you might think. Nearly all galaxies have supermassive black holes at their centers, and nearly all galaxies were the product of two smaller galaxies merging. When galaxies combine, so do their central black holes.

Loeb and Guillochon calculated that merging supermassive black holes would eject stars at a wide range of speeds. Only some would reach near light speed, but many of the rest would still be plenty fast. For example, Loeb says, the observable universe could have more than a trillion stars moving at a tenth of light speed, about 67 million miles per hour.

Because a single, isolated star streaking through intergalactic space would be so faint, only powerful future telescopes like the James Webb Space Telescope , planned for launch in 2018, would be able to detect them. Even then, telescopes would likely only see the stars that have reached our galactic neighborhood. Many of the ejected stars probably would have formed near the centers of their galaxies, and would have been thrown out soon after their birth. That means that they would have been traveling for the vast majority of their lifetimes. The star’s age could therefore approximate how long the star has been traveling. Combining travel time with its measured speed, astronomers can determine the distance between the star’s home galaxy and our galactic neighborhood.

If astronomers can find stars that were kicked out of the same galaxy at different times, they can use them to measure the distance to that galaxy at different points in the past. By seeing how the distance has changed over time, astronomers can measure how fast the universe is expanding.

These superfast rogue stars could have another use as well. When supermassive black holes smash into each other, they generate ripples in space and time called gravitational waves, which reveal the intimate details of how the black holes coalesced. A space telescope called eLISA, scheduled to launch in 2028, is designed to detect gravitational waves. Because the superfast stars are produced when black holes are just about to merge, they would act as a sort of bat signal pointing eLISA to possible gravitational wave sources.

The existence of these stars would be one of the clearest signals that two supermassive black holes are on the verge of merging, says astrophysicist Enrico Ramirez-Ruiz of the University of California, Santa Cruz. Although they may be hard to detect, he adds, they will provide a completely novel tool for learning about the universe.

In about 4 billion years, our own Milky Way Galaxy will crash into the Andromeda Galaxy. The two supermassive black holes at their centers will merge, and stars could be thrown out. Our own sun is a bit too far from the galaxy’s center to get tossed, but one of the ejected stars might harbor a habitable planet. And if humans are still around, Loeb muses, they could potentially hitch a ride on that planet and travel to another galaxy. Who needs warp drive anyway?

Source : wired.com

Cool gases ideal for star formation in galaxies


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Horsehead nebula (Click Image to Download)

Astronomers have discovered that a cool cosmic environment is ideal for the creation of new stars.

A surge of warm gas from a nearby galaxy – left over from the devouring of a separate galaxy – eliminates star formation by agitating the available chilled gas, the study says.

Astronomers wanted to understand why galaxies in the local universe fall into two major categories: younger, star-forming spirals (like our own Milky Way) and older ellipticals in which fresh star making has ceased.

The new study observed galaxy NGC 3226, which occupies a transitional middle ground so getting a lead on its star formation was critical.

“We have explored big data archives from NASA and European Space Agency’s space telescopes to pull together a picture of an elliptical galaxy that has undergone huge changes in its recent past due to violent collisions with its neighbours,” said Philip Appleton, project scientist for the NASA Herschel Science Center at the California Institute of Technology in Pasadena.

These collisions are modifying the condition of the gas that resides in it, making it hard for the galaxy to form many stars, he added.

NGC 3226 is relatively close, just 50 million light-years away from Earth.

The data from the three telescopes finds that NGC 3226 has a very low rate of star formation.

It appears that in this case, the material falling into NGC 3226 is heating up as it collides with other galactic gas and dust, quenching star formation instead of fueling it.

As the warm gas flooding NGC 3226 cools to star-forming temperatures, the galaxy should get a second wind, the authors said.

The paper appeared on Astrophysical Journal.

Source : ZEE NEWS

From the Hubble, a new image of a glittering cosmic wonderland with stars as old as the universe itself


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It kind of looks like a snow globe — or maybe like the glittering ornament atop a massive Christmas tree.

Or like your neighbor’s house during December, if you’re lucky enough to live next to an aggressive seasonal decorator.

But this image from the Hubble Space Telescope shows Messier 92. Messier 92 is a globular cluster, or a spherical group of old stars bound tightly together by gravity. Their density can make globular clusters appear quite bright, and this is one of the brightest in our whole galaxy.

You may even have seen this cosmic bauble before. It’s over 25,000 light years away from Earth, but with 330,000 stars packed tightly into it, it’s often visible with the naked eye. You can catch its occasional appearances in the constellation Hercules.

Astronomers know from Messier 92’s molecular composition that it isn’t just bright — it’s also very old. About as old as the universe itself, in fact.

Like this image? You could have been the one to create it. A version of this photo was submitted by Gilles Chapdelaine as part of the Hubble’s Hidden Treasures image competition. The Hubble has beamed back so much data that not all of it has been translated into visible images, but the public is welcome to sift through archives to try to find stellar shots worth sharing.Find out more at the Hubble Web site.

Source : Washington post

Ripples in Space-Time Could Reveal ‘Strange Stars’


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By looking for ripples in the fabric of space-time, scientists could soon detect “strange stars” — objects made of stuff radically different from the particles that make up ordinary matter, researchers say.

The protons and neutrons that make up the nuclei of atoms are made of more basic particles known as quarks. There are six types, or “flavors,” of quarks: up, down, top, bottom, charm and strange. Each proton or neutron is made of three quarks: Each proton is composed of two up quarks and one down quark, and each neutron is made of two down quarks and one up quark.

In theory, matter can be made with other flavors of quarks as well. Since the 1970s, scientists have suggested that particles of “strange matter” known as strangelets — made of equal numbers of up, down and strange quarks — could exist. In principle, strange matter should be heavier and more stable than normal matter, and might even be capable of converting ordinary matter it comes in contact with into strange matter. However, lab experiments have not yet created any strange matter, so its existence remains uncertain.

Why Are Quark Stars So Strange?

One place strange matter could naturally be created is inside neutron stars, the remnants of stars that died in catastrophic explosions known as supernovas. Neutron stars are typically small, with diameters of about 12 miles (19 kilometers) or so, but are so dense that they weigh as much as the sun. A chunk of a neutron star the size of a sugar cube can weigh as much as 100 million tons.

Under the extraordinary force of this extreme weight, some of the up and down quarks that make up neutron stars could get converted into strange quarks, leading to strange stars made of strange matter, researchers say.

A strange star that occasionally spurts out strange matter could quickly convert a neutron star orbiting it in a binary system into a strange star as well. Prior research suggests that a neutron star that receives a seed of strange matter from a companion strange star could transition to a strange star in just 1 millisecond to 1 second.

Continue reading Ripples in Space-Time Could Reveal ‘Strange Stars’

Evidence of ‘Starquakes’ on Neutron Star


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An earthquake can be a pretty awe-inspiring natural event – a testament to the sheer power and size of shifting landmass. But what about seismic activity on a star? NASA’s Fermi satellite recently spotted evidence of seismic waves rippling throughout a high-energy neutron star, resulting in an intense “storm” of high-energy blasts.

The star in question, called SGR J1550-5418, is a magnetar – an incredibly dense and highly magnetized neutron star that spins at an exceptionally high speed. The typical neutron star boasts a magnetic pull trillions of times stronger than the Earth’s. A magnetar, by comparison, is about 1,000 times more magnetic than that.

Within the last four decades, only 23 magnetars in all have been identified, and among these stars, only three massive flares have ever been seen. The flares were related to “starquakes,” in which instability of a neutron’s pressing magnetic field literally shakes its surface.

“Fermi’s Gamma-ray Burst Monitor (GBM) has captured the same evidence from smaller and much more frequent eruptions called bursts.

Source : nature world news